THE SIMPLE AND RAPID SPECTROPHOTOMETRIC DETERMINATION OF TRACE CHROMIUM(VI) AFTER PRECONCENTRATION AS ITS COLORED COMPLEX ON CHITIN

Preconcentration method with collection of metal complexes on a chitin has been applied to the spectrophotometric determination of chromium( VI) in water. The chromium(VI) is collected as its 1,5-diphenylcarbazi de(DPC) complex on a column of chitin in the presence of dodecyl sulfa te as counter-ion. The Cr-DPC complex retained on the chitin is eluted with a methanol-1 M acetic acid mixture (7:3, v/v), and the absorbanc e of the eluent is measured at 541 nm. Beer's law is obeyed over the c oncentration range of 0.05-0.6 mu g of chromium(VI) in 1 ml of the elu ent. The apparent molar absorptivity is 3.5 x 10(4) dm(3) mol(-1) cm(- 1). The tolerance limits for Fe(III) is low, i.e. ten times that of ch romium(VI), but some metal ions and common inorganic anions do not int erfere in concentration range of 100-10 000 times that of chromium(VI) . The present method call be applied to the determination of chromium( VI) in natural water samples. (C) 1998 Elsevier Science B.V. All right s reserved.