Home Development and validation of a high performance liquid chromatography/diode array detection method for estrogen determination: Application to residual analysis in meat products
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Development and validation of a high performance liquid chromatography/diode array detection method for estrogen determination: Application to residual analysis in meat products

  • Sadeem S. Alqahtani , Deema M. Bin Humaid , Sabreen H. Alshail , Dalal T. AlShammari , Hessa Al-Showiman , Nourah Z. Alzoman and Hadir M. Maher EMAIL logo
Published/Copyright: August 7, 2020
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Open Chemistry
From the journal Open Chemistry Volume 18 Issue 1

Abstract

In this work, an HPLC-DAD method was developed for the residual analysis of some estrogens such as estrone (E1), 17-β estradiol (E2), estriol (E3), natural estrogens, and 17-α ethinylestradiol (E4), an exoestrogen, in meat samples of different categories (chicken, n = 155, beef, n = 124, sheep, n = 122, and camels, n = 40), collected from the Saudi Market. Although banned, the use of E4 as a growth promoter in the black market is still encountered. Symmetry C18 column (3.5 µm, 4.6 mm × 150 mm) was used with a mobile phase consisting of 50% aqueous acetonitrile. Protein precipitation with acetonitrile was used for the sample preparation. The method was fully validated, as per the ICH guidelines, in the concentration ranges of 0.35–125 µg/g (E1, E2), 0.188–125 µg/g (E3), and 0.188–450 µg/g (E4). The method allowed the trace analysis of estrogens with LOD values of 0.094 (E3, E4) and 0.126 µg/g (E1, E2), and LOQ values of 0.188 (E3, E4) and 0.350 µg/g (E1, E2). The analyzed samples contained different levels of estrogens. Within the same category, processed products contained the highest levels of E4, while the internal organs contained the least estrogen content. Finally, the estimated daily intake, µg/kg bw/day, of estrogens through the consumption of meat-based food products was calculated.

Key words: estrogens; food analysis; HPLC-DAD; meat products; Saudi market

1 Introduction

Estrogens are sex-related steroidal hormones which are known for their regulatory effect on the estrus cycle in mammals and more specifically on the menstrual cycle of humans [1]. It has been reported that estrogens are not only considered as female sex hormones, but they also play a significant role in controlling the male sexual functions [2]. Additionally, estrogens play an important role in regulating critical body functions, e.g., brain function, lipid, protein, and glucose homeostasis, blood coagulation, in addition to follicular growth and skeletal muscles’ growth.

Estrogens are classified into two main groups, namely: natural estrogens, also known as endo-estrogens, and synthetic estrogens, known as exoestrogens. Estrone (E1), 17-β estradiol (E2), and estriol (E3) are the most common examples of natural estrogens. Synthetic estrogens include a large number of diverse compounds with estrogenic activities, e.g., pesticides, polychlorinated biphenyls, in addition to the well-known 17-α ethinylestradiol (E4), which is commonly used as a growth promoter [3].

The liability of finding estrogens in dietary meat samples is related to the presence of endogenous natural estrogens in different levels in meat-producing animals, as controlled by the estrus cycle, as well as the external use of estrogens, particularly E4, as a growth promoter [3]. Dietary intake of estrogen-containing food could result in the disturbance of different metabolic activities, including fat, sugar, and protein metabolism. Additionally, overexpression of estrogen receptors, as a result of an excessive estrogen intake, is related to the development of autoimmune diseases, as well as different types of cancers, particularly breast, ovarian, and prostate cancers [4,5]. Recently, the role of estrogens in modulating metastatic cascades of cancer cells has been emphasized [6].

For the sake of human health, the use of hormones as growth promoters in animals is prohibited by European Union regulations (Directive 2008/97/EC, 2008) [7], with no maximum residue level because of the possibility of the presence of natural estrogens in meat samples. Despite such a legislation, the illegal use of estrogens as growth promoters in the black market is still encountered in the veterinary field.

According to the statistics of the “Organization for Economic Co-operation and Development, OECD” in 2018 [8], Saudi Arabia consumes a large amount of meat with poultry meat being the first source of meat, Saudi annual consumption of 40 kg/capita compared with world consumption of 14.2 kg/capita, followed by sheep meat, Saudi annual consumption of 5 kg/capita compared with world consumption of 1.7 kg/capita, followed by beef and veal, Saudi annual consumption of 3.5 kg/capita compared with world consumption of 6.5 kg/capita. Moreover, Saudi Arabia is considered the largest market of camel consumption all over the whole world. Camels are one of the most popular livestock animals in Saudi Arabia. The demand for camel meat seems to be increasing, particularly due to an increased awareness of the health benefits of camel meat related to less fat and less cholesterol content, relative to other types of red meat [9].

As a result of health hazards of residual estrogen, there is a demand for its determination in meat products, including chicken, beef, sheep, and camel, which are widely consumed by the Saudi population. Different analytical techniques have been applied for the determination of steroid hormones in biological samples/edible tissues. They include immunoassay [10], gas chromatography with mass spectrometric detector (GC-MS) [11,12], and liquid chromatography with mass spectrometric detector (LC-MS) [13,14,15,16,17,18,19]. Despite that immunoassay is widely used for measuring steroid hormones in biological matrices, an occasional lack of specificity is still a major drawback. Also, great sensitivity of GC-MS in estrogen analysis is still faced by researchers while performing the derivatization procedure that is required prior to the actual analysis. LC-MS/MS is characterized by its sensitivity and selectivity, and is thus widely used in biological analysis. HPLC with UV [20,21,22,23,24] or fluorescence [25,26] detection has also been used in food analysis and it is considered advantageous for its lower cost and ease of operation, relative to the more sophisticated LC-MS/MS instrument.

Residual determination of estrogens in different food stuffs has been performed in many countries, namely, China [14,15,17,19,20,21,22,23,26], Spain [15], Iran [25], and Egypt [24].

Since Saudi Arabia is considered among the highest consumers of meat all over the world, Saudis, along with residents and religious visitors, are susceptible to a high estrogen intake from ingested meat samples. Despite the importance of this issue to public health, the screening of estrogens in food samples from the Saudi market – to our knowledge – has not been performed until now. Therefore, this work aims at carrying out the residual analysis of estrogens in meat samples of different categories (chicken, beef, sheep, and camel) available in the Saudi market by the HPLC-DAD. The obtained results were statistically analyzed.

2 Experimental

2.1 Materials and reagents

Reference standards of estrone (E1), purity > 98%, 17-β estradiol (E2), purity > 98%, estriol (E3), purity > 98%, and 17-α ethinylestradiol (E4), purity > 98%, were purchased from MedChemExpress, China. Esomeprazole (ESM), purity > 98%, was supplied by Themis Laboratories Pvt. Ltd, Thane. The ESM was used as an internal standard (IS) all over the study.

HPLC-grade acetonitrile was obtained from PanReac, E.U. Deionized water was obtained from the Millipore water purification system supplied with 0.2 µm membrane filters such as Nihon and Millipore (Yonezawa, Japan).

2.2 Instrumentation and HPLC operating conditions

The instrument used was Waters HPLC system (USA), equipped with a 1,525 binary HPLC pump, 2,707 autosampler, 2,998 photodiode array detector, and Breeze™ 2 software for data manipulation.

Chromatographic analysis was performed using Symmetry C18, 3.5 µm with dimensions of 4.6 mm × 150 mm (Waters, Ireland). The mobile phase consisted of acetonitrile/water mixture in the ratio of 50:50, v/v and adjusted at the flow rate of 1 mL/min. Before being introduced into the HPLC system, the mobile phase was filtered through 0.45 µm membrane filters supported on a Millipore vacuum filtration system and then sonicated for degassing. The injection volume was 10 µL and the detection wavelength was adjusted at 220 nm.

2.3 Preparation of solutions and matrix-based calibration standards

Stock solutions (1,000 µg/mL) of each of E1, E2, E3, E4, and ESM (IS) were prepared in acetonitrile. Whenever needed, further dilutions were made in acetonitrile.

Matrix-based calibration standards were prepared by spiking estrogen-free meat samples (4.0 g) with standard solutions of the four estrogens, along with 50 µL ESM (IS), 1,000 µg/mL. Spiked samples with different concentrations of estrogens, 0.188–125 µg/g (E3), 0.188–450 µg/g (E4), and 0.350–125 µg/g (E1, E2), were treated, as described later under “sample preparation”. Following the chromatographic analysis, the obtained peak area ratio of each analyte to the IS was related to the spiked concentrations to obtain the corresponding regression equation.

2.4 Application to estrogens’ analysis in meat samples

2.4.1 Sample collection

The analyzed samples were categorized into four main categories: chicken category, beef category, sheep category, and finally camel category. Samples belonging to the four categories were purchased from the local Saudi market (Riyadh, Saudi Arabia), over a three-month period (January–March 2019). Chicken samples (n = 155) were classified into six groups, namely, breast muscles (n = 24), thigh muscles (n = 44), wings (n = 20), and internal organs (n = 19), in addition to processed samples including chicken burgers, sausages, nuggets, and mortadella (n = 48). Beef samples (n = 124) were classified into muscles (n = 40), internal organs (n = 40), and processed products (n = 44). By analogy, sheep samples (n = 122) were classified into muscles (n = 41), internal organs (n = 40), and processed products (n = 41). The last category (camel category, n = 40) comprised only two types of samples: muscles (n = 20) and internal organs (n = 20). The purchased samples were stored in a refrigerator at −4°C until the day of analysis, for not more than three days.

2.4.2 Sample preparation

Finely cut samples were blended using a Dison food chopper (Zhengzhou Dison Electric Co., Ltd., China) at the highest velocity for 2 min. Into a series of screw-capped test tubes, accurate weights of 4.0 g of blended meat samples were spiked with 50 µL ESM (IS), 1,000 µg/mL, and then mixed with 5.0 mL acetonitrile. The samples were sonicated for 15 min using a Branson 3510 ultrasonic cleaner (Brandson Ultrasonics Corporation, CT, USA). The clear supernatants were separately transferred into clean vials and filtered using 0.45 µm membrane filters. Volumes of 10 µL of clean samples were introduced into the HPLC system for analysis.

