A flow injection system with ion-exchange for spectrophotometric determination of copper in rocks

A flow injection system is proposed for the spectrophotometric determination of copper in rocks. Samples are mineralized by treatment with hydrofluoric and perchloric acids and the solutions analysed after iron III precipitation. Copper is preconcentrated in a small CHELEX-100 resin column placed in the flow system, eluted with 2.5M nitric acid and further mixed with diethanoldithiocarbamate (DEDC) in basic medium. The coloured complex was monitored at 410 nm. With the proposed system, about 2-30 samples are run per hour with low reagent consumption. Beer's law is followed within 0.04 and 2.00, microg/ml. Precision and accuracy were assessed by using reference rock standards from USGS and GSJ with copper content as low as 0.4 microg/g with good precision and accuracy.