ABSTRACT
A sensitive and reliable method based on MEKC has been developed and validated for trace determination of neonicotinoid insecticides (thiamethoxam, acetamiprid, and imidacloprid) and the metabolite 6-chloronicotinic acid in water and soil matrices. Optimum separation of the neonicotinoid insecticides was obtained on a 58 cm long capillary (75 µm id) using as the running electrolyte 40 mM SDS, 5 mM borate (pH 10.4), and 5% (v/v) methanol at a temperature of 25°C, a voltage of 25 kV and with hydrodynamic injection (10 s). The analysis time was less than 7 min. Prior to MEKC determination, the samples were purified and enriched by carrying out extraction-preconcentration steps. For aqueous samples, off-line SPE with a sorptive material such as Strata-X (polymeric hydrophobic sorbent) and octadecylsilane (C18) was carried out to clean up and preconcentrate the insecticides. However, for soil samples, matrix solid-phase dispersion (MSPD) was applied with C18 used as the dispersant. Good linearity, accuracy, and precision were obtained and the detection limits were in the range between 0.01 and 0.07 µg mL⻹ for river water and 0.17 and 0.37 µg g⻹ for soil samples. Recovery levels reached greater than 92% for all of the assayed neonicotinoids in river water samples with Strata-X. In soil matrices, the best recoveries (63-99%) were obtained with MSPD.
Subject(s)
Chromatography, Micellar Electrokinetic Capillary/methods , Insecticides/analysis , Soil Pollutants/analysis , Solid Phase Extraction/methods , Water Pollutants, Chemical/analysis , Imidazoles/analysis , Imidazoles/chemistry , Imidazoles/isolation & purification , Insecticides/chemistry , Insecticides/isolation & purification , Limit of Detection , Linear Models , Neonicotinoids , Nicotinic Acids/analysis , Nicotinic Acids/chemistry , Nicotinic Acids/isolation & purification , Nitro Compounds/analysis , Nitro Compounds/chemistry , Nitro Compounds/isolation & purification , Oxazines/analysis , Oxazines/chemistry , Oxazines/isolation & purification , Pyridines/analysis , Pyridines/chemistry , Pyridines/isolation & purification , Reproducibility of Results , Soil Pollutants/chemistry , Soil Pollutants/isolation & purification , Thiamethoxam , Thiazoles/analysis , Thiazoles/chemistry , Thiazoles/isolation & purification , Water Pollutants, Chemical/chemistry , Water Pollutants, Chemical/isolation & purificationABSTRACT
The purpose of this study was to determine the residues of seven pesticides organophosphorus (methamidophos, diazinon, chlorpyriphos, parathion-methyl, dimethoate, malathion and tetrachlorvinphos), in some vegetables like: potato, lettuce, tomato, onion, red pepper and green onion cultivated in José María Vargas County in Táchira State, Venezuela. The research permitted to detect that 48.0% of the samples were contaminated with some of the pesticides studied. Methamidophos was founded in the vegetables in the rank of 6.3%-65.5%. The results show that 16.7% of the samples tested have residues higher than the maximum limits permitted.