  1. Ethical approval: The conducted research is not related to either human or animal use.

3 Results and discussion

3.1 Optimization of HPLC conditions

Although the LC-MS/MS is widely used nowadays to carry out the residual analysis of various drugs in different food matrices, the HPLC-UV/DAD is still of major interest. The simplicity of the use of HPLC-UV/DAD and its low price, compared with those of LC-MS/MS, are considered great advantages of the former technique, particularly in that the use of DAD detection impacts great specificity to the technique. The DAD offers the advantage of scanning the UV absorption spectrum at any point of the eluting compound and hence helps to assess the peak purity. This technique was previously used in the determination of estrogens in fishery samples [20,24], pork and chicken [21], dairy and meat samples [22], and milk samples [23].

3.1.1 Selection of optimum stationary phase and mobile phase

Different HPLC conditions were optimized for the purpose of obtaining a good separation between the analyzed estrogens, with a good response and within reasonable runtime. In this respect, both stationary and mobile phases were investigated.

Initially, the analysis was performed using a C 18 column, 10 µm (3.9 × 150 mm) with a mobile phase of acetonitrile/water mixtures. A complete overlap between the E1 and E2 peaks was observed, with mobile phases containing 50–35% acetonitrile with a partial separation starting at 30–28% acetonitrile. Although a complete separation was achieved with 25% acetonitrile, an increased runtime was recorded, with E1 being eluted in almost 50 min as broad peaks. The same results were nearly obtained when replacing acetonitrile with methanol, a mobile phase of 45–43% aqueous methanol resulted in a partial overlap between the E1 and E2 peaks with a complete separation with 40% aqueous methanol with a runtime exceeding 55 min.

In an attempt to get an optimum separation within reasonable runtime, a C 18 column with a smaller particle size, 3.5 µm (4.6 mm × 150 mm), was tried. Fortunately, a mobile phase of 50% aqueous acetonitrile resulted in sharp, symmetric, well-resolved estrogens’ peaks within reasonable runtime (<7 min). The analyzed estrogens were eluted in the following order: E3 (Rt 1.75 ± 0.05), E4 (Rt 4.30 ± 0.06), E2 (Rt 5.40 ± 0.09), and E1 (Rt 6.40 ± 0.08), being the last eluted compound. A lower acetonitrile content resulted in a decreased retention of the four estrogens with an increased runtime >45 min with 35% acetonitrile. A higher acetonitrile content (>50%) resulted in an accelerated elution of the estrogens, and E3 was eluted closer to the solvent front, which is generally not favored in the analysis of complex matrices (e.g., food analysis) with a partial overlap between the E2 and E4 peaks with 70% acetonitrile. Figure 1 shows the effect of acetonitrile% on the retention time of the studied estrogens using the two C 18 columns of different dimensions and particle sizes; 10 µm (3.9 × 150 mm) and 3.5 µm (4.6 × 150 mm).

Figure 1 The effect of acetonitrile % on the retention time of the studied estrogens using C 18 column, 10 µm (3.9 mm × 150 mm) (a) and C18 column, 3.5 µm (4.6 mm × 150 mm) (b).
Figure 1

The effect of acetonitrile % on the retention time of the studied estrogens using C 18 column, 10 µm (3.9 mm × 150 mm) (a) and C18 column, 3.5 µm (4.6 mm × 150 mm) (b).

3.1.2 Selection of the IS

The IS method is the method of choice, compared with the external standard method, particularly in the analysis of complex matrices (e.g., food samples). The IS should yield a comparable response to the analytes, with a closer retention time. Another important point is that it should not be an integral part, or even likely be present as an impurity/additive, in the analyzed matrix. In this respect, different compounds were tried. Some of them were eluted too early, before the elution of the least retained estrogen E3, e.g., caffeine, paracetamol, emtricitabine, salicylic acid, ascorbic acid, methyltrihydroxybenzoate, gallic acid, isoconazole, and valsartan. Some compounds showed an overlap with or incomplete separation from E3, e.g., lovastatin, hydrochlorothiazide, ornidazole, and benzoic acid. Other compounds were eluted too late, after the elution of the most retained estrogen E1, namely glibenclamide, gliclazide, and ibuprofen. In spite of the fact that parabens, methyl, ethyl, and propyl parabens, were eluted within the runtime as sharp, well-defined peaks, they could not be used as IS due to the likeliness of their occurrence as preservatives in the analyzed samples. Finally, ESM was eluted at 2.20 min as a sharp, symmetric, well-resolved peak with reasonable response, compared with the analytes. Thus, it was selected as the IS in the proposed method for the determination of estrogen residues in the analyzed meat samples. Figure 2 shows a typical HPLC chromatogram of a standard mixture of the studied estrogens with their corresponding absorption spectra.

Figure 2 A typical HPLC chromatogram of a standard mixture of 10 µg/mL of each of the studied estrogens (a), estriol (E3), 17α-ethinylestradiol (E4), 17β estradiol (E2), and estrone (E1), with the internal standard (IS) ESM, 10 µg/mL. The absorption spectra of the studied estrogens and the IS are also shown (b). The mobile phase consisted of acetonitrile/water mixture in the ratio of 50:50, v/v and adjusted at the flow rate of 1 mL/min.
Figure 2

A typical HPLC chromatogram of a standard mixture of 10 µg/mL of each of the studied estrogens (a), estriol (E3), 17α-ethinylestradiol (E4), 17β estradiol (E2), and estrone (E1), with the internal standard (IS) ESM, 10 µg/mL. The absorption spectra of the studied estrogens and the IS are also shown (b). The mobile phase consisted of acetonitrile/water mixture in the ratio of 50:50, v/v and adjusted at the flow rate of 1 mL/min.

3.2 Sample preparation

In this method, protein precipitation (PPT) was used as a sample preparation technique. Acetonitrile was used for the purpose of cleaning-up as well as for extraction of estrogens from meat samples. Although other works used more advanced sample preparation techniques, e.g., solid phase extraction (SPE) [17,20,22,24,25] or liquid-liquid extraction (LLE) [13], PPT is still considered advantageous in many ways [23,26]. Compared with SPE and LLE, PPT is simpler, less time-consuming, and requires less cost since it does not require any special apparatus or particular gases, machinery (supplies, pumps, syringes,…, etc.). Moreover, LLE requires the use of toxic organic solvents and the procedure is tedious and time-consuming. The use of acetonitrile for PPT [23,26] and extraction [20,21,23,24,26] of estrogens from edible samples was previously applied.

3.3 Method validation

With reference to the international conference on harmonization (ICH) guidelines [27], different validation parameters were evaluated, namely, linearity, limits of detection (LOD) and of quantitation (LOQ), extraction recovery, precision, and accuracy.

3.3.1 Linearity

The method’s linearity was evaluated by analyzing estrogen-free samples of the four analyzed meat categories: chicken, beef, sheep, and camel, spiked with different concentrations of estrogens, along with the IS. The obtained peak area ratio of each estrogen to the IS was related to the spiked concentrations to derive the matrix-based calibration graphs and the corresponding regression equations. Linearity was assessed in the concentration ranges of 0.188–125 µg/g (E3), 0.188–450 µg/g (E4), and 0.350–125 µg/g (E1, E2) with good correlation coefficients (r values ≥ 0.9981), as shown in Table 1.

Table 1

Matrix-based calibration parameters for the determination of estrogens in different meat categories using the proposed HPLC-DAD method

