Sample extraction and injection with a microscale preconcentrator.

Robinson, Alex Lockwood (Advanced Sensor Technologies, Albuquerque, NM) ; Chan, Helena Kai Lun

Sandia National Laboratories

关键词: Sample Holders;    Desorption;    Gas Chromatography;    Adsorption Isotherms Gas Chromatography.;    Indoor Air Pollution;   

DOI  :  10.2172/946562
RP-ID  :  SAND2007-0152
RP-ID  :  AC04-94AL85000
RP-ID  :  946562

美国|英语

来源: UNT Digital Library

【 摘 要 】

This report details the development of a microfabricated preconcentrator that functions as a fully integrated chemical extractor-injector for a microscale gas chromatograph (GC). The device enables parts-per-billion detection and quantitative analysis of volatile organic compounds (VOCs) in indoor air with size and power advantages over macro-scale systems. The 44 mm{sup 3} preconcentrator extracts VOCs using highly adsorptive, granular forms of graphitized carbon black and carbon molecular sieves. The micron-sized silicon cavities have integrated heating and temperature sensing allowing low power, yet rapid heating to thermally desorb the collected VOCs (GC injection). The keys to device construction are a new adsorbent-solvent filling technique and solvent-tolerant wafer-level silicon-gold eutectic bonding technology. The product is the first granular adsorbent preconcentrator integrated at the wafer level. Other advantages include exhaustive VOC extraction and injection peak widths an order of magnitude narrower than predecessor prototypes. A mass transfer model, the first for any microscale preconcentrator, is developed to describe both adsorption and desorption behaviors. The physically intuitive model uses implicit and explicit finite differences to numerically solve the required partial differential equations. The model is applied to the adsorption and desorption of decane at various concentrations to extract Langmuir adsorption isotherm parameters from effluent curve measurements where properties are unknown a priori.