Chromatography Forum

We use He for GC/HS analysis. What do you think would be best to replace He with, Ar or H2?

I would use Hydrogen.

I would try Argon and see if there was any great difference in results.

If not, then I would use the cheapest.

best wishes,

Rod

I would like to get some opinions from you on hydrogen generator. I am doing research on hydrogen generators, but I am seeing it may cost more than hydrogen tanks for a samll lab. Tell me if I have something wrong in my thinking.

From my readings, here is my collections:

1. There are two school of H2 generators, one uses ionic polymer based membrane to generate H2, then purify it using descants. This process can only generate H2 up to 99.995% purity, and probably good for fuel gas only. However, some machines use a slightly different purification method, which can reach 99.9999% purity, good for carrier gas. The other technology is palladium membrane based, and it can generate H2 up to 99.99999% purity, which is good for both carrier and fuel gas.

2. They cost roughly $10,000.

3. Now, the biggest problem is not mentioned much, actually quite scarcely. The central part of the machine, the membrane/cell has a expected life of 3 to 5 years. I only found this data on 2 websites (vaguely), and a call to one of the hydrogen generator manufacturer's tech support confirmed that is the case for all technology. The replacement cell will cost roughly about the half of the price of the generator I was told. This suddenly becomes $2000 per year, plus maintenance.

On the other hand, if we only have 1 GC that uses hydrogen as carrier gas at 15 ml/min, a ballpark calculation of a K size tank (291 cu ft) results in 278 days nonstop operation. Last time I checked, a research grade H2 tank (K size) costs about $150, and a research grade He tank (K size) costs about $360. Even considering the tank rental fee, still it will be cost effective to have gas cylinders.

I might be wrong, but as of right now, it is hard to believe a hydrogen generator is good choice for a lab with a single GC. I would like to get input from anyone who has been using this type of generators. Thanks.

[edit] Well, one thing I forgot is the safety benefit from hydrogen generator. But other than that, how financially is it feasible for a small lab to replace tanks?

Demand for Helium continues to rise , supply is reducing. As a vendor of Hydrogen generators we would certainly recommend changing over all your GC systems Our systems start from just over £2k

Tiggeria,

I am working for Peak Scientific and I was not aware that there is a service requirement for Hydrogen Cells or that they need to be replaced?

From what I understand is that if you are using the right quality water for your generator, the hydrogen cell should just keep on going. We have sold Hydrogen Systems for almost 15 years now and have only ever seen replacements where there was either an underlying technical fault or the wrong water quality has been used.

Maybe it depends on the quality of cell that is being used in the generator design- mind you this could have an impact on the overall purchasing price of the generator.

Hope this helps!

F.

Tiggeria,

I am working for Peak Scientific and I was not aware that there is a service requirement for Hydrogen Cells or that they need to be replaced?

From what I understand is that if you are using the right quality water for your generator, the hydrogen cell should just keep on going. We have sold Hydrogen Systems for almost 15 years now and have only ever seen replacements where there was either an underlying technical fault or the wrong water quality has been used.

Maybe it depends on the quality of cell that is being used in the generator design- mind you this could have an impact on the overall purchasing price of the generator.

Hope this helps!

F.

I can confirm a lifetime of a bit less than 4 years for a palladium membrane in a hydrogen generator fed only 18 MOhm water, and with (annual ?) changeouts of the electrolyte. That company does not make gas generators any more.

Peter

Peter,

Thank you for your confirmation on the lifetime of the a palladium membrane. That 20% NaOH solution costs $300/bottle, and it needs to be changed every once in a while. ( every 6 mos or yearly?).

Speaking of companies, it seems that Parker and Domnick Hunter are the same now. I heard that the respective division of Whatman may belongs to Parker now, but it could be a rumor.

I can confirm a lifetime of a bit less than 4 years for a palladium membrane in a hydrogen generator fed only 18 MOhm water, and with (annual ?) changeouts of the electrolyte. That company does not make gas generators any more.

Peter

Thank you for your input, Fheasgair.

I dig up 2 places which mention about the lifetime. One website is here, http://www.discoverysciences.com/print.aspx?id=3242, which hints that the lifetime of hydrogen generators is about 5 years.

Another place, one of your competitors had a presentation here at
ftp://ftp.bdal.de/data/support/Ion%20Tr ... tation.pdf

On page 53, it explicitly spells out that palladium membrane from Whatman machine has only 3-5 years lifetime. Also on page 52, it indicates cell deterioration problem from 3 companies, including Peak, although the way I am reading it it is directly related to lacking of deionizer bags. Well, this whole document could be marketing stuff, so I am not sure how much truth in there. On top of that, the presentation was probably written in 1999 since the first page has that data, things could have changed since then.

Nevertheless, I contacted some technical support people in one H2 generator manufacturer, and specifically asked about lifetime of the different hydrogen generation technologies. I was told that they all have about the same lifetime, i.e., 3-5 years. Replacement of the core, hydrogen cells, would cost about half of the price of a new machine.

Until I get more data points, the longevity is a suspicious subject as Peter confirmed in his reply.

