Separation of Sulfonylurea Herbicides and Determination of Bensulfuron-methyl Residues in Tapwater by HPTLC

JPC – Journal of Planar Chromatography – Modern TLC - In this work we have studied the separation of a mixture of the sulfonylurea herbicides (metsulfuron-methyl, chlorsulfuron,...     

Separation of Fenoxaprop-p-ethyl Biodegradation Products by HPTLC

JPC – Journal of Planar Chromatography – Modern TLC -     

Development of methods for determination of the residues of 15 pesticides in medicinal herbs Isatis indigotica Fort. by capillary gas chromatography with electron capture or flame photometric detection

Two multiresidue methods were developed for the determination of 15 pesticides (organochlorines, organphosphorus compounds, pyrethroids, and fungicides) in medicinal herbs Isatis indigotica Fort. and its formulations. The analytical procedure is based on ultrasonic assisted extraction and liquid-liquid extraction (LLE). After solvents were added, the raw material or granule sample was sonicated in an ultrasonic water bath and then centrifuged, filtered, and cleaned up by LLE. The infusion sample was extracted with petroleum ether by LLE. The pesticide residues were determined by capillary gas chromatography with electron-capture or flame photometric detection. Recoveries with the method at concentrations between 0.4 microg/kg and 10 mg/kg ranged from 70.2 to 119.5% for raw material, 73.2 to 105.1% for granule formulation, and 72.8 to 113.3% for infusion formulation. The relative standard deviation values were <20% for all of the pesticides studied. The pesticide detection limits were within the ranges 0.3-0.5 microg/L for endosulfan, 3-7.5 microg/L for pyrethroids, 0.7-32.5 microg/L for organophosphorus pesticides, and 0.1-0.6 microg/L for the other pesticides. The proposed methods are simple and rapid and provide simultaneous determination of pesticide residues in Isatis indigotica Fort. with acceptable recoveries and repeatability and an adequate limit of determination.     

Matrix solid-phase dispersion microextraction and determination of pesticide residues in medicinal herbs by gas chromatography with a nitrogen-phosphorus detector

A gas chromatography method for the determination of residues of 6 pesticides in Isatis indigotica Fort and Paeonia lactiflora Pall is described. Optimizations of different parameters were performed. The method used 0.5 g herb sample, silica gel as the matrix solid-phase dispersion sorbent, and acetone as the eluting solvent. Recoveries at spiked concentrations between 0.1 and 5 mg/kg were between 80.63 and 110.12%, with relative standard deviations ranging from 0.43 to 17.67%. The limits of quantitation were 0.01 mg/kg for metalaxyl, triadimefon, and paclobutrazol and 0.05 mg/kg for vinclozolin, tebuconazole, and fenarimol. The method may be useful as a screening protocol for the determination of these pesticides in medicinal herb samples.     

Self‐acidity induced effervescence and manual shaking‐assisted microextraction of neonicotinoid insecticides in orange juice

A novel dispersive liquid‐liquid microextraction that combines self‐induced acid‐base effervescent reaction and manual shaking, coupled with ultra high performance liquid chromatography with tandem mass spectrometry was developed for simultaneous determination of ten neonicotinoid insecticides and metabolites in orange juice. An innovative aspect of this method was the utilization of the acidity of the juice for a self‐reaction between acidic components contained in the juice sample and added sodium carbonate which generated carbon dioxide bubbles in situ, accelerating the analytes transfer to the extractant of 1‐undecanol. The total acid content of juice sample was measured to produce the maximum amount of bubbles with minimum usage of carbonate. Manual shaking was subsequently adopted and was proven to enhance the extraction efficiency. The factors affecting the performance, including the type and the amount of the carbon dioxide source and extractant, and ionic strength were optimized. Compared with conventional methods, this approach exhibited low limits of detection (0.001–0.1 µg/L), good recoveries (86.2–103.6%), high enrichment factors (25–50), and negligible matrix effects (?12.3–13.7%). The proposed method was demonstrated to provide a rapid, practical, and environmentally friendly procedure due to no acid reagent, toxic solvent, or external energy requirement, giving rise to potential application on other high acid‐content matrices.     

