extraction, preconcentration and spectrophotometric determination of trace levels of thiosulfate in environmental waters

In the existing study, a new vortex-assisted cloud point extraction (va-cpe) method was developed for determination of low levels of thiosulfate in environmental waters at 632 nm by spectrophotometry. the method is selectively based on charge-transfer-sensitive ion-pair complex formation of ag(s2o3)2 3−, which is produced by the reaction of thiosulfate with excess ag+ ions with toluidine blue (3-amino-7-dimethylamino-2-methylphenazathionium chloride, tb+) and then its extraction into micellar phase of polyethylene glycol 4-tert-octylphenyl ether (triton x-45) in presence of na2so4 as salting-out agent at ph 7.0. all the factors affecting complex formation and va-cpe efficiency were optimized in detail. under the optimized conditions, the linear calibration curves for thiosulfate were in the range of 0.2–120 and 5–180 µg l−1 with sensitivity improvement of 81-folds and 15-folds, respectively, as a result of efficient mass transfer obtained by cpe with and without vortex, while it changed in the range of 260–3600 µg l−1 without preconcentration at 642 nm. the limits of detection and quantification of the method for va-cpe were found to be 0.05 and 0.22 µg l−1, respectively. the precision (expressed as the percent relative standard deviation) was in range of 2.5–4.8% (5, 10 and 25 µg l−1, n: 5). the method accuracy was validated by comparing the results to those of an independent 5,5′-dithiobis(2-aminobenzoic acid) (dtnb) method as well as recovery studies from spiked samples. it has been observed that the results are statistically in a good agreement with those obtained by dtnb method. finally, the method developed was successfully applied to the preconcentration and determination of trace thiosulfate from environmental waters.