Determination by XRF of trace amounts of Ga and In in geological samples preconcentrated with macroporous resins loaded with 5-phenylazo-8-quinolinol(5-PHAQ)

An X-ray fluorescence method using chelating resins for preconcentration ha s been developed for the determination of trace amounts of Ga and In. The c helating resins are obtained by sorption of the reagent 5-phenylazo-8-quino linol (5-PHAQ) on macroporous resins Amberlite XAD-4 and XAD-7. All the var iables related to the adsorption of the organic reagent on the resin (pH, t emperature, time, concentration of the reagent, etc.) and the retention of the metals on the loaded resins were studied. X-ray fluorescence intensitie s of the analyte retained on the resins were measured on thin film supporte d on a membrane filter and concentrations were determined using calibration curves. The detection limits were 98 and 81 ng.mL(-1) for Ga and In, respe ctively. This method was applied to the determination of Ga and In in test samples and standard rocks of the USGS.