HPTLC Analysis of Octachlorodipropyl Ether in Insecticide Formulations

JPC – Journal of Planar Chromatography – Modern TLC - A simple, rapid, and sensitive high-performance thin-layer chromatographic method for analysis of octachlorodipropyl ether (OCDPE)...     

Degradation of amisulbrom and its metabolite IT-4 in cucumber under field conditions and processing

The study of the pesticide degradation and residue change is a global challenge during open field growing and processing of agricultural products. In this study, the degradation of a new fungicide, amisulbrom and its metabolite IT-4 in cucumber during field growing, home processing and storage was assessed. A combination method of modified QuEChERS and high performance liquid chromatography-tandem mass spectrometry with average recoveries of 86.3–107.1% and relative standard deviations of 2.9–7.0% was proposed to measure the concentrations of the two compounds in cucumber samples. The half-lives of amisulbrom under field condition were 4.5–5.8 days and the terminal residues ranged from 0.010 mg/kg to 0.11 mg/kg. Results from processing studies showed that gradual reduction of amisulbrom with 5.5–50.9% was presented with the increased operation time and temperature of washing or cooking. There was an obvious loss of 7.3–14.5% for amisulbrom from cucumber when stored at 4°C in dark for 120 h, and 5.8–37.7% reduction of amisulbrom stored at 25°C, respectively, whereas no significant loss of amisulbrom was observed in cucumber samples stored at ?20°C. The degradation of reduced amisulbrom residues to IT-4 was only found in cucumber samples during cooking with the concentrations of 0.0011–0.018 mg/kg. All of the processing factors were below 1 indicating these processing procedures could eliminate amisulbrom levels. This work is useful for evaluating degradation of amisulbrom and IT-4 in raw and processed cucumber, and also providing guidance to develop an effective approach for removing pesticide residues from commodities.     

Factors Affecting the Separation of Phthalate Esters,and their Analysis,by HPTLC

JPC – Journal of Planar Chromatography – Modern TLC - The phthalate esters (PAE) are ubiquitous in the environment because of the widespread use of plastic products. Reports of their...     

High-Performance Thin-Layer Chromatographic Determination of Carbamate Residues in Vegetables

JPC – Journal of Planar Chromatography – Modern TLC - A high-performance thin-layer chromatographic method has been developed for determination of four carbamate residues in vegetables....     

Development of a polyurethane-coated thin film solid phase microextraction device for multi-residue monitoring of pesticides in fruit and tea beverages

A novel solid-phase microextraction device coated with an efficient and cheap thin film of polyurethane was developed for trace determination of 13 widely used pesticides in fruit and tea beverages. A round-shaped polyurethane film covering the bottom of a glass vial was fabricated as the sorbent to exhibit a superior capacity for preconcentrating target compounds and reducing matrix interferences. After optimization of the key parameters including the film type, extraction time, solution pH, ionic strength, desorption solvent, and conditions, this device allowed an efficient adsorption-desorption cycle for the pesticides accomplished in one vial. Coupled with gas chromatography-electron capture detection, the polyurethane-coated thin film microextraction method was successfully established and applied for the analysis of real fruit and tea drinks, showing low limits of detection (0.001–0.015 μg/L), wide linear ranges (1.0–500.0 μg/L, r² > 0.9931), good relative recoveries (77.2%–106.3%) and negligible matrix effects (86.1%–107.5%) for the target pesticides. The proposed approach revealed strong potential of extending its application by flexibly modifying the type or size of the coating film. This study provides insights into the enrichment of contaminants from complex samples using inexpensive and reusable microextraction devices that can limit the environmental and health impact of the sample preparation protocol.