Linearity range (µg/g)Regression equationrLOD (µg/g)LOQ (µg/g)
Chicken category
E1Breast muscles0.350–125y = 0.0002 + 0.0048x0.99980.1260.350
Thigh muscles0.350–125y = −0.0052 + 0.0027x0.99920.1260.350
Wings0.350–125y = 0.0038 + 0.0088x0.99900.1260.350
Internal organs0.350–125y = −0.0012 + 0.0057x0.99740.1260.350
Processed products0.350–125y = −0.0071 + 0.0089x0.99870.1260.350
E2Breast muscles0.350–125y = 0.0066 + 0.0074x0.99710.1260.350
Thigh muscles0.350–125y = 0.0012 + 0.0051x0.99810.1260.350
Wings0.350–125y = −0.0003 + 0.0055x0.99900.1260.350
Internal organs0.350–125y = −0.0006 + 0.0074x0.99780.1260.350
Processed products0.350–125y = −0.0078 + 0.0091x0.99830.1260.350
E3Breast muscles0.188–125y = −0.0038 + 0.0082x0.99550.0940.188
Thigh muscles0.188–125y = −0.0028 + 0.0022x0.9921 0.094 0.188
Wings0.188–125y = 0.0092 + 0.0066x0.99920.0940.188
Internal organs0.188–125y = 0.0052 + 0.0094x0.99910.0940.188
Processed products0.188–125y = −0.0038 + 0.0081x0.9985 0.094 0.188
E4Breast muscles0.188–450 y = 0.0028 + 0.0060x0.99810.0940.188
Thigh muscles0.188–450y = 0.0088 + 0.0099x0.99750.0940.188
Wings0.188–450 y = −0.0026 + 0.0086x0.9986 0.094 0.188
Internal organs0.188–450y = −0.0068 + 0.0052x0.99930.0940.188
Processed products0.188–450 y = −0.0050 + 0.0088x0.99580.0940.188
Beef category
E1Muscles0.350–125y = −0.0092 + 0.01258x0.99850.1260.350
Internal organs0.350–125y = −0.0088 + 0.00918x0.99920.1260.350
Processed 0.350–125y = −0.0056 + 0.0089x0.99940.1260.350
E2Muscles0.350–125y = 0.0009 + 0.0084x0.99680.1260.350
Internal organs0.350–125y = 0.0019 + 0.0075x0.99580.1260.350
Processed 0.350–125y = 0.0022 + 0.0158x0.99390.1260.350
E3Muscles0.188–125y = −0.0063 + 0.0066x0.99910.0940.188
Internal organs0.188–125y = −0.0074 + 0.0238x0.9990 0.094 0.188
Processed 0.188–125y = 0.0151 + 0.0165x0.99850.0940.188
E4Muscles0.188–450 y = 0.0012 + 0.0287x0.99750.0940.188
Internal organs0.188–450y = −0.0025 + 0.0127x0.9993 0.094 0.188
Processed 0.188–450 y = 0.0037 + 0.0098x0.99700.0940.188
Sheep category
E1Muscles0.350–125y = 0.0007 + 0.0015x0.99900.1260.350
Internal organs0.350–125y = 0.0008 + 0.0019x0.99950.1260.350
Processed 0.350–125y = 0.0016 + 0.0036x0.99850.1260.350
E2Muscles0.350–125y = 0.0038 + 0.0022x0.99790.1260.350
Internal organs0.350–125y = 0.0005 + 0.0019x0.99870.1260.350
Processed 0.350–125y = 0.0202 + 0.0048x0.99550.1260.350
E3Muscles0.188–125y = 0.0332 + 0.0115x0.99810.0940.188
Internal organs0.188–125y = 0.0092 + 0.0157x0.9990 0.094 0.188
Processed 0.188–125y = 0.0089 + 0.0208x0.99580.0940.188
E4Muscles0.188–450y = 0.0128 + 0.0099x0.99670.0940.188
Internal organs0.188–450 y = 0.0299 + 0.0198x0.9991 0.094 0.188
Processed 0.188–450y = 0.0408 + 0.0880x0.99080.0940.188
Camel category
E1Muscles0.350–125y = 0.0032 + 0.0099x0.99770.1260.350
Internal organs0.350–125y = 0.0077 + 0.0367x0.99860.1260.350
E2Muscles0.350–125y = 0.0084 + 0.0258x0.99910.1260.350
Internal organs0.350–125y = 0.0081 + 0.0090x0.99950.1260.350
E3Muscles0.188–125y = 0.0112 + 0.0968x0.99550.0940.188
Internal organs0.188–125y = 0.0257 + 0.0999x0.99660.0940.188
E4Muscles0.188–450y = 0.0012 + 0.0112x0.9978 0.094 0.188
Internal organs0.188–450 y = 0.0091 + 0.0086x0.99520.0940.188

r: correlation coefficient, LOD: limit of detection, LOQ: limit of quantitation.

3.3.2 LOD and LOQ

Values of LOD and LOQ were selected, based on the concentrations providing a response of three times or ten times signal-to-noise ratio (S/N), respectively. As seen in Table 1, LOD values of 0.094 (E3, E4) and 0.126 µg/g (E1, E2), and LOQ values of 0.188 (E3, E4) and 0.350 µg/g (E1, E2) were obtained. The LOD and LOQ values were sufficiently low to allow the residual analysis of estrogens in different meat samples.

3.3.3 Extraction recovery studies

Extraction recovery of the sample preparation technique was assessed by analyzing estrogen-free meat samples which had been spiked with the analyzed estrogens at three different concentration levels, 25, 12.5, and 6.25 µg/g. Extraction recovery values were calculated by relating the responses obtained from spiked samples to those obtained from standard solutions with the same nominal concentrations. High values of extraction recovery % ranging from 74.89 to 91.38 of the four estrogens indicated the efficiency of the sample preparation technique in the determination of estrogens in meat samples.

3.3.4 Precision and accuracy

Precision and accuracy were evaluated by analyzing spiked samples, at the same concentration levels as those used in “recovery studies,” three times on the same day or on three successive days for intra-day and inter-day levels, respectively. The obtained responses were compared with the matrix-based calibration standards to derive the % recovery and errors for assessing the accuracy and % RSD for assessing the precision. Table 2 reveals that high values of recovery% (85.28–114.58) and RSD% (0.11–13.93) were obtained for all the analyzed estrogens, indicating a high degree of accuracy and precision of the proposed method, respectively.

Table 2

Average resultsa for evaluating the precision and accuracy for the determination of estrogens in different meat categories using the proposed HPLC-DAD method

Estrogen Type of matrix Intra-day level (n = 3)Inter-day level (n = 9)
Mean% recovery ± SDRSD%Er%Mean% recovery ± SDRSD% Er%
Chicken category
E1Breast muscles106.19 ± 8.608.106.19109.25 ± 5.765.279.25
Thigh muscles100.16 ± 0.560.560.16104.64 ± 1.93 1.844.64
Wings107.27 ± 0.330.317.27108.43 ± 1.67 1.548.43
Internal organs101.33 ± 1.15 1.141.33108.10 ± 7.63 7.068.10
Processed products90.47 ± 8.38 9.269.3390.30 ± 0.62 0.709.70
E2Breast muscles105.52 ± 6.62 6.285.52109.05 ± 4.81 4.419.05
Thigh muscles94.29 ± 2.83 3.00−5.7195.39 ± 8.11 8.50−4.61
Wings107.79 ± 0.52 0.487.79109.22 ± 0.48 0.449.22
Internal organs90.39 ± 0.100.11−9.6189.35 ± 2.252.52−10.65
Processed products109.80 ± 5.57 5.079.80110.47 ± 8.47 7.6610.47
E3Breast muscles105.82 ± 1.17 1.015.82106.46 ± 2.10 1.986.46
Thigh muscles96.57 ± 0.100.11−3.4396.38 ± 0.32 0.33−3.62
Wings88.27 ± 4.885.53−11.7385.43 ± 8.67 10.15−14.57
Internal organs87.92 ± 7.898.97−12.0885.59 ± 9.05 10.57−14.57
Processed products109.55 ± 4.253.889.55111.19 ± 7.546.7811.19
E4Breast muscles99.58 ± 10.898.106.1990.16 ± 12.5613.93−9.84
Thigh muscles112.27 ± 4.990.560.16114.27 ± 0.830.7314.27
Wings101.55 ± 3.080.317.2795.43 ± 2.67 2.80−4.57
Internal organs109.19 ± 3.6010.949.19103.19 ± 6.666.453.19
Processed products111.16 ± 7.566.8011.1691.16 ± 8.058.83−8.84
Beef category
E1Muscles105.33 ± 1.15 1.095.33107.55 ± 3.35 3.117.55
Internal organs112.47 ± 8.38 7.4512.47 98.30 ± 10.12 10.30−1.70
Processed 89.52 ± 10.55 11.795.5288.58 ± 7.77 8.77−11.42
E2Muscles112.88 ± 4.33 1.141.33108.98 ± 4.52 4.158.98
Internal organs88.47 ± 2.88 9.26−10.4886.30 ± 3.58 4.15−13.7
Processed 99.00 ± 3.58 3.62−1.0090.89 ± 10.25 11.28−9.11
E3Muscles87.55 ± 5.55 6.34−12.5486.88 ± 6.55 7.54−13.12
Internal organs87.00 ± 4.25 4.89−13.0095.30 ± 4.33 4.54−4.70
Processed 103.39 ± 1.251.213.39101.35 ± 7.257.151.35
E4Muscles105.22 ± 8.22 7.815.22107.47 ± 6.25 5.827.47
Internal organs110.89 ± 6.61 5.9610.89112.33 ± 3.88 3.4512.33
Processed 92.57 ± 3.353.62−7.4390.05 ± 4.25 4.72−9.95
Sheep category
E1Muscles107.93 ± 7.12 6.607.93109.55 ± 8.25 0.919.55
Internal organs104.55 ± 3.25 3.114.5588.25 ± 5.22 5.92−11.75
Processed 109.22 ± 1.89 1.739.22111.52 ± 7.77 6.9711.52
E2Muscles101.08 ± 5.08 5.031.08105.10 ± 6.88 6.555.10
Internal organs89.58 ± 2.33 2.60−10.4288.21 ± 1.58 1.79−11.79
Processed 90.33 ± 4.87 5.39−9.67107.89 ± 5.11 4.747.89
E3Muscles107.02 ± 8.02 7.497.02112.10 ± 2.38 2.1212.10
Internal organs88.44 ± 1.11 1.26−11.5685.28 ± 1.58 1.85−14.12
Processed 106.21 ± 3.28 3.096.21103.75 ± 3.88 3.743.75
E4Muscles102.58 ± 7.77 7.752.58112.18 ± 5.55 4.9512.18
Internal organs93.59 ± 9.97 10.65−6.4195.66 ± 5.23 5.47−4.34
Processed 112.01 ± 8.22 7.3412.01104.05 ± 8.58 8.254.05
Camel category
E1Muscles90.25 ± 6.62 7.34−9.7592.55 ± 9.88 10.68−7.45
Internal organs92.58 ± 7.77 8.39−7.4288.58 ± 5.22 5.89−11.42
E2Muscles111.20 ± 5.21 4.6911.2296.25 ± 6.98 7.25−3.75
Internal organs107.25 ± 2.55 2.387.25114.58 ± 1.25 1.0914.58
E3Muscles107.58 ± 8.25 7.677.58102.88 ± 3.58 3.482.88
Internal organs108.78 ± 4.58 4.218.7889.52 ± 1.58 1.76−10.48
E4Muscles107.66 ± 1.85 1.727.6687.20 ± 1.48 1.70−12.80
Internal organs105.44 ± 7.55 7.165.4488.36 ± 4.445.02−11.64
  1. a

    Results obtained as an average of three concentration levels for each analyte: 1.25, 12.5, and 100 µg/g. RSD%: relative standard deviation percentage. Er%: Percentage relative error.

3.3.5 Stability of solutions

Stock and standard solutions of the analyzed estrogens were found to be stable, when stored refrigerated (−4°C) for one month.

3.4 Method’s applicability to the residual analysis of estrogens in meat samples

The proposed method was applied to the determination of estrogen residues (E1, E2, E3, and E4) in meat samples of the four different categories, chicken, beef, sheep, and camel, collected from the Saudi market.

