Volume 68, Issue 6

An isocratic reversed-phase high-performance liquid chromatographic (RP-HPLC) method with diode array detection (DAD) was developed for the determination of aluminium tris(ethyl phosphonate) (fosetyl-aluminium, fosetyl-Al) in plant-protection products. The method involves extraction of the active ingredient by sonication of the sample with water and direct measurement by RPHPLC. The isocratic RP-HPLC method for the analysis of fosetyl-Al thus developed was then validated for specificity, linearity, precision, and accuracy. The chromatographic peak confirmation was performed by LC-MS using electron spray ionisation in the negative-ion mode. The repeatability of the method, expressed as relative standard deviation (RSD, %), was found to be 0.5 % and the limit of detection was 0.035 mg mL−1. The average recoveries of the three fortification levels varied from 96.7 % to 100.6 % and the RSDs ranged between 2.6 % and 6.3 %. The precision of the method was also considered to be acceptable as the experimental repeatability relative standard deviation (RSDr) was lower than the RSDr, calculated using the Horwitz equation. The method is rapid, simple, accurate, cost-effective, and provides a new and reliable means for the analysis of fosetyl-Al in formulated products.

Recent progress in nanotechnology has prompted research interest in immobilised enzymes on graphene oxide (GO) nanosheets for their large specific surface area and abundant functional groups. In the present work, acid pectinase was immobilised on the GO via the cross-linking of amino groups on pectinase and functional groups (e.g. carboxyl group) on the GO surface. Acid pectinase was effectively immobilised on the support and high loading densities were obtained (2400 mg per g of support). In addition, the immobilised enzyme achieved a better catalytic efficiency (K cat/K m) than its free counterpart; 3.7 mg−1 min−1 mL for immobilised pectinase, 3.5 mg−1 min−1 mL for free pectinase. Under acidic conditions, pectinase immobilised on GO will be agglomerated, but the addition of surfactant PEG 6000 could solve the problem and afford higher catalytic activity and catalytic efficiency.

Pseudomonas putida CGMCC3830 harboring nitrilase was used in isonicotinic acid production from 4-cyanopyridine. This nitrilase showed optimum activities towards 4-cyanopyridine at pH 7.5 and 45°C. The half-life of P. putida nitrilase was 93.3 h, 33.9 h, and 9.5 h at 30°C, 38°C, and 45°C, respectively. 4-Cyanopyridine (100 mM) was fully converted into isonicotinic acid within 20 min. The bench-scale production of isonicotinic acid was carried out using 3 mg of resting cells per mL in a 1 L system at 30°C and finally, 123 g L−1 of isonicotinic acid were obtained within 200 min without any by-products. The conversion reaction suffered from the product inhibition effect after the tenth feeding. The volumetric productivity was 36.9 g L−1 h−1. P. putida shows significant potential in nitrile hydrolysis for isonicotinic acid production. This paper is the first report on isonicotinic acid biosynthesis using Pseudomonas putida and it represents the highest isonicotinic acid production reported so far.

Two lipases, Novozyme 435 (lipase B from Candida Antarctica) and Lipozyme TL IM (Thermomyces lanuginosus) were used successfully for the kinetic resolution of racemic 1-(2-furyl)-3-pentanol, the key intermediate in synthesis of the bark beetle pheromone, chalcogran. The desired S-(+)-enantiomer was prepared in enantiomeric excesses higher than 98 % and with yields of 26.3 % and 32.5 %, respectively. Methyl tert-butyl ether and vinyl acetate were found to be the best reaction media and the acetyl donor to achieve fast and effective resolution.

The separation of Cd(II) and Ni(II) ions was studied in an aqueous sulphate medium using supported liquid membrane (SLM). D2EHPA/M2EHPA was used as a mobile carrier, microporous hydrophobic PTFE film was used as a solid support for the liquid membrane, and the strip phase was sulphuric acid. The effects of different parameters such as feed concentration, carrier concentration, feed phase pH, and strip phase pH on the separation factor and flux of Cd(II) and Ni(II) ions were studied. The optimum values obtained to achieve the maximum flux were 5.0 for feed pH, 40 vol. % for D2EHPA/M2EHPA concentration in the membrane phase, 0.5 for strip pH, and 0.012 mass % for feed concentration. Under these optimum conditions, the flux values of Cd(II) and Ni(II) were 15.7 × 10−7 kg m−2 s−1 and 2.6 × 10−7 kg m−2 s−1, respectively. The separation factors of Cd(II) over Ni(II) were studied under different experimental conditions. At a carrier concentration of 10 vol. % and feed concentration of 0.012 mass %, the maximum value of 185.1 was obtained for the separation factor of Cd(II) over Ni(II). After 24 h, the percentages of the extracted Cd(II) and Ni(II) were 83.3 % and 0.45 %, respectively.

