Electrospray ionization rapid screening (ESI-RS) sans LC column: A sensitive method for detection and quantification of chemicals in animal tissues and urine

Authors: CHAKRABARTY, SHUBHASHIS - Orise Fellow; Shelver, Weilin; Smith, David

Submitted to: Rapid Communications in Mass Spectrometry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2020
Publication Date: 7/6/2020
Citation: Chakrabarty, S., Shelver, W.L., Smith, D.J. 2020. Electrospray ionization rapid screening (ESI-RS) sans LC column: A sensitive method for detection and quantification of chemicals in animal tissues and urine. Rapid Communications in Mass Spectrometry. 34:8876. https://doi.org/10.1002/rcm.8876.
DOI: https://doi.org/10.1002/rcm.8876

Interpretive Summary: Liquid chromatography-mass spectrometry (LCMS) is a very powerful analytical tool that may be used to identify and quantify trace level chemicals in ‘difficult’ matrices such as blood, urine, and tissues. For a typical LCMS analysis, samples are purified, then introduced into a LCMS. Analysis of a single sample using LCMS can take several hours because of the requirement for extensive sample preparation and LC based separation prior to MS analysis. In this study, we have simplified sample clean-up considerably and have eliminated the chromatographic step prior to sample analysis. Consequently, the total analysis time was reduced from several hours to few minutes for screening a typical sample set of urine or tissues for nine veterinary drugs incurred into cattle, sheep, or swine urine or tissues. The technique was very sensitive, repeatable and capable of quantitative analysis in par with LCMS. Overall this technique could reduce the overall resources needed to screen and quantify chemical analytes in animal tissues.

Technical Abstract: Rationale: Electrospray ionization mass spectrometry (ESI-MS) in conjunction with liquid chromatography (LC) can provide accurate quantitative data, but it is not typically used for rapid screening (RS) of analytes incurred into complex matrices. This study was designed to determine the usefulness of ESI for the rapid detection and quantitation of 9 veterinary drugs from complex biological matrices under near real-time conditions. Methods: Nine veterinary drugs or metabolites including clenbuterol, erythromycin, flunixin, 5-hydroxyflunixin, meloxicam, ractopamine, salbutamol, tylosin, and zilpaterol present in cow urine, sheep urine, sheep tissues (kidney, muscle, liver and lung) or pig kidney were simultaneously analyzed. A simple sample clean-up procedure, which included dilution with 10% sodium carbonate followed by extraction with ethyl acetate was used. For tissues, an additional pre-extraction with hexane was performed to remove fat prior to MS analysis. Samples were introduced into the MS through the LC autosampler, but no chromatographic separation was employed. A Sciex 5600+ MS consisting of a dual-spray source, inter-faced with a Shimadzu Nexera LC was used. Samples were analyzed in positive ion mode. Results: Sample extraction times were typically 10 – 30 min or less and instrumental analysis time was 1 min per sample. Regression coefficients of matrix-matched standard curves across all compounds ranged from 0.9701 – 0.9999 in urine (cow and sheep) and tissues (sheep kidney, liver, lung, muscle and pig kidney). Limits of detection ranged from 0.11 to 2.03 ng/mL across analyte in urine and 0.11 to 8.00 ng/g across tissues. Correlations between ESI-RS and LC/MS/MS results were 0.956 to 0.998 for incurred residues of flunixin in cow urine, incurred residues of ractopamine in pig kidney, and incurred residues of zilpaterol in sheep urine. Conclusions: ESI-RS provided rapid, sensitive, and accurate analyses of nine veterinary drugs from complex matrices with very little sample preparation and produced quantitative data akin to LC/MS/MS.