Separation of microamounts of sulfide ion by collecting hydrogen sulfide in copper(II) absorbing solution

Application to spectrofluorimetric method using 2-(ο-hydroxyphenyl)benzoxazole.

Abstract

In order to use the 2-(ο-hydroxyphenyl)benzoxazole (HPB) method for the determination of sulfide in samples with interferring ions, separation by a hydrogen sulfide evolution method was examined. Absorbing agents for hydrogen sulfide hitherto proposed could not be used because they interfered with the HPB method. The use of a copper(II) ion, which is a principal reagent in the HPB method, as an absorbing agent was investigated. Hydrogen sulfide is stripped from an acidified sample solution by passing nitrogen at a flow rate of 30 cm³ min^-1 for 1h. The nitrogen gas bearing H₂S is introduced into 7 cm³ of absorbing solution {containing 5×10^-7 mol Cu(II) and 3cm³ of ethanol; pH4} in a teflon test tube through a teflon capillary tube with stirring. The H₂S-absorbed solution is diluted to 25 cm³ and a 1 cm³ aliquot is used for the spectrofluorimetric determination. By the proposed method, 0.212.8μg S^2- can be quantitatively recovered and can be determined with the precision of ±0.03₃μg (95%-confidence interval).