Hydrophilic-Interaction Liquid Chromatography (HILIC) with DAD and Mass Spectroscopic Detection for Direct Analysis of Glyphosate and Glufosinate Residues and for Product Quality Control

High-performance liquid chromatography with a hydrophilic-interaction liquid chromatographic (HILIC) column has been successfully used to retain and separate the polar phosphonic herbicides glyphosate and glufosinate. Online electrospray tandem ion-trap mass spectrometric and DAD detection were used. The effects on the separation of mobile phase acetonitrile content, buffer concentration, and flow rate, and of column temperature, were investigated. With UV-visible detection at 195 nm, LOQ were <850 mg kg(-1), showing the method is suitable for product quality control of these herbicides alone or in combination. Tandem mass spectrometric conditions were optimized for ion-trap detection. Quantification was by use of selected reaction monitoring transitions m/z 168 -> 150 in negative-ion mode for glyphosate and m/z 182 -> 136 in positive-ion mode for glufosinate. Limits of detection (LOD; S/N > 3) were 0.20 and 0.16 ng for glyphosate and glufosinate, respectively, and the respective limits of quantification (LOQ; S/N = 10) were 0.02 and 0.05 mg kg(-1). Sample derivatization was not necessary to achieve low detection limits in residue analysis in this study. Recovery from watermelon, spinach, potato, tomato, radish-root, and water fortified with the herbicides ranged from 63.6 to 107.3% and relative standard deviations were <15.3%.