3.4.1 Occurrence of estrogens in meat samples

3.4.1.1 Chicken samples

The developed HPLC-DAD method was applied for the determination of estrogen residues in chicken samples (n = 155), grouped as breast muscles (n = 24), thigh muscles (n = 44), and wings (n = 20), internal organs including liver, spleen, kidney, and heart (n = 19), in addition to processed products including chicken nuggets, chicken burger, mortadella, and sausages (n = 48). HPLC chromatograms of selected samples are shown in Figure 3a.

Figure 3 Typical HPLC chromatograms of selected samples of each meat category showing the estrogen found in each sample. (a) Chicken category: Burger chicken (5.5 µg/g E4, 0.50 µg/g E2) and Mortdella chicken (225 µg/g E4, 0.40 µg/g E2). (b) Beef category: Burger (250 µg/g E4) and Mortdella (70 µg/g E4). (c) Sheep category: Muscles (E2) and Burger (3.39 µg/g E2). (d) Camel category: Muscles (2.40 µg/g E1) and Muscles (3.36 µg/g E4).
Figure 3

Typical HPLC chromatograms of selected samples of each meat category showing the estrogen found in each sample. (a) Chicken category: Burger chicken (5.5 µg/g E4, 0.50 µg/g E2) and Mortdella chicken (225 µg/g E4, 0.40 µg/g E2). (b) Beef category: Burger (250 µg/g E4) and Mortdella (70 µg/g E4). (c) Sheep category: Muscles (E2) and Burger (3.39 µg/g E2). (d) Camel category: Muscles (2.40 µg/g E1) and Muscles (3.36 µg/g E4).

Occurrence of estrogen residues in different groups of chicken samples is summarized in Table 3. Figure 4a also illustrates the occurrence of different estrogens (E1, E2, E3, and E4) among different chicken groups. The results revealed that the processed products showed a much higher estrogen content, compared with other groups, followed by wings, breast and thigh muscles, and that the least estrogen content was noticed with the internal organs, notably E4.

Table 3

Occurrence of estrogen residues (µg/g) in chicken samples

Breast muscles (n = 24)Thigh muscles (n = 44)Wings (n = 20)Internal organs (n = 19)Processed products (n = 48)
E1Number of positive samples (% of total)7 (29.17)15 (34.09)8 (40)9 (47.37)8 (16.67)
Mean (µg/g)1.370.700.710.770.33
Mean of positive samples (µg/g)4.702.041.751.631.97
Median (µg/g)<LOD<LOD<LOD<LOD<LOD
Range of positive samples (µg/g)1.15–22.210.87–4.010.81–3.060.73–4.030.54–4.55
E2Number of positive samples (% of total)————17 (35.41)
Mean (µg/g)<LOD<LOD<LOD<LOD2.92
Mean of positive samples (µg/g)<LOD<LOD<LOD<LOD8.25
Median (µg/g)<LOD<LOD<LOD<LOD<LOD
Range of positive samples (µg/g)<LOD<LOD<LOD<LOD0.39–40.38
E3Number of positive samples (% of total)————4 (8.33)
Mean (µg/g)<LOD<LOD<LOD<LOD3.46
Mean of positive samples (µg/g)<LOD<LOD<LOD<LOD41.50
Median (µg/g)<LOD<LOD<LOD<LOD<LOD
Range of positive samples (µg/g)<LOD<LOD<LOD<LOD10.67–74.25
E4Number of positive samples (% of total)5 (20.83)15 (34.09)5 (25)2 (10.53)25 (52.08)
Mean (µg/g)1.020.720.290.02822.36
Mean of positive samples (µg/g)4.892.101.160.5742.93
Median (µg/g)<LOD<LOD<LOD<LOD0.59
Range of positive samples (µg/g)3.05–7.650.32–7.410.28–1.740.51–0.640.53–349.62
Figure 4 Occurrence of estrogens (µg/g) in different categories of meat samples: (a) chicken, (b) beef, (c) sheep, and (d) camel. The same scale of the y-axis was used for comparison.
Figure 4

Occurrence of estrogens (µg/g) in different categories of meat samples: (a) chicken, (b) beef, (c) sheep, and (d) camel. The same scale of the y-axis was used for comparison.

Processed products showed positive results for the analyzed samples, the highest existence was for E4 (52.08%, mean 22.36 µg/g) followed by E2 (35.41%, mean 2.92 µg/g), then E1 (16.67%, mean 0.33 µg/g), and the least occurrence was for E3 (8.33%, mean 3.46 µg/g).

It is noteworthy to mention that all analyzed groups showed negative results (<LOD) for E2 and E3, except for the processed products. The results also revealed that about 40% of wing samples contained E1 (mean 0.71 µg/g) and that about 25% of the samples contained E4 (mean 0.29 µg/g). Regarding breast and thigh muscles, although almost 30% (breast) and 34% (thigh) of the analyzed samples showed positive response for E1, the average content was not more than 1.37 µg/g for breast muscles and 0.71 µg/g for thigh muscles. Similarly, the content of E4 did not exceed 1.02 (breast) and 0.72 µg/g (thigh), accounting for nearly 21% and 34% of the analyzed breast and thigh samples, respectively.

It is clear from Table 3 and Figure 4a that despite thigh muscles and the internal organs having 0.70 and 0.77 µg/g as the mean E1 content, the E4 mean content in the internal organs was much less, 0.028 µg/g, compared with 0.72 µg/g in the internal organs and thigh muscles, respectively.

3.4.1.2 Beef samples

Determination of estrogen residues in beef samples (n = 124) was carried out using the proposed HPLC-DAD method. Samples were categorized into three main groups: muscles (n = 40), internal organs (n = 40), and processed products (n = 44). HPLC chromatograms of some beef samples are presented in Figure 3b. Results of the analysis of beef samples are summarized in Table 4. As in chicken meat, the highest E4 estrogen content was found in the processed products, as compared with muscles and internal organs as shown in Figure 4b (54.55%, mean 34 µg/g). E2 occurred in nearly 11.36% of the processed products (mean 0.48 µg/g), and E1 being of the least frequency and content, 2.27% (mean 0.03 µg/g). The absence of E3 in all the analyzed samples was also noticed. Muscles and internal organs had only E2 and E3, being the least in the internal organs.

Table 4

Occurrence of estrogen residues (µg/g) in beef samples

Muscles (n = 40)Internal organs (n = 40)Processed products (n = 44)
E1Number of positive samples (% of total)——1 (2.27)
Mean (µg/g)<LOD<LOD0.0263
Mean of positive samples (µg/g)<LOD<LOD1.1589
Median (µg/g)<LOD<LOD<LOD
Range of positive samples (µg/g)<LOD<LOD1.1589
E2Number of positive samples (% of total)11 (27.5)1 (2.5)5 (11.36)
Mean (µg/g)3.76220.00970.4793
Mean of positive samples (µg/g)13.68060.38644.2174
Median (µg/g)<LOD<LOD<LOD
Range of positive samples (µg/g)6.6150–15.57930.38640.6101–7.2065
E3Number of positive samples (% of total)———
Mean (µg/g)<LOD<LOD<LOD
Mean of positive samples (µg/g)<LOD<LOD<LOD
Median (µg/g)<LOD<LOD<LOD
Range of positive samples (µg/g)<LOD<LOD<LOD
E4Number of positive samples (% of total)6 (15)1 (2.5)24 (54.55)
Mean (µg/g)0.62260.031533.8985
Mean of positive samples (µg/g)4.15061.260262.1472
Median (µg/g)<LOD<LOD1.0890
Range of positive samples (µg/g)1.5514–10.69921.26020.7338–360.2211
3.4.1.3 Sheep samples

Representative chromatograms of the analyzed sheep samples are shown in Figure 3c. As per chicken and beef, the highest E4 content was found in nearly 61% of processed products (mean 61 µg/g), compared with only 0.16 and 0.25 µg/g of muscles and internal organs. E1 was only found in the processed products (4.88%, mean 0.17 µg/g). E2 was found in the three groups in nearly 4.88% of the analyzed muscles (mean 0.06 µg/g) and processed products (mean 0.09 µg/g), while at a higher frequency in the internal organs (15%, mean 0.15 µg/g). It was also noticed that none of the analyzed processed products contained E3, which was found in 0.37 µg/g in only one sample of the 41 analyzed muscles. On the other hand, 22.5% of the analyzed internal organs contained E3 in an average content of 0.49 µg/g. Results of the analysis are summarized in Table 5 (Figure 4c).

Table 5

Occurrence of estrogen residues (µg/g) in sheep samples

Muscles (n = 41)Internal organs (n = 40)Processed products (n = 41)
E1Number of positive samples (% of total)——2 (4.88)
Mean (µg/g)<LOD<LOD0.17
Mean of positive samples (µg/g)<LOD<LOD3.42
Median (µg/g)<LOD<LOD<LOD
Range of positive samples (µg/g)<LOD<LOD1.27–5.59
E2Number of positive samples (% of total)2 (4.88)6 (15)2 (4.88)
Mean (µg/g)0.060.150.09
Mean of positive samples (µg/g)1.160.971.94
Median (µg/g)<LOD<LOD<LOD
Range of positive samples (µg/g)0.54–1.780.39–2.320.50–3.39
E3Number of positive samples (% of total)1 (2.44)9 (22.5)—
Mean (µg/g)0.0090.49<LOD
Mean of positive samples (µg/g)0.372.17<LOD
Median (µg/g)<LOD<LOD<LOD
Range of positive samples (µg/g)0.370.21–8.68<LOD
E4Number of positive samples (% of total)9 (21.95)5 (12.5)25 (60.98)
Mean (µg/g)0.160.2560.98
Mean of positive samples (µg/g)0.712.02206.20
Median (µg/g)<LOD<LOD0.91
Range of positive samples (µg/g)0.40–1.611.22–2.470.34–419.65
3.4.1.4 Camel samples

Camel samples were divided into only two groups, muscles and internal organs, since no processed products were found in the commercial market. Results of the analysis are shown in Table 6 (Figure 4d). It was clear that none of the analyzed estrogens were detected in the internal organs. No residual E2 was found in the analyzed muscle samples and E4 was found in 5% of the samples, mean 0.17 µg/g. Also, E1 and E3 were only found in one of the analyzed muscles (n = 20) in the levels of 0.12 µg/g (E1) and 0.03 µg/g (E3).

