Nitrogen isn't all the same. Comparing technologies for on-site nitrogen production.

Nitrogen remains the most widely used inert gas in many analytical processes and in a variety of laboratory applications. The use of a high-purity gas for the carrier in gas cromatography and for supplying the interfaces of mass spectrometers is one of the key points to avoid noise on the baseline as well as an early maintenance and to obtain accurate and well-calibrated analysis results.

The scenario still breaks down into Hollow Fiber Membrane and Pressure Swing Adsorption (PSA) technology.The latter, enhanced by the Fast Purity Claind patent, is able to ensure a significantly longer lifespan than the average, in combination with a low energy impact and nitrogen purity levels of up to 99.999%.

 

Membrane Technology

The principle of membrane air separation consists in conveying the molecules inside a column with bundles of polymeric hollow fibres in order to obtain a molecular separation given by the chemical/physical affinity with the fibres themselves. The compressed air is conveyed to the membrane inlet where the molecules of oxygen, water vapour and carbon dioxide are directed towards the external "vent" outlet, allowing the nitrogen to flow to the end of the filter column and reach the generator outlet.

It is of course a simple and cost-effective system, but unfortunately, in addition to offering a nitrogen with purities of less than 99.5%, ensures a lifespan of less than 5 years, less than half of what the Pressure Swing Adsorption technology is able to guarantee.

PSA technology

 

The PSA adsorption process is based on filtration by molecular sieves, Carbon Molucular Sieves. The separation effect of the CMS is due to the high adsorption efficiency of molecular sieves that are able to retain not only O2, CO2 and H2O molecules, but also the hydrocarbons. The nitrogen separated from oxygen leaves the CMS column to pass into a reserve inside the generator. At the same time the other column undergoes depressurizing regeneration supported by a counter-flow (deadsorption).

The process thus goes on in a cyclic and fully automatic way, offering nitrogen purities exceeding 99.999% and an average column life that generally exceeds 10 years.

Membranes or PSA?

 

The low amount of oxygen guaranteed by PSA allows to avoid all the negative effects of sample oxidation and the different ionizations. Only PSA technology is able to guarantee nitrogen purities up to 99.999% and therefore only PSA can supply the GC. The membranes, suitable for applications where low purity (< 99%) is accepted, need additional filtration when moisture and hydrocarbons must be maintained at levels of a few tens of ppm.

Membrane technology cannot therefore guarantee the complete removal of hydrocarbons, making it difficult to achieve the high levels of purity that can be achieved through the PSA process.

PSA with fast purity patent

 

Our PSA technology differs from the others thanks to the patented FAST PURITY SYSTEM. This technology allows an effective regeneration of molecular sieve columns through the release of high purity nitrogen only a few minutes after switching on. The process requires that the CMS are exposed to less mechanical stress and that the incoming air flow peaks are reduced, decreasing both air/electricity consumption and maintenance needs on compressors and air filters.

The Claind range of GC and LCMS generators is therefore able, thanks to over 40 years of experience, to ensure the highest purity for different applications and maintain it over time.