Strategy of Fusion Bead Correction in Xrf Analysis of Powders

An empirical calibration method for fused bead analysis by XRF spectrometry with advanced corrections has been established. These calibrations include matrix effects, weighing inaccuracies, loss on ignition (LOI), gain on ignition (GOI), decomposition of oxidizing agent and evaporation of flux. The corrections for these common sources of error in the fusion method are incorporated into the basic calibration equation using actual weights for the sample, oxidizing agent, flux and fused bead. There are two correction models, a flux weight model using sample and flux weights and a bead weight model using sample and fused bead weights. The latter model is advantageous in correcting for flux evaporation when required. The fusion bead corrections are applied in the analysis of iron ore and copper concentrates to demonstrate how the various source of error are successfully corrected in a universal fashion using the advanced method. INTRODUCTION The fusion bead method is an effective sample preparation technique for accurate analysis of a wide variety of powder samples by XRF spectrometry such as ores, rocks and refractory materials since it eliminates heterogeneity effects associated with grain size and mineralogical composition. In order to obtain highly accurate results, it is necessary to provide a constant flux-to-sample ratio (flux ratio) in each preparation of a given sample type. Even if weighing is performed precisely, variation in flux ratio may occur owing to loss on ignition (LOI) or gain on ignition (GOI) of the sample, evaporation of the flux or decomposition of oxidizing agents during fusion. These influences introduce analytical errors in the fused bead method by altering the flux ratio and x-ray absorption properties of the matrix. Prior attempts to correct these sources of variation based on flux weight and sample weight and to correct for LOI/GOI were applied in the calibration equation for ore analysis via the fusion method (ISO9516-1: 2003(E)), but the application of these corrections is limited and inflexible. We have established a unique, easy-to-use, universal fusion bead correction method for the empirical calibration method with matrix correction for fusion bead analysis. The advanced correction equation has been derived from a theoretical intensity equation based on the principle of X-ray absorption characteristics. The equation consists of alpha coefficients computed by a fundamental parameter (FP) method. The software computing alpha coefficients is capable of Copyright ©JCPDS-International Centre for Diffraction Data 2012 ISSN 1097-0002 242