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

Dispersive micro-solid phase extraction using silica based sol-gel hybrid organic-inorganic material for analysis of organophosphorus pesticides in water samples

In 1930s, the insecticidal properties of organophosphorus pesticides (OPPs) and carbamate compounds were found and the compounds were developed for pesticides use in 1940s. They have been extensively used since 1970s when the environmentally persistent organochlorine pesticides were banned for use in the United States [1]. Although OPPs compounds are considered less dangerous than organochlorine, they are still highly neurotoxic to human and in some cases their degradation products have the potential to be more toxic with chronic exposure. The common method used for the analysis of pesticides is solid phase extraction (SPE) since it is more rapid, simple and economical than traditional liquid-liquid extraction. However, this method still has tendency to produce large secondary wastes, solvent loss, a long procedure and need for complex equipment [2,3]. Therefore to overcome this limitation, a quick, easy, cheap, rapid and simple (QuECheRS) microextraction method named dispersive micro-solid phase extraction (D-µ-SPE) has been developed. The developed method used synthesized silica based sol-gel hybrid cyanopropyltriethoxysilane-methyltrimethoxysilane (CNPrTEOSMTMOS) as sorbent for the analysis of selected pesticides namely methamidophos, monocrotophos and chlorpyrifos in water sample

Stir bar sorptive extraction of organic dyes from water samples using silica-based sol-gel hybrid adsorbent

The first synthetic dye ‘mauveine’ was discovered in 1856. Since then, other types of synthetic dyes are massively produced and used in several industries including textiles. Even though dyes are not strongly hazardous, they are considered as potential water pollutants due to their solubility in water which are usually high. Some cases reported that they are cytotoxic and carcinogenic to human [1]. The common technique used in the analysis of dyes is solid phase extraction (SPE). It provides a simple and economical analysis compared to liquid-liquid extraction (LLE). However, SPE has some drawbacks which include the production of organic waste, timeconsuming and complex set-up [2]. Therefore, a solventless technique namely stir bar sorptive extraction (SBSE) under the trade name TWISTERTM has been developed to overcome the limitations. However, commercial TWISTERTM is rather expensive and limited in the types of coating materials available. Thus this study attempts to synthesize new adsorbent materials based on silica for use in SBSE. Our successful hybridization of sol-gel materials [3, 4] have led us to the synthesis of another silica-based sol-gel hybrid adsorbent, mercaptopropyltrimethoxysilane-methyltrimethoxysilane (MPTMOS-MTMOS) as sorbent in the analysis of selected organic dyes namely crystal violet, methylene blue and methyl orange in water sample. The use of hybrid material as adsorbent enhanced the ability of the stir bar to extract polar compounds compared to the commercial stir bar [3], and reduced the production cost

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

Adsorption studies for removal of trace copper metal ions from aqueous samples using magnetic nanoparticles

Fe3O4 magnetic nanoparticles (MNPs) synthesized in-housed using co-precipitation method was assessed for the treatment of synthetic aqueous solutions contaminated by Cu(II) ions. Experimental results showed that at 25ºC, the optimum value for Cu(II) removal was pH 6.0 and an adsorbent dose of 60.0 mg. The adsorption capacity of Fe3O4 nanoparticles for Cu(II) is 16.28 mg g-1. Adsorption kinetic rates were found to be fast; total equilibrium was achieved after 180 min. Kinetic experimental data fitted very well the pseudo-second order equation and the value of adsorption rate constants was calculated to be 0.0006 and 0.0013 g mg-1 min at 5 and 40 mg L-1 initial Cu(II) concentrations, respectively. The equilibrium isotherms were evaluated in terms of maximum adsorption capacity and adsorption affinity by the application of Langmuir and Freundlich equations. Results indicate that the Langmuir model fits adsorption isotherm data better than the Freundlich model

Graphene oxide dispersed with ferrite nano - particles as magnetic solid phase extraction adsorbent for chlorpyrifos and diazinon