Table 6

Occurrence of estrogen residues (µg/g) in camel samples

Muscles (n = 20)Internal organs (n = 20)
E1Number of positive samples (% of total)1 (5%)—
Mean (µg/g)0.1198<LOD
Mean of positive samples (µg/g)2.3962<LOD
Median (µg/g)<LOD<LOD
Range of positive samples (µg/g)2.3962<LOD
E2Number of positive samples (% of total)——
Mean (µg/g)<LOD<LOD
Mean of positive samples (µg/g)<LOD<LOD
Median (µg/g)<LOD<LOD
Range of positive samples (µg/g)<LOD<LOD
E3Number of positive samples (% of total)1 (5%)—
Mean (µg/g)0.0259<LOD
Mean of positive samples (µg/g)0.5174<LOD
Median (µg/g)<LOD<LOD
Range of positive samples (µg/g)0.5174<LOD
E4Number of positive samples (% of total)1 (5%)—
Mean (µg/g)0.1680<LOD
Mean of positive samples (µg/g)3.3600<LOD
Median (µg/g)<LOD<LOD
Range of positive samples (µg/g)3.3600<LOD

A general outlook at Figure 4 revealed that samples of the four categories, chicken, beef, sheep, and camel, contained different levels of estrogens. Among the same category, the processed products contained the highest levels of E4, indicating that this growth promoter is still illegally used, with accumulation in the lipids constituting the major part of processed samples. Moreover, samples of the sheep category showed maximum abundance (61%) of E4 with the highest levels (mean 61 µg/g). Also within the same category, the internal organs contained the least estrogen content. This matches what was previously reported on the distribution of estrogen receptors (ER), being the highest in the mammary glands (ER α) or the ovary (ER β) and the lowest in the internal organs; liver, spleen, heart, lung, and kidney.

3.4.2 Calculation of the estimated daily intake (EDI) of estrogens from meat consumption

In order to provide a clear picture of estrogen exposure as a result of meat consumption among the Saudi population, the corresponding EDI was calculated. Based on the dietary pattern, estimated daily meat consumption, and the average body weight [28,29] in different age groups, the EDI was calculated using the average content of each type of estrogen (E1, E2, E3, and E4) found in each meat category, as summarized in Tables 3–6. As can be seen from Table 7, estrogen exposure as a result of meat consumption decreases in relation to the progression of age with the greatest exposure in the age group of 10–15 years. This could be attributed to the largest fast-food consumption among this young age group since the high content of estrogens, particularly E4, in processed products results in a high total estrogen intake. It is well known that hormonal changes occurring during the age of adolescence are responsible for the resulting changes in the body shape and psychological disturbances. Improper appearance, as a result of hormonal imbalance, can badly affect the adolescents’ psychology and may proceed to depression and even suicide in some cases [30]. In this respect, a particular concern should be paid to male adolescents where increased incidence of breast enlargement, called “Gynecomastia,” is partly related to the intake of exogenous estrogens in the age of puberty. Being a significant cause of psychological distress, it is recommended to limit the EDI of estrogens as low as possible [31]. Moreover, increased hormonal levels in puberty result in the prevalence of an ovarian cyst with a peak frequency in the age of 15 years [32].

Table 7

EDI, µg/kg bw/day, of estrogens through the consumption of meat-based food products by the Saudi adult based on different age groups (years)

CompoundMeat categorya10–1516–2425–39>40
E1Chicken0.361.31.130.911
Red meat0000
Processed0.150.040.030.009
E2Chicken0000
Red meat0.081.161.081.06
Processed1.390.330.250.08
E3Chicken0000
Red meat0.00020.0030.0020.002
Processed0.50.1250.090.03
E4Chicken0.120.440.370.3
Red meat0.0170.230.220.21
Processed14.353.4022.560.855
∑Estrogens17.017.15.83.5
  1. a

    Red meat (beef, sheep), chicken meat (breast, thigh, and wings), and processed meat (chicken, beef, and sheep).

3.4.3 Comparison of meat-related estrogen exposure among the Saudi population with worldwide estimations

In a previous Korean study concerned with the determination of estrogens in muscle tissues of beef cattle, the concentrations of the estrogens E1, E2, and E3 were below 0.1 µg/kg [12]. Also, E1, E2, and E3 determination in buffalo’s and cow’s meat in Iran showed that E1 was the highest in beef muscles (up to 16.2 ng/L), that E2 was dominant in buffalo muscles (up to 23.3 ng/L), and that E3 was only found in buffalo muscles (15.8 ng/L) [25]. Analysis of estrogens has also been conducted on fish samples, with variations in the obtained results ranging from the total absence of E1 and E3 [14] and of E1, E2, and E3 [26], to 0.775–11.884 µg/kg for E2 [24]. Determination of estrogens in milk and dairy products has gained much attention. In a study conducted on colostrum powder, E1 was found in the fat fraction, 7.59 µg/L, while in defatted milk and colostrum powder, E1 (5.51–15.0 µg/kg) and E2 (2.28–3.3 µg/kg) were detected with the total absence of E3 in different types of milk and colostrum powders [13]. In China, the absence of E1, E2, and E3 in all the analyzed milk samples was reported [15,18], while the estrogen concentration range of 0.05–3.2 µg/kg was found in milk samples that were analyzed in a different study [17]. For dairy products, estrone, 17β-estradiol, estriol, and 17α-ethynylestradiol were absent in all the analyzed samples [16]. In addition, determination of estrogens in eggs revealed the total absence of the analytes, E1 and E2, in the analyzed samples [19]. The current study revealed that the concentrations of estrogens in the analyzed meat samples were maximum in the processed products of chicken, beef, and sheep (up to 5.59 µg/g E1, 40.38 µg/g E2, 74.4 µg/g E3, and even up to 419.56 µg/g E4). It is obvious that these levels are considered to be much higher than those found in previous estimations in other countries. Thus, for the sake of health benefits, particular attention should be paid to monitor the estrogenic content in meat products available in the Saudi market.

3.5 Comparison of the performance of the proposed method with previous literature

The analytical performance of the proposed method was compared with those of HPLC-UV methods, previously applied in the determination of estrogen residues in edible tissues [20,21,22,23,24]. Regarding the four studied estrogens, E1, E2, E3, and E4, the proposed method enabled their simultaneous determination in meat samples, compared with only one of the cited estrogens in previous studies, E2 [24,25]. Despite that ref. [16] described the determination of the four estrogens in fishery samples, only spiked samples were analyzed. Regarding the sample preparation technique, this study employed PPT as a simple, efficient, and less-costly preparation technique where acetonitrile was used as both clean-up and extraction solvents. On the contrary, other reports used more complicated and tedious sample preparation techniques: molecularly imprinted solid phase micro-extraction [16,25] or PPT followed by stir bar sorptive extraction procedure [24] that needs many optimization procedures and is thus more complicated. Another important point is that only 4 g of the analyzed sample was sufficient to determine the estrogens’ residues, compared with 500 g in some of the previously reported HPLC-UV methods [25]. Finally, the high-throughput analysis was assessed by the short runtime (10 min), compared with nearly 22 min [21,22] or even up to 40 min [20].

4 Conclusion

An HPLC-DAD method for the determination of four estrogen residues in meat products has been developed and validated. PPT was used as a simple sample preparation technique. Moreover, the use of DAD impacts the advantage of specificity compared with the universal UV detector and is also less expensive and easily applicable, compared with the mass spectrometric detectors.

Four estrogenic compounds (E1, E2, E3, and E4) were determined in meat samples of different categories (chicken, n = 155, beef, n = 124, sheep, n = 122, and camels, n = 40) available in the Saudi market.

The content of estrogens in the analyzed meat samples was maximum in the processed products of chicken, beef, and sheep (up to 5.59 µg/g E1, 40.38 µg/g E2, 74.4 µg/g E3, and even up to 419.56 µg/g E4). These high levels have pointed out that, for the sake of health benefits, particular attention should be paid to monitor the estrogenic content in meat products available in the Saudi market.

tel: +20-3-4871317, fax: +20-3-4873273

Acknowledgments

The authors would like to extend their appreciation to the Deanship of Scientific Research at King Saud University for its funding of this research through the research group project no. RGPVPP-331.

  1. Conflict of interest: Authors declare no conflicts of interest.

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Received: 2020-05-18
Revised: 2020-07-12
Accepted: 2020-07-13
Published Online: 2020-08-07

© 2020 Sadeem S. Alqahtani et al., published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 International License.

