RESUMEN
A novel system for semi-automated potentiometric analysis by gradient titration has been devised. In this technique both the reagent gradient generation and the titration are carried out in the sample container. The determination of chloride ion, with two ion-selective electrodes used simultaneously as an end-point sensor, is chosen to illustrate the technique.
RESUMEN
A method is described for the determination of selenium by differential pulse cathodic-stripping voltammetry (DPCSV) at a hanging mercury-drop electrode. The dried sample is burnt in an oxygen flask and the selenium absorbed in a persulphate-sulphuric acid mixture. The solution is analysed by DPCSV following treatment with hydrochloric acid to destroy excess of persulphate and to reduce the Se(VI) to Se(IV). Results are given for two soils and a series of plant materials and compared with those obtained by fluorimetric analysis by means of the 2,3-diaminonaphthalene piazselenol complex.