Abstract
A technique for microscale ion-exchange separation of manganese at 0.1ng levels was developed and combined with flow-injection spectrophotometry based on manganese-catalyzed oxidation of malachite green with periodate. A sample (0.2 to 1.5g) was dissolved in less than 4.5ml of a 0.04M ammonia-0.16M ammonium chloride buffer solution (pH 9). The solution was then passed through a chelate resin micro column of 20 μl capacity (Dowex A-1, 50 to 100 mesh) to adsorb manganese and to remove the interfering matrix salt. The adsorbed manganese was eluted with 0.3ml of 2M nitric acid. A column of 10μl capacity could be used for less than 1ml of the sample solution. After evaporation of the effluent, the residue was dissolved with 0.1M acetate buffer solution (pH 4.4), and a 100μl aliquot was injected into a flowinjection system. The reduction of absorbance of malachite green was measured at 615nm after reaction for 6.5min at 50°C. Manganese of ppb levels in high purity salt is determined within a standard deviation of about 0.1ppb.
