Analytical Methodology for Trace Determination of Propoxur and Fenitrothion Pesticide Residues by Decanoic Acid Modified Magnetic Nanoparticles.

A sensitive, rapid, reliable, and easily applicable method based on magnetic solid phase extraction (MSPE) combined with HPLC-PDA was developed for monitoring propoxur (PRO) and fenitrothion (FEN) pesticides in environmental water samples. The effect of major experimental variables on the extraction efficiency of both the pesticides was investigated and optimized systematically. For this purpose, a new magnetic material containing decanoic acid on the surface of particles was synthesized and characterized by XRD, FT-IR, SEM, EDX, and TGA analysis in detail. The simultaneous determination of pesticide molecules was carried out by using a Luna Omega C18 column, isocratic elution of acetonitrile (ACN): Water (70:30 v/v) with a flow rate of 1.2 mL min-1. After MSPE, the linear range for pesticide molecules (r2 > 0.9982) was obtained in the range of 5-800 and 10-800 ng mL-1, respectively. The limit of detections (LOD) are 1.43 and 4.71 ng mL-1 for PRO and FEN, respectively while RSDs % are below 3.5%. The applicability of the proposed method in four different environmental samples were also investigated using a standard addition-recovery procedure. Average recoveries at two spiking levels were over the range of 91.3-102.5% with RSD < 5.0% (n = 3). The obtained results show that decanoic acid grafted magnetic particles in MSPE combined with HPLC-PDA is a fast and simple method for the determination of PRO and FEN in environmental water samples.

N-methylcarbamate pesticides and their phenolic degradation products: hydrolytic decay, sequestration and metal complexation studies.

We report on the rates of decomposition of a group of N-methylcarbamate (NMC) pesticides (carbaryl, carbofuran and propoxur) under pre-determined tropical field conditions. Rates of decomposition for three NMCs were determined at pH 7.08 and T = 20 °C and pH 7.70 and T = 33 °C respectively, as follows: carbaryl (78 days and 69 days); carbofuran (143 days and 83 days) and propoxur (116 days and 79 days). Investigation on methods for removal of NMCs and their phenolic decomposition products shows that activated charcoal outperforms zeolite, alumina, diatomaceous earth, cellulose and montmorillonite clay in the removal of both NMCs and phenols from aqueous solution. Furthermore, metal complexation studies on the NMCs and phenols showed that Fe (III) forms a complex with isopropoxyphenol (IPP) within which the Fe:IPP ratio is 1:3, indicative of the formation of a metal chelate complex with the formula Fe(IPP)3.

Application of an optimized dispersive nanomaterial ultrasound-assisted microextraction method for preconcentration of carbofuran and propoxur and their determination by high-performance liquid chromatography with UV detection.

An extraction method based on dispersive nanomaterial ultrasound-assisted microextraction was used for the preconcentration of carbofuran and propoxur insecticides in water samples prior to high-performance liquid chromatography with UV detection. ZnS:Ni nanoparticles were synthesized based on the reaction of the mixture of zinc acetate and nickel acetate with thioacetamide in aqueous media and then loaded on activated carbon (ZnS:Ni-AC). Different methods were used for recognizing the properties of ZnS:Ni-AC and then this nanomaterial was used for extraction of carbamate insecticide as new adsorbent. The influence of variables on the extraction method (such as amount of adsorbent (mg: NiZnS-AC), pH and ionic strength of sample solution, vortex and ultrasonic time (min), ultrasound temperature and desorption volume (mL) was investigated by a screening 2(7-4) Plackett-Burman design. Then the significant variables were optimized by using a central composite design combined with a desirability function. At optimum conditions, this method had linear response >0.0060-10 µg/mL with detection limit 0.0015 µg/mL and relative standard deviations <5.0% (n = 3).