Complex formation and enantioselectivity studies of triazole fungicide and organophosphorus pesticide enantiomers using capillary electrophoresis

Several cyclodextrin modified-micellar electrokinetic chromatography (CDMEKC) methods were developed for the successful triazole fungicides separation. In the first part, an efficient method was developed for the simultaneous enantioseparation of cyproconazole (4 stereoisomer), bromuconazole (4 stereoisomer) and diniconazole (2 stereisomer) enantiomers using CD-MEKC with a dual mixture of neutral cyclodextrins as chiral selector. The best simultaneous separation of cyproconazole, bromuconazole, and diniconazole enantiomers was achieved with a mixture of 27 mM HP-β-CD and 3 mM HP-γ-CD in 25 mM phosphate buffer (pH 3.0) containing 40 mM sodium dodecyl sulfate (SDS) and 15% iso-propanol as organic modifier. Complete separation of 10 stereoisomer of triazole fungicides were obtained in a single run with good resolution (Rs 1.74“26.31) and high peak efficiency (N > 400 000). In the second part of the study, enantioseparation of hexaconazole, penconazole, myclobutanil, and triadimefon was investigated. Simultaneous enantioseparation of penconazole, myclobutanil, and triadimefon was achieved under acidic condition (pH 3.0) using 25 mM phosphate buffer, 50 mM SDS, and 30 mM HP-γ-CD, with Rs greater than 0.9 whereas, simultaneous enantioseparation of hexaconazole, penconazole, and myclobutanil was successfully achieved under neutral condition (pH 7.0) using 25 mM phosphate buffer, 40 mM SDS, and 40 mM HP-γ-CD, with Rs greater than1.6. In order to improve detection sensitivity, on-line preconcentration technique was investigated. It was found that sweeping technique as an on-line preconcentration technique improved the detection sensitivity of the enantioseparation of cyproconazole, bromuconazole, and diniconazole by 30 to 60-fold, with good repeatabilities in the migration time, peak area and peak height were obtained with RSDs in the range of 0.08“0.32%, 0.03“ 2.44%, and 2.13“8.44% respectively. Furthermore, sweeping technique improved the detection sensitivity of the enantioseparation of hexaconazole, penconazole and myclobutanil by 62- to 67-fold. Good repeatabilities in the migration time, peak area and peak height were obtained with RSDs in the range of 2.39“3.90%, 1.96€“6.15%, and 2.80“6.64% respectively. Finally, the formation constant of diniconazole enantiomers with HP-γ-CD under neutral and acidic condition was investigated using CD-MEKC

Optimization of sol-gel hybrid mediated hollow fiber-solid phase microextraction for the analysis of selected aldehydes

Hexanal and heptanal are two promising aldehydes that have been found in biological samples of lung cancer patients. In general, aldehydes can be detected in trace level as low as part per billion or part per trillion levels. Since reliable technique is needed to detect the analyte of interest especially in complex matrices, a new hybrid silica-based material as the adsorbent of hollow fiber-solid phase microextraction (HF-SPME) was synthesized. In the present work, the solgel hybrid material was held in the pores of HF by in situ gelation and was used to extract the two test aldehydes using direct immersion sampling mode. Several solgel parameters affecting the extraction performance of the in-house sol-gel hybrid material were optimized. The extraction efficiencies of the new silica-based hybrid material for the target aldehydes were based on peak area response obtained from gas chromatography-flame ionization detector. The best extraction efficiencies of hexanal and heptanal were obtained using a mol ratio of 1:4 for the two precursors used, 6 mmol water, 6 mmol methanol and 2.5 mmol trifluoroacetic acid for in situ gelation HF-SPME. The new in situ sol-gel silicabased adsorbent material exhibits high potential for HF-SPME of hexanal and heptanal

New dispersive solid phase miroextraction sorbent based on so-gel bybrid material for non-sterioidal anti- inflammatory drug analyis in water

Dispersive solid phase microextraction (DSPME) is a simple and environmental friendly sample preparation technique. In DSPME, the sorbent is used for trapping the analyte/s out of the solution and then the analyte/s is to a smaller volume of a second desorption solvent. In this study, a new DSPME sorbent material based on a hybrid organic–inorganic methyltrimethoxysilane–cyanopropyltriethoxysilane (MTMOS–CNPrTEOS) was synthesized by using two steps sol–gel method. The new DSPME hybrid sorbent was used in determination of three selected NSAIDs namely, diclofenac sodium, ketoprofen and mefenamic acid in water samples prior to high performance liquid chromatography with ultraviolet (HPLC-UV) detection. Under the optimized conditions, the method demonstrated good linearity (0.2–500 µg L-1) with excellent coefficient of determination (r2 > 0.9991), good RSDs (<2.4%, n = 3), good limit of detection (0.03–0.12 µg L-1) and excellent recoveries (93.5–97.6%). The DSPME method using the new sol-gel hybrid MTMOS–CNPrTEOS material combined with HPLC–UV proved to be a simple, cost efficient and requires minimial amount of organic solvent that support green chemistry concepts