Articles in the same Issue

  1. Regular Articles
  2. Electrochemical antioxidant screening and evaluation based on guanine and chitosan immobilized MoS2 nanosheet modified glassy carbon electrode (guanine/CS/MoS2/GCE)
  3. Kinetic models of the extraction of vanillic acid from pumpkin seeds
  4. On the maximum ABC index of bipartite graphs without pendent vertices
  5. Estimation of the total antioxidant potential in the meat samples using thin-layer chromatography
  6. Molecular dynamics simulation of sI methane hydrate under compression and tension
  7. Spatial distribution and potential ecological risk assessment of some trace elements in sediments and grey mangrove (Avicennia marina) along the Arabian Gulf coast, Saudi Arabia
  8. Amino-functionalized graphene oxide for Cr(VI), Cu(II), Pb(II) and Cd(II) removal from industrial wastewater
  9. Chemical composition and in vitro activity of Origanum vulgare L., Satureja hortensis L., Thymus serpyllum L. and Thymus vulgaris L. essential oils towards oral isolates of Candida albicans and Candida glabrata
  10. Effect of excess Fluoride consumption on Urine-Serum Fluorides, Dental state and Thyroid Hormones among children in “Talab Sarai” Punjab Pakistan
  11. Design, Synthesis and Characterization of Novel Isoxazole Tagged Indole Hybrid Compounds
  12. Comparison of kinetic and enzymatic properties of intracellular phosphoserine aminotransferases from alkaliphilic and neutralophilic bacteria
  13. Green Organic Solvent-Free Oxidation of Alkylarenes with tert-Butyl Hydroperoxide Catalyzed by Water-Soluble Copper Complex
  14. Ducrosia ismaelis Asch. essential oil: chemical composition profile and anticancer, antimicrobial and antioxidant potential assessment
  15. DFT calculations as an efficient tool for prediction of Raman and infra-red spectra and activities of newly synthesized cathinones
  16. Influence of Chemical Osmosis on Solute Transport and Fluid Velocity in Clay Soils
  17. A New fatty acid and some triterpenoids from propolis of Nkambe (North-West Region, Cameroon) and evaluation of the antiradical scavenging activity of their extracts
  18. Antiplasmodial Activity of Stigmastane Steroids from Dryobalanops oblongifolia Stem Bark
  19. Rapid identification of direct-acting pancreatic protectants from Cyclocarya paliurus leaves tea by the method of serum pharmacochemistry combined with target cell extraction
  20. Immobilization of Pseudomonas aeruginosa static biomass on eggshell powder for on-line preconcentration and determination of Cr (VI)
  21. Assessment of methyl 2-({[(4,6-dimethoxypyrimidin-2-yl)carbamoyl] sulfamoyl}methyl)benzoate through biotic and abiotic degradation modes
  22. Stability of natural polyphenol fisetin in eye drops Stability of fisetin in eye drops
  23. Production of a bioflocculant by using activated sludge and its application in Pb(II) removal from aqueous solution
  24. Molecular Properties of Carbon Crystal Cubic Structures
  25. Synthesis and characterization of calcium carbonate whisker from yellow phosphorus slag
  26. Study on the interaction between catechin and cholesterol by the density functional theory
  27. Analysis of some pharmaceuticals in the presence of their synthetic impurities by applying hybrid micelle liquid chromatography
  28. Two mixed-ligand coordination polymers based on 2,5-thiophenedicarboxylic acid and flexible N-donor ligands: the protective effect on periodontitis via reducing the release of IL-1β and TNF-α
  29. Incorporation of silver stearate nanoparticles in methacrylate polymeric monoliths for hemeprotein isolation
  30. Development of ultrasound-assisted dispersive solid-phase microextraction based on mesoporous carbon coated with silica@iron oxide nanocomposite for preconcentration of Te and Tl in natural water systems
  31. N,N′-Bis[2-hydroxynaphthylidene]/[2-methoxybenzylidene]amino]oxamides and their divalent manganese complexes: Isolation, spectral characterization, morphology, antibacterial and cytotoxicity against leukemia cells
  32. Determination of the content of selected trace elements in Polish commercial fruit juices and health risk assessment
  33. Diorganotin(iv) benzyldithiocarbamate complexes: synthesis, characterization, and thermal and cytotoxicity study
  34. Keratin 17 is induced in prurigo nodularis lesions
  35. Anticancer, antioxidant, and acute toxicity studies of a Saudi polyherbal formulation, PHF5
  36. LaCoO3 perovskite-type catalysts in syngas conversion
  37. Comparative studies of two vegetal extracts from Stokesia laevis and Geranium pratense: polyphenol profile, cytotoxic effect and antiproliferative activity
  38. Fragmentation pattern of certain isatin–indole antiproliferative conjugates with application to identify their in vitro metabolic profiles in rat liver microsomes by liquid chromatography tandem mass spectrometry
  39. Investigation of polyphenol profile, antioxidant activity and hepatoprotective potential of Aconogonon alpinum (All.) Schur roots
  40. Lead discovery of a guanidinyl tryptophan derivative on amyloid cascade inhibition
  41. Physicochemical evaluation of the fruit pulp of Opuntia spp growing in the Mediterranean area under hard climate conditions
  42. Electronic structural properties of amino/hydroxyl functionalized imidazolium-based bromide ionic liquids
  43. New Schiff bases of 2-(quinolin-8-yloxy)acetohydrazide and their Cu(ii), and Zn(ii) metal complexes: their in vitro antimicrobial potentials and in silico physicochemical and pharmacokinetics properties
  44. Treatment of adhesions after Achilles tendon injury using focused ultrasound with targeted bFGF plasmid-loaded cationic microbubbles
  45. Synthesis of orotic acid derivatives and their effects on stem cell proliferation
  46. Chirality of β2-agonists. An overview of pharmacological activity, stereoselective analysis, and synthesis
  47. Fe3O4@urea/HITh-SO3H as an efficient and reusable catalyst for the solvent-free synthesis of 7-aryl-8H-benzo[h]indeno[1,2-b]quinoline-8-one and indeno[2′,1′:5,6]pyrido[2,3-d]pyrimidine derivatives
  48. Adsorption kinetic characteristics of molybdenum in yellow-brown soil in response to pH and phosphate
  49. Enhancement of thermal properties of bio-based microcapsules intended for textile applications
  50. Exploring the effect of khat (Catha edulis) chewing on the pharmacokinetics of the antiplatelet drug clopidogrel in rats using the newly developed LC-MS/MS technique
  51. A green strategy for obtaining anthraquinones from Rheum tanguticum by subcritical water
  52. Cadmium (Cd) chloride affects the nutrient uptake and Cd-resistant bacterium reduces the adsorption of Cd in muskmelon plants
  53. Removal of H2S by vermicompost biofilter and analysis on bacterial community
  54. Structural cytotoxicity relationship of 2-phenoxy(thiomethyl)pyridotriazolopyrimidines: Quantum chemical calculations and statistical analysis
  55. A self-breaking supramolecular plugging system as lost circulation material in oilfield
  56. Synthesis, characterization, and pharmacological evaluation of thiourea derivatives
  57. Application of drug–metal ion interaction principle in conductometric determination of imatinib, sorafenib, gefitinib and bosutinib
  58. Synthesis and characterization of a novel chitosan-grafted-polyorthoethylaniline biocomposite and utilization for dye removal from water
  59. Optimisation of urine sample preparation for shotgun proteomics
  60. DFT investigations on arylsulphonyl pyrazole derivatives as potential ligands of selected kinases
  61. Treatment of Parkinson’s disease using focused ultrasound with GDNF retrovirus-loaded microbubbles to open the blood–brain barrier
  62. New derivatives of a natural nordentatin
  63. Fluorescence biomarkers of malignant melanoma detectable in urine
  64. Study of the remediation effects of passivation materials on Pb-contaminated soil
  65. Saliva proteomic analysis reveals possible biomarkers of renal cell carcinoma
  66. Withania frutescens: Chemical characterization, analgesic, anti-inflammatory, and healing activities
  67. Design, synthesis and pharmacological profile of (−)-verbenone hydrazones
  68. Synthesis of magnesium carbonate hydrate from natural talc
  69. Stability-indicating HPLC-DAD assay for simultaneous quantification of hydrocortisone 21 acetate, dexamethasone, and fluocinolone acetonide in cosmetics
  70. A novel lactose biosensor based on electrochemically synthesized 3,4-ethylenedioxythiophene/thiophene (EDOT/Th) copolymer
  71. Citrullus colocynthis (L.) Schrad: Chemical characterization, scavenging and cytotoxic activities
  72. Development and validation of a high performance liquid chromatography/diode array detection method for estrogen determination: Application to residual analysis in meat products
  73. PCSK9 concentrations in different stages of subclinical atherosclerosis and their relationship with inflammation
  74. Development of trace analysis for alkyl methanesulfonates in the delgocitinib drug substance using GC-FID and liquid–liquid extraction with ionic liquid
  75. Electrochemical evaluation of the antioxidant capacity of natural compounds on glassy carbon electrode modified with guanine-, polythionine-, and nitrogen-doped graphene
  76. A Dy(iii)–organic framework as a fluorescent probe for highly selective detection of picric acid and treatment activity on human lung cancer cells
  77. A Zn(ii)–organic cage with semirigid ligand for solvent-free cyanosilylation and inhibitory effect on ovarian cancer cell migration and invasion ability via regulating mi-RNA16 expression
  78. Polyphenol content and antioxidant activities of Prunus padus L. and Prunus serotina L. leaves: Electrochemical and spectrophotometric approach and their antimicrobial properties
  79. The combined use of GC, PDSC and FT-IR techniques to characterize fat extracted from commercial complete dry pet food for adult cats
  80. MALDI-TOF MS profiling in the discovery and identification of salivary proteomic patterns of temporomandibular joint disorders
  81. Concentrations of dioxins, furans and dioxin-like PCBs in natural animal feed additives
  82. Structure and some physicochemical and functional properties of water treated under ammonia with low-temperature low-pressure glow plasma of low frequency
  83. Mesoscale nanoparticles encapsulated with emodin for targeting antifibrosis in animal models
  84. Amine-functionalized magnetic activated carbon as an adsorbent for preconcentration and determination of acidic drugs in environmental water samples using HPLC-DAD
  85. Antioxidant activity as a response to cadmium pollution in three durum wheat genotypes differing in salt-tolerance
  86. A promising naphthoquinone [8-hydroxy-2-(2-thienylcarbonyl)naphtho[2,3-b]thiophene-4,9-dione] exerts anti-colorectal cancer activity through ferroptosis and inhibition of MAPK signaling pathway based on RNA sequencing
  87. Synthesis and efficacy of herbicidal ionic liquids with chlorsulfuron as the anion
  88. Effect of isovalent substitution on the crystal structure and properties of two-slab indates BaLa2−xSmxIn2O7
  89. Synthesis, spectral and thermo-kinetics explorations of Schiff-base derived metal complexes
  90. An improved reduction method for phase stability testing in the single-phase region
  91. Comparative analysis of chemical composition of some commercially important fishes with an emphasis on various Malaysian diets
  92. Development of a solventless stir bar sorptive extraction/thermal desorption large volume injection capillary gas chromatographic-mass spectrometric method for ultra-trace determination of pyrethroids pesticides in river and tap water samples
  93. A turbidity sensor development based on NL-PI observers: Experimental application to the control of a Sinaloa’s River Spirulina maxima cultivation
  94. Deep desulfurization of sintering flue gas in iron and steel works based on low-temperature oxidation
  95. Investigations of metallic elements and phenolics in Chinese medicinal plants
  96. Influence of site-classification approach on geochemical background values
  97. Effects of ageing on the surface characteristics and Cu(ii) adsorption behaviour of rice husk biochar in soil
  98. Adsorption and sugarcane-bagasse-derived activated carbon-based mitigation of 1-[2-(2-chloroethoxy)phenyl]sulfonyl-3-(4-methoxy-6-methyl-1,3,5-triazin-2-yl) urea-contaminated soils
  99. Antimicrobial and antifungal activities of bifunctional cooper(ii) complexes with non-steroidal anti-inflammatory drugs, flufenamic, mefenamic and tolfenamic acids and 1,10-phenanthroline
  100. Application of selenium and silicon to alleviate short-term drought stress in French marigold (Tagetes patula L.) as a model plant species
  101. Screening and analysis of xanthine oxidase inhibitors in jute leaves and their protective effects against hydrogen peroxide-induced oxidative stress in cells
  102. Synthesis and physicochemical studies of a series of mixed-ligand transition metal complexes and their molecular docking investigations against Coronavirus main protease
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  104. A new phenyl alkyl ester and a new combretin triterpene derivative from Combretum fragrans F. Hoffm (Combretaceae) and antiproliferative activity
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https://doi.org/10.1515/chem-2020-0118
Keywords for this article
estrogens; food analysis; HPLC-DAD; meat products; Saudi market
Creative Commons
BY 4.0

