Determination of rare earth trace amounts in mixtures with complexone 3

Ways for effective masking complexone 3 (ethylenediaminotetraacetic acid) to determine trace amounts of r.e.e. in process solutions obtained during ion exchange and chromatographic processes of lanthanide separation are investigated. A unified procedural approach to analysis of such solutions has been developed. By selecting the corresponding nonrare-earth element it is possible to exercise selective control of process and experimental solutions. The patterns developed enable one to determine r.e.e. in mixtures with predominant amounts of complexone 3 and, in particular, with a ratio r.e.e.: complexone 3 = 1:1O0. In the aliquote part of the solution the total content of complexone 3 is determined by titrating with zirconium chloride in a medium of 0.5 N NCl with indicator arsenazo 3. The second aliquote part of the solution, equal to the first one, is treated with a calculated amount of cobalt chloride, then pH 3.0 - 3.2 is set up, a solution of arsenazo 3 is added, and a 0.2 M solution of acetic acid previously neutralized with ammonia to pH 3.1 is poured in up to the mark. The light absorption by the solution is measured at 656 nm, and the r.e.e. in the sample analyzed is determined using a previously plotted graph. Analysis of process solutions takes 5-10 min. The accuracy is 1-2 rel.%