肉制品中亚硝胺的形成机理及其影响因素分析

目的建立水蒸气蒸馏，液相色谱-大气压化学离子化-串联质谱法(LC-APCI-MS/MS)测定食品中的N-二甲基亚硝胺(NDMA)的方法。方法样品加入同位素内标后，采用改进的水蒸气蒸馏法进行处理，馏出液用二氯甲烷萃取。萃取液加水1 mL后采用减压旋转蒸发仪浓缩(水浴温度为35℃，真空度为50 kPa)至无二氯甲烷。浓缩液用大气压化学离子化源-液相色谱-四极杆串联质谱仪测定。色谱柱为Poroshell 120 EC-C18柱(2.7 μm，4.6 mm×100 mm)，流动相为甲醇-水系统。正离子多反应监测模式，内标法定量。结果在5~500 ng/mL范围内，N-二甲基亚硝胺的线性关系良好，加标回收率(添加水平分别为0.15、0.5、10 μg/kg)在80%~110%之间，相对标准偏差(RSD)小于7%，检出浓度为0.1 μg/kg。30批市售肉制品均未检出NDMA，30批市售熏烤鱼片、鱼干等水产制品中有19批检出NDMA，含量为0.38 μg/kg~15.7 μg/kg，其中2批样品的含量分别为8.45 μg/kg及15.7 μg/kg，超出国家标准中NDMA的限值规定(4.0μg/kg)。结论本方法灵敏度高，准确度好，适于食品中N-二甲基亚硝胺的测定。

Contamination of Chinese salted fish with volatile N-nitrosamines as determined by QuEChERS and gas chromatography-tandem mass spectrometry

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.