ONLINE PRECONCENTRATION OF REFRACTORY ELEMENTS FOR ATOMIZER, SOURCE, INDUCTIVELY COUPLED PLASMAS IN ATOMIC FLUORESCENCE SPECTROMETRY (ASIA)

A simple flow manifold coupled to an atomiser, source, inductively coupled plasmas in atomic fluorescence spectrometry (ASIA) system for the pre-concentration of refractory elements is described. A miniature column of Amberlite IRA-93 anion-exchange resin was used to pre-concentrate refractory elements such as tungsten, molybdenum, zirconium and vanadium as their oxyanions from synthetic aqueous solutions before detection. A study of the parameters that affect the performance of the method is described. The pre-concentrated species were eluted with a stream of ethanolic ammonia directly into the nebuliser of the atomiser plasma. The limits of detection based on a sample volume of 35 ml (sampling time 5 min at 7 ml min-1) were 65 and 15 ng ml-1 for tungsten and molybdenum, respectively. Relative standard deviations of 4.28 and 5.24% were obtained for 0.5 and 0.1 μg ml-1 concentrations of tungsten and molybdenum, respectively. Further improvements in detection limits were obtained after modification to the instrument; although the main objective of this work was to develop a pre-concentration method applicable to the simultaneous determination of a number of refractory elements, this was not achieved. However, the proposed method could be used for pre-concentration of tungsten and molybdenum.