Determination of chloramphenicol residues in rainbow trouts by gas chromatography–mass spectometry and liquid chromatography–tandem mass spectometry

Abstract

A methodology for the identification and quantification of chloramphenicol (CAP) residues was developed and validated. The method is based on gas chromatography–mass spectrometry (GC–MS) for screening, in electron impact (EI) mode, after a solid phase extraction (SPE) step using C18 columns, and data acquired in selective ion monitoring (SIM) mode with the following ions: m/z 225, m/z 208 and m/z 242. Confirmatory method consists on liquid chromatography–tandem mass spectrometry (LC–MS/MS), in ionspray-negative mode, after the same extraction and clean-up procedure. The m/z 321 was selected as a parent ion and m/z 152 and m/z 194 as daughter ions. The data were acquired in the negative multiple reaction monitoring (NMRM) mode, by monitoring the transitions 321 > 152 and 321 > 194. The method gave a decision limit (CCα) and a detection capability (CCβ) of 0.267 and 0.454 μg kg⁻¹, respectively. The described methodology was applied on 40 samples of rainbow trout, collected in supermarkets of the Centre Region of Portugal, in order to evaluate the presence of CAP residues. Positive results were confirmed in 9 of the 15 suspected samples, which correspond to 22.5% of the whole samples collected.