Direct and Derivative Spectrophotometric Determination of Chromium(VI) in Microgram Quantities Using 5-Bromo Salicylaldehyde Isonocotinoyl Hydrazone (5-BrSAINH)

A highly sensitive and selective spectrophotometric method was developed for the determination of trace amount of chromium (VI) in aqueous DMF medium. The chromate ion forms a light brown colored complex with 5-Bromo salicylaldehyde isonocotinoyl hydrazone (5-BrSAINH) in an acidic buffer of pH 6.0. The complex has an absorbance maximum at 430nm, was stable for more than 72 hours. Beer's law is obeyed in the range 0.16 - 3.90 μgml-1. The molar absorptivity and sandell's sensitivity of the colored solution were found to be 2.0 x 104 L.mol-1cm-1 and 2.6 X 10-3 μgcm-2, respectively. The light brown colored complex has 1:1 (Chromium (VI) - 5BrSAINH) Stoichiometry. The stability constant of the complex was determined as 1.40 X 106 by Job's method. The effect of foreign ions on the determination was studied. A sensitive and selective first and second order derivative spectrophotometry has also been proposed for the determination of Cr (VI). The interference of various cations and anions were studied. The developed methods were successfully employed in the determination of Cr (VI) in soil and standard steel samples.