Belt-Mounted Micro-Gas-Chromatograph Prototype for Determining Personal Exposures to Volatile-Organic-Compound Mixture Components

• Published in: Analytical chemistry (Washington) Vol. 91; no. 7; pp. 4747 - 4754
• Main Authors: Wang, Junqi, Nuñovero, Nicolas, Nidetz, Robert, Peterson, Seth J, Brookover, Bryan M, Steinecker, William H, Zellers, Edward T
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 02.04.2019
• Subjects: Analytical chemistry; Calibration; Chemistry; Detection limits; Exposure; Field tests; Gas chromatography; Gold; Injection; Microcontrollers; Nanoparticles; Organic compounds; Protective coatings; Real time; Recognition; Sensor arrays; Temperature sensors; Threshold limits; VOCs; Volatile organic compounds; Windows (intervals)
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/acs.analchem.9b00263

We describe a belt-mountable prototype instrument containing a gas chromatographic microsystem (μGC) and demonstrate its capability for near-real-time recognition and quantification of volatile organic compounds (VOCs) in moderately complex mixtures at concentrations encountered in industrial workplace environments. The μGC comprises three discrete, Si/Pyrex microfabricated chips: a dual-adsorbent micropreconcentrator–focuser for VOC capture and injection; a wall-coated microcolumn with thin-metal heaters and temperature sensors for temperature-programmed separations; and an array of four microchemiresistors with thiolate-monolayer-protected-Au-nanoparticle interface films for detection and recognition–discrimination. The battery-powered μGC prototype (20 × 15 × 9 cm, ∼2.1 kg sans battery) has on-board microcontrollers and can autonomously analyze the components of a given VOC mixture several times per hour. Calibration curves bracketing the Threshold Limit Value (TLV) of each VOC yielded detection limits of 16–600 parts-per-billion for air samples of 5–10 mL, well below respective TLVs. A 2:1 injection split improved the resolution of early eluting compounds by up to 63%. Responses and response patterns were stable for 5 days. Use of retention-time windows facilitated the chemometric recognition and discrimination of the components of a 21-VOC mixture sampled and analyzed in 3.5 min. Results from a “mock” field test, in which personal exposures to time-varying concentrations of a mixture of five VOCs were measured autonomously, agreed closely with those from a reference GC. Thus, reliable, near-real-time determinations of worker exposures to multiple VOCs with this wearable μGC prototype appear feasible.