[Determination of nine N-nitrosamines in animal derived foods by QuEChERS-isotope dilution combined with gas chromatography-tandem mass spectrometry]

[Rapid determination of 15 N-nitrosamines in air-dried yak meat using one-step QuEChERS-gas chromatography-triple quadrupole mass spectrometry]

A method based on gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) coupled with one-step QuEChERS technique was developed for the simultaneous determination of 15 N-nitrosamines in air-dried yak meat. The hydration volume, extraction solvent, extracting salt, and cleaning material were optimized according to the characteristics of the N-nitrosamines and sample matrix. The optimized conditions were as follows: 10 mL of purified water for sample hydration, acetonitrile as the extraction solvent for the sample after hydration, 4.0 g of anhydrous MgSO4 and 1.0 g of NaCl as extracting salts, 500 mg of MgSO4+25 mg of C18+50 mg of PSA as cleaning materials. Favorable recoveries of the 15 N-nitrosamines were obtained when the extraction solution was incompletely dried. Thus, the final extract was dried to below 0.5 mL under a mild nitrogen stream and then redissolved to 0.5 mL with acetonitrile. After filtration, 200 μL of the sample was transferred to an autosampler vial for GC-MS/MS analysis. The 15 N-nitrosamines were determined using GC-MS/MS on a DB-HeavyWAX column (30 m×0.25 mm×0.25 μm) with an electron impact ion source in multiple-reaction monitoring (MRM) mode, and quantified using an external standard method. Under the optimized experimental conditions, the results showed that the calibration curves exhibited good linearities for the 15 N-nitrosamines, with correlation coefficients (r2) greater than 0.9990. The limits of detection (LODs) and the limits of quantification (LOQs) ranged from 0.05 to 0.20 μg/kg and from 0.10 to 0.50 μg/kg, respectively. At spiked levels of 1LOQ, 2LOQ, and 10LOQ, the average recoveries were 79.4%-102.1%, 80.6%-109.5%, and 83.0%-110.6%, respectively, and the relative standard deviations were in the range of 0.8%-16.0%. The low matrix effects of the 15 N-nitrosamines indicated the high sensitivity of the proposed method. The method was applied to detect representative commercial air-dried yak meat samples obtained using different processing techniques. Seven N-nitrosamines, including N-nitrosodimethylamine, N-nitrosodiisobutylamine, N-nitrosodibutylamine, N-methyl-N-phenylnitrous amide, N-ethyl-N-nitrosoaniline, N-nitrosopyrrolidine, and N-nitrosodiphenylamine were detected in all samples. The average contents of the seven N-nitrosamines was 0.08-20.18 μg/kg. The detection rates and average contents of the N-nitrosamines in cooked air-dried yak meat samples were higher than those in traditional raw air-dried yak meat samples. Compared with the manual QuEChERS method, the one-step QuEChERS method developed integrated the extraction and clean-up procedures into one single run, and the detection efficiency was considerably improved. The developed method is simple, rapid, highly sensitive, and insusceptible to human errors. Thus, it is useful for the determination of N-nitrosamines in air-dried yak meat and can be extended to the qualitative and quantitative analysis of N-nitrosamines in other meat products. It also provides method support and a data reference for the general determination of N-nitrosamines, which is of great significance for food safety.

Advances of stable isotope technology in food safety analysis and nutrient metabolism research

Food quality, safety, and the regulatory metabolism of food nutrients in cells are primary factors in determining human health. However, residues of undesirable or hazardous compounds in food products and dysregulation in the nutrient metabolism inevitably occur occasionally. For years, chromatography-mass spectrometry technology has been recognized as an essential research tool in food analysis and nutrient metabolism research, and it is more accurate and robust when coupled with stable isotopes. In this study, we summarize the applications of stable isotope technology in the quantification of contaminant residues (pesticides, veterinary drugs, mycotoxins, polycyclic aromatic hydrocarbons, and other hazardous compounds) in foods and in the nutrients (glucose, lipids, amino acids and proteins) metabolism research. The aim of this review was to serve as a reference for providing effective analysis techniques for protecting food quality and human health, and to pave the way for the broader application of stable isotope technology.

Simultaneous determination of seven dimethylcyclosiloxanes in cosmetics of different formulation systems by gel permeation chromatography purification-gas chromatography-tandem mass spectrometry

鉴于当前化妆品中二甲基环硅氧烷的添加乱象,以及关于二甲基环硅氧烷在化妆品中安全风险评价的研究也未有实质性进展,因此建立适合不同配方体系化妆品中二甲基环硅氧烷的测定方法具有一定的理论和现实意义。基于此,建立了凝胶渗透色谱净化结合气相色谱-串联质谱测定不同配方体系化妆品中7种二甲基环硅氧烷的方法。方法采用乙酸乙酯-环己烷(1∶1, v/v)提取,凝胶渗透色谱净化,通过DB-5ms色谱柱(30.0 m×0.25 mm×0.25 μm)分离和气相色谱-串联质谱选择反应监测(SRM)模式进行确证和检测,以正十六烷为内标物内标法定量。分别对内标物、提取溶剂和净化方式的选择进行了优化。在最终确立的条件下,7种二甲基环硅氧烷在0.05~1.0 mg/L范围内线性良好,相关系数为0.994~0.998;方法的检出限(LOD, S/N=3)和定量限(LOQ, S/N=10)分别为0.04~0.08 mg/kg和0.12~0.24 mg/kg;针对不同配方体系的化妆品基质,进行了低、中、高3个添加水平的加标回收试验,目标物的加标回收率为85.3%~108.8%,相对标准偏差(RSD)为3.1%~9.4%。该方法操作简便,灵敏度高,重复性好,能够满足不同配方体系化妆品中7种二甲基环硅氧烷的测定要求。采用所建立的方法对市面上的化妆品进行检测,八甲基环四硅氧烷(D4)和十甲基环五硅氧烷(D5)均有不同程度的检出。该方法的建立将为我国化妆品中二甲基环硅氧烷的质量监督检查提供技术依据,有利于保障化妆品的安全,同时也为后续化妆品中二甲基环硅氧烷的健康安全风险评价提供了技术支撑。