Determination of Magnesium and Zinc in Iron and Steel by Atomic Absorption Spectrophotometry

Abstract

Trace amounts of magnesium and zinc in iron and steel were separated by an extraction with 2-thenoyltrifluoroacetone (TTA) in methylisobutylketone (MIBK) under the existence of ammonium tartrate and determined by atomic absorption spectrophotometry. The recommended procedure is as follows.
Take 0.1g of sample and decompose it with 10ml of 6N hydrochloric acid by heating. Oxidize the iron with several drops of nitric acid and evaporate the resulting solution to about 2 ml. After cooling, dilute the whole to about 10ml with water and add 10ml of 10% ammonium tartrate. Adjust the pH with 7N ammonia water to 8.5 when magnesium is determined or to 8 when zinc is determined. Transfer the solution to a separator) funnel and shake for about 2 min. with 10 ml of 0.01M TTA-MIBK solution when magnesium is determined or with 10 ml of 0.1M TTA-MIBK solution when zinc is determined. Discard the aqueous layer and transfer a part of the organic layer through a dry filter paper to a sample cell. Spray it into acetylene-air flame and measure the absorbance against the blank solution at 2852 rrip when magnesium is determined or at 213.8mμwhen zinc is determined.
By this procedure, from 0.0001 to 0.0050% of magnesium and from 0.0001 to 0.0100% of zinc in iron and steel were determined within 30 rnin. The interference of the co-existing impurities in iron and steel was negligible.