针对现行的三甲胺分析方法在采样、样品保存、前处理等方面存在的不足,在优化预浓缩仪的冷阱捕集温度和填料、色谱和质谱条件等基础上,提出了苏玛罐采样-气相色谱-质谱法(GC-MS)测定环境空气中三甲胺含量的方法。将采样后的苏码罐连接到自动进样器上,经预浓缩仪的三级冷阱浓缩、富集后,按照色谱、质谱条件进行分析,以质谱图和保留时间定性,外标法定量。结果表明:优化的一级冷阱捕集温度为80 ℃,二级冷阱捕集温度为10 ℃,解吸温度为240 ℃,二级冷阱填料为石墨化碳黑Carbopack B;色谱分析中使用GL InertCap For Amines色谱柱,柱流量为1.4 mL·min^-1,升温速率为15 ℃·min^-1,溶剂延迟时间为6.0 min。在优化的仪器工作条件下,三甲胺峰形较好,响应值较大,并且避免了残留的CO₂的干扰。三甲胺标准曲线的线性范围为12.5~200 nmol·mol^-1,检出限(3.143s)为0.003 mg·m^-3;对不同浓度水平的加标样品进行回收试验,三甲胺测定值的相对标准偏差(n=6)为0.20%~5.3%,回收率为92.1%~111%。

In view of the shortcomings of the existing trimethylamine analysis methods in sampling, sample preservation, pretreatment and so on, on the basis of optimizing the cold trap temperature and filler of preconcentrator, as well as the conditions of chromatography and mass spectrometry, a method for the determination of trimethylamine in ambient air by gas chromatography-mass spectrometry (GC-MS) with Summa canister sampling was proposed. The Summa canister sampled was connected with the automatic sampler. After concentration and enrichment by the three-stage cold trap of the preconcentrator, the analysis was carried out according to the conditions of chromatography and mass spectrometry. The mass spectrum and retention time were used for qualitative analysis, and the external standard method was used for quantitative analysis. It was shown that the optimized trapping temperature of primary cold trap was 80 ℃, and the trapping temperature of secondary cold trap was 10 ℃, with desorption temperature of 240 ℃. The filler of secondary cold trap was graphitized carbon black Carbopack B. In chromatographic analysis, GL InertCap For Amines chromatographic column was used, and the flow rate of column was 1.4 mL·min^-1, with heating rate of 15 ℃·min^-1, and solvent delay time of 6.0 min. Under the optimized instrument operating conditions, the peak shape of trimethylamine was better, and its response value was higher, meanwhile the interference of residual CO₂ could be avoided. The linear range of standard curve for trimethylamine was 12.5-200 nmol·mol^-1, with detection limit (3.143s) of 0.003 mg·m^-3. Test for recovery on the spiked samples at different concentration levels was made, with RSDs (n=6) of trimethylamine determined values ranged from 0.20% to 5.3%, and the recoveries were in the range of 92.1%-111%.