Spectrophotometric determination of chromium(iii) with complexans

Selective spectrophotometric determinations of milligrain amounts of chromium(III) with complexans are described, based on the fact that the chromium(IIl) complexes are formed rapidly at boiling temperatures, but very slowly at room temperature, while the formation of some interfering complexes takes place instantaneously. Determinations with EDTA are more sensitive, but the combined presence of cobalt and other metals still interferes; there is no interference with the less sensitive NTA. The combined presence of a l00-fold amount of copper, nickel, cobalt and iron generally has no effect on the results. The use of DCTA, DTPA and HEDTA is discussed.