Investigation of Nanoflow Liquid Chromatography High-Resolution MS (nanoLC-HRMS) for the Analysis of Veterinary Drug...

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.

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

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.

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.

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.

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.