Determination of glyphosate Residue in Rice using High Performance Liquid Chromatography coupled with Diode Array Detector

Glyphosate is a post-emergence herbicide utilized broadly after planting and before harvesting to control weeds of different types of crops in Iran and globally. Low molecular weight, amphoteric character, high polarity, and insolubility in organic solvents preclude the use of these solvents for easy extraction of glyphosate from the sample matrix and, on the other hand, the absence of chromophore or fluorophore groups in these compounds limits the ability to use conventional measurement systems with common detectors such as fluorescence or ultraviolet. This study presents a highly sensitive pre-column derivatization by phenyl isothiocyanate and HPLC method coupled with universal diode array detector for determination of glyphosate residue in rice. After extraction of glyphosate and derivatization with phenyl isothiocyanate, separation of derivatized thiophenyl carbamoyl glyphosate was optimized on reversed phase stationary phase C18 by applying a gradient elution of a mobile phase containing 70% water (0.1% Formic Acid) and 30% ACN in 254 nm and flow rate of 1 ml/min. Investigating the detector response whitch is in the range of 0.05-5 μg/mL and correlation coefficient whitch is  equal to 0.9869 proved as an ideal linearity for the proposed method.  The LOQ was determined as 0.05 µg/ml which is in the range of MRLs for various crops.  The proposed method provides a simple derivation process that is not matrix-dependent and is applicable to other matrices, too.