Speciation of Chromium in Organicfruit Samples with Cloud Point Extraction Separation and Preconcentration and Determination by UV-VIS Spectrophotomety

Due to the toxicity of chromium, species depend on their chemical properties and bioavailability, speciation of chromium is very important in environmental samples.A speciation procedure for chromium (III), chromium (VI) and total chromium in environmental samples is presented in this work, based on cloud point extraction (CPE) separation and preconcentration prior to UV-Vis determination of chromium. The method is based on the reduction of Cr (VI) by iodide in acidic media and subsequently formation of I3- anion. Cerium (IV) ammonium sulphate was chosen as an oxidizing reagent for pre-oxidation step of Cr (III) to Cr (VI) species before the addition of iodide to the system, up to chromium in trivalent can be determined by the procedure. The I3- formed can further react with cetyltrimethylammonium bromide (CTAB) and induce its clouding due to formation of an ion-association complex. The formed complex was separated from solution and dissolved in ethanol for spectrophotometric measurement. Experimental parameters for both spectrophotometric reaction and extraction procedure have been optimized. Under optimized conditions Cr (VI) can be determined in the range 0.02-0.9 ?gml-1 (R2 = 0.999). Detection limit and relative standard deviation were0.0125 ?g mL−1 and8.246×10-4 ?g mL−1 (n=3), respectively with 10 mL sample volumes. The proposed method has been successfully applied for determination of chromium (VI) in Organic Fruit: Chino, Lemon, Orange samples with average recoveries of 94, 92 and 95.8 % respectively.