Volume 68, Issue 8

Liquid-based micro-extraction is a novel “green” sample preparation technique using micro-litre levels of organic solvent to extract target analytes from various sample matrices for subsequent instrumental analysis. This technique developed rapidly from its introduction in the mid-1990s. Micro-extraction methods can be conveniently combined with a wide selection of instruments commonly used in a chemical laboratory; they significantly reduce analysis time and costs of solvents’ use and waste disposal. This review focuses on recent advances in several liquid-based micro-extraction methods, including single-drop micro-extraction, hollow fibre-liquid phase micro-extraction, and dispersive liquid-liquid micro-extraction. Examples of application of these methods to environmental, food, and biomedical analysis are listed.

This work was concerned with developing an electrophoretic method for rapid determination of nitrites and nitrates in drinking water. The background electrolyte was Tris-HCl buffer with an addition of cetyltrimethylammonium chloride to reverse the electro-osmotic flow. Online preconcentration of samples using the field-amplified sample stacking method provided detection limits of 0.003 mg L−1 (i.e. 65 nM) for nitrites and 0.010 mg L−1 (i.e. 160 nM) for nitrates, which are sufficiently low for quality control of drinking water. The method was tested in a concentration range corresponding to real drinking water samples and the differentiation between nitrites and nitrates was sufficient for simultaneous determination of nitrites at their concentrations of the order of tenths of mg L−1 and nitrates at their concentrations of the order of units to tens of mg L−1. A number of authors have neglected this important aspect when concentrating only on achieving the lowest possible detection limits. Separation of the two analytes and iodate as an internal standard was achieved in only three minutes. Total analysis time including preconditioning was eight minutes.

In this study, four digestion methods used to determine total phosphorus in river sediments, including Na2CO3 fusion, the H2SO4 and H2SO4 + H2O2 methods and the SMT protocol were investigated. Interference effects of iron, calcium and organic matter in river sediments, and the substances contained in the digestion agents on the photometric determination of the phosphates were analysed. The digestion methods were tested on ten river sediment samples. Statistical analysis of the results showed significant differences between sample treatments relating to the mean total phosphorus concentration.

Experimentally developed ceramic pots, with two different sizes of grain, were half-filled with wine and subjected to thermal alteration at constant elevated temperature ((60 ± 2)°C) in darkness for 12 weeks. This work sought to characterise the samples thereby obtained from chemical and mineralogical perspectives using scanning electron microscopy and an energy-dispersive X-ray microanalysis system (SEM-EDX), Fourier transform infrared spectroscopy (FTIR) and capillary electrophoresis (CE) with UV detection as an alternative to chromatographic methods, due to its good resolution, automation, simplicity, high speed, low consumption of chemicals and short time required for sample preparation. The capillary electrophoresis method was used for the detection of five wine biomarkers: succinic acid, malic acid, tartaric acid, citric acid and lactic acid. In general, it was noted that the fine-grained ceramic assortment retained the organic material better than the coarser-grained ceramics. An interesting observation derived from this study was that not only could tartaric acid be considered as a biomarker for wine residues in archaeological pottery, but malic acid could also act similarly for white wine and lactic acid for red wine.

In this study, a modified genome shuffling method was used to improve γ-decalactone (GDL) production of Yarrowia sp. China General Microbiological Culture Collection Center (CGMCC 2.1405). Five UV mutant strains with higher GDL production or shorter fermentation time were selected as the initial strains for genome shuffling. Conditions of protoplast preparation, regeneration, inactivation, fusion, sporulation of recombinant fusants and ascospore isolation were optimized. Four hereditarily stable haploid recombinants with high GDL production were obtained by three rounds of genome shuffling. Among them, a high GDL-producing recombinant, G3-3.21, producing 3.75 g L−1 of GDL in the fermentation medium after 64 h was obtained. This value is 6.54-fold higher than that of the parent strains CGMCC 2.1405, at the peak production shortened by 8 h. Mathematical kinetic models of CGMCC 2.1405 and G3-3.21 were established to well predict the cell growth and GDL production. The cell growth of G3-3.21 was significantly faster than that of CGMCC 2.1405. The product synthesis constant associated with the strain growth of G3-3.21 was higher than that associated with CGMCC 2.1405. Long-chain fatty-acyl-CoA oxidase activities of G3-3.21 were 833 mU mg−1 and 6.83 times higher than that of CGMCC 2.1405.

