DETERMINATION OF ~(87)Rb IN FOODS BY ATOMIC ABSORPTION SPECTROPHOTOMETRY

Ashed food samples are first treated with concentrated HNO_3 and HClO_4 inTrflon Crucible at 200℃, evaporated to dryness, and then H_2O_2 and HF areadded and again the mixture is evaporated to dryness. The residue is dissolved indilute HNO_3 and the resulting solution transfered to a volumetric flask after theaddition of small amount of KNO_3. The solution in volumetric flask is subject to atomic absorption spectropho--tometry and absorbance at 7800 A is measured to give the total Rb, and theamount of ~(87)Rb is calculated from its abundance in natural Rb. With 0.1 g sample using this method, 0.06 μg Rb/ml gives an absorbanceof 0.01. No interference is found from impurities frequenlty found in thesesamples.