Gas purifiers are necessary 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 plans to protect the instrumentation along with other analytical columns from different types of contaminants. Still, the gas purifiers will never be able to convert low purity gases into high purity gases. Because of this important factor, it’s important to select the right grade of gases with different purity levels for proper use in gas chromatographic applications.
Collection of Right Gas Purifier to Suit 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 need to think about several factors during the selection procedure for gas purifiers, considering your specific applications. These factors will include 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 are the most common purifiers used in most the gas chromatography (GC) applications. Oxygen traps are normally 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 usually packed with activated charcoal, which can absorb organic compounds that are larger 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 a great extent but it may also reflect on trap efficiency to some extent.
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 usually 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 may fit the cavity. Water fits perfectly into this cavity but this trap may also be in a position to remove gases like carbon dioxide, sulfur dioxide, hydrogen chloride, and chlorine or other gases which have effective diameters lesser than water.
Process of Contaminants Affecting Gas Stream
If you wish to understand how the contaminants affect the gas stream, you must follow the path that the carrier gas takes to find yourself in the gas chromatograph. headspace sampler does apply for detector fuel gases also. The gases begin from a gas tank or perhaps a special gas generator. The gas travels through long lengths of tubes, pressure gauges, valves, and different other fittings. Each one of these areas is really a potential culprit to introduce contaminants in to the gas stream. This leads not only in degrading the results of chromatography but also 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 can get degraded easily when they are exposed to oxygen or moisture, especially at high temperatures. These contaminants may also compromise detector performance. Because the detectors actually ‘see’ these contaminants, the effect is baseline noises, spikes, and drifts.
It is advisable to install gas purifiers in a vertical position as wall mounted types to prevent channeling. Channeling occurs once 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.