Liquid chromatography with triple quadrupole mass spectrometry (LC-MS/MS) is considered the gold standard for screening and quantitation of pesticides in various food matrices. However, high-resolution accurate mass (HRAM) LC-MS/MS is growing in popularity, in part because it allows for retrospective analysis on additional analytes of interest and screening for unknown or unexpected pesticides is possible. This is because all ions can be collected and fragmented whereas triple quadrupole mass spectrometry requires a target list of compounds. Furthermore, method development time is often shorter by orders of magnitude with HRAM LC-MS/MS, enabling the screening of a large number of compounds compared to triple quadrupole mass spectrometers.
Stringent regulations on allowable pesticide residues in various foods (link to U.S. EPA site) have fueled the need for very sensitive analytical methods for the quantitation of pesticide residues. With HRAM LC-MS/MS, this often means that a full-scan data-dependent MS/MS (FS-ddMS2) approach is taken. I recently read an application on this topic, Application Note 617, Quantitative and Qualitative Confirmation of Pesticides in Beet Extract Using a Hybrid Quadrupole-Orbitrap Mass Spectrometer, (downloadable pdf), where a generic chromatographic method and a FS-ddMS2 mass spectrometric method with library searching and fragment confirmation was developed to screen, quantitate, and confirm pesticides in beets. The high resolution and mass accuracy enabled quantification of the compounds over a wide dynamic range (0.05–200 ng/mL) with linear fit, correlation better than 0.99, and %RSD below 15% for 29 pesticides. Limits of quantitation (LOQ) were all well below strict European Union regulation limits for pesticides (link to EU pesticide database page).
Another approach can be taken for multi-residue analysis. This method is called variable data independent analysis (vDIA). This method can produce selectivity and sensitivity comparable to data dependent MS2 measurements while also generating a complete record of full scan and fragmentation data for each sample. This technique was used to detect multi-class veterinary drugs in Application Note 64249, Quick and Sensitive Analysis of Multiclass Veterinary Drug Residues in Meat, Plasma, and Milk on a Q Exactive Focus LC-MS System, (downloadable PDF). It features the use of one of our hybrid, quadruple mass spectrometers (Thermo Scientific Q ExactiveM Focus MS).
Do you already use or are you considering HRAM mass spectrometry for residue analysis? Why or Why not? I’d love to hear your comments.
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Jennifer Massi is a former genomics scientist who contributed to the sequencing of the human genome through the Human Genome Project and now works on connecting laboratories with food safety testing workflows. Her journey from science research to marketing has spanned developing marketing strategies for consumables for genomics and proteomics, developing educational programs for sample preparation, chromatography, and mass spectrometry, and developing relationships with regulatory agencies and key opinion leaders. Jennifer is a market development manager for the food and beverage markets in the chromatography and mass spectrometry division at Thermo Fisher Scientific.Jennifer completed her B.S. in Biochemistry & Molecular Biology, Honors at UC Santa Cruz and received an M.B.A., Honors from Saint Mary’s College of California.