RESIN-PHASE PHOTOMETRIC DETERMINATION OF VANADIUM(Ⅴ) WITH PYROGALLIC ACID AS COLOR REAGENT

In an acetate buffer medium of pH 6.6,a colored complex was formed between pentavalent vanadium ion and pyrogallic acid.The colored complex was then adsorbed onto 717 strongly alkaline anion exchange resin,and its absorbance was measured on the resin phase at the wavelength of 600 nm againt a resin blank treated in the same way as in the sample analysis.The conditions of the color reaction,the adsorption of the colored complex onto the resin,the interference of co-existing ions and its elimination were studied and optimized.Under the condition of resin-phase photometry,Beer′s law was kept in the range of 0-37 μg per 25 mL of solution with a molar absorptivity of 5.57×104L·mol-1·cm-1,which is 10 time greater than the value measured in aqueous solution.Vanadium in steel was determined by this method after removal of the matrix iron(Ⅲ) by solvent extraction and masking by adding CyDTA.RSD of the results was found to be less than 3%,recoveries obtained were in the range of 98.6%-102.6%.