A method of determining and removing sulphide to allow the determination of sulphate,phosphate, nitrite and ammonia by conventional methods in small volumes of anoxic waters

Mercury(II) chloride is used to precipitate free sulphide from <10-ml samples of anoxic water. The sulphide-free supernatant solution can be used for estimation of sulphide by measuring the concentration of unreacted mercury(II) ion and for determinations of sulphate, inorganic phosphate, ammonia and nitrite by spectrophotometric methods which normally cannot be used because of sulphide interference. Concentrations that can be determined lie within the ranges: sulphide 0.5–180 000 μg S l^?1, sulphate 0.024–2.77 g S l^?1, ammonia 1–70 000 μg N l^?1, nitrite 1–3000 μg N l^?1, inorganic phosphate 1–4000 μg P l^?1. Interstitial waters from estuarine sediments, tidal flats, mangrove swamps, and an anoxic estuarine basin were examined.