A micro passive preconcentrator for micro gas chromatography. Issue 23 (23rd September 2020)

• Record Type: Journal Article
• Authors: Zhan, Changhua; Akbar, Muhammad; Hower, Robert; Nuñovero, Nicolas; Potkay, Joseph A.; Zellers, Edward T.
• Is Part Of: Analyst. Volume 145:Issue 23(2020)
• Page Start: 7582
• Page End: 7594
• Publication Date: 2020-09-23
• Subjects: Chemistry, Analytic -- Periodicals; 543
• DOI: 10.1039/d0an01485k
• Languages: English
• ISSNs: 0003-2654

Abstract

Abstract : We demonstrate "zero-power" sampling at known rates for up to 24 h, high capacity, and high desorption (transfer) efficiency for downstream separation and detection. Abstract : We describe a microfabricated passive preconcentrator (μPP) intended for integration into gas chromatographic microsystems (μGC) for analyzing volatile/semi-volatile organic compounds (S/VOC). Devices (8 × 8 mm) were made from a silicon-on-insulator top layer and a glass bottom layer. The top layer has 237 apertures (47 × 47 μm) distributed around the periphery of a circular region (5.2 mm o.d.) through which ambient vapors diffuse at predictable rates. Two internal annular cavities offset from the apertures are packed with ∼800 μg each of commercial carbon adsorbents. Thin-film heaters thermally desorb captured vapors, which are drawn by a pump through a central exit port to a micro injector for analysis with a bench scale GC. The 15 test compounds spanned a vapor pressure range of 0.033 to 1.1 kPa. Effective (diffusional) μPP sampling rates ranged from 0.16 to 0.78 mL min −1 for short-duration exposures to ∼mg m −3 vapor concentrations. Observed and modeled sampling rates generally agreed within 15%. Sampling rates for two representative compounds declined by ≤30% between 0.25 and 24 h of continuous exposure. For one of these, the sampling rate declined by only 8% over a ∼2300-fold concentration range (0.25 h samples). Desorption (transfer) efficiencies were >95% for most compounds (250–275 °C, 60 s, 5 mL min −1 ). Sampling rates for mixtures matched those for the individual compounds. Dissipating no energy while sampling, additional advantages of this novel device include short- or long-term sampling, high capacity and transfer efficiency for a diverse set of S/VOCs, low transfer flow rate, and a robust fabrication process.