Liquid-liquid microextraction of glyphosate, glufosinate and aminomethylphosphonic acid for the analysis of agricultural samples by liquid chromatography

A new technique for measurement of glufosinate (GLU), glyphosate (GLY) and its metabolite aminomethylphosphonic acid (AMPA) using liquid chromatography with tandem mass spectrometry with a triple quadrupole (LC-QqQ-MS/MS) is proposed for the analysis of vegetables, agricultural soil and irrigation water. An ion-pair liquid-liquid microextraction (IP-LLME) procedure using 9-fluorenylmethyl chloroformate as the derivatizing reagent, methyl isobutyl ketone as the extraction solvent and hexadecyltrimethylammonium bromide as the ion-pair reagent was performed for preconcentration purposes, because the herbicides are present at very low concentrations. Limits of quantification (LOQs) of 0.5 ng mL(-1), 2.5 mu g kg(-1) and 1.6 mu g kg(-1) were obtained for water, vegetables and soil, respectively. Repeatability and reproducibility were calculated using the relative standard deviation, and values ranged between 6 and 11%, depending on the analyte. Enrichment factors were 62, 60 and 85 for GLY, GLU and AMPA, respectively.