A method for extracting coenzyme Q10 (CoQ10) from Artemia was developed. 1 g of fresh Artemia was incubated with 75 % acetic acid at (30 ± 2)°C for 24 h, followed by three consecutive extractions with a mixture of 5 mL of hexane and 5 mL of ethanol, then analysis by a validated high-performance liquid chromatography with a diode-array detector. The calibration curve for CoQ10 was linear in a range of 1–50 μg mL−1. The limits of detection and quantification were 0.3 μg mL−1 and 1.1 μg mL−1, respectively. Mean recoveries were 94–100 % with a high precision of below 10 %. The method developed was found to be simple, efficient and the time required for releasing CoQ10 from Artemia was short. The method provides not only low energy consumption but is also practical for industrial applications.

Effects of the anion type on the structure, thermal stability, and catalytic performance of La-doped Cu-Mn catalysts prepared by co-precipitation were characterized by X-ray diffraction, Brunauer-Emmett-Teller, temperature-programmed reduction, temperature-programmed reduction of oxidized surfaces, and temperature-programmed desorption. The Cu-Mn catalyst was tested for the water-gas shift (WGS) reaction. The main crystalline phase of samples prepared with sulfate, acetate, chloride, and nitrate as the starting materials was a Cu1.5Mn1.5O4 spinel structure, following the WGS reaction, the main crystalline phases were transformed into Cu and MnO. The sample prepared with acetate as the starting material showed the most obvious MnCO3 characteristic diffraction peaks, with better synergistic effects of Cu and MnO, increased adsorption of CO2 and improved dispersion of Cu on the catalyst surface; also, the best thermal stability and the highest low temperature catalytic activity were observed. The sample prepared with nitrate as the starting material maintained high thermal stability and catalytic performance in the range of 400°C to 450°C, but CO conversion decreased below 350°C. Catalytic performance of the sample prepared with sulfate and chloride as the starting materials was poor, ranging from 200°C to 450°C.

In the present study, dietary fibre rich powders obtained from two apple cultivars (Gala, Golden Delicious) were analysed for their chemical composition and functional properties. Apple powders contained more than 50 mass % of total dietary fibre and showed high values of hydration properties such as water holding (11.73–18.34 g g−1), water retention (11.31–11.68 g g−1) and swelling capacity (7.19–8.03 cm3 g−1). Incorporation of apple pomace powders (5 mass %, 10 mass %, and 15 mass %) to wheat dough resulted in a significant increase of water absorption (58.60–71.80 mass %), dough development time (from 3.43 min to 5.53 min) and dough stability (from 9.40 min to 10.90 min). The results also indicate that an addition of higher amounts (10 mass % and 15 mass %) of apple pomace powders negatively affects the volume, thickness, width, and spread ratio of biscuits and reduces their overall acceptance. Sensory analysis also showed that no significant differences between the control biscuits and biscuits containing 5 mass % of apple pomace powder from cultivar Gala were found.

The inhibitory activity of caffeine (1,3,7-trimethyl xanthine) on artificial saliva was studied on a CoCrMo alloy using different electrochemical methods: open circuit potential (OCP), potentiodynamic measurements and electrochemical impedance spectroscopy (EIS). The results show that caffeine produces an inhibitory effect on the anodic currents due to its adsorption on the surface of the alloy. Temperature is another parameter with an influence on corrosion processes, so thermodynamic data were obtained from Arrhenius plots and Langmuir adsorption isotherms. The protective action of caffeine is enhanced at high temperatures at OCP, while for potentiodynamic experiments high temperatures block the inhibitory activity of caffeine and the corrosion rate increases. The process may also be studied by a simulation, determining the functional dependence between OCP, corrosion current density (i corr), corrosion potential (E corr), breakdown potential (E bd) and temperature and amount of caffeine in artificial saliva, for Heraenium® CE. The neural network-based methodology applied in this work provides accurate results, thus proving to be an efficient modelling technique.

The influence of cetyltrimethylammonium bromide and ethylene glycol on the size and dispersion of indium oxide nanoparticles prepared under hydrothermal conditions was investigated. The precursor compound, indium hydroxide, obtained by the hydrothermal method in the absence as well as the presence of cetyltrimethylammonium bromide, was converted to indium oxide by sintering at 400°C. The formation of nanoscale indium oxide upon sintering was ascertained by the characteristic infrared adsorption bands and X-ray diffraction patterns of indium oxide. Transmission electron microscopy and band gap values confirmed that the cetyltrimethylammonium bromide facilitated the formation of indium oxide nanoparticles smaller in size and narrower in distribution than those prepared without the assistance of cetyltrimethylammonium bromide.

