MUTUAL SEPARATION AND PRECONCENTRATION OF VANADIUM(V) AND VANADIUM(IV) IN NATURAL-WATERS WITH CHELATING FUNCTIONAL-GROUP IMMOBILIZED SILICA-GELS FOLLOWED BY DETERMINATION OF VANADIUM BY INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION-SPECTROMETRY

The mutual separation and preconcentration of V(v) and V(IV) using chelating functional group immobilized silica gels (CISs) has been studied, based on inductively coupled plasma atomic emission spectrometric detection. Ethylenediamine-bonded (ED-CIS) and ethylenediaminetriacetate-bonded (ED3A-CIS) silica gels were used. A two-column system consisting of a first column of ED-CIS and a second column of ED3A-CIS was developed for on-line separation and preconcentration of V(V) and V(IV). In the pH range 2.5-3.0, ED-CIS retains V(V) and separates it completely from V(IV), whereas ED3A-CIS collects both V(V) and V(IV). The second column can be used to preconcentrate V(IV) in the breakthrough solution from the first column. Separation is achieved with recoveries of 91-105%. The recovery of both ions is 98% or better. An enrichment factor of 40 is obtained, with which the detection limit of V with inductively coupled plasma atomic emission spectrometry is improved down to 60 pg ml-1. The method was applied successfully to V speciation in natural waters.