Determination of thiosulfate in a meromictic lake

An analytical procedure using a new high performance liquid chromatography (HPLC) for the sensitive measurement of thiosulfate (S2O32-) in natural wat er was examined. Using a Shodex Asahipak NH2P-50 (4E) column and the HPLC s ystem, thiosulfate was identified clearly by UV absorption at 215 nm with 1 00 mM Na2HPO4 (pH 8.5) as a solvent. Thiosulfate could be quantified in les s than 20 min with a detection limit of about 10 pmol which corresponds to an injection of 20 muL from a standard with a concentration of 0.5 muM. Sta rting at the lowest detectable concentration, the calibration curve for thi osulfate was linear over a concentration range of four orders of magnitude. Thiosulfate analysis was not affected by the saline concentration of sampl es at up to 1 M NaCl. This procedure was applied to water samples of a mero mictic lake, Lake Suigetsu, Fukui, Japan. Thiosulfate was found in lake wat er sampled below the chemocline at a concentration of less than 1-60 muM bu t not in the oxic surface water.