Bio-Science CI-900, Operation Manual, Page: 12 / 94

CI-900 Instruction Manual 8/10/2015
1554 NE 3
rd
Ave, Camas, WA 98607, USA Phone: (360) 833-8835
sales@ cid-inc .com www.cid-inc.com
7
Table 1: Interfering Gas and the CI-900 sensor
Ripening fruit emit a complex mixture of hydrocarbons, including ethylene. Oxidation of these other
gases in the electrochemical sensor cannot be readily distinguished from ethylene. This causes the
ethylene value to be falsely high in the presence of interfering gas. CID Bio-Science has tested a
method to absorb some of the competing gases and provide better ethylene measurements. This
method, PolarCept, uses distilled water in conditioning Chamber In and has been shown to filter out
alcohols and produce less interference.
PolarCept
PolarCept is the use of distilled water in conditioning Chamber In to filter out or trap some of the
interfering gases. Gas from the sample environment is passed through the water trap. Some of the
polar molecules are held in the trap, while ethylene passes through the water trap to the sensor,
where oxidation occurs. CO
2
is released as the oxidation product from the sensor. The water being
used can become saturated after several minutes, so it must be cleaned of the trapped interfering
gas molecules. Trapped interfering gases are driven out of the water during the cleaning time by a
concentration gradient.
It is recommended to always use the PolarCept filter when measuring a gas mixture or
interfering gases present will be reported by the instrument.