Determination of gamithromycin in an injection by ultra-performance liquid chromatography-tandem quadrupole-time-of-flight mass spectrometry.

In this study, a sensitive and precise method was developed for the determination of gamithromycin in an injection using ultra-performance liquid chromatography-tandem quadrupole-time-of-flight mass spectrometry (UPLC-QTOF-MS) and the results were compared with a similar analysis for the ion fragments of gamithromycin in MS/ MS. The sample was dissolved in methanol then filtered and separated on a C18 column using acetonitrile-0.1% formic acid (containing 2 mmol/L ammonium acetate) as the mobile phase. The flow rate was 0.4 mL/min and the column temperature was 40 °C. The mass spectrometry conditions were electrospray ionization (ESI) operated in positive ion full scan mode and quantified using external calibration. Subsequently, ion fragments of the MS/MS were compared and analyzed. The linear range was 10 ∼ 200 μg/L with a correlation coefficient of 0.9992. The limit of detection (LOD) was 0.77 μg/L and the limit of quantitation (LOQ) was 2.55 μg/L. The average recoveries of the intra-assay were 98.8%-105.6% with a relative standard deviation ranging from 1.79% to 2.38% and the inter-assay were 89.3%-110.7% with a relative standard deviation ranging from 4.93% to 6.27%. After the comparative analysis of the fragments with a Molecular Structure Correlator, the score of the total matching degree reached 83.19 and the scores of each ion fragment matching degree were all greater than 90, which supplied the basis for the confirmation of gamithromycin. The results indicated that the method was simple, sensitive and precise and could be applied in the determination of gamithromycin in real samples.