CONFIRMATION OF RESIDUAL OXOLINIC ACID, NALIDIXIC-ACID AND PIROMIDIC ACID IN FISH BY THERMOSPRAY LIQUID-CHROMATOGRAPHY MASS-SPECTROMETRY

A thermospray high-performance liquid chromatographic-mass spectrometric (TSP LC-MS) method has been developed tor analysis of pylidonecarboxylic acid (quinolone) antibacterials such as nalidixic acid (NA), oxolinic acid (OXA) and piromidic acid (PMA). The LC separation was carried out on an Inertsil ODS-2 (150 x 4.6mm i.d.) using 0.1M ammonium acetate buffer(pH 4.5)-acetonitrile (6:4) as the mobile phase at a flow rate of 0.8 ml/min. The vaporizer temperature was 165-degrees-C and the ion source block temperature was 260-degrees-C. The mass spectra obtained from NA. OXA and PMA were very simple, with base peaks corresponding to the protonated molecule, MH+ . The calibration curve for NA was rectilinear from 1 to 20 ng with a detection limit by selected ion monitoring (SIM) of about 100 pg (signal to noise ratio of 2).