Mechanisms of atomization of molybdenum in graphite furnace atomic absorption spectrometry

Abstract

Mechanisms of atomization of molybdenum in graphite furnace atomic absorption spectrometry have been investigated using platform technique along with X-ray diffraction spectrometry, scanning electron micrography, energy dispersive X-ray and Auger electron spectrometry. Three molybdenum oxides: MoO 2(s), MoO 3(s) and Mo 4O 11(s), have been identified—all formed at relatively low temperatures (< 1500 K). Crystallites of MoO 2 of relatively large size are formed on the pyrolytic graphite surface. When molybdenum is atomized from a pyrolytic graphite surface, the charring curve of molybdenum shows a dip in absorbance in the temperature range 1200–1800 K. Hence, a charring temperature < 1200 K should be used for determination of molybdenum when a pyrolvtically coated graphite tube or a platform made of pyrolytic graphite is used. Mo s, MoC s and Mo 2C (s) have been found on both pyrolytic graphite and electrographite surfaces in the charring step. Formation of Mo g, by direct sublimation of Mo (s) and/or dissociation of MoC (g) are all spontaneous reactions at the temperatures considered.