Magnetic graphene oxide, Fe3O4-GO has been synthesized through oxidation of graphite via modified Hummer’s method followed by a one step co-precipitation method. Fe3O4-GO was used in the extraction of two organophosphorus pesticides (OPPs), namely chlorpyrifos and diazinon using magnetic solid phase extraction (MSPE) technique. The GO and Fe3O4-GO synthesised was characterized using Fourier transform infrared spectroscopy (FT-IR), and field emission scanning electron microscopy (FESEM). Optimum conditions obtained from the optimization process were as follows: 80 mL sample volume, 50 mg of adsorbent, 10 min extraction time followed by desorption process using 500 µL of acetonitrile. Under the optimum conditions, Fe3O4-GO MSPE method showed excellent linearity in the range of 0.1-10 µg L-1 with coefficient of determination (R2) of 0.9997 for both OPPs. Precision studies found that the repeatability of this Fe3O4-GO MSPE method (RSD, n = 3) were 9.95% and 9.05% for chlorpyrifos and diazinon respectively. Meanwhile the reproducibility (RSD, n = 9) observed was 11.45% for chlorpyrifos and 13.35% for diazinon. The limit of detection (LOD = 3 S/N) for chlorpyrifos was 0.034 µg L-1 and 0.40 µg L-1 for diazinon. Lake water sample was spiked with 0.5 µg L-1 of each of the OPPs after confirming the non-detection in the sample using gas chromatography-electron capture detector (GC-ECD). Percentage recoveries of the two OPPs from lake water samples were found to be 57.71% for chlorpyrifos and 73.86% for diazinon. The Fe3O4-GO MSPE method was found to be susceptible to matrix effect from the lake water sample analysed. The Fe3O4-GO MSPE method was also applied to the determination of the two OPPs from tomato sample using matrix-matched calibration curve in the range of 1-50 µg L-1. Good coefficient of determination (R2) value of 0.9963 and 0.9897 for chlorpyrifos and diazinon respectively was observed. Both OPPs were found to be present in the tomato sample analysed (0.19 µg L-1 of chlorpyrifos and 7.88 µg L-1 of diazinon

Ferrite-calcium alginate as magnetic solid phase extraction adsorbent of copper(II) ions in water prior to flame atomic absorption spectroscopy

A magnetic solid phase extraction (MSPE) procedure using ferrite-calcium alginate (Fe3O4-CaAlg) as adsorbent for Cu(II) ions prior to flame atomic absorption spectroscopy (FAAS) was developed. The extraction of Cu(II) ions using Fe3O4-CaAlg MSPE is simpler and faster than the conventional method such as solid phase extraction and traditional method such as liquid-liquid extraction. The simple extraction is based on the use of magnetisable adsorbent to extract Cu(II) ions, which can be readily isolated from water samples as a matrix with an external magnet. The adsorbent was prepared by mixing sodium alginate solution with Fe3O4 magnetic particles and calcium chloride solution to form magnetic alginate beads. Important parameters influencing the extraction and desorption process including type and volume of desorption solvent, agitation time, extraction time, weight of adsorbent and ample volume were optimized. Under the optimized conditions, calibration graph (external standard method) with coefficient of determination (R2) of 0.974 in the linearity range 20-100 µg/L was observed. Good limit of detection (1.70 µg/L), and limit of quantification (5.6 µg/L) was obtained. Acceptable repeatability (n = 3) with RSDs 2.37% while reproducibility (n = 9) with RSD 5.15% were obtained for Cu(II) ions using the developed MSPE method. Finally, the proposed method was successfully applied for the determination of Cu(II) ion in tap water sample with relative recovery of 78.9% and 4.72% RSD. However, the proposed method was found to be less suitable for the determination of Cu(II) ion in river water sample with lower relative recovery (45.7% , 1.76% RSD) indicating that the method is sensitive to the matrix

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

Copper(ii)ion determination in water samples using magnetite-calcium alginate sorbent and flame atomic absorption spectrometry analysis

Conventional technique such as liquid-liquid extraction (LLE) is widely used in the analysis of Cu(II) ions from water samples. However, LLE is time consuming, tedious, and consume lots of high purity organic solvents. Solid phase extraction (SPE) is an interesting alternative to LLE but it is prone to channelling and is rather expensive. A greener technique such as magnetic solid phase extraction (MSPE) avoids the use of column cartridge and overcome channelling problem. MSPE using magnetite-calcium alginate (Fe3O4-CaAlg) as sorbent is proposed for the extraction of Cu(II) ion from tap and lake water samples and analysis performed using flame atomic absorption spectrometry (FAAS). Characterization of the synthesised sorbent was performed using Fourier transform infrared spectroscopy and scanning electron microscope. The optimum conditions for Fe3O4-CaAlg MSPE of Cu(II) were achieved at a sample solution of pH 6 with 100 mL sample volume and the existence of interfering ions (Na+, K+, Mg2+, and Cl-) was found not to affect the extraction efficiency of the sorbent for Cu( II) ion significantly at the concentrations tested. Other MSPE parameters used were 10 min extraction time, 50 mg sorbent, 10 mL of 0.1 M HNO3 as desorption solvent and 5 min desorption time (sonication assisted). The calibration graph was linear from 20 - 600 ppb with good coefficient of determination (R2 = 0.9998). The LOD (3SD/slope) and LOQ (10SD/slope) of Cu(II) using Fe3O4-CaAlg MSPE with FAAS were in 6.75 and 22.5 ppb, respectively. The LOD achieved with the Fe3O4-CaAlg MSPE with FAAS is applicable to the determination of Cu(II) in real water samples (tap water and UTM lake water). Good relative recoveries and precision were achieved with this proposed method. The Fe3O4-CaAlg has great potential as an alternative sorbent for Cu(II) determination from water samples using the greener MSPE method

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