An automated method for the determination of molybdenum in geological and biological samples

Abstract

A Technicon AutoAnalyzer is used for the colorimetric determination of molybdenum on the basis of its catalytic action on the potassium iodide-hydrogen peroxide reaction. The procedure is sensitive enough to determine 0·2 µg l^–1 of molybdenum with no pre-concentration. The method has been applied to the direct determination of the element in marine and fresh waters, milk and plant samples after dry ashing, and standard rock samples after alkaline fusion. Chromate interference can be removed if necessary by evaporation of the sample solution to dryness with hydrogen peroxide. A correction must be applied if vanadium is present in 2-fold excess over molybdenum. Large variations in ionic strength have a marked effect on the determination.