Gas purifiers are necessary because they help in providing a clean gas stream, that may 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 span of the column. Gas purifiers are like plans to protect the instrumentation and other analytical columns from different types of contaminants. Still, the gas purifiers will not be able to convert low purity gases into high purity gases. Due to this important factor, it’s important to select the proper grade of gases with different purity levels for proper used in gas chromatographic applications.
Selection of Right Gas Purifier to fit your Applications
Numerous kinds of gas purifiers are available in the market. Although some gas purifiers remove just one single specific contaminant, other types remove multiple contaminants simultaneously from the gas stream. You must reflect on several factors during the selection procedure for gas purifiers, taking into consideration your unique applications. These factors includes the potential contaminants within 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 Used in Gas Purifiers
Oxygen, hydrocarbon, carbon dioxide, and moisture traps are the most common purifiers used 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 every analytical columns. Oxygen is with the capacity of producing irreversible oxidation damage, especially to polar stationary phases. Hydrocarbon traps are typically filled with activated charcoal, that may absorb organic compounds which are larger than methane. Still, the molecular weight and size of the organic contaminants will have a definite influence on the capability of the hydrocarbon trap to a great extent but it will also think about trap efficiency to some extent.
Activated charcoal possesses an increased capacity to trap larger hydrocarbons that are greater than C4, compared 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 lose 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 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 should follow the road that the carrier gas takes to find yourself in the gas chromatograph. This path 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 various other fittings. Each one 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 can handle wreaking havoc with the columns and detectors of CG. The packed and capillary columns will get degraded easily when they face oxygen or moisture, especially at high temperatures. These contaminants may also compromise detector performance. Since the detectors actually ‘see’ these contaminants, the effect is baseline noises, spikes, and drifts.
headspace sampler 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 can be found as compact panels having multiple purifiers or single panel that has multi-absorbent capabilities.