ObjectiveTo establish a method for determination of N-dimethylnitrosamine in food by steam distillation-liquid chromatography-atmospheric chemical ionization-tandem mass spectrometry (LC-APCI-MS/MS).
MethodsThe sample spiked with isotope internal standard was processed by improved steam distillation method, and the distillate extracted by dichloromethane.After adding 1 mL of water, the extract was concentrated to no dichloromethane by vacuum rotary evaporator (water bath temperature 35℃, vacuum 50 kPa).The concentrate was determined by LC-APCI-MS/MS.The residue was separated on a Poroshell 120 EC-C18 column (2.7 μm, 4.6 mm×100 mm) with the mobile of methanol-water system, then was monitored by positive multiple reaction monitoring (MRM) mode and quantified by internal Standard.
ResultsThe calibration relations showed good linearity between 5 and 500 ng/mL.Recoveries at 0.15, 0.5 and 10 μg/kg were within 80%-110% with relative standard deviation (RSD) less than 7%.The detection concentration was 0.1 μg/kg.NDMA was not detected in 30 batches of meat products, but detected in 19 out of 30 batches of smoked and roasted fish fillets with content ranging from 0.38 μg/kg to 15.7 μg/kg.The content of NDMA in two batches of samples (8.45 μg/kg and 15.7 μg/kg, respectively) exceeded the limits of NDMA in Chinese GB 2762 (4.0 μg/kg).
ConclusionThe method in this study is sensitive, accurate, and suitable for the determination of N-dimethylnitrosamine in food.
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