Gas purifiers are essential because they help in providing a clean gas stream, which can guarantee the quality 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 along with other analytical columns from various kinds of contaminants. Still, headspace sampler 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 use in gas chromatographic applications.
Selection of Right Gas Purifier to Suit Your Applications
Numerous kinds of gas purifiers are available in the market. Although some gas purifiers remove just one specific contaminant, other styles remove multiple contaminants simultaneously from the gas stream. You must think about several factors through the selection process of gas purifiers, taking into consideration your specific 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 Found in Gas Purifiers
Oxygen, hydrocarbon, skin tightening and, and moisture traps are the most common purifiers used in majority of the gas chromatography (GC) applications. Oxygen traps are normally packed with metal catalysts. Oxygen is considered as 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 packed with activated charcoal, which can absorb organic compounds which are bigger than methane. Still, the molecular weight and size of the organic contaminants could have a definite influence on the capability of the hydrocarbon trap to a great extent but it may also reflect on trap efficiency somewhat.
Activated charcoal possesses a higher capacity to trap larger hydrocarbons which 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 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 will also be in a position to remove gases like skin tightening and, sulfur dioxide, hydrogen chloride, and chlorine or other gases which have effective diameters lesser than water.
Procedure for Contaminants Affecting Gas Stream
If you want to know how the contaminants affect the gas stream, you will need to follow the path that the carrier gas takes to get into the gas chromatograph. This path does apply for detector fuel gases also. The gases start 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 in to the gas stream. This leads not merely in degrading the outcomes of chromatography but also shortens the life 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 can get degraded easily when they are exposed to oxygen or moisture, especially at high temperatures. These contaminants may also compromise detector performance. Since the detectors actually ‘see’ these contaminants, the result is baseline noises, spikes, and drifts.
It is advisable to 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.
