Determination of Trimethylamine in Ambient Air by Gas Chromatography-Mass Spectrometry with Summa Canister Sampling

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%.