An automated method for the determination of lead in calcareous materials utilising liquid ion exchange

Abstract

An automated method for the determination of lead in calcium carbonate, lime and limestone with the Technicon AutoAnalyzer is described. The method is based on the extraction of lead from an acidic chloride solution of the sample with a long-chain amine liquid ion exchanger, followed by re-extraction into an ammonia-ammonium citrate buffer at pH 9. Finally, the lead is extracted as the lead-dithizone complex into chloroform and the optical density of the complex measured at 510 nm. The separation of lead prior to formation of the lead-dithizone complex results in low background and blank readings. Lead levels of 0 to 20 p.p.m. can be determined at a rate of twenty samples per hour. Other trace metals which occur in calcareous materials do not interfere.