Chlorate ion standard solution established by multipath titration techniques

Analyses of chlorate ion are essential in evaluating water quality; however, there is no standard solution of chlorate ion characterized by a metrologically valid procedure. This paper describes the measurement procedures and assays of chlorate ions with the linkage to the International System of Units (SI) by multipath gravimetric titration techniques. Three different titration techniques were employed to assay chlorate ions: oxidimetric-reductometric back titration with an iron(II) solution standardized with standard potassium dichromate, precipitation titration with a silver nitrate solution standardized with standard sodium chloride, and oxidimetric-reductometric titration with a thiosulfate solution standardized with standard potassium iodate. The results obtained through three different reactions were in good agreement with each other within their uncertainties. A certified reference material of chlorate ions with the linkage to the SI was first established by evaluating the storage stability of the solution and estimating measurement uncertainties. The assay (mass fraction) of sodium chlorate was characterized by using a weighted mean of the results of three methods; 99.829% +/- 0.029% (the value following +/- gives a level of confidence of approximately 95%, coverage factor k = 2). Providing with the standard solution through Japan Calibration Service System (JCSS) under Japanese Measurement Act widely allows all analysts to obtain their reliable analytical results.