CONTINUOUS-FLOW SYSTEM FOR THE DETERMINATION OF TRACE VANADIUM IN NATURAL-WATERS UTILIZING IN-LINE PRECONCENTRATION SEPARATION COUPLED WITHCATALYTIC PHOTOMETRIC DETECTION/

A sensitive and rapid method is presented for the determination of van adium at ng to sub-ng ml(-1) levels in natural waters, in which in-lin e preconcentration/separation is directly coupled with catalytic detec tion of vanadium in a flow-injection system. Vanadium was adsorbed on a small column packed with Sephadex G-25 gel and desorbed with a small volume of 0.010 M HCl. The catalytic action of vanadium on the oxidat ion of chromotropic acid (1,8-dihydroxy-3,6-naphthalenedisulphonic aci d) by bromate in pH 3.8 buffered media was used in the sensitive deter mination of vanadium. Effective preconcentration/separation of trace v anadium can be achieved from Fe(III), Cu(II) and a large excess of sod ium chloride in seawater sample. A linear calibration using a 5 m samp le loop was obtained for vanadium in the range 0-2.5 ng ml(-1). The li mit of detection was 0.02 ng ml(-1) and the relative standard deviatio n was 1.2% for 1.0 ng ml(-1) vanadium (n = 5). The present FIA system is rapid and sensitive and can be readily applied to river water and c oastal seawater samples. (C) 1998 Published by Elsevier Science B.V.