Total Reflection X-Ray Fluorescence (TXRF) is a very useful technique for a multi-elemental analysis of diverse matrices samples. It has been used for environmental purposes and offers lower detection limits for devices traditionally used for chemical laboratories. TXRF can be performed on small samples with volumes of a few microliters and masses of nanograms to micrograms. Such small sample sizes ensure that total reflection at the sample substrate will not be disturbed and, above all, that the fluorescence radiation will not be absorbed or enhanced by the sample mass itself. Because matrix absorption and enhancement effects are avoided, the calibration curves for TXRF are straight lines characterized only by slope or sensitivity and are independent of the properties of the sample matrix. Quantification can thus be performed by internal one - element standardization, in which a single standard element is added either before the sample is prepared or after it is placed on the substrate. Concentrations of the unknown elements can then be calculated by comparing the net intensity of the unknowns with the net intensity and concentration of the internal standard. However, one difficulty is that this technique has the choice of the optimal concentration of the internal standard to be used. Based on this, we apply a series of different concentrations of the internal standard solution Gallium to check the influence of the concentration of this element in determining the levels of a multi-elemental contents in a standard solution.

Sponsored by CNPq and FAPEMIG.