Articles in the same Issue

  1. Regular Articles
  2. Electrochemical antioxidant screening and evaluation based on guanine and chitosan immobilized MoS2 nanosheet modified glassy carbon electrode (guanine/CS/MoS2/GCE)
  3. Kinetic models of the extraction of vanillic acid from pumpkin seeds
  4. On the maximum ABC index of bipartite graphs without pendent vertices
  5. Estimation of the total antioxidant potential in the meat samples using thin-layer chromatography
  6. Molecular dynamics simulation of sI methane hydrate under compression and tension
  7. Spatial distribution and potential ecological risk assessment of some trace elements in sediments and grey mangrove (Avicennia marina) along the Arabian Gulf coast, Saudi Arabia
  8. Amino-functionalized graphene oxide for Cr(VI), Cu(II), Pb(II) and Cd(II) removal from industrial wastewater
  9. Chemical composition and in vitro activity of Origanum vulgare L., Satureja hortensis L., Thymus serpyllum L. and Thymus vulgaris L. essential oils towards oral isolates of Candida albicans and Candida glabrata
  10. Effect of excess Fluoride consumption on Urine-Serum Fluorides, Dental state and Thyroid Hormones among children in “Talab Sarai” Punjab Pakistan
  11. Design, Synthesis and Characterization of Novel Isoxazole Tagged Indole Hybrid Compounds
  12. Comparison of kinetic and enzymatic properties of intracellular phosphoserine aminotransferases from alkaliphilic and neutralophilic bacteria
  13. Green Organic Solvent-Free Oxidation of Alkylarenes with tert-Butyl Hydroperoxide Catalyzed by Water-Soluble Copper Complex
  14. Ducrosia ismaelis Asch. essential oil: chemical composition profile and anticancer, antimicrobial and antioxidant potential assessment
  15. DFT calculations as an efficient tool for prediction of Raman and infra-red spectra and activities of newly synthesized cathinones
  16. Influence of Chemical Osmosis on Solute Transport and Fluid Velocity in Clay Soils
  17. A New fatty acid and some triterpenoids from propolis of Nkambe (North-West Region, Cameroon) and evaluation of the antiradical scavenging activity of their extracts
  18. Antiplasmodial Activity of Stigmastane Steroids from Dryobalanops oblongifolia Stem Bark
  19. Rapid identification of direct-acting pancreatic protectants from Cyclocarya paliurus leaves tea by the method of serum pharmacochemistry combined with target cell extraction
  20. Immobilization of Pseudomonas aeruginosa static biomass on eggshell powder for on-line preconcentration and determination of Cr (VI)
  21. Assessment of methyl 2-({[(4,6-dimethoxypyrimidin-2-yl)carbamoyl] sulfamoyl}methyl)benzoate through biotic and abiotic degradation modes
  22. Stability of natural polyphenol fisetin in eye drops Stability of fisetin in eye drops
  23. Production of a bioflocculant by using activated sludge and its application in Pb(II) removal from aqueous solution
  24. Molecular Properties of Carbon Crystal Cubic Structures
  25. Synthesis and characterization of calcium carbonate whisker from yellow phosphorus slag
  26. Study on the interaction between catechin and cholesterol by the density functional theory
  27. Analysis of some pharmaceuticals in the presence of their synthetic impurities by applying hybrid micelle liquid chromatography
  28. Two mixed-ligand coordination polymers based on 2,5-thiophenedicarboxylic acid and flexible N-donor ligands: the protective effect on periodontitis via reducing the release of IL-1β and TNF-α
  29. Incorporation of silver stearate nanoparticles in methacrylate polymeric monoliths for hemeprotein isolation
  30. Development of ultrasound-assisted dispersive solid-phase microextraction based on mesoporous carbon coated with silica@iron oxide nanocomposite for preconcentration of Te and Tl in natural water systems
  31. N,N′-Bis[2-hydroxynaphthylidene]/[2-methoxybenzylidene]amino]oxamides and their divalent manganese complexes: Isolation, spectral characterization, morphology, antibacterial and cytotoxicity against leukemia cells
  32. Determination of the content of selected trace elements in Polish commercial fruit juices and health risk assessment
  33. Diorganotin(iv) benzyldithiocarbamate complexes: synthesis, characterization, and thermal and cytotoxicity study
  34. Keratin 17 is induced in prurigo nodularis lesions
  35. Anticancer, antioxidant, and acute toxicity studies of a Saudi polyherbal formulation, PHF5
  36. LaCoO3 perovskite-type catalysts in syngas conversion
  37. Comparative studies of two vegetal extracts from Stokesia laevis and Geranium pratense: polyphenol profile, cytotoxic effect and antiproliferative activity
  38. Fragmentation pattern of certain isatin–indole antiproliferative conjugates with application to identify their in vitro metabolic profiles in rat liver microsomes by liquid chromatography tandem mass spectrometry
  39. Investigation of polyphenol profile, antioxidant activity and hepatoprotective potential of Aconogonon alpinum (All.) Schur roots
  40. Lead discovery of a guanidinyl tryptophan derivative on amyloid cascade inhibition
  41. Physicochemical evaluation of the fruit pulp of Opuntia spp growing in the Mediterranean area under hard climate conditions
  42. Electronic structural properties of amino/hydroxyl functionalized imidazolium-based bromide ionic liquids
  43. New Schiff bases of 2-(quinolin-8-yloxy)acetohydrazide and their Cu(ii), and Zn(ii) metal complexes: their in vitro antimicrobial potentials and in silico physicochemical and pharmacokinetics properties
  44. Treatment of adhesions after Achilles tendon injury using focused ultrasound with targeted bFGF plasmid-loaded cationic microbubbles
  45. Synthesis of orotic acid derivatives and their effects on stem cell proliferation
  46. Chirality of β2-agonists. An overview of pharmacological activity, stereoselective analysis, and synthesis
  47. Fe3O4@urea/HITh-SO3H as an efficient and reusable catalyst for the solvent-free synthesis of 7-aryl-8H-benzo[h]indeno[1,2-b]quinoline-8-one and indeno[2′,1′:5,6]pyrido[2,3-d]pyrimidine derivatives
  48. Adsorption kinetic characteristics of molybdenum in yellow-brown soil in response to pH and phosphate
  49. Enhancement of thermal properties of bio-based microcapsules intended for textile applications
  50. Exploring the effect of khat (Catha edulis) chewing on the pharmacokinetics of the antiplatelet drug clopidogrel in rats using the newly developed LC-MS/MS technique
  51. A green strategy for obtaining anthraquinones from Rheum tanguticum by subcritical water
  52. Cadmium (Cd) chloride affects the nutrient uptake and Cd-resistant bacterium reduces the adsorption of Cd in muskmelon plants
  53. Removal of H2S by vermicompost biofilter and analysis on bacterial community
  54. Structural cytotoxicity relationship of 2-phenoxy(thiomethyl)pyridotriazolopyrimidines: Quantum chemical calculations and statistical analysis
  55. A self-breaking supramolecular plugging system as lost circulation material in oilfield
  56. Synthesis, characterization, and pharmacological evaluation of thiourea derivatives
  57. Application of drug–metal ion interaction principle in conductometric determination of imatinib, sorafenib, gefitinib and bosutinib
  58. Synthesis and characterization of a novel chitosan-grafted-polyorthoethylaniline biocomposite and utilization for dye removal from water
  59. Optimisation of urine sample preparation for shotgun proteomics
  60. DFT investigations on arylsulphonyl pyrazole derivatives as potential ligands of selected kinases
  61. Treatment of Parkinson’s disease using focused ultrasound with GDNF retrovirus-loaded microbubbles to open the blood–brain barrier
  62. New derivatives of a natural nordentatin
  63. Fluorescence biomarkers of malignant melanoma detectable in urine
  64. Study of the remediation effects of passivation materials on Pb-contaminated soil
  65. Saliva proteomic analysis reveals possible biomarkers of renal cell carcinoma
  66. Withania frutescens: Chemical characterization, analgesic, anti-inflammatory, and healing activities
  67. Design, synthesis and pharmacological profile of (−)-verbenone hydrazones
  68. Synthesis of magnesium carbonate hydrate from natural talc
  69. Stability-indicating HPLC-DAD assay for simultaneous quantification of hydrocortisone 21 acetate, dexamethasone, and fluocinolone acetonide in cosmetics
  70. A novel lactose biosensor based on electrochemically synthesized 3,4-ethylenedioxythiophene/thiophene (EDOT/Th) copolymer
  71. Citrullus colocynthis (L.) Schrad: Chemical characterization, scavenging and cytotoxic activities
  72. Development and validation of a high performance liquid chromatography/diode array detection method for estrogen determination: Application to residual analysis in meat products
  73. PCSK9 concentrations in different stages of subclinical atherosclerosis and their relationship with inflammation
  74. Development of trace analysis for alkyl methanesulfonates in the delgocitinib drug substance using GC-FID and liquid–liquid extraction with ionic liquid
  75. Electrochemical evaluation of the antioxidant capacity of natural compounds on glassy carbon electrode modified with guanine-, polythionine-, and nitrogen-doped graphene
  76. A Dy(iii)–organic framework as a fluorescent probe for highly selective detection of picric acid and treatment activity on human lung cancer cells
