Investigation of Nanoflow Liquid Chromatography High-Resolution MS (nanoLC-HRMS) for the Analysis of Veterinary Drug Residues in Fish and Shrimp.

Abstract

Background: A wide-scope screening method for veterinary drugs and other contaminants in aquaculture products using liquid chromatography (LC) high-resolution mass spectrometry (HRMS) was developed previously. Using nanoflow LC could significantly increase the sensitivity of this method.

Objective: The objective of this study was to evaluate the potential advantages of nanoLC-HRMS as a screening method for veterinary drug residues in seafood.

Method: Preliminary nanoLC-HRMS investigations included comparison of nanospray source options and evaluation of nanoLC columns, mobile phases, and gradient programs. The optimized method was tested using tissue fortified with a mixture of veterinary drugs and pesticides.

Results: Using nanoLC columns with integrated emitters provided stable electrospray ionization resulting in chromatographic peaks with reproducible retention times and peak areas; diagnostic MS2 product ions were also detected. Coupling nanoLC to HRMS increased the area counts for many target analytes by 2-3 orders of magnitude. Less concentrated extracts could be analyzed with simplified preparation and minimal ion suppression. Replicate extractions of fortified fish generally gave relative standard deviations under 20%. Most analytes could be identified at concentrations 10-fold less than the target testing levels with detection limits in final extracts corresponding to 0.01-0.02 picograms injected on-column. Acceptable linearity was observed using solvent, matrix-matched, and matrix-extracted standard curves. Disadvantages of nanoLC-HRMS included the inability to detect some classes of compounds, i.e., dyes and avermectins, and longer wait times between chromatographic analyses.

Conclusions: Significant increases in sensitivity were observed with nanoLC-HRMS. Analytical results from fortified fish and shrimp showed the method to be suitable for qualitative screening, analyte identification, and quantification with minimal matrix effects.

Highlights: A wide variety of veterinary drugs and pesticides could be reproducibly detected and identified in fortified fish and shrimp using nanoLC-HRMS with minimal cleanup. Residues from imported laboratory samples were also detected and identified using this method.