Samples Containing Molybdenum

Overview

Molybdenum (Mo) is the least abundant of the group 6 elements (Cr, Mo, W) with an average concentration in the earth's crust of 1.2 ppm and existing predominately as molybdenite (MoS₂) and wulfenite (PbMoO₄) (Minerals yearbook 2009, USGS Volume1. Metals and Minerals).

Molybdenum is most commonly used in alloy steels where relatively small amounts result in great increases in strength and hardness. It is also used in catalysts, lubricants, corrosion inhibitors and pigments.

Mo exists in oxidation states ranging from +6 to +2 but the +5, +4, +3 and +2 states are typically air sensitive. Consequently, for the analyst the most common oxidation state for Mo is +6. Molybdenum has a chemistry that is somewhat unusual for the transition elements in that it is stable in a wide variety of matrices ranging from strongly basic solutions to water (less soluble at pH7), to acidic solutions containing, sulfuric acid, nitric acid, HF, HCl, and various acid combinations. Inorganic Ventures prepares single element 1000 µg/mL and 10,000 µg/mL Mo CRMs from MoO₃ (Mo VI) in dilute ammonium hydroxide/water giving the analyst the option of which matrix to use for the final calibration or QC solution. At Inorganic Ventures we prepare multi elemental blends of Molybdenum in all of these matrices, but tend to favor dilute nitric with trace HF where we have found solutions down to the low ppb level to be chemically stable for months to years.

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