Concentration of aqueous solutions of salts using silica gel treated with a mixture of liquid anion exchanger and Eriochrome Black T prior to analysis for trace amounts of bivalent and trivalent metals

Abstract

Silica gel and silanised silica gel retain very strongly ion pairs formed with Aliquat 336 and Eriochrome Black T; the dyestuff is not eluted from the sorbent even with 5–6 M hydrochloric acid or 0.6–1 M perchloric acid. The strong retention of many bivalent and trivalent metals on sorbents prepared in this way was utilised for the pre-concentration of trace amounts of copper, lead, iron(III) and alkaline earth metals from water and from aqueous solutions of analytical-reagent grade sodium, potassium and ammonium salts. The retained metals were eluted from the column with dilute perchloric acid and determined by atomic-absorption spectrometry. It was found that at least a 250-fold concentration of trace amounts of the retained metals can be achieved. The sorbent was also applied to the purification of sodium, potassium and ammonium salts; it was found on the basis of anodic-stripping voltammetry that the concentrations of lead, cadmium and zinc in the eluates were lower than 10^–9M.