Applying Micro Flow LC and High Speed Data Acquisition MS/MS to the Analysis of Pesticides Residues in Complex Spice Matrix

There are several notable challenges in food control; a large chemical space, the need to reduce cost, faster results with high data quality, emerging new matrices (as a consequence of global trade) and problematic matrices. Spices are known as "difficult" matrices, since they contain a bulk of extractable compounds (essential oils, pigments, etc.) causing significant problems during LC-MS/MS analysis including loss of chromatographic performance, matrix effects and isobaric interference. An extensive clean-up usually limits the scope of target analytes, thus, it is not practical when faced with multi-residue analysis. Given the high likelihood of residues in spices, care must be taken to ensure identification criteria are met and to avoid the reporting of false positives due to isobaric interference.
To meet these challenges we present the use of triggered MS/MS product ion scanning and library matching for residue confirmation, as opposed to the conventional use of SRM ion ratios. Searching the complete molecular fingerprint against a mass spectral library reduced the number of false positives in comparison to MRM ratio calculation, and thus resulting in higher confidence in identification. The use of product ion scanning in the detection of pesticide residues lowers the possibility of reporting false positives, particularly in complex matrices such as spices. Due to the complexity of the matrix, analyte suppression is common in spice matrix. Consequently, to minimise suppression, microflow LC was utilised. Micro flow LC can provide increased S/N in comparison to higher flow LC (typically 500 μL/min), therefore proportionally lower injection volumes may be used and thereby decreasing matrix effects.