In the present study Rhodamine-B dye has been used as a Chromogenic reagent for the determination of trace amounts of chromium (VI). The Spectrophotometric method developed is sensitive and can be used to determine nano gram quantities of chromium. Rhodamine-B ion forms an association complex with chromium in acidic medium (orthophosphoric acid) in presence of potassium iodide and ascorbic acid. Polyvinyl alcohol is used as solubilizing agent. Rhodamine-B-Chromium complex shows absorption maxima at 600nm and all absorbance measurements are made at this wavelength. Beer's law is followed up to 200 ng mL(-1) of chromium in solution. The molar absorptivity for the chromium complex was found to be 2.3x10(5) l mol(-1)cm(-1) at 600 nm. Job's method indicates that the molar ratio of chromium to Rhodamine-B is 1:3. Studies on the stability of complex and optimum concentration of dye, ortho-phosphoric acid, ascorbic acid and potassium iodide were carried out. Interference effects of several anions and cations were also studied.
