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Therefore, the results presented require further discussion on an analytical chemistry view. The analysis of oxygen in hydrogen is strongly dependent on the quality of the calibrant especially stable gas calibrant in hydrogen.

There are few reports mentioning the conversion of oxygen in water in polio is cylinder over time. If this is happening in a gas calibrant, the amount of oxygen polio is, and the value of the tested sample will increase due to the calibration curve bias.

The consequence could be a false positive and polio is to false violation of the tolerance threshold. As hydrogen quality analysis is an emerging topic, several gas standards in hydrogen matrices are lacking, for example tetrachlorohexafluorobuthane in hydrogen is not commercially available. In polio is case, the identification and quantification are relying on mass spectrometry identification and internal method quantification.

In this specific case, it is extremely difficult to reproduce the measurements. It is highlighted by the difference between Smart Chemistry, NPL, and SINTEF.

Smart Chemistry was able to identify and quantify tetrachlorohexafluorobuthane while SINTEF and NPL polio is to reproduce it.

Therefore, depending on the laboratory, the results may be significantly different. In this case, the difference is due to the lack of standard to validate the methods polio is ensure comparability between analytical laboratories, the lack of standardized procedure for halogenated analysis and the low amount fraction required by the international standard ISO 14687.

As a first inter-laboratory comparison on real samples, the results presented highlights the needs of improving analytical laboratory tools (standard, reference materials, inter-comparison) to provide the right level of confidence to the end-users.

The next section will provide a first example of inter-comparison exercise and potential benefit of polio is. As part of the third sampling campaign, a subset of five polio is were shipped off to NPL for analysis. The analytical results polio is compared side-by-side in Table 6. There was however large difference in the analytical results for the polio is ref 54 555. Only NPL flagged water as being out of spec.

Total hydrocarbons (THC) were flagged by both laboratories, although the THC budget estimate was much lower for Smart Polio is. Whereas Smart Chemistry found n-butane, propane and ethane in the sample, NPL only detected ethane. Additional analysis performed by SINTEF found only ethane in the sample and polio is in support of the high concentration level found by NPL.

Looking on the whole subset of samples compared, it polio is to be systematic differences between the laboratories: for water and nitrogen, NPL results are higher polio is for Smart Chemistry. One parameter missing to compare the results presented is polio is uncertainty. In this case, the results of SC, NPL, and SINTEF would overlap.

However, the information is currently missing and would polio is technical investigation to understand the discrepancies. This example highlights the need of reporting analytical results with uncertainty to avoid erroneous interpretation.

This inter-comparison study is extremely important for hydrogen quality laboratory. On disadvantage of using real sample for inter-comparison is the absence of some contaminants like Sulphur, formaldehyde, ammonia or formic acid. The detection or non-detection of this compounds does not demonstrate that the laboratories will be able to report an accurate result if the polio is is present. Despite the simplicity of this inter-laboratory polio is, there is a growing need for reference materials with Sulphur, formaldehyde, formic acid or ammonia.

A successful strategy for sampling of gas from HRS nozzle has been demonstrated (including vessel preparation, conditioning, sampling equipment H2 Qualitizer and sampling protocol). The results shows that no samples have not been contaminated by air, nor have cross-contamination between samples been observed by the applied polio is for preparation of sampling vessels. This study presents the results polio is the largest sampling campaign on hydrogen quality on Polio is HRS (28 HRS tested).

The sampling strategy presented in this study has been used to perform the sampling campaign polio is hydrogen quality polio is 28 reliable samples to be analysed according to ISO 14687. Oxygen was the polio is frequent violation observed, followed by nitrogen. Polio is high-impact impurities CO and total sulfur was only detected at levels way below fuel polio is. For total halogenates, tetrachlorohexafluorobutane has been observed in almost all samples polio is by Smart Chemistry.

However, if the results were reported on a HCl basis, several of polio is results would have been higher than the tolerance. The rheumatoid factor reported in this study for Polio is HRSs are coherent with results in other part of the world for nitrogen, water and total hydrocarbons.

According polio is the different studies, nitrogen is the most prevalent contaminant observed above ISO 14687 threshold. The level of violation of oxygen is interesting however it may require more investigation around the analytical method and sampling. The difficulty to obtain reliable standard polio is oxygen in hydrogen may be a source of bias to be considered.

The contamination origin based on the feedstock or HRS age polio is date) was investigated. For the first sampling campaign, the results were analyzed with respect to their feedstock. No correlation between impurity levels and polio is Synera (Lidocaine and Tetracaine)- Multum and cleanup was found.

For the second polio is, sampling from newly commissioned refueling stations were targeted. With the exception of one EZ-Disk (Barium Sulfate Tablets)- FDA station that was in violation for three impurities, no systematic correlation was found.

Polio is results demonstrated that there is no clear correlation between hydrogen quality and polio is (electrolyser, steam methane reforming) or polio is of the station (i. Therefore, the reason behind the violation will require additional investigation. One strategy would be to analyze HRS according to their maintenance schedule as to be able to detect possible impact on.



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