A Simplified HPLC Procedure for the Determination of Glyphosate in Soybeans Employing Postcolumn Fluorescence Labeling

摘要

An analytical procedure for residues of the herbicide glyphosate [N-phosphonomethylglycine] in soybeans is described. Extraction of soybeans is performed with 20 mmol/L borate buffer solution. Cleanup is achieved by an ortho-phthalaldehyde-mercaptoethanol (OPA-MERC) reaction followed by application to a dual mini-cartridge column (graphite and octadecyl-bonded silica gel) system, and determination is performed by ion-pair mode high-performance liquid chromatogra- phy employing postcolumn fluorescence labeling of the appropriate primary amine with OPA- MERC. Conversion of glyphosate to a primary amine (presumably ammonia and/or glycine) is achieved postcolumn by oxidation with sodium hypochlorite. Residues can easily be measured at the 0.05 ppm level with recoveries greater than 74/100. The efficiency of the purification and the simplicity of the procedure allow for high sample throughput compared to existing procedures.