  77. A Zn(ii)–organic cage with semirigid ligand for solvent-free cyanosilylation and inhibitory effect on ovarian cancer cell migration and invasion ability via regulating mi-RNA16 expression
  78. Polyphenol content and antioxidant activities of Prunus padus L. and Prunus serotina L. leaves: Electrochemical and spectrophotometric approach and their antimicrobial properties
  79. The combined use of GC, PDSC and FT-IR techniques to characterize fat extracted from commercial complete dry pet food for adult cats
  80. MALDI-TOF MS profiling in the discovery and identification of salivary proteomic patterns of temporomandibular joint disorders
  81. Concentrations of dioxins, furans and dioxin-like PCBs in natural animal feed additives
  82. Structure and some physicochemical and functional properties of water treated under ammonia with low-temperature low-pressure glow plasma of low frequency
  83. Mesoscale nanoparticles encapsulated with emodin for targeting antifibrosis in animal models
  84. Amine-functionalized magnetic activated carbon as an adsorbent for preconcentration and determination of acidic drugs in environmental water samples using HPLC-DAD
  85. Antioxidant activity as a response to cadmium pollution in three durum wheat genotypes differing in salt-tolerance
  86. A promising naphthoquinone [8-hydroxy-2-(2-thienylcarbonyl)naphtho[2,3-b]thiophene-4,9-dione] exerts anti-colorectal cancer activity through ferroptosis and inhibition of MAPK signaling pathway based on RNA sequencing
  87. Synthesis and efficacy of herbicidal ionic liquids with chlorsulfuron as the anion
  88. Effect of isovalent substitution on the crystal structure and properties of two-slab indates BaLa2−xSmxIn2O7
  89. Synthesis, spectral and thermo-kinetics explorations of Schiff-base derived metal complexes
  90. An improved reduction method for phase stability testing in the single-phase region
  91. Comparative analysis of chemical composition of some commercially important fishes with an emphasis on various Malaysian diets
  92. Development of a solventless stir bar sorptive extraction/thermal desorption large volume injection capillary gas chromatographic-mass spectrometric method for ultra-trace determination of pyrethroids pesticides in river and tap water samples
  93. A turbidity sensor development based on NL-PI observers: Experimental application to the control of a Sinaloa’s River Spirulina maxima cultivation
  94. Deep desulfurization of sintering flue gas in iron and steel works based on low-temperature oxidation
  95. Investigations of metallic elements and phenolics in Chinese medicinal plants
  96. Influence of site-classification approach on geochemical background values
  97. Effects of ageing on the surface characteristics and Cu(ii) adsorption behaviour of rice husk biochar in soil
  98. Adsorption and sugarcane-bagasse-derived activated carbon-based mitigation of 1-[2-(2-chloroethoxy)phenyl]sulfonyl-3-(4-methoxy-6-methyl-1,3,5-triazin-2-yl) urea-contaminated soils
  99. Antimicrobial and antifungal activities of bifunctional cooper(ii) complexes with non-steroidal anti-inflammatory drugs, flufenamic, mefenamic and tolfenamic acids and 1,10-phenanthroline
  100. Application of selenium and silicon to alleviate short-term drought stress in French marigold (Tagetes patula L.) as a model plant species
  101. Screening and analysis of xanthine oxidase inhibitors in jute leaves and their protective effects against hydrogen peroxide-induced oxidative stress in cells
  102. Synthesis and physicochemical studies of a series of mixed-ligand transition metal complexes and their molecular docking investigations against Coronavirus main protease
  103. A study of in vitro metabolism and cytotoxicity of mephedrone and methoxetamine in human and pig liver models using GC/MS and LC/MS analyses
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  105. Erratum
  106. Erratum to: A one-step incubation ELISA kit for rapid determination of dibutyl phthalate in water, beverage and liquor
  107. Review Articles
  108. Sinoporphyrin sodium, a novel sensitizer for photodynamic and sonodynamic therapy
  109. Natural products isolated from Casimiroa
  110. Plant description, phytochemical constituents and bioactivities of Syzygium genus: A review
  111. Evaluation of elastomeric heat shielding materials as insulators for solid propellant rocket motors: A short review
  112. Special Issue on Applied Biochemistry and Biotechnology 2019
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  114. Study on online soft sensor method of total sugar content in chlorotetracycline fermentation tank
  115. Studies on the Anti-Gouty Arthritis and Anti-hyperuricemia Properties of Astilbin in Animal Models
  116. Effects of organic fertilizer on water use, photosynthetic characteristics, and fruit quality of pear jujube in northern Shaanxi
  117. Characteristics of the root exudate release system of typical plants in plateau lakeside wetland under phosphorus stress conditions
  118. Characterization of soil water by the means of hydrogen and oxygen isotope ratio at dry-wet season under different soil layers in the dry-hot valley of Jinsha River
  119. Composition and diurnal variation of floral scent emission in Rosa rugosa Thunb. and Tulipa gesneriana L.
  120. Preparation of a novel ginkgolide B niosomal composite drug
  121. The degradation, biodegradability and toxicity evaluation of sulfamethazine antibiotics by gamma radiation
  122. Special issue on Monitoring, Risk Assessment and Sustainable Management for the Exposure to Environmental Toxins
  123. Insight into the cadmium and zinc binding potential of humic acids derived from composts by EEM spectra combined with PARAFAC analysis
  124. Source apportionment of soil contamination based on multivariate receptor and robust geostatistics in a typical rural–urban area, Wuhan city, middle China
  125. Special Issue on 13th JCC 2018
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  127. Preparation of magnetite-silica–cetyltrimethylammonium for phenol removal based on adsolubilization
  128. Topical Issue on Agriculture
  129. Size-dependent growth kinetics of struvite crystals in wastewater with calcium ions
  130. The effect of silica-calcite sedimentary rock contained in the chicken broiler diet on the overall quality of chicken muscles
  131. Physicochemical properties of selected herbicidal products containing nicosulfuron as an active ingredient
  132. Lycopene in tomatoes and tomato products
  133. Fluorescence in the assessment of the share of a key component in the mixing of feed
  134. Sulfur application alleviates chromium stress in maize and wheat
  135. Effectiveness of removal of sulphur compounds from the air after 3 years of biofiltration with a mixture of compost soil, peat, coconut fibre and oak bark
  136. Special Issue on the 4th Green Chemistry 2018
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  138. Special Issue on the International conference CosCI 2018
  139. Disintegration, In vitro Dissolution, and Drug Release Kinetics Profiles of k-Carrageenan-based Nutraceutical Hard-shell Capsules Containing Salicylamide
  140. Synthesis of amorphous aluminosilicate from impure Indonesian kaolin
  141. Special Issue on the International Conf on Science, Applied Science, Teaching and Education 2019
  142. Functionalization of Congo red dye as a light harvester on solar cell
  143. The effect of nitrite food preservatives added to se’i meat on the expression of wild-type p53 protein
  144. Biocompatibility and osteoconductivity of scaffold porous composite collagen–hydroxyapatite based coral for bone regeneration
  145. Special Issue on the Joint Science Congress of Materials and Polymers (ISCMP 2019)
  146. Effect of natural boron mineral use on the essential oil ratio and components of Musk Sage (Salvia sclarea L.)
  147. A theoretical and experimental study of the adsorptive removal of hexavalent chromium ions using graphene oxide as an adsorbent
  148. A study on the bacterial adhesion of Streptococcus mutans in various dental ceramics: In vitro study
  149. Corrosion study of copper in aqueous sulfuric acid solution in the presence of (2E,5E)-2,5-dibenzylidenecyclopentanone and (2E,5E)-bis[(4-dimethylamino)benzylidene]cyclopentanone: Experimental and theoretical study
  150. Special Issue on Chemistry Today for Tomorrow 2019
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  152. Multivariate analysis for the classification of copper–lead and copper–zinc glasses
  153. Special Issue on Advances in Chemistry and Polymers
  154. The spatial and temporal distribution of cationic and anionic radicals in early embryo implantation
  155. Special Issue on 3rd IC3PE 2020
  156. Magnetic iron oxide/clay nanocomposites for adsorption and catalytic oxidation in water treatment applications
  157. Special Issue on IC3PE 2018/2019 Conference
  158. Exergy analysis of conventional and hydrothermal liquefaction–esterification processes of microalgae for biodiesel production
  159. Advancing biodiesel production from microalgae Spirulina sp. by a simultaneous extraction–transesterification process using palm oil as a co-solvent of methanol
  160. Topical Issue on Applications of Mathematics in Chemistry
  161. Omega and the related counting polynomials of some chemical structures
  162. M-polynomial and topological indices of zigzag edge coronoid fused by starphene
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