(71g) Detection of Benzene, Toluene, Ethylbenzene and Xylene in Air Using Micro-Preconcentrator/Solid Phase Micro-Extraction/Gas Chromatography Mass Spectrometry

The detection of volatile organic compounds (VOCs) is a thriving research area for many applications such as monitoring indoor air quality, environmental air, industrial safety, and health applications because of their potential adverse effects on human health and environment. Benzene, Toluene, Ethylbenzene, and Xylene (BTEX) are considered the most toxic VOCs due to their toxicity, carcinogenic nature, and inducing cardiovascular diseases at trace levels. Therefore, it is crucial to analyze these compounds accurately to monitor air quality. This work demonstrates the detection and quantification of trace BTEX in environmental air using a microfabricated preconcentrator combining with solid-phase micro-extraction/gas chromatography-mass spectrometry (SPME/GCMS) for concentration of these target analytes.

A micro-electro-mechanical system (MEMS) based preconcentrator was fabricated on a silicon wafer using deep reactive ion etching (DRIE). The inside cavity was packed with Carboxen-1000 adsorbent. 1L to 5L air samples were passed through micropreconcentrator where BTEX were adsorbed on the adsorbents at ambient temperature, then desorbed at 325° C and collected to a volume of 50 mL in a glass syringe using synthetic air. The adsorption and desorption flow parameters were optimized to 50 mL/min and 60 mL/min, respectively. Solid-phase micro-extraction for 15 minutes from the collected BTEX was performed using 75 µm Carboxen/Polydimethylsiloxane (CAR/PDMS) coated fiber. Then the fiber was inserted into GCMS to analyze compounds. Good linearity was observed for each standard analyte at a range of 1 ppb to 100 ppb (R² = 0.9988−0.9994) and the limits of detection (LOD) of the standard analytes achieved for benzene, toluene, ethylbenzene, m/p-xylenes, and o-xylene were 0.84, 0.85, 0.98, 0.82, 0.84 ppb, respectively. Three separate devices were compared by analyzing the same concentration of BTEX mixture and similar peak areas (relative standard deviation, % RSD < 8%) were observed, suggesting reproducibility among devices.