New sol-gel silica nanoparticles coated cyanopropyltriethoxysilane as alternative solid phase extraction sorbent for organophosphorus pesticides

Sorbents based on silica are widely used in solid phase extraction (SPE). The most common SPE material is C18.Recently nanoparticleshave gained interest as sorbent materials for analytical purpose. In this study silica-based nanoparticles with polar and non-polar groups were synthesized using cyanopropyltriethoxysilane (CNPrTEOS) and tetraethoxysilane (TEOS) as precursor in the presence of ammonia solution as catalyst and ethanol as solvent via sol-gel technology. The sol-gel SiO2-NPs-CNPrTEOS was used for the simultaneous extraction of three organophosphorus pesticides (OPPs) of different polarity namely dicrotophos, diazinon and chlorpyrifos prior to LC-UV detection at 270 nm. The sorbent produced was characterized using FTIR, FESEM, nitrogen gas adsorption and TGA. The surface area and average pore diameter of the sorbent are 570 m2 g-1 and 31Å (mesoporous), respectively. The average particle size of SiO2-NPs-CNPrTEOS is 54 nm. The mesoporous SiO2-NPs-CNPrTEOS showed superior extraction capability for the polar dicrotophos and also for the non-polar diazinon and chlorpyrifos compared to commercial cyano SPE. The new SiO2-NPs-CNPrTEOS exhibits high potential as a bipolar sorbent for the simultaneous extraction of polar and non-polar OPPs. Keywords Sol-gel, Solid phase extraction, Nanoparticles sorbent, Cyanopropyltriethoxysilane, Tetraethoxysilane, Organophosphorus pesticides, Liquid chromatography-UV detection

Gelatin-alginate coated cellulose acetate membrane for the extraction of heavy metal ions from water samples

Heavy metal ions are a common water pollutant from industrialized areas and extraction is one of the most popular methods to remove the target analytes. However, extraction and determination of metal ions in water are often very difficult to perform due to their solubility in water. In order to resolve some of the issues in the extraction of trace metal ions from aqueous samples, this study explores newly prepared polyelectrolyte films coated on cellulose acetate membrane as extracting phase. Optimization coating materials showed that gelatin-alginate coated cellulose acetate membrane have the best performance to adsorb metal ions from water. The results open a possibility of the method to be successfully applied as extracting phase to adsorb and enrich heavy metal ions from aqueous matrices

New application of magnetic nanoparticles for adsorption of nickel(II) metal ions from aqueous solution by batch method

Ni(II) is toxic for living organism at trace levels. Currently the Environmental Protection Agency (EPA) standard for Ni(II) in drinking water is 0.04 mg/L [1]. The adsorption of metal ions using magnetic nanoparticles is preferred due to their lower costs, have high adsorption capacities, durability and high efficiency, especially for metal ions with trace and ultra-trace concentration level [2]. In this study, an in-house synthesized Fe3O4 MNPs adsorbent was evaluated for its feasibility in the adsorption of Ni(II) metal ions from aqueous solutions. Adsorption experiments were investigated by kinetic and isotherm adsorption models

Solid phase microextraction using new sol-gel hybrid polydimethylsiloxane-2-hydroxymethyl-18-crown-6-coated fiber for determination of organophosphorous pesticides

A new sol–gel hybrid coating, polydimethylsiloxane–2-hydroxymethyl-18-crown-6 (PDMS–2OHMe18C6) was prepared in-house for use in solid phase microextraction (SPME). The three compositions produced were assessed for its extraction efficiency towards three selected organophosphorus pesticides (OPPs) based on peak area extracted obtained from gas chromatography with electron capture detection. All three compositions showed superior extraction efficiencies compared to commercial 100 µm PDMS fiber. The composition showing best extraction performance was used to obtain optimized SPME conditions: 75 °C extraction temperature, 10 min extraction time, 120 rpm stirring rate, desorption time 5 min, desorption temperature 250 °C and 1.5% (w/v) of NaCl salt addition. The method detection limits (S/N = 3) of the OPPs with the new sol–gel hybrid material ranged from 4.5 to 4.8 ng g-1, which is well below the maximum residue limit set by Codex Alimentarius Commission and European Commission. Percentage recovery of OPPs from strawberry, green apple and grape samples with the new hybrid sol–gel SPME material ranged from 65 to 125% with good precision of the method (%RSD) ranging from 0.3 to 7.4%

