Balasubramanian N, Kumar B S
Department of Chemistry, Indian Institute of Technology, Madras.
Analyst. 1990 Jun;115(6):859-63. doi: 10.1039/an9901500859.
A sensitive spectrophotometric method for the determination of trace amounts of hydrogen sulphide (H2S) after fixing in a modified zinc acetate-disodium ethylenediaminetetraacetate-sodium hydroxide solution is described. The fixed H2S is stable for 3 d. The reaction of iodate with H2S in the presence of acid and an excess of chloride leads to the formation of ICI which is stabilised as ICI2-. The species formed reacts with 2',7'-dichlorofluorescein to form 2',7'-dichloro-4',5'-diiodofluorescein which is extracted into a mixture of 15% isoamyl acetate in isoamyl alcohol. The colour system obeys Beer's law in the range 0-2.5 micrograms of H2S. The coefficient of variation is 4.5% for ten determinations of 2.0 micrograms of H2S. The effect of interfering gases on the determination is discussed. The method was applied to the determination of residual amounts of H2S present in a laboratory fume cupboard and the results obtained were compared with those given by the widely used Methylene Blue method. The method can be used to determine down to 0.3 micrograms of H2S.
本文描述了一种灵敏的分光光度法，用于测定在改良的醋酸锌-乙二胺四乙酸二钠-氢氧化钠溶液中固定后的痕量硫化氢（H₂S）。固定后的H₂S在3天内稳定。在酸性条件下，碘酸盐与H₂S在过量氯化物存在下反应生成ICl，并以ICl₂⁻形式稳定存在。生成的物质与2',7'-二氯荧光素反应形成2',7'-二氯-4',5'-二碘荧光素，然后被萃取到异戊醇中15%异戊酸乙酯的混合物中。该颜色体系在0 - 2.5微克H₂S范围内符合比尔定律。对2.0微克H₂S进行十次测定时，变异系数为4.5%。讨论了干扰气体对测定的影响。该方法应用于测定实验室通风橱中存在的H₂S残留量，并将所得结果与广泛使用的亚甲基蓝法给出的结果进行比较。该方法可用于测定低至0.3微克的H₂S。
