COPPER INTERFERENCE ON THE SPECTROPHOTOMETRIC DETERMINATION OF IRON AND THEIR SIMULTANEOUS DETERMINATION USING BATHOPHENANTROLINE-DISULFONIC ACID DISODIUM SALT

The interference of copper on the spectrophotometric determination of iron with bathophenantroline-disulfonic acid disodium salt was studied using an experimental design. Copper interferes even below pH 5 [1], forming a yellow complex with bathophenantroline which turned to green after 5 min. This complex showed a maximum at 425 nm with a molar abs orptivity of 7.5 x 10(3) L mol(-1) cm(-1). Microgram quantities of iro n and copper were determined simultaneously in water standard samples using bathophenantroline-disulfonic acid disodium salt at pH 4.8 and m easuring the absorbances at two wavelengths. The interference of iron on the copper determination was also estimated. The RSDs of the method for both Cu and Fe were below 1.7%. Recoveries for Cu and Fe were wit hin the ranges 97.2% to 98% and 99.7 to 100.5%, respectively. The meth od was applied to the determination of copper and iron in the waste wa ter from a water treatment plant. The results obtained by spectrophoto metry were compared with those obtained by flame AAS.