Abstract: The method was specifically developed for the simultaneous determination of streptomycin and dihydrostreptomycin residues in tomato paste by tandem dual solid phase extraction (SPE) column cleanup-liquid chromatography-tandem mass spectrometry. The residues were extracted from the samples with phosphate buffer solution (pH 4). The cleanup was performed by the way of dispersive solid phase extraction and tandem dual solid phase extraction column. The polar chromatographic column was used to complete the separation of the analytes under gradient elution and the analytes were detected in multiple reaction monitoring (MRM) mode via positive electrospray ionization (ESI+). The external standard calibration curves were used for the quantification. The linear ranges were from 0.01 to 0.2 mg/L with a good linear relationship (r＞0.999) for streptomycin and dihydrostreptomycin. The limit of quantification (LOQs) was 0.02 mg/kg for the both analytes. The recovery range was from 71% to 101% with the relative standard deviations (RSDs) between 2.3% and 15%. It was indicated that this method is accurate, easier, more sensitive, and has a better purification effect in the monitoring and analysis. The method is accurate and specific to monitor and analyze of streptomycin and dihydrostreptomycin residues in tomato paste and its products.

Key words: dihydrostreptomycin, liquid chromatography-tandem mass spectrometry (LC-MS/MS), streptomycin, tomato paste, tandem dual solid phase extraction column cleanup