Examination and Refinement of the Determination of Aqueous Hydrogen Sulfide by the Methylene Blue Method

The accurate and precise measurement of total sulfide has been of major interest for well over a century. The most commonly used method involves the formation of a methylene blue-sulfide complex and spectrophotometric measurement of its concentration. The study presented herein compares the two most commonly used methods as outlined in Standard Methods for the Examination of Water and Wastewater (in APHA, Standard methods for the examination of water and wastewater, Washington, 1960) and by Cline (Limnol Oceanogr 14:454-458, 1969). In addition, this study clarifies the existing confusion of Cline's reagent preparation procedure, as it is apparent that various interpretations exist among research groups regarding reagent preparation. After evaluating both methods with respect to precision and accuracy, detection limit, sample storage time, and ease of use, the method outlined in Cline was determined to be superior. Furthermore, we suggest that the reagent concentration has to be optimized depending on the range of sulfide concentrations to increase the accuracy and precision of the method.