Comparison of different fast gas chromatography - mass spectrometry techniques (Cold EI, MS/MS, and HRMS) for the analysis of pyrethroid insecticide residues in food

Authors: MICHLIG, NICOLAS - Oak Ridge Institute For Science And Education (ORISE); AMIRAV, AVIV - Tel Aviv University; NEUMARK, BENNY - Tel Aviv University; Lehotay, Steven

Submitted to: Analytical Methods
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/22/2024
Publication Date: 7/23/2024
Citation: Michlig, N., Amirav, A., Neumark, B., Lehotay, S.J. 2024. Comparison of different fast gas chromatography - mass spectrometry techniques (Cold EI, MS/MS, and HRMS) for the analysis of pyrethroid insecticide residues in food. Analytical Methods. 16,5599–5618. https://doi.org/10.1039/d4ay00858h.
DOI: https://doi.org/10.1039/d4ay00858h

Interpretive Summary: Pesticide residues in food need to be monitored in the U.S. and worldwide to ensure compliance with laws as well as for food safety and environmental protection. Pyrethroid insecticides are one of the most difficult classes of pesticides to monitor in multiclass, multiresidue methods. In this study, a comparison was made using fast gas chromatography with three different mass spectrometric analyzers for the detection of 15 pyrethroids in a barley matrix. All three techniques had advantages and disadvantages with respect to each other depending on the specific analyte, but a clear conclusion was that the two targeted approaches achieved lower detection limits than the nontargeted method. This research demonstrates that further improvement is needed in nontargeted analytical technology if it to replace the current targeted practices.

Technical Abstract: In the multiclass, multiresidue analysis of pesticides in food and environmental samples, pyrethroid insecticides are generally more difficult than other types of analytes. They do not ionize well in electrospray ionization, which leads to their higher detection limits in common methods using liquid chromatography – mass spectrometry (LC-MS). They are typically more suitable for analysis by gas chromatography (GC)-MS, but selectivity is often insufficient because the molecular ion is rarely present when using standard electron ionization (EI). Many pyrethroids tend to have the same fragments ions in MS or high-resolution (HR)MS, and similar ion transitions in tandem MS/MS, leading to difficulties in distinguishing different pyrethroids from each other and chemical interferences in complex matrices. In this study, different forms of fast GC coupled with different types of MS detectors were compared for the analysis of up to 15 pyrethroids in barley extracts as a test case to assess which approach was most advantageous. The three studied MS techniques consisted of: Cold EI using supersonic molecular beams in selected ion monitoring (SIM) mode with a single quadrupole instrument; triple quadrupole MS/MS; and HRMS using an orbital ion trap (orbitrap). Higher flow rate was used in Cold EI, and low pressure (LP) GC was employed in the MS/MS and orbitrap methods, to speed the GC analyses (<10 min chromatograms in all cases). Each technique had some advantages over the others depending on specific pyrethroid analytes in the matrix. Nontargeted LPGC-orbitrap typically yielded the most selectivity, but it rarely achieved the needed detectability to quantidentify the residues at 10 ng/g. Cold EI-SIM and LPGC-MS/MS usually met the needed detection limits and generally achieved similar capabilities for the targeted pyrethroids.