Non-targeted high resolution screening of tobacco for potential contaminants (pesticides and chemical toxins) using UPLC/QTOF-MS
In this study a UPLC coupled to high resolution mass spectrometry (QTOF-MS) was used to increase the scope of analysis for multi-residue pesticides and other chemical contaminants in tobacco. Analytical methods for high throughput contaminant screening require non-targeted acquisition under generic conditions followed by targeted processing against a scientific library typically containing retention time and accurate mass data for both precursor and fragment ions for hundreds of chemical contaminants. The key to implementation of UPLC-HRMS for routine screening of tobacco to accurately detect residues at the required regulated concentrations was evaluated.
Reference and commercially available tobacco samples with incurred residues and varying complexity and moisture content were included in the study. The sample extraction was achieved using a generic QuEChERS method. Representative tobacco samples were pre- and post- spiked with a mixture of LC amenable pesticides at 0.01 and 0.05 mg Kg-1. The experiments were performed using UPLC/QTOF-MS, run in electrospray positive (ESI+) mode and the data was acquired using MSE, a data independent acquisition mode which simultaneously collects both accurate mass precursor and fragment ion data.
After automated data processing, data review workflows were used to quickly review HRMS data in a consistent and accurate manner and to reduce false positives and eliminate false negatives for routine tobacco screening. The contaminant identifications were made on the basis of retention time, accurate mass precursor and fragment ions and isotopic pattern score matching with the entries in the scientific library. Analytical strategies to increase compound coverage and confidence in identification of potential contaminants from high throughput screening of tobacco will be discussed.