Rocket science! FTIR analysis in space!

12/11/2012
FTIR gas analysis in the testing of satellite launch systems and on board satelite

Europe’s leading space technology company Astrium, has employed a sophisticated portable FTIR gas analyser as part of a test programme for satellite launch systems. The analyser, a ‘Gasmet DX4030‘, was supplied by instrumentation specialist Quantitech.

Astrium Propulsion Test & Launch Services Manager, Greg Richardson, says: “Many of the satellites that we design, build and launch are worth millions of Euros, so our test methods have to be extremely rigorous.

“The DX4030 was chosen because of its ability to provide highly accurate results for almost any gas. However, its intuitive software, compact size and portability were significant considerations because we use the technology at a number of our locations around the world.”

One of the tests that are performed on the propulsion systems is to check the integrity of the chambers that contain rocket fuel. To achieve this, the tanks are filled with a simulant (often isopropyl alcohol and demineralised water) and exposed to launch simulation conditions – pressure, heat, vibration etc. The simulant is then removed and the DX4030 is used to check for contamination or leaks.

LISA Pathfinder

The DX4030 was first utilised in the testing of the LISA Pathfinder; a project for which Astrium was selected by the European Space Agency to build and launch a spacecraft that will be packed with radical instrumentation and technology to pave the way for LISA (Laser Interferometer Space Antenna), the world’s first space-based gravity wave detector which will open a new window on the Universe by measuring gravitational waves generated by exotic objects such as collapsing binary star systems and massive black holes. In doing so, this project will be able to test a phenomenon predicted by Einstein’s General Theory of Relativity in 1916.

Star census
The analyser has also been used in testing the Gaia satellite which will conduct a census of a thousand million stars in our Galaxy, monitoring each of its target stars about 70 times over a five-year period. Gaia will precisely chart their positions, distances, movements, and changes in brightness. It is expected to discover hundreds of thousands of new celestial objects, such as extra-solar planets and failed stars called brown dwarfs. Gaia should also observe hundreds of thousands of asteroids within our own solar system.

DX 4040 with PDA

The DX4030 employs FTIR gas detection technology to obtain infrared spectra by first collecting an ‘interferogram’ of a sample signal with an interferometer, which measures all infrared frequencies simultaneously to produce a spectrum. This means that data is collected for the required parameters in addition to spectra for almost all others.

Sample identification is possible because chemical functional groups absorb light at specific frequencies. As a result, the DX4030 can measure any gas, with the exception of noble (or inert) gases, homonuclear diatomic gases (e.g., N2, Cl2, H2, F2, etc) and H2S (detection limit too high).

Commenting on the work at Astrium, Quantitech’s Dr Andrew Hobson said: “This has to be one of the more unusual applications for the DX4030. It is more commonly used for chemical spill, security and forensic investigations, and for occupational health, anaesthetic gas monitoring and research. The same technology is also employed to monitor industrial processes and gaseous emissions. However, Astrium’s work clearly demonstrates the flexibility of the device and we are delighted to have been involved.”


FTIR analyser reveals surprising solution

09/10/2012

Emissions analysers have to be checked annually by certified testers and during recent functionality tests for a Gasmet FTIR continuous emissions monitor (CEM) at a British Energy from Waste plant, the Nitrogen Dioxide span check results were found to be incorrect. A subsequent investigation revealed surprising results that would not have been apparent had the plant been using traditional CEMs.

NO2 values should have been 76mg/m3 but the FTIR was reading 31mg/m3, so Dominic Duggan from Quantitech, the company which installed the monitor, was contacted to investigate.

As a multigas monitoring technology, FTIR provides a complete analysis spectrum from the sample gas and as a result it was possible to investigate the response peaks for NO2 in addition to any other gases present. Duggan’s investigation showed peaks for NO2 and also found peaks for NO and HCl. In addition he found an unknown peak at 1750-1850 cm-1 in the sample spectrum.

