Environmental context. The importance of hydrogen sulfide as well as some of the reduced sulfur species such as polysulfides as environmental pollutants is a result of their toxicity, unpleasant odour, and their reactivity with metals and metallic ions found in various environmental samples. Although known to be popular, the effectiveness of N,N-diethyl-p-phenylenediamine and other related compounds in the spectrophotometric analysis of such sulfur compounds in water as well as in other environmental samples has not been fully investigated. Our results show that although the quantification of simple sulfides in the environmental samples may be easily accomplished spectrophotometrically by using N,N-diethyl-p-phenylenediamine, the level of difficulty in analysing such compounds may increase with their increasing sulfur chain.

Abstract. The analysis of polysulfides, polythionates and other sulfur species likely to be found in poorly aerated environmental samples such as water is presented. In-depth spectrophotometric testing carried out using N,N-diethyl-p-phenylenediamine shows that the well known acidification-and-purge method is not sufficiently suitable for the analysis of polysulfides and other low oxidation-state sulfur compounds that contain a sulfur chain longer than two. Further, this study finds that the use of chromium(II) which acts as a reducing agent to the sulfur-containing compounds improves the spectrophotometric analysis of the polysulfides and polythionates in water, but only slightly. The extent of reduction of polysulfides and polythionates to sulfide by chromium appears dependent upon the oxidation state of sulfur as well as the chain length in the polysulfidic compounds.