A method for the redox substoichiometric determination of thallium employing chlorate as an oxidant has been developed. The substoichiometric amount of Tl (III) formed was isolated by extraction with isoamyl acetate. 5-50μg of thallium can be determined with an accuracy of ±1.3%.
By sodium nickel ferrocyanide coprecipitation, 60Co and137Cs are simultaneously collected by nearly 99% recoveries from the unaged seawater. But this coprecipitation is not effective for the recovery of the60Co complexed with organic ligands which would exist in natural seawater. In order to obtain the effective recoveries for these complexed60Co, various pretreatments were investigated by using model samples containing the60Co aged with several amino acids. In the acidification of these samples by nitric acid as 1 pretreatment, a large portion of these complexed60Co was dissociated, especially by heating samples at 90-95°C. The recoveries of60Co were ranging from 90 to 97%. On the other hand, the usage of potassium peroxodisulfate (4.0×10-4-2.0×10-2M) as another pretreatment method elevated the recoveries of these complexed60Co by more than 99% by heating samples above 90°C. These 2 pretreatment methods were also effective for recoveries of137Cs ion.