MEMS-Based Selective Preconcentration of Trace Level Breath Analytes

This paper presents high-performance micropreconcentrators (mu PCs) aimed at breath analysis and a method for eliminating unwanted species from breath samples by using a two-step preconcentration procedure. The mu PC consists of embedded high aspect-ratio three-dimensional (3-D) micro pillars coated with an adsorbent polymer. The silicon-glass die has outer dimensions of 7 mm 7 mm, total inner surface area of 10 m(2) and a total inner volume of similar to 6.5 mu L. The mu PC has on-chip thermal desorption capability and comprises more than 3500 micro pillars with dimensions of 30 mu m x 120 mu m x 240 mu m. The preconcentration factor of the presented mu PCs was measured to be above 10000. Results showed the possibility of selective preconcentration by cascading multiple mu PCs with temperature and flow control. The work presented here has profound implications for handheld point-of-care breath analysis instrumentation by first concentrating trace levels of VOCs found in human breath undergoing anesthesia such as n-decane (C-10), n-dodecane (C-12 2,6-diisopropylphenol (Propofol), n-tetradecane (C-14), and n-hexadecane (C-16). Second, it succeeded in eliminating water-like solvent (1-propanol) from the sample to be analyzed. Third, it selectively preconcentrated target compound such as Propofol which is used for medical procedures. The relative concentration of Propofol to C-14 was changed from 50% (with one mu PC) to 99.8% (with cascaded mu PC). The water-like solvent was also eliminated by 99.9%.