Improving Chromatographic Performance of Underivatised Anionic Polar Pesticides in Food to Overcome Renowned Analytical Challenges

Monitoring for Contaminants in Foods & Beverages
Oral Presentation

Prepared by K. Rosnack1, B. Wuyts2, E. Ross2, S. Hird2, D. Shah1
1 - Waters Corporation, 34 Maple Street, Milford, MA, 01757, United States
2 - Waters Corporation, Stamford Avenue, Altrincham Road, Wilmslow, SK9 4AX, United Kingdom


Contact Information: [email protected]; 508-482-4639


ABSTRACT

Various multi-residue LC-MS/MS methods are available to analyze food for pesticide residues, some pesticides are not amenable to such generic methods because they are highly polar and/or ionic in nature and so are not extracted and/or show poor retention under the generic C18 conditions typically employed. The chromatographic analysis of glyphosate, its metabolites and similar compounds are challenging due to the lack of retention by reverse phase techniques. Common alternatives include derivatization and ion chromatography. However, due to time-consuming sample preparation, MS incompatible solvents and the need for specialized equipment and/or reagents, the underivatized LC-MS/MS approach is still preferred. Due to the physicochemical characteristics of these compounds, repeatable peak shape and robust methodologies can be challenging to run routinely.

A simple UPLC-MS/MS method will be presented for the direct analysis of highly polar pesticides, which provides analyte retention and excellent sensitivity, robustly, to exceed enforced MRLs. A panel of representative anionic polar pesticides, including aminomethylphosphonic acid (AMPA), glufosinate and glyphosate have been targeted in a selection of relevant foodstuffs prepared using a modified version of the Quick Polar Pesticides (QuPPe) extraction method. Chromatographic separation was achieved on a novel hydrophilic interaction liquid chromatography (HILIC) column, applying an ammonium formate mobile phase gradient.

Method performance was evaluated, in the absence of isotopically labelled internal standard, by assessing chromatographic repeatability, linearity, accuracy and sensitivity. Satisfactory linearity was found for all pesticides over a range of 5 to 200 g/Kg in food matrix (R > 0.995, residuals < 20%). The repeatability (%RSD) of the method was determined using spiked food matrix prepared in replicates (n=5). Incurred residues of phosphonic acid detected in some samples were quantified using standard addition calibration curves and identified in accordance with the SANTE guidelines 11813/2017.