DETERMINATION OF POTASSIUM AND CALCIUM IN MILK POWDER BY ENERGY-DISPERSIVE X-RAY-FLUORESCENCE SPECTROMETRY

A rapid method for the simultaneous determination of postassium and calcium in milk powder by energy-dispersive x-ray fluorescence (EDXRF) spectrometry was developed. The measurement system consists of a Si(Li) detector, an x-ray tube coupled with titanium as a secondary target, a DEC-350 computer and a nonlinear fitting least-squares program. The methods of calibration and standard preparation are discussed. Milk powder was analysed as pressed pellets using counting times of 100 s. Concentrations were determined by a standard calibration graph method using synthetic standards. The minimum detection limits are 0.011% and 0.007% for potassium and calcium, respectively. The accuracy was ascertained by analysing standard reference materials from the International Atomic Energy Agency. Good agreement was found between the certified and measured values. Potential applications of this method are indicated.