Analysis of veterinary drug residues in shrimp: a multi-class method by liquid chromatography-quadrupole ion trap mass spectrometry.

A liquid chromatography-mass spectrometry (LC-MS) method was developed to screen and confirm veterinary drug residues in raw shrimp meat. This method simultaneously monitors 18 drugs of different classes, including oxytetracycline (OTC), sulfonamides, quinolones, cationic dyes, and toltrazuril sulfone (TOLS). The homogenized shrimp meat is extracted with 5% trichloroacetic acid. The extract is further cleaned using polymer-based SPE. A 50 mm phenyl column separates the analytes, prior to analysis with an ion trap mass spectrometer interfaced with an atmospheric pressure chemical ionization source. This method is able to confirm oxytetracycline residues at 200 ng/g, toltrazuril sulfone at 50 ng/g, sulfaquinoxaline at 20 ng/g, and the other 15 drugs at 10 ng/g or lower levels. An estimate of the level of residues can also be made so that only confirmed samples above action levels will be sent for quantitation. The method is validated with both fortified and incurred samples, using multiple shrimp species as well. This multi-class method can provide a means to simultaneously monitor for a wide range of illegal drug residues in shrimp.