São Paulo State University, Department of Analytical Chemistry, UNESP, CEP 14800-970, Araraquara, SP, Brazil.
Analyst. 2014 Jan 7;139(1):198-203. doi: 10.1039/c3an01793a. Epub 2013 Nov 21.
Hydrogen sulfide is a highly corrosive, harmful, and toxic gas produced under anaerobic conditions within industrial processes or in natural environments, and plays an important role in the sulfur cycle. According to the U.S. Occupational Safety and Health Administration (OSHA), the permissible exposure limit (during 8 hours) is 10 ppm. Concentrations of 20 ppm are the threshold for critical health issues. In workplace environments with human subjects frequently exposed to H2S, e.g., during petroleum extraction and refining, real-time monitoring of exposure levels is mandatory. Sensors based on electrochemical measurement principles, semiconducting metal-oxides, taking advantage of their optical properties, have been described for H2S monitoring. However, extended response times, limited selectivity, and bulkiness of the instrumentation are common disadvantages of the sensing techniques reported to date. Here, we describe for the first time usage of a new generation of compact gas cells, i.e., so-called substrate-integrated hollow waveguides (iHWGs), combined with a compact Fourier transform infrared (FTIR) spectrometer for advanced gas sensing of H2S. The principle of detection is based on the immediate UV-assisted conversion of the rather weak IR-absorber H2S into much more pronounced and distinctively responding SO2. A calibration was established in the range of 10-100 ppm with a limit of detection (LOD) at 3 ppm, which is suitable for occupational health monitoring purposes. The developed sensing scheme provides an analytical response time of less than 60 seconds. Considering the substantial potential for miniaturization using e.g., a dedicated quantum cascade laser (QCL) in lieu of the FTIR spectrometer, the developed sensing approach may be evolved into a hand-held instrument, which may be tailored to a variety of applications ranging from environmental monitoring to workplace safety surveillance, process analysis and clinical diagnostics, e.g., breath analysis.
硫化氢是一种在工业过程或自然环境中厌氧条件下产生的高腐蚀性、有害和有毒气体，在硫循环中起着重要作用。根据美国职业安全与健康管理局（OSHA）的规定，允许的暴露限值（8 小时内）为 10ppm。20ppm 的浓度是临界健康问题的阈值。在经常有人类暴露于 H2S 的工作场所环境中，例如在石油开采和精炼过程中，必须实时监测暴露水平。基于电化学测量原理、利用其光学性质的半导体金属氧化物传感器已被用于 H2S 监测。然而，迄今为止报道的传感技术普遍存在响应时间延长、选择性有限和仪器体积庞大等缺点。在这里，我们首次描述了新一代紧凑型气体池（即所谓的基板集成空心波导（iHWG））与紧凑型傅里叶变换红外（FTIR）光谱仪结合使用，用于 H2S 的先进气体传感。检测原理基于立即进行的紫外辅助将较弱的 IR 吸收体 H2S 转化为更为明显和响应更灵敏的 SO2。在 10-100ppm 的范围内建立了校准，检测限（LOD）为 3ppm，这适用于职业健康监测目的。所开发的传感方案提供了小于 60 秒的分析响应时间。考虑到使用专用量子级联激光器（QCL）代替 FTIR 光谱仪进行实质性的小型化潜力，所开发的传感方法可以演变成一种手持式仪器，可以针对各种应用进行定制，从环境监测到工作场所安全监控、过程分析和临床诊断，例如呼吸分析。