The investigators speculated that there may be a problem with the regulator, which had previously been used to deliver HCl test gas and a quick piece of internet research revealed that Nitrosyl Chloride (NOCl) can be formed if NO2 and HCl are mixed. This gas is a decomposition product of Aqua Regia and was found to be responsible for the ‘unknown’ peak.

Aqua Regia (a mixture of Nitric and Hydrochloric acids) is so-called because it is able to dissolve royal or noble metals such as gold. As an interesting aside, when Germany invaded Denmark in World War II, a cunning chemist dissolved the gold Nobel Prizes of two German physicists in aqua regia to prevent the Nazis from confiscating them because Nobel Prizes had been banned in Germany. He placed the resulting solution on a shelf in his laboratory and it avoided the attention of the Nazis who thought the jar contained common chemicals. After the war, the chemist returned to find the jar still on the shelf, so he precipitated the gold from the acid and returned it to the Nobel Foundation which re-cast the medals.

This shows the sample spectrum with NOCl and NO2 peaks (in black) plus NOCl reference spectrum (in red) for comparison.

Clearly, aqua regia is a highly corrosive chemical, so it is important to avoid its generation. A clean regulator was therefore fitted to the CEM and subsequent analysis showed the correct result for NO2.

Dominic Duggan says “The main advantage of FTIR is that it provides continuous analytical data for an almost endless list of chemicals. Most CEMs are configured to monitor up to 50 parameters, the most common configurations include H2O, CO2, CO, SO2, NO, NO2, N2O, HCl, HF and NH3, however, it is also a simple and low cost process to add further parameters at a later date, which means that the monitoring regime is ‘future proof’.

“This investigation highlights a further advantage of FTIR; if traditional single parameter analysers, such as chemiluminescence or NDIR, had been in place, the logical conclusion would have been to blame the analyser for reading incorrectly, resulting in a costly exercise to have it replaced. But the FTIR enabled us to study the complete spectrum and quickly identify and resolve the problem.”


Gases trapped in High Arctic could tip climate scales!

07/10/2011
By Dominic Duggan, Quantitech.

Enormous quantities of greenhouse gases (GHG) exist within Arctic ice and frozen soils, so with the threat of global warming, a clear understanding of the relationship between GHG in the atmosphere and in the ice/soil is vital because melting of permafrost could cause a dangerous climate tipping point. There can be few more challenging environments for monitoring gases, but PhD researcher Martin Brummell from the University of Saskatchewan has successfully employed a Gasmet DX4015 FTIR analyser to do so in the High Arctic of Canada. This article explains the procedures and challenges of multiparameter gas detection in freezing remote locations.

Is this beautiful Arctic scene hiding a climate tipping point?

Working in the field imposes a number of requirements for analytical equipment. However, the extreme weather conditions of the High Arctic impose a new level of capability that is rarely available as standard. Field work in such conditions must be simple, flexible and fast, but most importantly, Martin Brummell says, “The equipment must also be extremely reliable because you do not have the luxury of a local Quantitech engineer.

“The Gasmet DX4015 was also the ideal choice because, as an FTIR analyser, it is able to monitor almost any gas, which is normally a feature of mains powered laboratory instruments, but the DX4015 is portable and powered by a small generator, so it is ideal for monitoring in remote locations.”

Sampling and analysis in the Arctic
A set of simple, perforated steel tubes were driven in to the soil, to the point of the permafrost threshold. Inside these tubes gases within the soil were allowed to reach equilibrium via diffusion over 24 hours. This allowed Brummell to analyse gas concentrations to a depth of 1 metre. The procedure was simple and therefore reliably repeatable. Furthermore, measurement of gas concentrations at different depths enabled direct comparison with soil analysis.

Using FTIR in the ‘field’

Ready to measure!