Sol–gel coated polypropylene hollow fiber-based liquid-phase microextraction of triazine herbicides in real water samples

A sol–gel coated hollow fiber-based liquid-phase microextraction (LPME) method was developed for the extraction of triazine herbicides. The polypropylene hollow fiber was coated with polydimethylsiloxane–divinylbenzene using sol–gel method and characterized. The developed method was compared with uncoated hollow fiber LPME method for the extraction of simazine, atrazine, and propazine prior to gas chromatography–mass spectrometry analysis. Optimized conditions for both coated and uncoated hollow fibers LPME methods were toluene as an acceptor phase, length of hollow fiber (1.5 cm), volume of acceptor phase (3.0 µL), stirring rate (1200 rpm), and no addition of salt (sodium chloride). The optimized volumes of donor phase for uncoated fiber and coated fiber were 4.0 and 4.5 mL, respectively, while the optimized extraction times were 30 min for uncoated hollow fiber and 10 min for coated hollow fiber. The developed sol–gel coated hollow fiber LPME method provided good enrichment factors (EFs) ranging from 100 to 139, good recoveries (75.27–104.47%), and good reproducibility (relative standard deviations [RSDs] < 0.83%). Meanwhile, uncoated hollow fiber LPME method showed lower EFs ranging from 80 to 90 and relatively low recoveries of 60.72–68.17%, whereas it has good reproducibility with RSDs < 0.94%. The proposed method was successfully applied to the analysis of real water samples and the analyte recoveries for spiked water samples was in the range of 42.54–78.75%

Microemulsion electrokinetic chromatography coupled with dispersive micro-solid phase extraction for determination of isoflavones in soybean products

A new method based on microemulsion electrokinetic chromatography (MEEKC) coupled with dispersive micro solid phase extraction (D-µ-SPE) was developed for the determination of isoflavones in soy products. D-µ-SPEs of real samples were carried out using multi-walled carbon nanotubes (MWCNTs) as adsorbent prior to MEEKC. Separations of selected isoflavones namely daidzein, genistein and formononetin by MEEKC were carried out using fresh daily-prepared microemulsion background electrolyte (BGE). The optimized MEEKC conditions for the separation of isoflavones were 4 mM borate buffer pH 8.5, 6.6% (w/v) 1-butanol, 0.9% (w/v) sodium dodecyl sulphate, 0.75% (w/v) ethyl acetate, 3% (w/v) acetonitrile at 3 s injection time, 27 kV and 35 °C. Meanwhile, the optimum D-μ-SPE conditions were 5 mg of MWCNTs and 300 µL of methanol as desorption solvent. Under the optimized conditions, the developed D-µ-SPE-MEEKC method showed good linearity in the concentration range of 1-10 mg/L with coefficients of determination (r2) > 0.99 and limits of detection of 0.27-0.95 mg/L. The method was successfully applied to the determination of isoflavones in five soybean products namely soy supplement, tofu, tempeh, egg tofu and fujook and good recoveries were obtained in the range of 74.5-112.5% with RSDs of < 3%. The method has proved to be simple and offers low consumption of organic solvent and relatively short analysis time, thus it is a potentially viable green alternative method for extraction and determination of isoflavones in soybean products

Magnetic micro-solid-phase extraction based on magnetite-MCM-41 with gas chromatography–mass spectrometry for the determination of antidepressant drugs in biological fluids

A new facile magnetic micro‐solid‐phase extraction coupled to gas chromatography and mass spectrometry detection was developed for the extraction and determination of selected antidepressant drugs in biological fluids using magnetite‐MCM‐41 as adsorbent. The synthesized sorbent was characterized by several spectroscopic techniques. The maximum extraction efficiency for extraction of 500 μg/L antidepressant drugs from aqueous solution was obtained with 15 mg of magnetite‐MCM‐41 at pH 12. The analyte was desorbed using 100 μL of acetonitrile prior to gas chromatography determination. This method was rapid in which the adsorption procedure was completed in 60 s. Under the optimized conditions using 15 mL of antidepressant drugs sample, the calibration curve showed good linearity in the range of 0.05–500 μg/L (r2 = 0.996–0.999). Good limits of detection (0.008–0.010 μg/L) were obtained for the analytes with good relative standard deviations of <8.0% (n = 5) for the determination of 0.1, 5.0, and 500.0 μg/L of antidepressant drugs. This method was successfully applied to the determination of amitriptyline and chlorpromazine in plasma and urine samples. The recoveries of spiked plasma and urine samples were in the range of 86.1–115.4%. Results indicate that magnetite micro‐solid‐phase extraction with gas chromatography and mass spectrometry is a convenient, fast, and economical method for the extraction and determination of amitriptyline and chlorpromazine in biological samples