Objective The detection method of hydrogen sulfide in the workplace air by continuous flow analysis-methylene blue photometric method was established to improve the stability of hydrogen sulfide absorption solution and provide a scientific basis for the determination of hydrogen sulfide in workplace air.

Methods Sodium carboxymethyl cellulose was used as a protective colloid in the alkaline solution containing triethanolamine. Hydrogen sulfide was determined by methylene blue spectrophotometry using a continuous flow injection apparatus.

Results The linear relationship between the mass concentration of hydrogen sulfide was good in the range of 0.05 to 5.00 mg/L. The correlation coefficient was 0.999 7, the minimum detectable concentration was 0.001 mg/m³, and the minimum quantitative concentration was 0.004 mg/m3 (calculated using 5.00 mL absorption solution and 7.5 L sample collection). Sampling efficiency was 100%. The intra-lot relative standard deviation and inter-lot relative standard deviation were 0.19% to 1.07% and 1.53% to 2.41%, respectively. The recoveries were 98.9% to 103.2%. Samples could be stored at 20 to 25℃ for at least 5 days and at 4 to 8 ℃ for at least 10 days.

Conclusions The method is accurate, efficient, rapid, environmentally friendly, with a low detection limit and good stability, making it suitable for batch detection of hydrogen sulfide in workplace air.