The Gasmet DX4015 is a portable FTIR gas analyser for ambient air analysis. FTIR, an abbreviation for fourier-transform infrared, is an interferometric spectroscopic instrument (interferometer) that uses the infrared component of the electromagnetic spectrum for measurements. A fourier-transform function is applied by the interferometer to obtain the absorption spectrum as a function of frequency or wavelength. Consequently, this unit is able to simultaneously analyse up to 50 gas compounds. The analyser is typically set up to measure a variety of different gases, including VOC´s, acids, aldehydes, and inorganic compounds such as CO, CO2, and N2O.

The DX4015 is operated using a laptop computer running Calcmet™ software, a program that not only controls the analyser but also undertakes the analysis. This software is capable of simultaneous detection, identification and quantification of ambient gases, which gives the DX4015 its ability to simultaneously analyse multiple gases in near-real-time.

The FTIR’s many beneficial traits, such as reliability, precision and flexibility make it a vital piece of analytical equipment in a very wide variety of applications including industrial emissions monitoring, occupational safety surveys, engine exhaust testing, process monitoring, leak detection, emergency response, chemical spill and fire investigations, and many others.

Brummell’s use of the DX4015 on his most recent research expedition investigating the soils in the polar deserts of the High Arctic, highlights the model’s capabilities in the field. Carried out on Ellesmere Island in the Baffin Region of Nunavut in Canada, the DX4015 had to perform reliably in extreme environmental conditions. The analyser was used to monitor the production, consumption and atmospheric exchange of the greenhouse gases Carbon Dioxide (CO2), Methane (CH4) and Nitrous Oxide (N2O); all three being major components of natural biogeochemical cycles. These gases are each released and up-taken by soil microbes in the Arctic.

The DX4015 was used to examine both the flux of gases from the soil surface and the concentration profiles of gases in the soil’s active layer above the permafrost. In doing so the FTIR provides raw data consisting of gas concentrations in parts-per-million (ppm).

Explaining his reasoning behind choosing the Gasmet DX4015, Martin Brummell highlighted some of the analyser’s key advantages: “The real-time nature of the Gasmet FTIR, allows me to see results within minutes of setting up in the field. This permits me to make changes to the experimental design and further investigate unexpected results whilst in the field. This contrasts with traditional methods of soil gas analysis, which employ lab-based gas chromatography systems and collection of samples ‘blind’ in the field.”

Results
Surprisingly, the work revealed areas of strong CO2 and CH4 production immediately above the permafrost. Brummell believed this was the result of the relative disparity in carbon distribution in Arctic soils in comparison with warmer climes. Carbon accumulates far lower in Arctic soils due to a process known as cryoturbation; the constant mixing and burying of organic matter, which fuels microbial activity at a deeper level.

Comparisons between the surface flux and the soil profile for each of the greenhouse gases was a key objective within Brummell’s investigation. Most notably, he observed a negative surface flux for NO2, but no significant regions of consumption were identified. The location of the NO2 sink is not yet clear, nor the organisms and biogeochemical processes responsible.

Conclusions
Martin Brummell’s research provided a new but complex insight into the production, consumption and exchange of greenhouse gases and soil microbe pathways in the Arctic. His work highlighted the importance of reliability, ruggedness, flexibility and accuracy in the equipment which is employed in such work. However, the ability of the DX4015 to provide simultaneous measurement of multiple gases in near real-time was a major advantage.

In comparison with all of the equipment that is necessary for research in Arctic conditions, one might imagine that a highly sensitive analytical instrument would be the most likely to be adversely affected. However, Martin Brummell found this not to be the case with the Gasmet DX4015: “In contrast to other field equipment I have used in the High Arctic, including self-destructing sledgehammers, unreliable generators and broken fibre-optic cables, the Gasmet DX4015 has never failed even in the most difficult field conditions. It has happily survived air-transport, inconsistent electrical supply, low temperatures, rain, snow, mud and all other insults, and always gives me accurate, precise measurements of gas concentrations.”