I need help in devising a procedure to determine the molar absorptivity of an iron-dye complex in two solutions at a wavelength of 660nm. I have a UV-VIS spectrophotometer. Solution 1 is an acidic buffer (R1) containing the iron-binding dye Chromazurol B and ferric chloride. Some amount of an iron standard will be added to this solution, hopefully forming a colored complex with the dye. Solution 2 is Solution 1 with the addition of a neutral buffer (R2) raising the pH. I believe the molar absorptivity will change under varying pH. Accounting for dilution of Solution 1 would have to be taken into account. The ratios of the volumes of iron standard to R1 to R2 are 16:200:60.