Establishment and Evaluation of a Method for Analyzing Atmospheric Volatile Organic Compounds

An automated cumulative sampling system and a method that combines a two-step cryo-concentrated system and gas chromatography/mass spectrometry (CCS-GC/MS) are introduced. The method is evaluated by a set of special experiments and the results are presented. The lowest measurement detection limit was expanded from 10-6 nmol mol-1 to 10-12 nmol mol-1 by using CCS-GC/MS instead of the simpler method of gas chromatography/mass spectrometry (GC/MS), with the average responsible factor of 39 object compounds being 2.9×10-12. When the volume of air sample reached 1000 cm3, the lowest detection limit reached up to 7×10-12--40×10-12 nmol mol-1. The CCS-GC/MS method can potentially identify all objective chemical species in an atmospheric sample, with an average 2.5 s bias error of retention time for 39 gas chromatography (GC) peaks. Within the range 0--400×10-9 nmol mol-1, the concentration of 39 kinds of objective compounds can be individually calculated very accurately by a standard curve average r2 (coefficient of determination) value of above 0.99. The recovery efficiency was 88%--111%, with an average of 100.8% ±5.6%. The bias error of precision was 2%--14%, with an average of 6.6%.