Functions and setup of the contrAA 600
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Edition 01/2014
contrAA 600
selected dynamically for each spectrum by a specific algorithm that is based on criteria
which guarantee the most accurate possible approximation to the actual base line at the
measurement pixel. For analysis wavelength overlaps with fine-structured background, a
multivariant method can be applied. Reference spectra for matrix components are then used
for the polynomial-generating "least squares" adjustment. If atomic lines overlap directly with
the analysis wavelength, an inter-element correction (IEC) can be performed. Neighboring
spectral lines in the observation width of the interference element are use for the correction
(e.g.: correction of the spectral interference of Fe at the wavelength of Zn at 213 nm or Se at
196 nm).
The automatic and simultaneous background correction with the use of correction pixels
corrects the lamp drift and all broadband effects directly from the spectra. The result is a
simultaneous double beam system with just a single optical path, which results in much
higher measurement stability compared to the traditional LS AAS. The sensitivity comparable
to the LS AAS is achieved when using 3 to 5 measurement pixels per absorption profile. The
extremely low-noise CCD line receiver in the contrAA 600 allows a signal-to-noise-ratio that
is, to some extent, considerably improved compared to the photomultipliers that are normally
used with the LS AAS and thus present much better detection and determination limits.
5.2
Xenon lamp
The contrAA 600 has a Xenon short arc lamp as a continuum source.
Due to a special electrode geometry, a hot focal spot (hot spot) is created. This hot spot has
a high intensity of radiation over the whole spectral range that is relevant for the AAS from
185 - 900 nm.
During each measurement the image of the focal spot is controlled at the entrance gap and
automatically readjusted. Start-up behavior due to lamp drift is not to be expected. All drifts
of the xenon lamp are calculated simultaneously from the spectra with the use of correction
pixels.
Fig. 7
Xenon lamp without housing
