Analysis of K, Ca, Fe, and Zn in Calcium-rich Powdered Milk

Powdered milk must contain many vitamins and minerals in order to correctly supplement an infant's nutrition. Iron is one such important nutrient and its concentration should be carefully controlled. A quick, reliable, and, above all, robust technique is required in order to be able to constantly monitor iron and other important minerals.

Energy-dispersive X-ray fluourescence analysis, in combination with special excitation filters, results in a procedure that can detect the most important elements without expensive sample preparation. The small X-ray spectrometer presented here is equipped with a programmable 35kV/9W X-ray tube and a high-resolution Si PIN diode. It offers high flexibility, selectivity, and precision for the analysis. In comparison with conventional methods, the method presented here results in time savings.

 Instrumentation: All measurements were performed with the SPECTRO TITAN SCD in the following configuration ­ 35kV­9W Rh side-window X-ray tube; five excitation filters, software-controlled, for improved selectivity and sensitivity; SiPIN diode. The analysis time per sample was equal to 200sec (Life Time).

Sample preparation: Ca. 5g of the sample material was pressed into a pellet with a diameter of 32mm.

Calibration: Synthetic powdered-milk samples were used for calibration. The evaluation is done with the help of the intensity correction model (a correction).

The IUPAC definition was used for calculating the detection limits (LOD).

LOD= 3xaUxC0/N0

where U: background pulse count; C0: concentration of sample (near LOD); N0: net pulse count. p Reproducibility. Typical powdered-milk sample was analysed 10 times.

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SPECTRO Analytical Instruments, Kleve, Germany. www.spectro-ai.com

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