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Introduction
This section intends to introduce the reader to basic dispensing techniques and to
familiarize him or her to the XFP-01.
Flux weighing
basics
When preparing samples for XRF by fusion, the spectrometer will measure the
concentration of the sample atomic components in the flux matrix. This means
that the matrix itself must be accurately known and prepared.
This assumption means that there are two methods to dispense the sample and
flux: an “absolute” (fixed weights) method and a “relative” (ratio) method.
In the absolute method, both the sample and the flux are dispensed in pre-
established amounts, e.g. 7.0000g flux and 0.2000g sample. This is the traditional
method, when both the sample and the flux are weighed by hand.
In the ratio method, the sample is weighed first, and then the flux is added in an
accurate proportion. In the previous example, the ratio is 7:0.2. If the amount of
sample was actually, say, 6.9303g then the amount of flux should be 0.1980g to
maintain the desired ratio. As long as the ratio is maintained, there will be no
analytical difference, but that requires manual calculations, unless an automatic
dispenser is used.
Automatic
dispensers
Because of the risk of human errors, and to increase productivity, many
laboratories are now adopting automated flux dispensers as the standard
equipment to weigh the fusion flux.
Furthermore, while the XFP-01 does not dispense the sample, it can dispense the
flux as a function of the sample amount, which does not need to be accurate as
the dispenser will ensure that the desired ration is maintained.
