APPLICATION NOTE
LD13-01 Analysis of UHP Hydrogen production using Plasmadetek-2 & micro GC Multidetek-2
The high purity hydrogen production demand is rising quickly and the need of measuring low ppb trace in a quick analysis run is then required. Most of the GC technologies available on the market use the same methods for years which required quite complex systems. Those systems require the use of different detectors to cover the application and a complex chromatograph configuration what make the price of such system increasing. The complexity of the chromatograph operations, the long analysistime and the limitations to achieve low ppb measurement are often faced.
THE SOLUTION:With its integrated plasma technology, The MultiDetek-2 from LDetek becomes the ideal tool to measure the hydrogen purity. Itscapability to monitor the permanent gases and hydrocarbons from ppb level up to high ppm level using only one plasma detector givesthe ideal solution. In comparison to the existing method, the PlasmaDetek-2 gives the advantage of being selective to the desiredimpurities and then block the interference coming from the matrix gas. In the case of UHP hydrogen production, measuring low ppb traces of O2 and N2 is complex since their elution time is very close to the hydrogen matrix. Then, to allow the analysis of O2 and N2, relatively long molecular sieve columns are required in combination with multiple valves for flushing out the hydrogen gas. In some cases, a hydrogen trapping module may be necessary. It then increases the cost of the system and extends the analysis time. Peaks shape can be also affected with the use of longer columns. With the PlasmaDetek-2, a simple system having one valve and one Molecular Sieve column is required. The detector is configured with two sensors to measure O2 and N2 respectively in selective mode. Refer to Figure 1 for the configuration drawing. Going this way, the analysis time can be reduced, the sensitivity increased and it gives an easy to use system with no consumable or maintenance required. An analysis example of impurities O2 & N2 in a hydrogen sample, using a standard ionization detector in combination with the same configuration that appears on Figure 1, has been used to generate the chromatogram that appears on Figure 2. We can clearly see the interference of the hydrogen over the traces O2 and N2. The hydrogen matrix interference overlaping the traces O2 will be amplified when going lower at low ppb level and it will becomes not possible to measure the impurities without using another techniques requiring more long columns, additional valves and H2 trap.At the opposite, on Figure 3 appears a chromatogram of traces O2 and N2 with the use of the PlasmaDetek-2 using its selective mode. It is clearly demonstrated that the selectivity gives an important benefit that makes such type of analysis possible with a simplified chromatography method demonstrated on Figure 1.
