DefinePK

Abstract

Chromium commonly presence in two different oxidation states, the Cr(III) which is an essential micro-element in living body, and also Cr(VI) which is toxic though in a trace level. Because of its different character for each species, determination of total chromium in water did not provide precise information for its toxicity. Meanwhile, many speciation methods had been developed. In this study, speciation chromium had been done by flow reaction system Sequential Injection Analysis Lab-At-Valve (SIA-LAV) modified by presence of Lab-At-Valve for maximized reaction process. Its determination based on complexed-reaction between 1,5-diphenylcarbazide (DiPC) complexing agent with Cr(VI) that formed Cr(VI)-DiPC complex which can be determined by colorimetric method in 548 nm. Total Chromium level could be achieved by oxidized Cr(III) by H2O2 in alkaline solution, so that Cr(VI) produced by an oxidation process along with Cr(VI) that naturally presence in the artificial samples reacted with DiPC, afterward, the formed Cr(VI)-DiPC determined as total chromium by the same colorimetric method. The optimization of this method was conducted by testing several parameters. Based on the optimization result, the optimum condition obtained: H2O2 concentration 10-5 M and volume 20 µL, DiPC concentration 2x10-5 M and volume 50 µL, the sample volume 60 µL and the delay time 10 seconds, flow rate to detector 25 µL s-1. The detection limit of Cr(VI) and Cr total were 0.0089 mg/L and 0.0103 mg/L, respectively, and Cr(III) was 0,0043 mg/L. The Chromium speciation by SIA-LAV method outlined above allows the simple, sensitive, rapid and cost-effective analysis for chromium speciation, the Cr(III) and Cr(VI). This result suggests that this method is prospective method to be used for monitoring of chromium species in fresh water.