Determination of acidic herbicides in water samples by in situ derivatization, single drop microextraction and gas chromatography-mass spectrometry

Abstract

Um método para a determinação de quantidades traços de herbicidas ácidos em amostras de água foi desenvolvido. O procedimento analítico envolve derivatização in situ dos analitos para seus ésteres metílicos com sulfato de dimetilo, amostragem usando microextração com única gota (SDME) e cromatografia gasosa-espectrometria de massa (GC-MS). Os efeitos do pH, força iônica, tempo de extração, solvente de extração assim como condições de derivatização foram estudados. Ésteres metílicos foram extraídos com 2 µL de n-heptano. A resposta foi linearmente dependente da concentração na faixa de 0,05-10,0 ng mL . A análise por derivatização-SDME/GC-MS rendeu boa precisão (RSD entre 7,0 e 15,2%). O método foi validado pela análise de amostras enriquecidas.A method for the determination of trace amounts of acidic herbicides in water samples was developed. The analytical procedure involves in situ derivatization of analytes to their methyl esters with dimethyl sulfate, sampling using single drop microextraction (SDME) and gas chromatography-mass spectrometry (GC-MS). The effects of pH, ionic strength, extraction time, solvent of extraction as well as derivatization conditions were studied. Methyl esters were extracted using 2 µL of n-heptane. The response was linearly dependent on the concentration in the range 0.05-10.0 ng mL -1 . Limits of detection were achieved at the level of 1.8-3.0 ng L -1 . Derivatization-SDME/GC-MS analysis yielded good precision (RSD between 7.0 and 15.2%). The method was validated by analysis of spiked matrix samples.

A sensitive and efficient method for the determination of 8 chlorophenoxy acid herbicides in crops by dispersive liquid–liquid microextraction and HPLC with fluorescence detection and identification by MS

“…Many methods, such as capillary electrophoresis (CE), 7,8 gas chromatography (GC), [9][10][11][12] and high-performance liquid chromatography (HPLC) [13][14][15][16][17][18] have been applied to detect the residues of CPAHs. Among these techniques, HPLC is considered as the most suitable and common method for the separation and quantication of CPAHs, because HPLC not only possesses better reproducibility than CE but also can avoid the asymmetry peak by GC due to the low volatility and polarity of CPAHs.…”