Direct rapid determination of traces of sulfide in environment samples

Abstract

An improved ethylene blue method for determination of sulfide is developed. It has been adapted to a direct determination of sulfide by both common spectrophotometric method and total differential spectrophotometric method. In common spectrophotometric method, the calibration curve is A=1.69ρ+0.006 and the correlation coefficient is 0.9994. The apparent molar absorptivity is 5.42 × 10⁴ L·mol⁻¹·cm⁻¹ and calibration curve is liner when ρ is in the range of 0–0.9 mg·L⁻¹. In total differential spectrophotometric method, the calibration curve is A=9.25ρ + 0.004 and the correlation coefficient is 0.9996. The apparent molar absorptivity is 2.96 × 10⁵ L·mol⁻¹ L·mol⁻¹·cm⁻¹ and calibration curve is liner when ρ is in the range of 0–0.10 mg·L⁻¹. The sensitivity of this method is increased significantly compared with the former ethylene blue method. The speed of reaction is also faster than the former one. The limit of detection is found to be 1.0 ng·mL⁻¹ by both common spectrophotometric method and total differential spectrophotometric method. Ten replicate analyses of a sample solution containing 100 ng·mL⁻¹ sulfide give a relative standard deviation of 1.8%. The effects of various cations and anions on the determination of sulfide are studied and procedures for removal of interference is described. The method is used for the determination of sulfide in environment samples with satisfactory results.