Use of two-layer supports for the sorption-spectrometric determination of chromium(VI), copper(H), and nickel(II) from a single sample in a flow system

The determination of three elements from a single sample on a two-layer sup port in the flow mode was studied. One layer is a disk of a fiber material filled with the AV-17 anion exchanger, and the other is a disk of a materia l filled with the KU-2 cation exchanger. The method is based on the simulta neous preconcentration of elements by pumping a test sample through two dis ks in a flow cell, the separation of layers, and subsequent detection of ch romium on the support filled with AV-17 using 1,5-diphenylcarbazide. The su pport filled with KU-2 is used for the sequential determination of nickel w ith dimethylglyoxime and copper with sodium diethyldithiocarbamate in I M H Cl. The nickel dimethylglyoximate is decomposed under the action of I M HCl ; its 10-fold amounts do not interfere with the determination of copper. Th is method provides the determination of chromium, copper, and nickel at a l evel below the maximum permissible concentration for potable water; at the ratio Cr : Ni : Cu = I : 10 : 20, RSD is lower than 10%. The time of the de termination of the three elements from a single sample is 25-30 min.