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%.