Evaluation of a Transportable Gas Chromatograph for Monitoring of Indoor Airborne Volatile Organic Compounds with a Gas Sampling Valve or a Concentrator

Abstract

An organic vapour concentrator with Tenax-TA as the adsorbent or a gas- sampling valve was used in combination with a transportable gas chromato graph (GC) for measurement of indoor airborne organics in the range of 5- 15,000 μg/m³. With the gas-sampling valve, detection limits were, approxi mately 50-200 and 10-100 μg/m³ with flame ionisation (FID) and photo-ion isation detectors (PID), respectively. By substituting the concentrator for the valve, detection limits were improved significantly. The detection limits, based upon a signal-to-noise ratio of 3 : 1, were approximately 2, 3 and 4 μg/m³, respectively, for toluene, α-pinene and 1,4-dichlorobenzene with an air sample of 100 ml collected with the concentrator and analysed with the GC/FID. The respective detection limits were improved by factors of 5, 6 and 8, with the PID. Instrument response was linear over the range of 2-2,000 μg/m³ with the GC/FID and 0.2-2,000 μg/m³ with the GC/PID for the test compounds. The precision of the method determined by repeat injections of a gas standard was better than 5% relative standard deviation. The instrument response factor varied by less than 15 % over a 12-day period as determined with a certified gas mixture of test compounds.