Development of a cobinamide-based end-of-service-life indicator for detection of hydrogen cyanide gas

Abstract

We describe an inexpensive paper-based sensor for rapid detection of low concentrations (ppm) of hydrogen cyanide gas. A piece of filter paper pre-spotted with a dilute monocyanocobinamide [CN(H2O)Cbi] solution was placed on the end of a bifurcated optical fiber and the reflectance spectrum of the CN(H2O)Cbi was monitored during exposure to 1.0–10.0 ppm hydrogen cyanide gas. Formation of dicyanocobinamide yielded a peak at 583 nm with a simultaneous decrease in reflectance from 450–500 nm. Spectral changes were monitored as a function of time at several relative humidity values: 25, 50, and 85% relative humidity. With either cellulose or glass fiber papers, spectral changes occurred within 10 s of exposure to 5.0 ppm hydrogen cyanide gas (NIOSH recommended short-term exposure limit). We conclude that this sensor could provide a real-time end-of-service-life alert to a respirator user.

Development of a hydrogen sulfide end-of-service-life indicator for respirator cartridges using cobinamide

“…Glass fiber filter paper was used as the sensor medium; in previous studies, this specific type of paper demonstrated larger reflectance signals, presumably because it is thicker than traditional cellulose filter paper and allowed more light to reach the detector in the presented reflectance configuration [19]. Additionally, glass fiber filter paper is less affected by water vapors.…”

“…Additionally, glass fiber filter paper is less affected by water vapors. The concentration of Cbi concentration (50.0 ± 0.2 µM) was chosen to directly compare results with previously performed experiments of similar nature using HCN gas [19]. This Cbi concentration on paper was sufficient in detecting small changes in the Cbi reflectance spectrum; higher concentrations of Cbi on paper decreased the sensitivity to slight changes in H 2 S concentration upon exposure, where lower Cbi concentrations had undesirable signal-to-noise ratios.…”

“…The responses of Cbi exposed to 10.0 ppm H 2 S (using OH(H 2 O)Cbi) and 5.0 ppm HCN (using CN(H 2 O)Cbi) for 10 min exposure at 25 %RH were compared and shown in Figure 5 (experiments performed separately) [19]. 5.0 ppm is the NIOSH REL for HCN.…”

“…Cbi-impregnated paper circles were inserted into a custommade, light-tight holder constructed of black, Delrin ® plastic described previously and shown in Figure S2 [19]. Two holes in each side of the holder allowed H 2 S to pass through the holder.…”

“…Cobinamide [OH(H 2 O)Cbi] was chosen as the indicator because it has a high affinity for HS − and is currently under study as a H 2 S-poisoning antidote [17]. Recently, Cbi [CN(H 2 O)Cbi] on paper showed rapid detection of hydrogen cyanide (HCN) with characteristic spectral shifts at 583 nm [19]. Here, OH(H 2 O)Cbi on paper will be used to study the effects of reaction with H 2 S to determine if a dual-ESLI could be developed, or if an interfering effect from H 2 S would occur.…”