Molecular level investigation of the role of peptide interactions in the glyphosate analytics

The detection of the herbicide glyphosate (GLP) in environmental samples is most often conducted after derivatizing the target molecule with the chromophore 9-fluorenylmethyloxycarbonyl chloride (FMOC-Cl). However, this method is sensitive to all primary and secondary amines, which can occur in the sample matrix as well. In order to quantify the interference of primary and secondary amines on GLP detection, we have used the oligo peptide pentaglycine (PG) as an example. PG has been added to the derivatization solution of GLP at different constant concentration levels and UV extinction coefficients have been determined. Data analysis supported by quantum chemical modeling of the GLP–PG, FMOC–GLP, and FMOC–PG complexation reactions facilitated the identification of two interfering impacts of PG on GLP derivatization: (i) increase of the signal due to its reaction with FMOC-Cl leading to an overestimation of GLP concentration and (ii) decrease of GLP recovery due to complex formation and therefore inhibition of GLP derivatization, which leads to an underestimation.