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

摘要

Bis(salicylaldehyde)orthophenylenediamine (BSOPD) has beenproposed as new analytical reagent for the direct spectrophotometricdetermination of chromium. It reacts with chromium(VI) in slightlyacidic (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 ofthis method is that the molar absorptivities of the Cr^{VI} -- BSOPDcomplex formed in the presence of nonionic TritonX -- 100 surfactantare almost 10 times higher than the value observed in aqueoussolution. This results in enhancing the sensitivity and selectivityof the method. The reaction is instantaneous and the maximumabsorbance was obtained at 482 nm and remains constant for over 24h.The average molar absorption coefficient and Sandell's sensitivitywere found 3.5 imes 10^5 L mol^{-1} cm^{-2} and 5 ng cm^{-2} ofCr(VI), respectively. Linear calibration graphs were obtained for0.01 -- 12.0 mgL^{-1} of Cr(VI) with correlation coefficient value0.9987 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 thevalidity of the method and the results of analyses were found to be in excellent agreement with those of certified values. The developedmethod was also used for the determination of chromium in someenvironmental 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.