DIFFERENT FIELDS OF APPLICATIONS - Total-Reflection X-Ray Fluorescence Analysis and Related Methods - page 307

For routine analyses of sediments, microwave digestion with nitric acid can
be recommended [60]. Up to 20 elements were determined in sediments of the
German shoals (“Wattenmeer”), that is, for the fine-grained fraction of less
than 20 μ m diameter. The mass fractions ranged from mg/g down to ng/g,
covering five orders of magnitude. Coastal sediments were also analyzed with
regard to heavy metals [61]. Metals of the lanthanides were determined in ore
minerals [62]. Rock CRMs were investigated after digestion or fusion [63].
Digestion of the powdered samples was carried out with HF, HNO 3 , and
HClO 4 by heating. Fusion of the powders was applied with LiBO 2 (lithium
metaborate) at 1100 ° C followed by dissolution of the glass melt. Sample
powder of 50-100 mg was decomposed with ∼ 5 ml solutions. In each case,
selenium was added as an internal standard and 10 μ l of the final solutions was
pipetted on quartz-glass carriers. The uncertainty of sample preparation could
be neglected in comparison to that of measurements. In comparison to simple
suspension, a digestion or fusion of samples deteriorates detection limits
threefold. A comparison with certified values of the CRMs showed a good
agreement for all three methods of sample preparation.
A further example of TXRF analysis refers to approximately 300 different
soil samples that were collected at Mt. Kenya in the forest area above
1600 m [64]. The samples were dried, ground, milled, and sieved. By addition
of an aqueous solution of Triton X-100 and selenium as an internal standard,
slurries were prepared and 10 μ l droplets with 180 μ g soil were analyzed by
TXRF. Elements from Al to Zn were detected; QXAS/AXIL software was
used for quantification. The elemental composition could be determined
between 0.01 and 100 mg/g with a standard deviation smaller than 1% and
a recovery rate of 90-110%. Topsoil and subsoil samples could be distinguished
and compared with Canadian soil samples.
A comprehensive review of TXRF applied to samples of geological origin
was given by Revenko with 219 references [65].
5.2BIOLOGICALANDBIOCHEMICALAPPLICATIONS
In addition to biomonitoring, the application of TXRF in the field of bio-
chemical and biological research has become a focus of attention in the last
decade. The analysis of biological matrices can have an environmental aspect as
well as a nutrimental one. The environmental aspect is concerned with pollution
and its monitoring by appropriate plants like moss or lichen [66,67]. The
nutrimental aspect deals with the assimilation and metabolism of various
foodstuffs by an organism. The effects that certain elements and in particular
some element species have on health are examined. Biochemical studies of
macromolecular systems can be of medical, clinical, or pharmaceutical impor-
tance as well (Section 5.3).
A review on TXRF analyses of biological samples was presented by Marcó
etal . [68]. Slurry sampling, insitu microwave digestion, insitu chemical