IOSR Journal of Applied Chemistry (IOSR-JAC) e-ISSN: 2278-5736.Volume 13, Issue 1 Ser. I (January. 2020), PP 30-33 www.iosrjournals.org DOI: 10.9790/5736-1301013033 www.iosrjournals.org 30 |Page Spectrophotometric Determination of Chromiumin(III) in Water Using Sodium Bismuthate as an Oxidizing Reagent N. LAL, A. Tiwari, A. K. Dixit and D. K. Singh* Department of Chemistry, VSSD College, CSJM University, Kanpr-208002, India. * Ex-Professor, Department of chemistry, H. B. Technological Institute, Kanpur-208002 (India) Corresponding Author: N. Lal, A. Tiwari Abstract: A simple, sensitive, inexpensive and rapid spectrophotometric method for the determination of trace amounts of chromium (III) in water through oxidation using sodium bismuthate (NaBiO 3 ) is described. NaBiO 3 is found to be an effective oxidizing agent for aforesaid oxidation and carries advantages such as easy handling, non-toxic and eco-friendly. Chromium (VI) forms a pink/purple colored complex with diphenyl carbazide (DPC) having λ max 540 nm. Major cations and anions did not show any interference. Beer’s law is applicable under concentration range 20.8 – 104.0 μg/l of chromium. The method is highly reproducible and has been tested for chromium estimation in synthetic water samples. The correlation coefficient R 2 is greater than 0.999. Key words: Spectrophotometric determination; Chromium(III); Sodium bismuthate; Diphenyl carbazide --------------------------------------------------------------------------------------------------------------------------------------- Date of Submission: 10-01-2020 Date of Acceptance: 27-01-2020 -------------------------------------------------------------------------------------------------------------------------------------- I. Introduction Chromium compounds have numerous applications in industry; however their discharge into ground water is of great concern due to their hazardous effect. Chromium is an essential nutritional supplement for humans and animals. It plays an important role in glucose metabolism 1,2 In nature, chromium is found usually in trivalent and hexavalent states. Chromium (III) is toxic in aquatic life when its concentration in water is more than 5 mg/l while Chromium (VI) is more toxic and maximum permissible limit in toxic water is 0.05 mg/l 3 . Determination of Cr(VI) in micro-quantities is of increasing interest to analytical chemists. Although atomic absorption spectrometry (AAS) is the sensitive, successful and commonly used method for chromium determination 4 , AAS has the disadvantage of being unable to differentiate between the oxidation states of chromium. Other sensitive methods described for chromium (VI) determination includes ion chromatography (IC) 5 , electrophoresis 6 , neutron activation 7 and ICP-MS 8 . These methods are quite sensitive and selective but very expensive and complex. With growing concerns for safeguarding our environment, there is need to determine the chromium content in water by a method which is sensitive and selective and at the same time is simple and cost effective too. Spectrophotometric methods are generally used for analysis of chromium in water 9-11 . The oxidation of Cr(III) is reported by various oxidizing agents such as KMnO 4 12 , H 2 O 2 13 , MnO 2 14 , etc. but use of sodium bismuthate in the oxidation of Cr(III) is not explored. In the present work, we report a sensitive, selective and simplified approach for determination of Cr(III) in the water. Herein, a small quantity of chromium is readily determined spectrophotometrically by the oxidation of Cr(III) to Cr(VI) which was further characterized by diphenylcarbazide (DPC) method 15 . Sodium bismuthate has been reported earlier for the oxidation of organic compounds 16,17 . Herein, Sodium bismuthate is found to be an effective oxidizing agent for oxidation of Cr (III) to Cr(VI). Sodium bismuthate has many advantages like not expensive, easy to handle and non-toxic. Cr(III) was oxidized to Cr(VI) which in acidic medium develops a pink color with DPC and the species so formed absorbs at 540 nm II. Experimental 2.1 Apparatus: A Lab India UV-VIS 3200 double beam spectrophotometer equipped with quartz cuvette of 1 cm optical path was used for all the absorbance measurements. ELICO pH meter (LI 120) was used for pH measurements. 2.2. Reagents: Chromium(III) nitrate nonohydrate (Cr(NO 3 ) 3 .9H 2 O, Sigma Aldrich) was used to prepare the stock solution of Cr(III). All other reagents used were of analytical grade. Stock solution of Chromium(III) (1mg/ml) was prepared by dissolving Cr(NO 3 ) 3 .9H 2 O (0.7698 g) in 2 N sulfuric acid and diluted to 100 ml with deionized water. DPC solution was prepared by dissolving 0.01 g of diphenylcarbazide in 10 ml acetone.