Cationic Polar Pesticides in Food and Beverage Matrices by IC-MS/MS

Recent developments in the analysis of anionic polar pesticides have led to an increase in testing and regulation in surface and drinking water as well as food and beverages samples. However, developments in the analysis of cationic polar pesticides have lagged their anionic counterparts, primarily because of the analytical challenges. Advances using the Quick Polar Pesticides (QuPPe) method combined with IC-MS/MS have successfully demonstrated the applicability for the analysis of anionic polar pesticides, particularly glyphosate. However, for cationic polar pesticides, previous work has demonstrated an inability to resolve the Diquat / Paraquat peak pair. This combined with their similar m/z ratios makes it difficult to use IC-MS/MS methods for this application. Cationic polar pesticides such as chlormequat, diquat, mepiquat and paraquat may occur as residues in food, but may not be included in pesticide monitoring programs due to the difficulty in the determination of these target analytes using generic multi-residue methods. To address this analytical challenge, we have recently developed the Thermo Scientific™ Dionex™ IonPac™ CS21-Fast-4µm column to provide satisfactory separation of the four key quaternary polar pesticides: chlormequat, diquat, mepiquat and paraquat. This work demonstrates a new IC-MS/MS method to identify and quantify low concentrations of quaternary amine cationic polar pesticides in foods and beverages using a Thermo Scientific™ Dionex™ ICS-6000 Ion Chromatography System and IonPac CS21-Fast-4µm column coupled with a Thermo Scientific™ TSQ Altis™ triple quadrupole electrospray mass spectrometer. In this paper, we will discuss the IC-MS/MS method and demonstrate its applicability for determination of chlormequat, diquat, mepiquat and paraquat in the extracts of food and beverage samples prepared using the QuPPe sample preparation technique.