D4294_16e1_8
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If you employ reusable cups,
clean and dry cells before use.
Disposable sample cups
are not to be reused.
Window material usually has less
than 10 micrometer polyester
or polycarbonate film
(See section 7.6).
Polycarbonate is preferred
due to its high transmissivity
of sulfur x-rays.
Renewal of the window
of the sample cup
is essential for the
measurement of each sample.
Avoid touching the inside
of the sample cup or portion
of the window film in the cup
or in the instrument window
that is exposed to x-rays.
Oil from fingerprints
can affect the reading
when analyzing for
low levels of sulfur.
Wrinkles in the film
will affect the number
of sulfur x-rays transmitted.
Therefore, the importance of the
film smoothness and cleanliness
cannot be over stressed to
ensure reliable results.
The analyzer will
need recalibration
if the type or thickness of
the window film is changed.
Impurities which may
affect the measurement
of low levels of sulfur have
been found in polyester films
and may vary from lot to lot.
Therefore, if using
a polyester film,
the calibration
should be checked
after starting each new roll.
Samples of high
aromatic content may
dissolve polyester,
polypropylene and polycarbonate
films.
In these cases, other
materials besides these films
may be used for x-ray
windows, provided
that they do not contain
any elemental impurities.
An optional window material is
6-micrometer-thick polyimide
foil.
While polyimide
foil absorbs sulfur
x-rays more than other films,
it may be a preferred window
material as it is much more
resistant to chemical attack
by aromatics and exhibits
higher mechanical strength.