To detect low concentrations of substances in some cases it is impossible to avoid concentrating them in special catchers. An example of such necessary concentration is detection of impurities in permanent gases (Ne, He, H2, Ar, O2, N2, Kr, Xe), at that concentration of impurities is no less than 1 ppm. Taking into account that such impurities may not be only hydrocarbons but also permanent gases themselves it is impossible to use katharometer for direct detecting of impurities. It is also not always possible to use high-sensitive, but expensive detectors (PDD, ECD, etc.).
Photo: Cryoconcentration device
In such cases cryoconcentration is used, that is concentration of impurities in the catcher (usually it is U-form pipe filled with sorbent) placed in Dewar vessel filled with liquid gas, for example nitrogen (boiling temperature of nitrogen -196°C).
Extraction of concentrated impurities is done by temperature rise, for example by putting the catcher into the can with room temperature water.
- Catcher volume — 5 ml.
- Dewar vessel volume (serial metal thermos) — 1200 ml.
- Concentration temperature range from -88,6 (ethane) to -269 °C (helium).
- Possibility of chromatograph calibration from the tank without breaking gas scheme.
- ВPossibility to do gas purification of the gas meant for catcher blowdown from impurities (in similar catcher) together with concentrating.
- Overall dimensions, no more than 290×470×615 mm.
- Mass, no more than 8 kg.