(441d) Determination of a Broad Range of Volatile Organic Compounds in Environmental Air

Aldehydes including formaldehyde, acetaldehyde and acrolein and benzene, toluene, ethylbenzene, and xylene (BTEX), trichloroethylene (TCE) are toxic organic compounds in environmental air. Currently, there is no single method for sampling these compounds and no single method for analysis of these compounds. Current sampling and analytic methods for these compounds are not only time consuming, but also inducing more variation and errors. This work reports a novel microfabricated silicon preconcentrator device to combine physical adsorption of BTEX and derivatization of aldehydes in environmental air samples to enable analysis by a portable gas-chromatography-photo-ionization-detector (GC-PID). The captured compounds in the micropreconcentrator were eluted by solvent. GC-PID was used for analysis of the eluted liquid samples. The microprecocentrator was designed to have two separated compartments to accommodate two different sorbents. One compartment was loaded with physical sorbent like Carbopack X to capture BTEX, and the other was filled with silica gel particles coated with reagent O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine (PFBHA) to capture aldehydes via oximation. Both the single compartment devices with Carbopack X and PFBHA coated silica gel were first characterized for capture efficiencies of carbonyl compounds and BTEX. Then, the microprecocentrators with dual-compartments were tested for capture efficiencies of a mixture of BTEX and carbonyls in air. About 90% of recovery was obtained for BTEX, formaldehyde, acetaldehyde, and acetone by the micropreconcentrators. The limit of detection (LOD) was obtained in a range of 0.03 – 1.2 μg/m³. The dual-chamber microfluidic devices were used to detect airborne BTEX and carbonyl compounds of environmental air samples in chemical industrial sites. The results indicate that the micropreconcentrators can be used for capture and analysis of a broad range of volatile organic compounds including aldehydes and BTEX by a portable GC-PID.