Quantification of elements in dietary supplements by total reflection x-ray fluorescence and inductively coupled plasma optical emission spectrometry

The main purpose of this study was the comparison of the results of quantification obtained via different sample preparation approaches such as microwave-assisted wet digestion (MAWD) and suspension preparation. Two total reflection x-ray fluorescence (TXRF) spectrometers equipped with Mo x-ray tubes were used to compare results obtained via two different paths of sample preparations which would further be compared to the conventional way of analysis by inductively coupled plasma optical emission spectrometry (ICP-OES) including MAWD. Three dietary supplement samples with different sets and concentrations of elements were analyzed. The benefits and limitations of the simplified path of sample preparation were highlighted. A round-robin test between TXRF and ICP-OES was discussed. Accuracy as the percentage of recovery in all measurements ranged from 80 to 120. Precision for all results did not exceed 8% for TXRF and 5% for ICP-OES. Limits of quantification by TXRF are ranged from 1 to 0.01 mg/pill for different elements. It was shown that suspension preparation of samples might be a useful response to increasing demand for quality control of dietary supplements since it is less time consuming and cost efficient.