Your Local Gas Generation Webinar: Hydrogen as an alternative to Helium for GC
Dr. Ed Connor takes us through some real examples of converting carrier gas successfully under 3 different conditions and GC analyses.
1. FAMEs analysis method re-validation from helium to hydrogen for GC
2. Detailed hydrocarbon analysis (DHA) using ASTM method D6729 & D6729 Appendix X2
3. The Effect of Draw-out Lens Diameter on Sensitivity of GC-MS analysis
Dr. Ed Connor answers all the questions from the webinar Q&A below.
Is a gas generator environmentally friendly?
The production of H2 is via electrolysis of DI water. The process is a repeatable process, so once a generator is in the lab, there is no need for repeated deliveries of gas, meaning lower emissions from delivery trucks. If the supply of electricity is from renewable sources, the generator is a very environmentally friendly option.
What are the safety risks in using H2 instead of N2?
When supplied by a gas generator, the risks of H2 are minimised, so there should be little risk using H2 carrier for any GC or GC-MS analysis. N2 bulk supply (dewars and cylinders) also poses a risk to lab personnel, so should not be underestimated as a risk. Generators of any kind are a safer alternative to cylinders and bulk supply.
If hydrogen is 5 minutes faster than helium in the FAMEs analysis, could it be faster if we reduce column width/length?
Yes, reducing column width and length would be a way to improve separation and speed up analysis.
Do you know of any issues with helium supply to labs in Europe recently?
We have had reports from labs worldwide in regards to the current helium shortage, including customers in Europe. In areas where labs can obtain regular supply, the price of helium has risen starkly over the past few years.
Can we use H2 gas simultaneously for carrier and combustion in FID?
Yes, the supply from the generator can be connected to the ‘carrier’ and ‘H2 detector’ inlets on the GC by making a T-piece.
How many GCs can one generator supply? And how many GC-FID can a generator supply?
This will depend on the total carrier gas flow of the methods being run and how many FID detectors need gas. PEAK have H2 generators producing up to 1200cc/min which can support multiple GCs and for larger labs, multiple generators can be cascaded to give multiple litres of H2 per minute.
Have you tried the DHA analysis using 100 Micron ID column?
We did not try using a small diameter column, but this would be an interesting option to speed up the analysis further. We would need to double-check the requirements of the ASTM method, in terms of recommended column to be sure whether this could be done.
What is the loss in sensitivity when you change from helium to hydrogen without any BG subtraction?
On an Agilent system, typically a 2-5x reduction in sensitivity is expected in full scan mode, although this will depend on the analyte.
Can you discuss the safety implications of using hydrogen? I.e. if there is a leak in the system into the oven etc
The risk of a leak into the GC oven is possible, but most leaks are seen at the inlet. If the inlet cannot maintain pressure, the GC would normally shut down and the generator would go into standby. If there was a leak at the detector end of the column, there is a risk that back pressure would allow the system to run as normal, so there is a small risk that in this situation, the LEL could be reached. All PEAK H2 generators have a safety shut down if they supply H2 at maximum flow for 20 minutes, to prevent this from happening. Additionally, PEAK offer an in-oven leak detector that can be connected to the generator to shut it down if a significant H2 concentration is detected in the GC oven. However, we have never heard of any customers without an H2 detector having any significant problems with a build-up of H2 in their GC.
Risk of H2 gas leakage in column oven. Hence, labs do not recommend use of H2 as carrier gas. Do you agree on this?
As mentioned in the previous response, there is a small, but very low risk of leaks causing a problem in the GC. Modern GCs are very sensitive to pressure and flow changes and can be equipped with in-oven detectors. PEAK also offer a leak detector that can be connected to the generator.
Did you have any application with Shimadzu GCs?
Yes we have application notes with Shimadzu GCs on GC-MS applications. Please see https://www.peakscientific.com/discover/articles/gc-ms-ms-pcbanalysis-on-site-gas-generators/ as an example.
Are there any classes of chemical which tend to react with hydrogen when used with GCMS?
The key concern that most people have is reaction with Chlorinated solvents and the subsequent formation of HCl. This can be avoided by using pulsed pressure injection, which will reduce residence time of H2 in the GC inlet, where reactions are most likely to occur.
Are there any classes of chemical which tend to react with the hydrogen when used with GCMS? We are particularly interested in aromatic VOCs.
We are not aware of any specific classes of compounds where reactivity is a problem. Terpenes have been cited as a risk, previously, but in testing at PEAK we have not had any difficulty in analysing terpene samples.