A Liquid Crystal-Based Passive Badge for Personal Monitoring of Exposure to Hydrogen Sulfide

• Published in: Journal of occupational and environmental hygiene Vol. 11; no. 11; pp. 741 - 750
• Main Authors: Robinson, Sheila E., Grinwald, Bart A., Bremer, Laura L., Kupcho, Kurt A., Acharya, Bharat R., Owens, Patrick D.
• Format: Journal Article
• Language: English
• Published: England Taylor & Francis 02.11.2014; Taylor & Francis LLC
• Subjects: Air Pollutants - analysis; Algorithms; Assessments; Colorimetry; Dosimeters; Dosimetry; Environmental monitoring; Environmental Monitoring - instrumentation; Equipment Design; Exposure; Film Dosimetry; Glass substrates; Human exposure; Humans; Hydrogen sulfide; Hydrogen Sulfide - analysis; Liquid Crystals; Natural gas; occupational exposure; Occupational Exposure - analysis; Occupational health; passive monitoring; Perchlorates; Petroleum refineries; Sensors; Studies; Time Factors; TLV; TWA; hydrogen sulfide; passive monitoring; occupational exposure; TLV; TWA
• ISSN: 1545-9624; 1545-9632
• DOI: 10.1080/15459624.2014.916808

A new liquid crystal (LC)-based passive dosimeter badge for personal monitoring of exposure to hydrogen sulfide (H 2 S) gas is reported. When a thin film of LC supported on a surface functionalized with lead perchlorate Pb(ClO 4 ) 2 (the LC sensor) is exposed to H 2 S, the orientation of LC molecules in the film changes from perpendicular to parallel. This reorientation induces a change in the appearance of the LC film when viewed between crossed polarizers. A H 2 S dosimeter was fabricated by pairing a LC sensor with a glass substrate forming a headspace between the two surfaces, to control diffusion of H 2 S across the LC film. When the dosimeter is exposed to H 2 S, a bright front appears as a function of exposure time. An algorithm has been developed to correlate this response length and exposure dose. The dosimeters are functionally stable when subjected to extreme temperature and humidity fluctuations, and are immune to a number of potentially interfering chemicals, except mercaptans. These dosimeters detect H 2 S at 0.2 ppm TWA (8 hr) with ±20% overall accuracy. The dosimeters were used to monitor the personal exposure of personnel working in an oil refinery. The TWA concentrations measured by the LC-based dosimeters correlate strongly with the NIOSH 1063 method that uses a sorbent tube and a pump followed by laboratory analysis. Thus, the LC-based dosimeters can provide a sensitive tool for on-site assessment of personal exposure to H 2 S in different environments.