Estimation of tungsten in complex matrices using toluene 3,4-dithiol and thiocyanate

 A rapid less labour-intensive procedure for complete decomposition of tungsten bearing complex matrices by potassium pyrosulphate and its determination using toluene 3,4-dithiol and thiocyanate is reported. The analytical results of various standard reference materials are presented (Jasperoid GXR-1, Deposit GXR-3, copper mill head GXR-4, tin-tungsten ore IGS-26, Mo-W ore IGS-27, tungsten concentrate SRM-277, scheelite ore SRM-2430, reference tungsten ore TLG-1, CT-1, BH-1 and Mo-W ore MP-2) along with two manganese nodules (GSPN-2 and GSPN-3) recently introduced by the Chinese Academy of Geological Sciences and one Polish soil sample (SRM-2710). For most of the samples the agreement between the observed value and the published data have been found to be extremely good. Derivations have been noted in some samples where published concentrations are indicative values only, indicating that more data are still required to upgrade the status from proposed/unspecified to the certified level. Results of various statistical analyses (intermethod comparison, F-test and regression analysis) reveal that the methods are matrix dependent. Separation of tungsten from molybdenum is straightforward, hence can be used for a quality control programme and in the evaluation of reference materials. Received: 30 December 1996 / Revised: 12 March 1997 / Accepted: 15 March 1997