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

Sol-gel hybrid cyanopropyltriethoxysilane-methyltrimethoxysilane as adsorbent for dispersive-micro solid phase extraction of selected organophosphorus pesticides in water samples

Commercial solid phase extraction (SPE) sorbents normally used for organophosphorus pesticides (OPPS) analysis is C18. However, it show low retention for polar compounds and is rather expensive. The limitations are overcome through the development of a new sol-gel hybrid material, cyanopropyltriethoxysilane-methyltrimethoxysilane (CNPrTEOS-MTMOS). Sol-gel hybrid CNPrTEOS-MTMOS was successfully synthesized and applied as an adsorbent for dispersive-micro-SPE (D-μ-SPE) of three selected OPPs from several water samples. Extracted analytes were analyzed using gas chromatography-mass spectrometry. Under the optimum conditions (100 mg CNPrTEOS-MTMOS as adsorbent, 10 mL water samples, 7 min extraction time, 300 μL methanol as desorption solvent and 3 min desorption time), the method showed excellent detection limits (0.01-0.004 μg L−1 at S/N = 3) and linear range achieved were 0.01-10 μg L−1. The CNPrTEOS-MTMOS sorbent offers an alternative sorbent material for the extraction of OPPs of various polarity. The developed D-μ-SPE method was successfully applied for the simultaneous analysis of OPPs in several water samples and results were compared with published results. Sol-gel hybrid CNPrTEOS-MTMOS showed high potential as an alternative adsorbent for D-μ-SPE technique for OPPs

Poly(dimethylsiloxane)-poly(vinyl alcohol) coated solid phase microextraction fiber for chlorpyrifos analysis

Traditional liquid – liquid extraction of pesticides consumes large volumes of organic solvent which are hazardous to the operator and is not environment friendly. Solid phase microextraction (SPME) is a solvent less extraction method which is safer to the operator and is environmental friendly. A sol-gel hybrid fibre coating material, poly(dimethylsiloxane)-poly(vinyl alcohol) (PDMS-PVA) was synthesized and used in head space solid phase microextraction (HS-SPME) of chlorpyrifos. The thickness of the synthesised PDMS-PVA fiber coating was 13.5 μm and it is thermally stable up to 400 °C. The PDMS-PVA sol-gel hybrid fiber was also stable to two organic solvents tested, acetonitrile and dichloromethane (1 hour dipping) and showed no significant changes in extraction performance for chlorpyrifos. Extracted chlorpyrifos was analysed using gas chromatography electron capture detector (GC-ECD). Optimum SPME parameters affecting the PDMS-PVA HS-SPME performance namely extraction time (15 min), extraction temperature (50 °C), desorption time (5 min), desorption temperature (260 °C) and stirring rate (120 rpm) were used for extraction. It was found that HSSPME using PDMS-PVA sol-gel fiber gave significantly better extraction performance of chlorpyrifos compared to commercial 100 μm PDMS fiber. The PDMS-PVA fiber showed excellent operational performances such as temperature stability (up to 380 °C), coating lifetime (up to 170 times use) and organic solvent stability. The PDMS-PVA-HS-SPME method showed excellent recovery for chlorpyrifos from tomatoes (98.0 , 5.9 RSD) at 0.01 μg/g spiked level (5 times lower than maximum residue limit set by European Union)

Removal of nickel from aqueous solution using supported zeolite-Y hollow fiber membranes

This work describes the development of supported zeolite-Y membranes, prepared using the hydrothermal method, for the removal of nickel from an aqueous solution. Alumina hollow fibers prepared using the phase inversion and sintering technique were used as an inert support. The supported zeolite-Y membranes were characterized using the field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), and the water permeation and rejection test. The performance of the supported zeolite-Y membranes for heavy metal removal using batch adsorption and filtration test was studied using the atomic absorption spectroscopy (AAS). The adsorption study shows that the removal of nickel was pH-dependent but affected by the presence of α-alumina. The seeded zeolite-Y membrane gave the highest adsorption capacity which was 126.2 mg g−1. This enabled the membrane to remove 63% of nickel ions from the aqueous solution within 180 min of contact time. The adsorption mechanism of nickel onto the zeolite-Y membrane was best fitted to the Freundlich isotherm. The kinetic study concluded that the adsorption was best fitted to pseudo-second-order model with higher correlation coefficient (R2 = 0.9996). The filtration study proved that the zeolite-Y membrane enabled to reduce the concentration of heavy metal at parts per billion level

Composite zeolite hollow fiber membrane for the removal of nickel using forward osmosis

This work discusses the preparation, characterization, and feasibility test of composite zeolite hollow fiber membranes, with UV-curable resin as a secondary coating material, in removing Ni (II) using FO process. The preparation of the membrane started by depositing zeolite membrane onto alumina hollow fiber, followed by photopolymerization process once the outer layer was fully covered. Various characterization techniques were used on the composite membrane, namely field emission-scanning electron microscopy (FESEM), X-ray diffraction analysis, Fourier transform infrared (FTIR) spectroscopy, Brunauer–Emmett–Teller (BET) analysis, contact angle measurement, and performance tests using FO. The results show that the membranes enabled a reduction of reverse solute once incorporated with UV-curable resin. The lowest reverse solute flux obtained was 0.008 kg m-2 h-1, when pure water was flowed in the outer surface and 100,000 mg L-1 sodium chloride (NaCl) was used in the lumen. The UV-curable resin was unstable in the presence of Ni (II), which later formed complex ions. Adsorption of Ni (II) ions caused agglomeration of zeolite particles, causing membrane defects