Rapid Screening of Food with TXRF

In the interest of nutrition science and food safety it is of big interest to have a fast screening method for metals in nutrients. Bruker has undertaken extensive research to determine the suitability of total reflection X-ray fluorescence analysis (TXRF) for this purpose. Here a focus was laid on the analysis of fish (including a DORM-3 fish protein standard by the National Research Council of Canada) and vertebrate samples (chicken, beef and horse muscle tissue). Results were checked against measurements with ICP-MS (inductively-coupled-plasma mass-spectrometry).

Samples for fast element screening were ground in a bench top ball mill with Zr jar for 3 min at 50 Hz. A Se standard solution was added (end concentration 4 mg/kg) as an internal standard for TXRF. Part of the samples were applied to microwave digestion. TXRF measurements were performed on suspended samples as well as on the digested samples using the Bruker S2 PICOFOX TXRF spectrometer. The digested samples were also analyzed with the Bruker aurora M90 ICP-MS for comparison.

The analysis of the certified reference fish standards and typical fish and vertebrate samples show that that rapid screening of macro and trace elements by TXRF is possible. For many elements (Ka, Ca, Mn, Fe, Ni, Cu, Zn, As, Se) results are in good accordance with those by ICP-MS. Some elements are a little more difficult to measure, either because of absorption effects (Na, Mg) or due to high spectral background (Ti, V, Cr) but in all cases detection limits sufficient for screening can be attained. Therefore, TXRF is a powerful complementary tool to more sensitive, but highly sophisticated ICP-MS.