SPECTROPHOTOMETRIC DETERMINATION OF TRACE AMOUNTS OF LEAD IN HIGH-PURITY ZINC MATERIALS WITH IODIDE AND RHODAMINE 6G

A highly selective and sensitive spectrophotometric procedure for the determination of lead is developed. This is based on the interaction o f iodide complex of lead with Rhodamine 6G to form a pink product whic h absorbs maximally at 575 nm that is stable for 24 h when stabilized with gelatin. The Pb-I--Rhodamine 6G ternary complex was fully formed in the pH range 3.5-4.5 and solution should contain appropriate concen trations of I-and Rhodamine 6G. 100 fold amounts of various cations an d anions do not interfere in the determination of 0-20 mu g of lead (e psilon = 8.5x10(4) l mol(-1) cm(-1)). The method is precise and has be en applied to synthetic ''sea water'' samples and high purity zinc mat erials.