ThermoFisher Scientific 43iQHL, Instruction Manual

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Calibration
Equipment Required
4-2 43iQHL Instruction Manual Thermo Scientific
An SO
2
-free (< 0.0005 ppb) air supply is required for the proper calibration
and checkout of the instrument. There are several methods that are
acceptable to generate this zero air.
Generation of a good span from cylinder gases presents a special set of
circumstances. Many cylinder multi-blend span gases containing NO and
SO
2
are delivered in a balance gas of ultra high purity Nitrogen. Since NO
produces a positive interference in the 43iQHL, gases such as these can
produce an inaccurate span. There is no problem in real-world sampling
because they contain both oxygen and carbon dioxide, both of which
quench the NO interference ( Figure 4–1 ). Therefore, the solution is that
span gases approximate the composition of typical stack gases and should
contain a minimum of 10%, 100000 ppm, of carbon dioxide.
Figure 4–1. NO Interference Data
Commercial heatless air dryers filled with a mixed bed of activated charcoal
and a 13X molecular sieve have been found effective in removing SO
2
from
compressed air. The use of this type of zero gas system is recommended
when minimum maintenance is of prime importance. This system requires
a source of compressed air. Refer to the manufacturer’s recommendations
for installation of such a system.
Zero Air Generation
Commercial Heatless Air
Dryers