A Simple and Rapid Spectrophotometric Determination of Trace Level Simple and rapid spectrophotometric determination of trace level chromium using bis (salicylaldehyde) orthophenylenediamine in nonionic micellar media

Authors: RUBINA SOOMRO, JAMALUDDIN AHMED, NAJMA MEMON

Abstract: Bis(salicylaldehyde)orthophenylenediamine (BSOPD) has been proposed as new analytical reagent for the direct spectrophotometric determination of chromium. It reacts with chromium(VI) in slightly acidic (0.1 -- 0.3 M H_2SO_4) micellar medium to form a yellow - orange chelate with a molar ratio 2:3. The most remarkable point of this method is that the molar absorptivities of the Cr^{VI} -- BSOPD complex formed in the presence of nonionic TritonX -- 100 surfactant are almost 10 times higher than the value observed in aqueous solution. This results in enhancing the sensitivity and selectivity of the method. The reaction is instantaneous and the maximum absorbance was obtained at 482 nm and remains constant for over 24h. The average molar absorption coefficient and Sandell's sensitivity were found 3.5 \times 10^5 L mol^{-1} cm^{-2} and 5 ng cm^{-2} of Cr(VI), respectively. Linear calibration graphs were obtained for 0.01 -- 12.0 mgL^{-1} of Cr(VI) with correlation coefficient value 0.9987 for Cr -- BSOPD complex. Large excess of over 50 cations, anions and complexing agents do not interfere in the determination. The method was successfully used in the determination of chromium(VI) from synthetic mixture and certified reference materials to test the validity of the method and the results of analyses were found to be in excellent agreement with those of certified values. The developed method was also used for the determination of chromium in some environmental waters (potable and polluted), biological samples (blood and urine) and to determine chromium species. The results of the biological analyses by the proposed method were in good agreement with those of by AAS.

Keywords: Micellar spectrophotometry, chromium determination, Bis(salicylaldehyde)orthophenylenediamine, environmental and biological samples

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