Microchemical detection of several elements using ion-exchange resin

Abstract

A new method of carrying out confirmatory tests is proposed. Colourless or slightly yellow anion-exchange resins are used as media for the tests. Both sensitivity and selectivity can be increased because of the well-known properties of ion-exchange resins. Co(IT) and Cr(VI) can be detected by very simple procedure; to a drop of sample solution a few particles of anion-exchange resin (RCl form) are added and after some time a drop of reagent [ammonium thiocyanate to Co(II) and hydrogen peroxide to Cr(VI)] is added. The change in colour of the particles of ion exchange resin is observed with the aid of magnifying glass. The limit of identification of sky blue colour of the cobalt complex is 0.16μg and its limiting concentration is 1 ∶ 1.3×105. The limit of identification of violet-blue colour of the Cr(VI) complex is 0.3μg and its limiting concentration is 1 ∶ 105. Ge(IV) can also be detected easily by a slightly modified method; the particles of an anion-exchange resin with low cross linking are previously impregnated with hematoxylin solution and those yellow particles are transfered to a drop of sample solution. The limit of identification of the red-violet colour of the Ge(IV) complex is 0.005μg and its limiting concentration is 1 ∶ 6×106. Interfering substances, such as Fe3+ and Bi3+, can be removed completely with the aid of a cation-exchange resin which is added just before adding the particles of anion-exchange resin. The limiting proportions are also described in each case.