Development of a microfabricated impinger for on-chip gas phase sampling

The design and development of a glass fabricated microimpinger for gas phase sampling of hydrogen cyanide is described. Using standard glass microfabrication techniques, a microimpinger consisting of a gas sample inlet, gas delivery arms, and an extraction reservoir was used to extract dilute hydrogen cyanide vapor from a gas delivery system using a basic aqueous trapping buffer. A Teflon membrane was utilized for containing the liquid sample in the extraction reservoir. Extraction efficiency for sampling hydrogen cyanide was monitored by forming a fluorescent cyanide isoindole in the reaction of cyanide with naphthalene-2,3-dicarboxaldehyde and taurine. Experiments using a flow of 2 mL min−1 and a sampling time of 1 min were used to measure cyanide vapors as low as 1.9 mg m−3, with a calculated limit of detection of 0.486 mg m−3. The effects of the vacuum flow rate and sampling time were also investigated.