Comparison of filter membranes in the analysis of 183 veterinary and other drugs by liquid chromatography-tandem mass spectrometry

Authors: MICHLIG, NICOLAS - Oak Ridge Institute For Science And Education (ORISE); Lehotay, Steven; Lightfield, Alan

Submitted to: Journal of Separation Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/16/2024
Publication Date: 2/1/2024
Citation: Michlig, N., Lehotay, S.J., Lightfield, A.R. 2024. Comparison of filter membranes in the analysis of 183 veterinary and other drugs by liquid chromatography-tandem mass spectrometry. Journal of Separation Science. 47:2300696. https://doi.org/10.1002/jssc.202300696.
DOI: https://doi.org/10.1002/jssc.202300696

Interpretive Summary: Membrane filtration of final extracts is one of the most common steps performed in analytical chemistry just prior to analysis, especially in chromatography. However, many analytical chemists take this step for granted and do not fully evaluate this step or consider alternatives. In this study, five different commercial types of membrane filters were evaluated in the analysis of 183 veterinary drugs in mixed bovine muscle, kidney, and liver extracts. All filter types partially retained several of the drug analytes, leading to reduced scope of analysis, and they were also found to introduce leachates into the filtered solutions that increased the chance of analytical interferences. This study demonstrated that filtration of final extracts should be carefully considered during method development, and ultracentrifugation may serve as a cost-effective alternative.

Technical Abstract: Filtration is one of the most common steps in sample preparation for chemical analysis, especially prior to chromatography. However, filter membrane materials can leach contaminants into the solution and/or retain some analytes in the filtered solutions depending on the chemical properties of each component. In multiclass, multiresidue analysis of veterinary (and human) drugs, it is challenging to find one type of filter membrane that does not retain at least some of the analytes in the final extracts prior to injection in ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). In this study, several different filter membranes were tested for use in UHPLC-MS/MS analysis of up to 183 diverse drugs in animal tissue extracts (bovine muscle, kidney, and liver). The effect of water content in acetonitrile solutions was also assessed. Membranes evaluated consisted of polytetrafluoroethylene (PTFE), polyvinylidene difluoride (PVDF), polyethersulfone (PES), nylon, and regenerated cellulose (RC). Drug classes represented among the analytes included ß-agonists, ß-lactams, anthelmintics, macrolides, tetracyclines, sulfonamides, tranquilizers, (fluoro)quinolones, anti-inflammatories, nitroimidazoles, coccidiostats, phenicols, and others. In general, more water in solutions led to more analyte retention on all membrane types. Although the presence of matrix helped reduce binding of analytes on surface active sites, all of the filter types partially retained at least some of the drugs in the final extracts. In testing by flow-injection (FI) analysis, all of the membrane filters were also observed to leach interfering components with the same ion transitions as some of the analytes. Ultimately, filtration was avoided altogether in the final sample preparation approach known as the QuEChERSER mega-method, and ultracentrifugation was chosen as an alternative.