Mesoporous spinel Co3O4 nanosheets were synthesised via a simple sol-gel route using the Pluronic P123 triblock copolymer as the stabilising agent. Their structural, morphological, and textural properties were characterised. FTIR spectrum revealed the formation of cobalt oxide without any surface adsorbed impurities. Face centered cubic phase of spinel Co3O4 with the mean crystalline size of 26 nm was assigned by the X-ray diffraction analysis without the formation of other phases. Porous nanosheets and cave-like morphologies were identified from the scanning electron microscopy (SEM) images. Highly agglomerated more or less spherical particles with well separated lattice fringes, representing the oriented growth of nanocrystals, were noticed on the transmission electron microscopy photographs. Surface area analysis revealed that the spinel has high surface area of about 25 m2 g−1 with monomodal mesoporosity. The average pore size distribution was found to be about 15.8 nm. The as-prepared spinel photocatalyst showed a mild photocatalytic activity in the degradation of methylene blue (2.5 mg L−1) under UV light irradiation with air as the oxidising agent. Photocatalytic activity of the as-prepared reusable Co3O4 was found to be higher than that of the commercial spinel powder.

A novel application of highly stable Fe(OTf)3 as an efficient catalyst for the synthesis of a variety of β-enamino ketones and esters under solvent-free conditions is described. Notably, this protocol of a “green synthesis”, which produced β-enamino ketones and esters by the reaction of a variety of β-dicarbonyl compounds and primary amines, exhibits attractive properties including high yields, short reaction periods, lower loading of catalyst and chemo- and regio-selectivity. In addition, the catalyst was easily recovered from the reaction system and readily reused with minimal loss of activity.

2-Amino-4-aryl-4H-benzo[h]chromenes and 3-amino-1-aryl-1H-benzo[f]chromenes were prepared by treating cyano-methylene compounds (malononitrile or ethyl cyanoacetate), substituted aromatic aldehydes, and naphtholic compounds in the presence of potassium phthalimide as a green, mild, efficient, and commercially available organocatalyst in aqueous media. The procedure was readily conducted and affords remarkable advantages such as safety, short reaction times, environmentally benign milder reaction conditions, no organic solvent required, and high yields.

The derivatisation of aldehydes in their α-position is an important facet of organic synthesis. Organocatalytic radical reactions afford α-functionalised aldehydes via a SOMO activation pathway. New organo-SOMO reactions of aldehydes with copper(I)-acetylide and alkylindium reagents are detailed. These reactions proceed well under the catalysis of chiral imidazolidinones. The corresponding functionalised aldehydes were obtained with acceptable yields, but with only low enantiomeric ratios.

Anatoxin-a and epibatidine are natural toxins with a high affinity to nicotinic acetylcholine receptors (nAChR). Nicotinic ligands have the potential to become novel therapeutic agents for various cognitive disorders such as Alzheimer’s and Parkinson’s diseases. The determination of the physicochemical and biological properties of anatoxin-a and epibatidine derivatives is important because these might lead to the development of new cholinergic therapeutic agents. To study these features, the toxins and a set of their derivatives were subjected to a molecular modelling study and QSAR analysis. The structural analyses indicated that the geometric and steric features are important determinants of the compound’s activities. The descriptors selected for the QSAR model also highlighted the roles of the geometric and steric features, together with the importance of electronic features.

A class of stereo-isomerically-pure alkanediol monoglycosides, 2-hydroxyethyl per-O-acetyl pyranosides (IIIa-IIIf), was conveniently prepared by a one-pot reaction of per-O-acetylated pyranoses (Ia-If) and 2-(tert-butyldimethylsilyloxy)ethanol (II) with catalysis by BF3·OEt2. The α-(IIIa) or β-linked glycosides (IIIb-IIIf) with 1,2-trans-configuration were obtained from glycosyl donors with participation of the neighbouring 2-O-acetyl group. BF3·OEt2, along with hydrogen fluoride released from BF3·OEt2 under the experimental conditions used, facilitates the subsequent de-protection of siloxane to successfully afford 2-hydroxyethyl per-O-acetyl-pyranosides.

The fluorescence emission spectra and fluorescence quantum yields of hemicyanine dyes LDS 698, LDS 722, and LDS 730 were measured in different media. No transient species was detected in the laser flash-photolysis experiments performed with Ar-saturated solutions of the dyes in methanol. However, in the presence of 0.08 M potassium iodide, the absorption of the triplet states was clearly observed. Oxygen consumption measurements in the absence and presence of a chemical trap (furfuryl alcohol) in MeOH: H2O (φ r = 1: 1) solutions of the dyes containing KI confirmed the generation of singlet molecular oxygen.