HPLC-MS Analysis of Chloramphenicol Residues in Milk and Powdered

Chloramphenicol (CAP) is a broad-spectrum antibiotic with bacteriostatic action but also has toxic properties, which is why its presence in food and feed is prohibited in Croatia and the Euro-pean Union. In the aim of consumer protection it is essential to develop a sensitive analytical method for de-tection of CAP fractions lower than w = 0.3 g kg–1. For the efficient control and monitoring of CAP, a rapid, sensitive, and selective method for its identification and quantification, using high performance liquid chromatography in combination with mass spectrometry LC-MS, has been developed. The cleaning procedure was based on the AOAC official method 993.32. HPLC-MS analysis used the ODS Hypersile column and the water/acetonitrile gradient. Electrospray negative ionization (neg ESI) was used before single ion monitoring (SIM) detection of three m/z 321, 323 and 325. As additional criteria, the ratio between these masses in real and spiked milk samples was also inve-stigated in accordance with theoretical values of the isotope pattern for 2 chlorine atoms present in the analyte. The detection limit of 0.1 g kg–1 was achieved. The mean value of recovery was 94 %, the corre-lation coefficient of the calibration curves calculated for 2 m/z values was higher than 0.99. Fourty samples of milk and milk products were tested with the HPLC-MS method, and obtained results showed that samples had CAP 0.37, 0.29, 0.39 g kg–1, respectively. All the other analysed samples contained CAP concentrations below the detection limit. Key words: Chloramphenicol, liquid chromatography, mass spectrometry, mil