Chromatography Forum

I have a query. As all of know vergin Helium is very expensive, Cant we recover Helium from Effluent GC-MS carrier Gas , i think it may reduce our expenditure? Please give your opinions on this topic

The helium would by contaminated by analytes .. in any aspect it would no longer be He 5.0

There might be something in this - cleaning it up could not be more difficult than separating it from the filthy natural gas that it is mixed with naturally. Capture from the split and septum purge as well, scrub it, pressurize to 5 bar and put it back into the GC.

Good one

Peter

Helium recover is suprising difficult. When I was working at a university research institute after my graduate work a group on the other side of the parking lot had a cryogenically cooled gravity wave detector. When experiments were being conducted my memory says the instruments used about 240 L of liquid nitrogen per hour, and around 40 L of liquid helium per hour. They did try to recover the helium, but the recovery was less than 100%. They also had a small setup to re-liquify the helium.

There might be something in this - cleaning it up could not be more difficult than separating it from the filthy natural gas that it is mixed with naturally. Capture from the split and septum purge as well, scrub it, pressurize to 5 bar and put it back into the GC.

Good one

Peter

may be we need to lookinto it deeply

Recovery from liquid gas cryogenics has the problem that the gas comes out all over the place - the hardware is simply not put together with gas management in mind. And re-liquifying helium must be an horrific job, while in GC we only want it at about 5 bar pressure - you could get a metal diaphragm pump to do that for less than the price of a cylinder of helium.

I am getting a serious attack of "I wish I'd thought of that"

Peter

Recovery from liquid gas cryogenics has the problem that the gas comes out all over the place - the hardware is simply not put together with gas management in mind. And re-liquifying helium must be an horrific job, while in GC we only want it at about 5 bar pressure - you could get a metal diaphragm pump to do that for less than the price of a cylinder of helium.

I am getting a serious attack of "I wish I'd thought of that"

Peter

I think in GC-MS using membrane interface between GC-MS will help us in both ways like recovering effluent stream and reducing load on vacuum pump. do u have any idea about typical effluent purge stream flow rates and typically to howmuch extent He can be contaminated by analytes

Back of envelope calculations: 1 ul sample in hexane injected every 30 min with a total flow of 50 ml/min (including split plus septum purge) ignoring gas savers and other such fancy stuff is 0.6 mg in 1500 ml, say 0.4 mg/l, 10 mg/mole, 100 ppm volume:volume, in other words 99.99 pure. This is very optimistic best case; the main contaminants will be pump oil, plus some air from diffusive leaks.

Peter

Seems like someone could make a pretty penny if they came up with equipment that would allow this, you could even have it as a service provided by the gas provider where you give them back the slightly contaminated helium and they reduce your bill.

It does seem inefficient blowing so much helium out the various exhausts and vents.

Hi,
I would have thought it might be feasible to recover helium from split vents - the activated carbon trap is a start. Wonder if anyone has tried recovering / analysing that.
I would have thought helium at the vacuum end impractical?
WK

Hi,
I would have thought it might be feasible to recover helium from split vents - the activated carbon trap is a start. Wonder if anyone has tried recovering / analysing that.
I would have thought helium at the vacuum end impractical?
WK

They do it already by an easier way: gas saver feature of the S/SP Injector.

WK is right - in normal practise at least 90% of the gas goes out of the split, and as much goes out through the septum purge as into the column.

A gas saver reduces consumption by maybe 1/2, recovering split and septum purge would cut total consumption by 90%.

Peter

Hi Peter and thohry,
Forgive me please - but which GCs have this gas saver feature and how does it work again?
Does it divert flow back from the split back into the carrier line?
Regards
WK

Hi WK

The gas saver just reduces the total flow of carrier gas to the inlet once the injection and transfer of the sample to the columnn has taken place. For most of the GC run the flow to the nlet is reduced, but the column flow remains under the control of the inlet pressure.

Peter

Hello WK,

The idea is simple. We just need the split flow during injection. So about 2 min after the start, the Inlet will reduce the split flow to very low while maintaining the column pressure as normal.
I should think all the modern GCs have this type of feature. I used an Agilent 6890 (from 1996) and it has gas saver mode already.