Catalytic-kinetic potentiometric determination of thyroxine

A kinetic method is described for the determination of thyroxine (0.4–4 μg ml^?1), based on its catalytic effect on the reduction of cerium(IV) by arsenic(III). The reaction is monitored potentiometrically; the time required for a 20-mV change in potential is inversely proportional to the thyroxine concentration. The method is applicable to tablets.     

Flow-injection chemiluminometric analysis of some steroids by their sensitizing effect on the bromate-sulphite reaction

The chemiluminescent oxidation of sulphite by bromate was investigated and compared with that by cerium(IV). The reaction is sensitized by various steroid hormones which can thus be determined in the ranges 0.50–20.0μg ml ¹ for cortisone; 0.50–5.00 μg ml^?1 for hydrocortisone and progesterone and 0.50–6.00 μg ml^?1 for testosterone and corticosterone.     

Flow-injection determination of iron(II), iron(III) and total iron with chemiluminescence detection

Iron(II) (1.0 × 10^?9–1.0 × 10^?6 M) is determined by the production of chemiluminescence in a luminol system in the absence of added oxidant. Iron(III) (2.0 × 10.8^?8–2.0 × 10^?6 M) is determined after reduction to iron(II) in a silver reductor mini-column in the flow system. Cobalt, chromium, copper and manganese interfere.