KINETIC DETERMINATION OF CARBIMAZOLE, METHIMAZOLE AND PROPYLTHIOURACIL IN PHARMACEUTICALS, ANIMAL FEED AND ANIMAL LIVERS

Kinetic methods are proposed for the determination of carbimazole(CBZ) , methimazole(MMI) and propylthiouracil(PTU) based on their inhibitory effects on the palladium(lr)-catalysed reaction between the pyronine G and hypophosphite ions, The reactions are monitored spectrophotometr ically at 548 nm, The influence of reaction variables and the interfer ing effect of other substances were studied. Under the selected experi mental conditions (CBZ: 3.6 X 10(-5) mol l(-1) pyronine G; pH 3.0; 0.7 mu g ml(-1) Pd-II and 0.2 mol l(-1) H2PO2-; MMI: 6 X 10(-5) mol l(-1) pyronine G, pH 3.0; 0.7 mu g ml(-1) Pd-II, 0.4 mol l(-1) H2PO2-; PTU: 3.6 X 10(-5) mol l(-1) pyronine G; pH 3.0; 0.7 mu g ml(-1) Pd-II and 0.3 mol l(-1) H2PO2-), these three antithyroids were determined in the following ranges: CBZ, 0.04-0.70 mu g ml(-1); MMI, 0.04-0.50 mu g ml( -1); PTU 0.08-1.00 mu g ml(-1). The methods were applied to the determ ination of CBZ, MMI and PTU, in pharmaceuticals, animal feed and anima l livers.