Gas purifiers are essential because they assist in providing a clean gas stream, which can guarantee the grade of the gas chromatographic analysis and the reliability of the results. Further, such gas purifiers minimize detector noise and prolong the life of the column. Gas purifiers are like insurance policies to safeguard the instrumentation and other analytical columns from various kinds of contaminants. Still, the gas purifiers will not be able to convert low purity gases into high purity gases. For this reason important factor, it is necessary to select the proper grade of gases with different purity levels for proper used in gas chromatographic applications.
Collection of Right Gas Purifier to fit your Applications
Numerous kinds of gas purifiers can be found in the market. Although some gas purifiers remove just one specific contaminant, other types remove multiple contaminants simultaneously from the gas stream. You must think about several factors through the selection procedure for gas purifiers, taking into consideration your specific applications. These factors includes the potential contaminants present in the gas stream, the limitations on flow and pressure, levels of gas purity required, desired convenience in replacement of spent gas traps, and space availability.
Common Traps Found in Gas Purifiers
Oxygen, hydrocarbon, carbon dioxide, and moisture traps will be the most common purifiers found in majority of the gas chromatography (GC) applications. Oxygen traps are usually packed with metal catalysts. Oxygen is considered as probably the most detrimental contaminating gas in all analytical columns. Oxygen is capable of producing irreversible oxidation damage, especially to polar stationary phases. Hydrocarbon traps are typically filled with activated charcoal, that may absorb organic compounds that are bigger than methane. Still, the molecular weight and size of the organic contaminants will have a definite effect on the capacity of the hydrocarbon trap to an excellent extent but it will also reflect on trap efficiency somewhat.
Activated charcoal possesses a higher capacity to trap larger hydrocarbons which are greater than C4, in comparison to smaller hydrocarbons, which are lesser than C4. Moisture traps are often packed with unique molecular sieves. When put through extensive heating, the crystalline structures are forced to reduce their hydration or water content. This opens a cavity which gets filled readily with any compound that can fit the cavity. Water fits perfectly into this cavity but this trap will also be in a position to remove gases like carbon dioxide, sulfur dioxide, hydrogen chloride, and chlorine or other gases that have effective diameters lesser than water.
Process of Contaminants Affecting Gas Stream
If you want to understand how the contaminants affect the gas stream, you will need to follow the road that the carrier gas takes to get into the gas chromatograph. This path is applicable for detector fuel gases also. The gases start from a gas tank or a special gas generator. The gas travels through long lengths of tubes, pressure gauges, valves, and different other fittings. headspace sampler of these areas is really a potential culprit to introduce contaminants into the gas stream. This leads not only in degrading the outcomes of chromatography but additionally shortens the life span of the column of CG.
Major contaminants like oxygen, hydrocarbons, and moisture are capable of wreaking havoc with the columns and detectors of CG. The packed and capillary columns will get degraded easily if they face oxygen or moisture, especially at high temperatures. These contaminants will also compromise detector performance. Since the detectors actually ‘see’ these contaminants, the effect is baseline noises, spikes, and drifts.
You should install gas purifiers in a vertical position as wall mounted types to avoid channeling. Channeling occurs when you install the gas purifier in a horizontal position. Gas purifiers are available as compact panels having multiple purifiers or single panel that has multi-absorbent capabilities.