ELISA screening and liquid chromatography-tandem mass spectrometry confirmation of chloramphenicol residues in chicken muscle, and the validation of a confirmatory method by liquid chromatography-tandem mass spectrometry.

In the period December 2008 to August 2009, 180 chicken meat samples, including 90 thigh and 90 breast meats in Bursa province, Turkey, were collected. The determination of chloramphenicol (CAP) residues in the samples was screened by ELISA, and a confirmatory method based on liquid chromatography coupled with tandem mass spectrometry was described and validated. The ELISA screening of the samples was performed after extraction with ethyl acetate and defatting with n-hexane. The results showed that 15 (8.3%) of the chicken meat samples were positive for CAP residues from 12.64 to 226.22 ng/kg, with a mean of 45.32 ng/kg. Confirmatory analysis of the results from ELISA was practiced after an extraction with ethyl acetate. Chromatographic seperation was carried out by using a Synergy MAX-RP 80A column and the mixture of acetic acid-water as a mobile phase. The mass spectral acquisition was done in the negative-ion mode applying selective reaction monitoring with the following ions (mass-to-charge ratio, m/z): m/z 321 → 152 and m/z 321 → 194 for CAP. By liquid chromatography-tandem mass spectrometry, CAP was confirmed in 2 of 15 ELISA positive samples and 1 of 45 negative samples, with concentration levels that varied between 150 and 361 ng/kg. The method was validated according to Commission Decision 2002/657/EC. The calibration curves were linear with a typical r(2) value of 0.9966. The recovery values ranged from 97.3 to 104.0% and within-laboratory repeatability was lower than 5%. The decision limit was 0.10 µg/kg and detection capability was 0.11 µg/kg. To evaluate the presence of CAP residues, this method was successfully implemented in chicken meat samples.