TN-05
8Pages

TN-05 The Power of Spectral Compensation for Fast Nitrogen Measurement in Oxygen with the Enhanced Plasma Discharge Technology AUGUST 2019 Marc-Antoine Langevin, Ph.D. malangevin@asdevices.com Andre Lamontagne, Ing. alamontagne@asdevices.com Yves Gamache ygamache@asdevices.com

ABSTRACT fdsf The detection of trace impurities in UHP gases can be challenging with universal type detectors such as TCD, DID, HID and PDID, as complex and expensive chromatographic methods are often required to properly separate them from the sample matrix. Other selective technologies such as the plasma emission detector have been introduced, but they still suffer from instability in the presence of high levels of sample matrix gases such as oxygen. In this document, we demonstrate how the Enhanced Plasma Discharge (Epd) technologypatent pending, with its focusing/stabilising and...

algorithm with a high-speed data stream. This algorithm, known as spectral compensation, performs high speed real-time computation in the frequency domain to reduce noise and perform arithmetic and compensation calculus between the two wavelengths. In parallel, the plasma discharge is maintained stable in the presence of high-level oxygen with our patent pending focusing/stabilising and electron injection electrodes. This is what makes this measurement possible and our technology unique. Traditional plasma technologies are based on figure 2 architecture, which means that a single wavelenght...

EXPERIMENTAL INFORMATION Enhanced Plasma Discharge (Epd) All the measurements were done with the SePddTM from ASDevices (See Figure 1). It is a fully scalable development kit for OEM and system integrators based on our Enhanced Plasma Discharge Technology. Due to its high sensitivity, versatility, ease of use and low maintenance cost, Epd is an interesting alternative to DID, PDID, HID, FPD, FID and TCD on most GC systems. With its highly energetic stabilised and focused plasma discharge, most molecules can be ionised and consequently measurable. It can be operated with argon, helium,...

it corresponds to a strong emission line from nitrogen (see Figure 6). Another narrow optical filter centered at 345nm (±1nm) was added to the third optical module as a reference wavelength. This wavelength was chosen because there is no emission line from nitrogen or other common impurities at this wavelength. Therefore, any signal variation at this wavelength can be attributed to the oxygen matrix disturbing the plasma. Thanks to our real-time correction algorithm, the spectrally compensated measurement was instantly traced by the software without post-processing. The pre-amplification...

importance of our stabilising electrodes, as the plasma is only slightly quenched and light-emission from nitrogen is still measurable. With other types of detectors, such oxygen concentration may completely extinguish the signal or even cause damages to the detector. Measurement compensation A chromatogram showing only the effect of oxygen on the plasma was recorded by using an optical filter centered at 345 nm, since there is no spectral line from nitrogen or any common impurity at this wavelength (Figure 8 (a), blue line). The spectrally compensated measurement, obtained from our...

Figure 9 - Chromatograms acquired for samples of oxygen containing 30 ppm (blue line), 76 ppm (green line) and 467 ppm (red line) of N2. Each sample was injected 5 times every 30 seconds CONCLUSIONS In conclusion, universal detectors cannot be used for the quantification of trace impurities, unless they were properly separated from the matrix. Other currently available plasma emission technologies can be used, but still require additional hardware such as longer columns and heartcut valves, which add complexity and cost to the system and result in longer analysis time. The Epd technology...

and time savings compared to the traditional analytical methods. With spectral compensation, trace nitrogen in UHP oxygen can be measured in less than 30 seconds, while other methods can take 3 to 5 minutes per sample. This application is only one example of the great versatility of spectral compensation. It could easily be implemented to further improve other chromatographic methods. REFERENCES [1] Extract up to 5% more profit: Utilising trace nitrogen analysis to optimise ASU argon yield, Dr Stephen Firth, Servomex, 2014 [3] M.-A. Langevin and A. Lamontagne, TN-01 Proving Leak Integrity...