Production of in situ mixed gas phase volatile organic compound standards for sorbent tube applications

Volatile organic compounds (VOCs) are a significant class of air pollutants, as they pose a risk to human health and the environment. Precise quantification of VOCs sampled onto sorbent tubes requires gas phase standards at suitable concentrations. Herein, we present a: - gas standard preparation method for benzene, toluene, ethylbenzene and xylene (BTEX) prepared from liquid standards by means of evaporation and dynamic dilution with nitrogen - demonstration of the applicability of the LiqMix Cascade gas mix system. Repeatability and reproducibility were first successfully demonstrated via direct GC-MS analysis of generated gas mixtures. Then µg levels of generated gas standards were adsorbed onto sorbent tubes employed in active sampling and ng levels were collected onto Radiello cartridges used in passive sampling, followed by liquid extraction or thermal desorption and GC-MS analysis. Accuracy was verified by a BTEX certified reference material (99 % recovery). The LiqMix Cascade gas mix system was shown to produce precise and repeatable concentrations of BTEX gas phase standards for sorbent tube sampling applications for the first time.