EFFICIENCY AND EVALUATION - Total-Reflection X-Ray Fluorescence Analysis and Related Methods - page 397

Figure6.6. Results from all participants of IMEP-14 (sediment) related to the content of zinc [82].
The fitted black curve shows the form of a deckchair, which is typical for proficiency tests with a
large number of participants. The shaded band contains the reference value 4.95 mmol/kg (yellow
straight line) with a confidence interval of ± 10%. Individual values were determined by FAAS
(green), by ICP-MS (blue), and by TXRF (red). Figure from Ref. [83], reproduced with permission.
Copyright2001, Royal Society of Chemistry.
FAAS, and 5.6% for ICP-MS. These values show a rather equal ranking of
the three techniques.
The final report of IRMM represents an overview of the results of all
participants [82]. For any element, the results are ordered and plotted in
diagrams with increasing values. Figure 6.6 gives a typical example for the
element zinc [83]. The three bars of TXRF, FAAS, and ICP-MS are colored
red, green, and blue, respectively, and are lying within the uncertainty band of
the reference value almost completely. The test demonstrates the high accuracy
and multielement capability of the three techniques, even for a complex matrix.
FAAS seems to be slightly superior to TXRF and ICP-MS, although it is more
laborious and time consuming. TXRF shows somewhat poorer detection limits;
however, it requires a much smaller amount of sample volume and it is the most
simple and rapid technique.
6.2UTILITYANDCOMPETITIVENESSOFTXRFANDGI-XRF
Total reflection XRF is a universal and economic method of multielement
analysis. It is a microanalytical tool suitable for cases when only small sample
amounts are available. The minute specimens have only to be placed on flat,
totally reflecting carriers. In addition, TXRF is effectively applied to trace
analyses of the elements when larger sample amounts are available. Aqueous
solutions, high-purity acids, and body fluids are analyzed down to the pg/ml