Tiggeria,

I am working for Peak Scientific and I was not aware that there is a service requirement for Hydrogen Cells or that they need to be replaced?

From what I understand is that if you are using the right quality water for your generator, the hydrogen cell should just keep on going. We have sold Hydrogen Systems for almost 15 years now and have only ever seen replacements where there was either an underlying technical fault or the wrong water quality has been used.

Maybe it depends on the quality of cell that is being used in the generator design- mind you this could have an impact on the overall purchasing price of the generator.

Hope this helps!

F.

Since even my limited chemistry skills extend as far as making up a sodium hydroxide solution I see no sense in paying $300 for a bottle of it.

The switch to gas generators from cylinders is not usually driven by the relative costs of the gas, but perceived safety issues and requirements that cylinders be outside buildings etc. In a lab that I worked in previously we were obliged by "safety" concerns to move cylinders out of the labs. That would have required capital investment for the gas store etc, and long tube runs into the lab, so it worked out cheaper (but was by no means trouble free) to go for generators.

Peter

Ah, now I understand why my information is different- we do not use Palladium Technology in our hydrogen generators...

The Palladium Dryer is used to dry and purify the hydrogen generated by cell. It achieves a very high purity hydrogen, however it is prone to technical faults and does have a limited lifetime. From my experience a life time of 5 years for a palladium dryer is a bit on the optimistic side...

The actual Hydrogen Cell generates the hydrogen and as long as a good quality water is used with a good quality cell, the generator should enjoy a long and uncomplicated life.

If you are unsure about the Palladium Dryer and would consider a hygrogen generator with a purity of 99.9999% purity (instead of 99.99999%), then you may want to look into generators that use a PSA Dryer. Peak does one (just launched this year), but I think there are also some other European manufacturers who do these, such as Schmidlin.
The technology should, if working right, be self- regenerating.

If you do not mind using a few traps and are not doing any trace analysis, you may also be satisfied by the use of a more basic hydrogen generator that only does 99.995%. These usually only work with a Silica Gel Dryer column or Nafion Dryer.

Tiggeria I think you must be almost the only person considering a generator when you only have one GC!

Haha, I am debating on switching to hydrogen as a carrier gas, so the safety benefit of hydrogen generator is quite attractive.

My calculation was a bit off in my previous post. I am actually using a HP 5890, and a 30m * 0.32mm * 0.25mm df column, so the carrier gas flowrate in the column will be more like ~2 ml/min. Then if my split ratio is 50, it will be 100 ml/min. adding about 30 ml/min for the FID,. the total H2 flowrate will be about 130 ml/min. So a K size tank of H2 can only last about 1 month nonstop, or 3 months for only running 8 hours/per day.
Still does not make much sense financially. The only reason to use hydrogen generator in a small lab is for the safety advantage than keeping a big high pressured gas tank.

Tiggeria I think you must be almost the only person considering a generator when you only have one GC!

I was told that ALL hydrogen cells would deteriorate or fail in 3 to 5 years. I guess that was wrong.

Anyway, the H2 generator idea is out of window now. I will be using gas cylinder.

Thank you for your input. At least I know what to look, if I ever need to buy a H2 generator.

Ah, now I understand why my information is different- we do not use Palladium Technology in our hydrogen generators...

The Palladium Dryer is used to dry and purify the hydrogen generated by cell. It achieves a very high purity hydrogen, however it is prone to technical faults and does have a limited lifetime. From my experience a life time of 5 years for a palladium dryer is a bit on the optimistic side...

The actual Hydrogen Cell generates the hydrogen and as long as a good quality water is used with a good quality cell, the generator should enjoy a long and uncomplicated life.

If you are unsure about the Palladium Dryer and would consider a hygrogen generator with a purity of 99.9999% purity (instead of 99.99999%), then you may want to look into generators that use a PSA Dryer. Peak does one (just launched this year), but I think there are also some other European manufacturers who do these, such as Schmidlin.
The technology should, if working right, be self- regenerating.

If you do not mind using a few traps and are not doing any trace analysis, you may also be satisfied by the use of a more basic hydrogen generator that only does 99.995%. These usually only work with a Silica Gel Dryer column or Nafion Dryer.

We use He for GC/HS analysis. What do you think would be best to replace He with, Ar or H2?

I'd try both and evaluate the results (and costs !).
I'm mostly engaged in natural gas / biogas analysis, detection of hydrogen traces is quite important; for that reason I switched from He over to Ar.

You can't really use hydrogen for HS as you heat and pressurise it. Maybe a bit paranoid to some but I'd say it's a bad idea. You could use something else for the HS carrier and hydrogen for the GC carrier provided the final mixture entering the column is going to be consistent. To be honest if you're thinking of argon then why not just use nitrogen, it's a lot cheaper and just use an in-line trap. We do for a couple of packed column trace analysis methods.

Hmmm - hydrogen generators look to me like a piece of equipment that perhaps needs more maintenance than a cylinder system. The 6 labs I have worked at over the years have all run thier stuff until it is totally broken and then scream for help. That makes me worry about the generators.

(I am in the midst of moving our entire laboratory and dealing with Sandy - these labs build up a lot of neglected baggage - having a bit of a fit by now ).