Nitrogen and on-site nitrogen generators
Nitrogen generators are now used in laboratories all over the world to supply various analytical instruments with nitrogen gas at the push of a button. A nitrogen generator is the most efficient way to supply instrument gas as, unlike gas cylinders, a gas generator never runs out of gas and constantly supplies a consistent purity of gas.
Nitrogen use in the lab
Nitrogen gas has been used in laboratory analysis for decades. In the past, labs were required to have their nitrogen gas supply delivered in cylinders or in bottles from their closest nitrogen plant, which for some labs could take several days to deliver. These cylinders or bottles would then supply an LC-MS (Liquid Chromatograph-Mass Spectrometer) instrument, or perhaps a detector in the case of GC (Gas Chromatograph), allowing the lab to carry out its analysis.
Nitrogen generators in the lab
There is an alternative to nitrogen cylinders, this is an on-site nitrogen generator. A nitrogen generator not only removes the hassle of having to change over cylinders, it provides an uninterrupted supply of gas at a consistent purity. This consistency is generated using one of two technologies, namely, Pressure Swing Adsorption (PSA) and membrane nitrogen generators.
Membrane nitrogen generators
The principle of operation for a membrane nitrogen generator is where atmospheric air is compressed by an air compressor and passed through a hollow fibre membrane, filtering out parts of air (primarily oxygen) leaving behind a high purity nitrogen gas.
More advanced nitrogen generation systems can include multiple stages of filtration before reaching the membrane, this removes more of the other particles in the gas such as dust and moisture. Fine mesh filters are commonly used in the nitrogen generation process, these are for removing particles in air whilst air dryers are used to remove moisture. Beyond ensuring higher purity of nitrogen, these extra filtration stages will also protect the membrane.
Pressure Swing Adsoprtion (PSA) nitrogen generators
A Pressure Swing Adsorption nitrogen generator works in a similar way to a membrane nitrogen generator in terms of compressing atmospheric air with an air compressor. Instead of passing through a membrane, a PSA nitrogen generator will pass air through a column of tightly packed material at pressure made of carbon called a Carbon Molecular Sieve (CMS). The CMS only allows the smaller nitrogen molecules to pass through whilst the larger molecules of oxygen and other molecules are adsorbed by the CMS leaving high purity nitrogen. Two CMS columns are required for a PSA nitrogen generator, as one column is deprussirized the other pushes the air through the sieve at pressure hence the name Pressure Swing Adsorption.
Similar again to the membrane nitrogen generator, an advanced PSA nitrogen generator will also contain prefiltration stages to remove dust particles and moisture from the air before entering the CMS.
Peak Scientific on-site nitrogen generators
Nitrogen generators vs nitrogen cylinders
For most mass spectrometers, a high volume of nitrogen gas is required meaning that cylinders or bottles could be consumed in a matter of days, when using an LC-MS instrument. This can result in regular interruptions of analysis and the inconvenience of having to switch over cylinders or wait for nitrogen deliveries. There is also the added inconvenience of the inconsistent purity delivered by cylinders and bottles when they reach the lower end of their capacity. This is because contaminants can enter the empty space in the cylinder. These impurities can have an impact on the integrity of analysis as they can react with the sample.
These inconsistencies and inconveniences are eliminated by a nitrogen gas generator which is why more and more labs are turning to nitrogen generators to supply their instrument gas. Also, a nitrogen generator is especially suitable for time-critical applications where there is no time for the analysis to be halted while gas cylinders are changed over.
On-site nitrogen gas generation is also a safer solution than using cylinders as staff are not required to move heavy cylinders around the laboratory. There are also cost benefits as on-site nitrogen generator reduces the administrative burden of ordering cylinders (raising purchase orders and scheduling deliveries), paying delivery fees. On top of this, the price for gas which is delivered in cylinders can fluctuate from month to month, as the market price of nitrogen gas is subject to supply and demand volatility. It is also necessary to consider the environmental benefits of eliminating continuous deliveries of gas. The production of the gas itself must also be taken into account as producing gas at a nitrogen plant requires vast amounts of energy consumption.
Nitrogen generators for the modern laboratory
The modern landscape of laboratory nitrogen gas has been permanently altered with the introduction of nitrogen generators bringing
What is Nitrogen?
Nitrogen, for those who don’t know, is an inert gas meaning it is not very reactive with other elements and chemicals. Nitrogen is highly abundant, accounting for around 78% of the earth’s atmosphere meaning we breathe in more nitrogen than any other element every day.
Atomic number 7, discovered in 1772 by Daniel Rutherford, nitrogen is an inert gas meaning it is not very reactive with other elements and chemicals. Nitrogen is highly abundant, accounting for around 78% of the earth’s atmosphere meaning we breathe in more nitrogen than any other element every day.
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