Fluorometric method using fluorescein mercuric acetate reagent for determination of hydrogen sulfide in the atmosphere

Hydrogen sulfide concentration in the atmosphere is sub-parts per billion. Few existing analytical methods are adequately sensitive for actual measurements at such low concentrations. Determinations of H₂S in the ppb range using these methods require larger volumes of air. But, both long sampling time and high flow rate result the low efficiency of capture of H₂S. H. D. Axelord et al. used a fluorometric method for the determination of atmospheric hydrogen sulfide. The authors modified the method and developed a method for determining of H₂S in the ppb range. This analytical method depends on the quenching of the fluorescence of the FMA reagent solution according to the amount of H₂S absorbed. The method shows high sensitivity and reliability, and the analytical operation is simple. Atmospheric hydrogen sulfide is collected by passing the air through bubbler containing 0.1N NaOH. After the sampling period, the FMA reagent is pipetted into the sampling solution. The solution is mixed well and the fluorescence of the solution is measured. At low rates { (0.2~0.5) l/min}, the efficiency of capture of H₂S by 0.1 N NaOH was 81%, but two bubblers in series can capture more than 95% of atmospheric H2S. The useful range of analysis of H₂S in 0.1N NaOH is 0.5 to 5.0×10^-8 M by 1.0×10^-7M FMA. In case of 10 l air sampling, determination range of H₂S is from 0.1 to 4.0 ppb, and the fluorometric method is suitable for the measurement of H₂S background levels. Summer 1975, this method was used to the measurement of atmospheric H₂S in Yokohama. The average of measurements was 2.7 ppb.