HALOGEN-ASSISTED CLEANING AFTER-TREATMENT IN GRAPHITE-FURNACE ATOMIC-ABSORPTION SPECTROMETRY FOR ANALYSIS OF MOLYBDENUM-BASED MATERIALS

Carbon tetrachloride and carbon tetrafluoride were tested as possible halogen precursors in the cleaning after-treatment stage in graphite furnace atomic absorption spectrometry for the removal of the interfering molybdenum matrix. The results show that applying sample masses up to 0.1 mg of molybdenum introduced as metal, oxide and silicide, the matrix can be effectively volatilized. Interference effects caused by residual halogenated pyrolytic products retained in the atomizer after the carbon tetrafluoride treatment can be effectively eliminated by using a mixture of hydrogen and argon as a purge gas in the atomization stage. By this gas-phase modification procedure, the signals of Co, Cr, Cu, Fe, Mg, Mn and Ni can be recovered to the original level. The procedure improves the analytical lifetime of the graphite atomizer to up to 200-300 replicate runs.