Rapid Analysis of Glyphosate, Glufosinate and N-Acetyl Glufosinate in Sesame by Liquid Chromatography-Tandem Mass Spectrometry

The European legislation sets the maximum residue levels for glyphosate in sesame seeds at 0.1 mg/kg (EU Regulation n. 293/2013) and for glufosinate and N-Acetyl-glufosinate expressed as glufosinate at 0.03 mg/kg (EU Regulation n. 2016/1002). The present work describes a rapid methodology to determine glyphosate, glufosinate and its metabolite and N-Acetyl-glufosinate in sesame seeds by LC/MS/MS. The method was studied in the framework of EU proficiency tests on sesame seeds. The analytical method was developed using methanol acidified with formic acid (1%, v/v) extraction with an isotope internal standard, followed by LC/MS/MS detection. The recoveries were performed in the range of 0.05–0.5 mg/kg for glyphosate and 0.02–0.2 mg/kg for glufosinate and N-Acetyl-glufosinate. All the recovery values were between 70 and 114%, which is the acceptable interval according to SANTE/11312/2021; the relative standard deviation (%RSD) values met the requirement of <20%. Linearity for each substance in solvent and matrix was studied, and the response was linear with R2 > 0.999. We considered precision, matrix effect, LOD and LOQ in the validation. All the parameters were in agreement with the acceptability criteria of the document SANTE/11312/2021. The method was considered suitable for the determination of the studied substances on sesame seeds.