A method to measure in a sample the concentrations of free H 2 S, of acid-labile sulfide, and of sulfane-bound sulfur; said method comprising the following steps: (a) placing separate portions X, Y, and Z of the sample into three individual evacuated containers, whereby most of the free H 2 S will partition into the headspaces of each of the respective containers; (b) combining portion X with an alkaline buffer, a chelating agent to chelate any trace metals that may be present in the sample, and monobromobimane, and incubating under low oxygen conditions; whereby free H 2 S will react with the monobromobimane to form a sulfide-dibimane product; chromatographically separating the sulfide-dibimane product from other components of the resulting mixture; and fluorimetrically measuring the amount of the separated sulfide-dibimane product as a measure of the concentration of free H 2 S in the sample ( Result B); (c) combining portion Y with an acid buffer having a pH of less than about 5.4 and incubating to release acid-labile sulfide as free H 2 S; combining portion Y with an alkaline buffer, a chelating agent to chelate any trace metals that may be present in the sample, and monobromobimane, and incubating under low oxygen conditions; whereby free H 2 S will react with the monobromobimane to form a sulfide-dibimane product; chromatographically separating the sulfide-dibimane product from other components of the resulting mixture; and fluorimetrically measuring the amount of the separated sulfide-dibimane product as a measure of the combined concentration of acid-labile sulfide and free H 2 S in the sample ( Result A); (d) combining portion Z with an acid buffer having a pH of less than about 5.4 and a reducing agent to release both acid-labile sulfide and sulfane sulfur as free H 2 S; combining portion Z with an alkaline buffer, a chelating agent to chelate any trace metals that may be present in the sample, and monobromobimane, and incubating under low oxygen conditions; whereby free H 2 S will react with the monobromobimane to form a sulfide-dibimane product; chromatographically separating the sulfide-dibimane product from other components of the resulting mixture; and fluorimetrically measuring the amount of the separated sulfide-dibimane product as a measure of the combined concentration of sulfane sulfur, acid-labile sulfide, and free H 2 S in the sample ( Result C); and (e) determining the concentration of free H 2 S in the sample as equal to Result B; determining the concentration of acid-labile sulfide in the sample as equal to the difference between Result A and Result B; and determining the amount of sulfane sulfur as equal to the difference between Result C and Result A. (a) placing separate portions X, Y, and Z of the sample into three individual evacuated containers, whereby most of the free H 2 S will partition into the headspaces of each of the respective containers; (b) combining portion X with an alkaline buffer, a chelating agent to chelate any trace metals that may be present in the sample, and monobromobimane, and incubating under low oxygen conditions; whereby free H 2 S will react with the monobromobimane to form a sulfide-dibimane product; chromatographically separating the sulfide-dibimane product from other components of the resulting mixture; and fluorimetrically measuring the amount of the separated sulfide-dibimane product as a measure of the concentration of free H 2 S in the sample ( Result B); (c) combining portion Y with an acid buffer having a pH of less than about 5.4 and incubating to release acid-labile sulfide as free H 2 S; combining portion Y with an alkaline buffer, a chelating agent to chelate any trace metals that may be present in the sample, and monobromobimane, and incubating under low oxygen conditions; whereby free H 2 S will react with the monobromobimane to form a sulfide-dibimane product; chromatographically separating the sulfide-dibimane product from other components of the resulting mixture; and fluorimetrically measuring the amount of the separated sulfide-dibimane product as a measure of the combined concentration of acid-labile sulfide and free H 2 S in the sample ( Result A); (d) combining portion Z with an acid buffer having a pH of less than about 5.4 and a reducing agent to release both acid-labile sulfide and sulfane sulfur as free H 2 S; combining portion Z with an alkaline buffer, a chelating agent to chelate any trace metals that may be present in the sample, and monobromobimane, and incubating under low oxygen conditions; whereby free H 2 S will react with the monobromobimane to form a sulfide-dibimane product; chromatographically separating the sulfide-dibimane product from other components of the resulting mixture; and fluorimetrically measuring the amount of the separated sulfide-dibimane product as a measure of the combined concentration of sulfane sulfur, acid-labile sulfide, and free H 2 S in the sample ( Result C); and (e) determining the concentration of free H 2 S in the sample as equal to Result B; determining the concentration of acid-labile sulfide in the sample as equal to the difference between Result A and Result B; and determining the amount of sulfane sulfur as equal to the difference between Result C and Result A.