EXTRACTIVE SPECTROPHOTOMETRIC DETERMINATION OF RHODIUM (III) USING 2-(5- BROMO-2- OXOINDOLIN-3-YLIDENE) HYDRAZINECARBOTHIOAMIDE AS AN ANALYTICAL REAGENT

2-(5bromo-2oxoindolin-3-ylidene) hydrazine carbothioamide, [5-Bromoisatin thiosemicarbazone (HBITSC)] extracts Rhodium (III) quantitatively (99.20%) into n-amyl alcohol. The n-amyl alcohol extract shows an intense peak at 495nm (λ max). Beer’s law is obeyed over the Rh (III) concentration range 1.0 – 6.0ug/ml. The molar absorptivity is 3345 dm molecm at 495 nm and Sandel’s sensitivity is 30.76 ng/cm. The composition of extracted species found to be 1:3 (Rh: HBITSC) by Job’s continuous variation and Mole ratio method. Interference by various ions has been studied. The proposed method has been applied for the determination of Rh (III) in synthetic sample. KEYWORD: HBITSC, Iridium, Spectrophotometry, Molar Absorptivity. Barhate et al. European Journal of Pharmaceutical and Medical Research www.ejpmr. com 476 hydrochloric acid to get 10 mg per cm solution of Rh(III). Working solutions of Rh (III) were made by suitable dilutions. All other reagents used were of AR grade and all the solutions were prepared in doubly distilled water. Extractive Spectrophotometric Determination of Rh (III) To an aliquot of aqueous solution containing 10.0 to 60.0 μg of Rh (III), 3.0 cm of citrate buffer solution of pH 5.5 and 1.5cm of 1% solution of HBITSC prepared in DMF was added. Resulting solution was digested for 30 min in boiling water bath. After cooling the volume of solution was made up to 10 cm with distilled water and then equilibrated for 1 min with 10cm of n-amyl alcohol and the phases were allowed to separate. The n-amyl alcohol extract was collected in a 10 cmmeasuring flask and made up to the mark with n-amyl alcohol. The absorbance of n-amyl alcohol extract was measured at 495 nm against a reagent blank prepared under identical conditions. The Rhodium content of the sample solution was determined from calibration curve. To study the effect of other ions, the respective foreign ions were added to aqueous phase before the extraction and adjustment of pH. Determination of Rh (III) in alloy sample 0.1 to 0.2 gm sample was dissolved in boiling with 10 ml of aquaregia. The resulting solution was evaporated to dryness and the residue was then dissolved in 10 cm of 1M HCl, filter, if required and solution was diluted to 100 cm with doubly distilled water. The working solution was prepared by appropriate dilution of stock solution. To an aliquot of this solution 1cm was analyzed for Rh(III) by the procedure as described earlier. RESULTS AND DISCUSSION Rh (III) could be extracted quantitatively (99.20%) by HBITSC into namyl alcohol from an aqueous solution of pH 4.0 to 6.2 and in the presence of 3.0 cm of buffer solution (citrate buffer) of pH 5.5 and 1.5 cm of 1% solution of HBITSC prepared in DMF. Solvents used for extraction of Rh (III) can be arranged on the basis of their extraction coefficient values as namylalcohol>nbutylalcohol> ethylacetate>benzylalcohol>chloroform> carbontetrachloride> toluene> nitrobenzene>xylene> chlorobenzene. Here namyl alcohol was found to be the best extracting solvent hence; it was selected for the extraction throughout the work “Fig-1” The namyl alcohol extract of Rh -HBITSC complex showed an intense peak at 495 nm “Fig – 2”. The absorbance due to the reagent is negligible at this wavelength, so the absorption measurements were taken at this wavelength. The result shows that the system confirmed to Beer’s law at this wavelength over a Rh (III) concentration range of 1.06. 0 μg/ cm “Fig -3”. The molar absorptivity of the extracted complex on the basis of Rh (III) content was calculated to be 3345 dm 3 mole –1 cm –1 . It was found that 1.5 cm of 1% solution of HBITSC prepared in DMF was sufficient to extract 60 μg of Rh (III). The colour of the namyl alcohol extract was found to be stable at least 36 hrs. at room temprature. Fig. 1 Percentage Extraction of Rh (III) into Various