In this study, the glycerol solutions were fermented using Lactobacillus casei bacteria. The broths were pre-treated by microfiltration, followed by a further separation with nanofiltration. The latter process was carried out in two stages, using the NF270 and NF90 membranes, respectively. The concentrates thus obtained were enriched with citric acid (first stage) and then with lactic acid and glycerol (second stage). By means of SEM and AFM microscopy, as well as ATR-FTIR analysis, the intensity of membrane-fouling was studied. The colloidal fouling and bio-fouling caused a more than two-fold decrease in the permeate flux during microfiltration of the broth. This pre-treatment stage was effective, and a permeate turbidity of less than 0.2 NTU was obtained. However, the nanofiltration membranes exhibited a 30 % flux decline over the course of the process, mainly due to the organic fouling.

Two-stage adsorption was used for selective removal of Cu(II) and phosphate from aqueous solutions. In the first stage, adsorption of Cu(II) and phosphate on oxyhumolite (OX) was examined. The pseudo second-order equation was found to be the best fit for the kinetic adsorption data. The adsorption capacity of OX for Cu(II) and phosphate depends on the adsorption time, the equilibrium pH influences only the adsorption of Cu(II). The high adsorption efficiency (E = 95 %, pH 3.5, 0.5 g of the solid sorbent and 50 cm3 of the solution, c = 4 mmol dm−3) of OX for Cu(II) is caused by the presence of humic acids (HA). In the second stage, blast furnace slag (BFS) and activated blast furnace slag (BFS-A) were used to remove phosphates. The presence of OX in the first stage positively influences the adsorption efficiency of sorbents in the second stage due to the soluble humic compounds and residues of humic acids (HA) which support the precipitation of Ca-phosphates on BFS and the ions exchange reactions on BFS-A. Adsorption equilibrium of phosphate on both slags at 298 K can be well described by the Langmuir isotherm equation. Desorption of Cu(II) from OX was around 70 %. The presence of OX in the first stage also influences the desorption of phosphate bound in the second stage. Desorption efficiency of both slags for phosphate was about 60 %.

A cellulose-PCC composite was synthesised using the CaCl2 reaction with dimethyl carbonate (DMC) under alkaline conditions and in the presence of cellulose fibrils made from highly refined bleached softwood kraft pulp. The results showed that the ash content in the synthesised cellulose-PCC composite increased by increasing the reaction temperature from 25°C to 70°C, the reaction time from 3.5 min to 7.5 min and the cellulose consistency from 0.05 % to 0.1 %. The ratio of calcium carbonate generated to the calcium chloride used initially was increased by increasing the reaction temperature and time. The XRD pattern of the cellulose-PCC composite indicated no modification micro-crystal habit of the deposited CaCO3. The SEM images showed that the cellulose-PCC composite filler had a rhombohedral shape as opposed to the scalenohedral shape of common PCC. The paper filled with the cellulose-PCC composite had much higher bursting and tensile strengths, at a tearing strength similar to common PCC.

A study was conducted on the treatment of landfill leachate by combining the sequencing batch biofilm reactor (SBBR) method with the electro-Fenton method. The reduction of chemical oxygen demand (COD), biological oxygen demand (BOD5), and ammonia nitrogen (NH4+-N) from the leachate by the SBBR method was investigated. For the electro-Fenton experiment, the changes in COD and total organic carbon (TOC) with the increase in H2O2 dosage and electrolysis time under optimal conditions were also analysed. The results showed that the average efficiencies of reduction of COD, BOD5, and NH4+ -N achieved using the SBBR method were 21.6 %, 54.7 %, and 56.1 %, respectively. The bio-effluent was degraded by the subsequent electro-Fenton process, which was rapid over the first 30 min then subsequently slowed. After 60 min of the electro-Fenton treatment, the efficiencies of reduction of TOC, COD, and BOD5 were 40.5 %, 71.6 %, and 61.0 %, respectively. There is a good correlation between the absorbance of leachate at 254 nm (UV254) and COD or TOC during the electro-Fenton treatment.

Phase pure nano nickel oxide was synthesized by the chemical precipitation method and sintered at 200°C, 400°C and 600°C, respectively, to study the effect of sintering on the charge distribution and magnetism. The samples were analyzed by X-ray diffraction for electron density distribution studies, vibrating sample magnetometry for magnetic behavior and by UV-VIS spectrophotometry for optical characteristics. Rearrangement of charge density distribution with respect to sintering temperature was analyzed through the maximum entropy method employed using powder X-ray diffraction data. The observed magnetic transition with respect to the temperature/size effect was analyzed and correlated with electron density distribution studies.

