B - 1
HAPSITE ER Operating Manual
Appendix B
Calibrating Gas Mixtures
B.1 Acquisition, Preparation, and Handling
Failure to calibrate the instrument may give you
inaccurate identifications when sampling.
When using chemicals, wear the appropriate PPE
according to the MSDS.
HAPSITE (or any GC/MS instrument) must be calibrated at one or more
concentration levels of the organic compound(s) of interest for quantitative
analysis. In the case of the HAPSITE, the compounds of interest must be supplied
to the instrument as a gaseous mixture of known volume/volume composition
(mole/mole % or ppmv levels in air or nitrogen) and at atmospheric pressure.
There are a number of important factors to consider in acquiring, preparing, and
handling gaseous standard calibration mixtures. These can be organized in three
groups:
1 How to establish the desired concentrations of the required compounds. See
section B.1.1 on page B-1.
2 Correct delivery of the mix to the inlet of the HAPSITE. See section B.1.2 on
page B-3.
3 Gas cylinder safety, contamination checks and corrective steps in the
equipment. See section B.1.3 on page B-5.
B.1.1 How to Establish the Desired Concentrations
There are two basic ways to obtain several concentrations of a given mix of
compounds. The compounds can be bought, premixed to specification, in cylinders
containing the several concentrations desired. A master cylinder of the compounds
can also be purchased at the highest concentration needed, and diluted to the
lower required concentrations. Each of these options is discussed in the following
sections.
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