Confirmation of spectinomycin in milk using ion-pair solid-phase extraction and liquid chromatography-electrospray ion trap mass spectrometry.

A confirmation procedure is described for residues of spectinomycin in bovine milk. Spectinomycin is extracted from raw milk using ion-pair reversed-phase solid-phase extraction. The extracts are ion-pair chromatographed on a polymeric reversed-phase column and analyzed on a quadrupole ion trap mass spectrometer equipped with an electrospray interface. MS-MS data are acquired in the scan mode of product ions deriving from m/z 333, the protonated molecular ion. The estimated limit of confirmation is between 0.05 and 0.1 microg/ml. The procedure was validated with control milk, fortified milk (0.1-5.0 microg/ml), and milk from cows dosed with spectinomycin.