The optimum content of cotton microfiber, initiator, cross-linker, and sodium hydroxide were determined using the central composite design method. Polymer hydrogels (PHGs) were characterized using Fourier-transform infrared (FT-IR), scanning electron microscopy, and thermal gravimetric analysis. A comparison between plain PHG and the polymer hydrogel composite (PHGC) in terms of biodegradation, swelling rate, and re-swelling capacity was carried out. The effect of PHGC on the sandy soil holding capacity, urea leaching loss rate (ULLR), and okra plant growth were evaluated. The highest water absorption capacity was obtained at 1.30 mass %, 0.15 mass %, 13.00 mass %, and 13.50 mass % of the initiator, cross-linker, sodium hydroxide, and cotton microfiber, respectively. Cotton microfiber has a prominent effect on the swelling rate, re-swelling capacity, and biodegradability of PHG. Okra plant growth and ULLR were positively affected by PHGC and the best leaching loss rate of 33.3 mass % was observed for the lowest urea loaded sample.

In this study, Cu(II)-ion-imprinted membrane adsorbents were prepared via cross-linking of blended chitosan/poly(vinyl alcohol) using glutaraldehyde as cross-linker and copper ions as template. The ability of IIMs to adsorb copper ions from aqueous solutions was assessed using a batch of experiments under different conditions by changing cross-linking density (0.05 mass %, 0.1 mass %, and 0.2 mass %), template content (0.2 mass %, 0.5 mass %, and 0.9 mass %), initial analyte concentration (50 mg L−1, 100 mg L−1, and 150 mg L−1), and adsorbent concentration (0.5 g L−1, 1.0 g L−1, and 2.0 g L−1). The Taguchi method was used to plan a minimum number of experiments. The following optimal levels were thus determined for the four factors: cross-linking density: 0.1 mass %; template content: 0.5 mass %; initial analyte concentration: 150 mg L−1; and adsorbent concentration: 0.3 g L−1.

This study concerns the preparation of a new eburnamine-type alkaloid, methyl (3α,14β,15β,16α)-17,18-didehydro-14,15-dihydroeburnamine-15-methoxy-14-carboxylate (VIII). This alkaloid was prepared from (+)-17,18-dehydroapovincamine (V) using Lewis acid and/or ion exchange resin as catalyst. The hydroalkoxylation reaction of V with methanol was investigated in terms of catalyst, solvent, temperature, and time of reaction. A one-pot method for synthetising this alkaloid was established. The optimal conditions for the reaction are discussed.

The results of research into obtaining an ecological wetting agent for wildfires are presented. First, measurements of the equilibrium and dynamic surface tension for anionic and non-ionic commercial surfactants and their binary mixtures were conducted. Next, the parameters of adsorption facilitating a quantitative description of the process in both binary systems as well as single-component solutions were estimated. In addition, the static and dynamic contact angles on model surfaces with different hydrophobicity were studied (glass, polyethylene, pressed peat). In a few mixed systems, a synergism in reducing the critical micelle concentration and/or a synergy of the ability to wetting model surfaces was identified. Next, research into the sorptivity and wettability of peat (loose and pressed) was conducted. It was found that non-ionic and anionic surfactants exhibit different abilities in respect of foaming and moistening of peat. From an analysis of the preliminary results, the surface-active components were selected to obtain a wetting agent composition. The wettability and adsorption characteristics and an evaluation of the foaming ability using solutions of the prepared compositions were tested. The effectiveness of the wetting composition thus obtained was confirmed in the laboratory and in field firefighting. The test results confirmed the better wettability and sorptivity on peat and the effectivity for combating wildfires, compared with some typical commercial products.

A combination of ultrasonic (US) and [bmim]AlCl4 ionic liquid is used as an alternative to conventional acid catalysts in the Kabachnik-Fields reaction of an amine and aryl aldehyde with phosphite leading to the formation of aminophosphonates. The reaction time was significantly reduced and the reaction progressed very smoothly.

Molecularly imprinted polymer-coated bacterial cellulose nanofibers have been prepared by immersing solvent treated-bacterial cellulose into a dilute pre-polymerization mixture solution prior to the polymerization process. The quercetin-imprinted polymer coating bacterial cellulose (QIP-BC) nanofibers show discrete nanoparticles encapsulated along the BC nanofibers. The binding capacity of dried QIP-BC was approximately 3 mg per gram of the polymer. The obtained results indicated that QIP-BC nanofibers provided a three fold higher recognition ability for quercetin than quercetin-imprinted nanospheres. This technique can be easily used to combine two fascinating materials like BC nanofibers and molecularly imprinted polymers (MIPs) to afford promising polymer composites that are useful in various innovative applications in biomedical, pharmaceutical, and industrial sectors.

The pK a values of N-alkyl-N,N-dimethylamine-N-oxides were determined from the pH dependences of chemical shifts in 1H NMR and 13C NMR spectra. The dependences were measured at concentrations below and above the critical micelle concentration of the amine oxides. Above the critical micelle concentration, the plots of the peak positions vs. pH were either sigmoid (the groups close to the nitrogen) or “peak type” (farther groups). The sigmoidal behaviour was a direct result of the acid-base reaction; on the other hand, the “peak type” behaviour was probably an indirect consequence of the pH variation, mediated with the change in micelle size.