The 491M Modular Gas Standards Generating System, from Kin-Tek Laboratories Inc., dynamically blends calibration standards for common contaminants in food grade carbon dioxide. Trace Source? permeation tubes are used to add known concentrations of typical sulfur and oxygenate species to a flow of purified beverage grade CO2. Since there may be background contamination remaining in the diluent CO2, the standard additions technique is used. Calibration is based on the known difference in analyte concentration due to the addition. A secondary dilution feature gives low ppb and ppt concentrations adjustable over a 400:1 range. Mixture concentrations are traceable to NIST through physical standards.
Trace sulfur, oxygenates, and other naturally occurring impurities in carbon dioxide used for carbonation can create "off taste" and "off odor" in beverage products, so the CO2 purity must be monitored. Effective calibration of the monitoring systems requires traceable reference standards at multiple concentrations for each of the potential contaminants. Typically, static mixtures containing trace concentrations of the typical contaminant compounds are not stable in storage.
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