[Determination of 104 volatile organic compounds in air by double column gas chromatography-mass spectrometry/flame ionization detector coupled with electronically controlled cryo-focusing unit].

Abstract

A method for the determination of 104 volatile organic compounds (VOCs) in ambient air based on double column multi dean switching gas chromatography-mass spectrometry/flame ionization detector (GC-MS/FID) coupled with sorbent assisted electronically controlled cryo-focusing unit was developed and evaluated. The sorbent assisted electronically controlled cryo-focusing unit was used for trapping, dehydration and focusing of VOCs sampled in summa canisters. The VOCs were split into two parts by the multi dean switching unit in GC-MS/FID. The C2-C3 components were determined in a PLOT capillary column with an FID detector, while the C4-C12 components were determined in an Intercap-624 capillary column with a MS detector. The C2-C3 components were qualitatively confirmed from the retention time and quantified by the calibration curves, while the C4-C12 components were qualitatively confirmed from the retention time and the relative abundance ratio of characteristic ions, and quantified by the internal standard calibration curves. The major factors influencing the cryo-focusing performance including the type of sorbent tube, the pressure employed in assisted pressure control unit (APC), and the split point in multi dean switching unit were investigated. The chromatographic and MS parameters were optimized. Under optimum conditions, a linear relationship was observed with the content of VOCs ranging from 0.0446 to 0.892 μmol/m3, and correlation coefficients (r) no less than 0.9984. The average spiked recoveries of the six VOCs at two levels of 0.0446 μmol/m3 and 0.223 μmol/m3 were 86.4%-116.1%, with relative standard deviations in the range of 0.9%-11.3% The method detection limits (MDLs) and the limits of quantification (LOQs) were 0.145-1.90 μg/m3 and 0.435-5.70 μg/m3, respectively. The method is accurate, sensitive and simple, and is suitable for the determination of the 104 VOCs in ambient air.