Implementation and optimisation of a high-temperature loading strategy of liquid standards in the quantification of volatile organic compounds using solid sorbents.

ABSTRACT

High-temperature liquid standard loading strategy onto solid sorbent traps for calibration of thermal desorption-GC-MS techniques for the analysis of volatile organic compounds is evaluated and optimised. With this proposed set-up, volatilised liquid-loaded standards interact in gas phase with solid sorbent particles. Response factor for 15 volatile compounds with different vapour pressures have been evaluated and compared with common strategies based on liquid matrix interactions. Using gas matrix strategy improves signal output in the range 10-700%. Average increase for benzene, toluene, ethylbenzene and xylenes is 480%. Reported systematic bias between liquid standards and gas samples are reduced, enhancing thermal desorption methodologies on one of its more important issues. In addition, the proposed system improves the average repeatability to a 3.2%, over 13 times some reported data. The use of an ultra-thin GC capillary column of 150 µm id performs better peak resolution in about 60% the time with usual 250 µm id capillary columns. The usefulness of this proposed optimised procedure has been proved in real air matrix samples, through a large study with the reliable characterisation of 93 different volatile compounds in the ambient air of a municipal solid waste treatment area.