Measurement of parts per million level gaseous concentration of hydrogen sulfide by ultraviolet spectroscopy using 1,1,1,5,5,5-hexafluoropentan-2,4-dione as a derivative by reaction of Cu(hfac)(1,5-cyclooctadiene)

Hydrogen sulfide reacts rapidly and quantitatively at ppm levels with cycloocta-1,5-diene-1,1,1,5,5,5-hexafluoropentan-2,4-dionatocopper(I) (Cu(hfac)(COD)) to yield 1,1,1,5,5,5-hexafluoropentan-2,4-dione (Hhfac) having a strong ultraviolet absorption at 268 nm, and which can be used without interference as a derivative in the continuous, fast online spectroscopic determination of the H2S concentration. The analytical method has excellent selectivity and can be used in the presence of N2, H 2, CO, COS, SO2, moist air, CH3OH, C 2H4, C6H6, and light alkanes including fuel gases. Using a standard spectrometer, the level of detection is about 10 ppb. Concentrations down to 1 ppm H2S can be analyzed readily, usually with an error in the range 0 to -7% dependent largely on the sorption characteristics of the apparatus. These are systematic errors due to adsorption; however, the analytical apparatus was very stable, and relative standard deviations as low as 0.1% of the mean can be obtained. The method can also be applied to the analysis of methanethiol. © 2009 American Chemical Society.