Diode laser-based trace detection of hydrogen-sulfide at 2646.3 nm and hydrocarbon spectral interference effects.

This paper presents the first diode laser-based measurements of trace hydrogen sulfide at the 2646.35 nm absorption line and evaluates the feasibility of this line for natural gas sensing applications. The balanced detection technique is used to achieve a detection limit of 25 parts per million-meter H₂S in 150 Torr (T) balance N₂. Spectral interference effects of major natural gas constituents (methane, ethane, and propane) are also presented. It is shown that methane interference can be avoided by lowering the sample pressure, while propane has no interference. However, strong interfering lines of ethane are observed around the 2646.35 nm region. To our knowledge, this is the first report where individual ethane lines in this spectral region are observed. These observations make the 2646.35 nm H2S line unfavorable for natural gas applications. This line, however, still remains attractive for H₂S sensing applications with low ethane content. [ABSTRACT FROM AUTHOR]