Hi there,

I also use the mentioned Supelco 23801 device and downstream the OMI
triple trap (Supelco 28867-U). We use Carabagas Alphagaz 1 Helium
(>=99.999 % purity)

Once I had to change the He bottle and experienced higher blanks for trace
methane isotope analysis. Leaks were ruled out and another (new) bottle
showed the same methane blanks. Background (magnet) scans for m/z 18, 28,
32, 40, 44 which I monitor daily are normal.

Why do I write this?

I changed the Supelco getter oven and the OMI trap, which both have been
installed for 5 years. After a day of flushing the backgrounds for the
above mentioned main species are the same as with the old getter and OMI
trap. (Methane blanks still high.)

summary:

- In my case the mentioned purifying devices last for 5 years (or more).
- (I am sure you know this) The purity one obtains is species dependent.
- While the specifications of the He were met I guess that the 2 bottles
contained roughly 100ppb CH4 (the specs allow 500ppb for CnHm). Bottles
purchased before May 2011 contained definitely less methane. Has anyone
else experienced varying methane concentrations in He?

I use a cold trap (filled with Hayesep) to freeze out methane (and other
condensible gases).

my 2 Rappen
Best,
Michael





On Thu, June 9, 2011 9:11 pm, Sergei Verenitch wrote:
> We have been using UHP He for years without any additional purification.
> We
> use it on our two EA-IRMS and one Varian GC-MSMS. Once in a while (from on
> supplier) there was a high Ar background in He. After we changed the
> supplier, it has been fine for years.
> Cheers
>
>
> On 11-06-08 8:57 PM, "Robert Van Hale" <[log in to unmask]>
> wrote:
>
>> Hi Brett,
>> Probably not. And at that meagre price who would care. You guys just dig
>> it
>> out of the ground?
>>
>> We use 4-9-8 (BOC "Zero Grade") straight out of the bottle for EA,
>> gasbench
>> and TCEA and I couldn't say that we have ever had problems related to
>> gas
>> purity. For the GC we have high capacity thermal purifier plus that
>> Supelco
>> 23800. I have no way of knowing if this does any good or if it gives any
>> improvement in performance. We have not used oxygen-sensitive stationary
>> phases or particularly water-sensitive either so do we need it? Reading
>> the
>> table of analysis from label on a He bottle: the principle contaminant
>> is N2,
>> then water, O2, Ar are the next most abundant all of which are either
>> harmless
>> or are seemingly produced in the source/prep system in far greater
>> amounts.
>> The only organic contaminant listed (ethane) being of low molecular
>> weight
>> would not affect chromatography(?), would merely add a baseline signal
>> to CO2
>> measurements.
>> Lab Note - There is no bleed valve on our cylinder regulator so we have
>> to
>> fuss around cooling the heated trap and venting the line when changing
>> the
>> bottle, just to prevent the small slug of air from reaching the traps.
>> All the best
>> Robert
>>
>>
>> -----Original Message-----
>> From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On
>> Behalf
>> Of Brett James Kuskopf
>> Sent: Thursday, 9 June 2011 12:16 p.m.
>> To: [log in to unmask]
>> Subject: Re: [ISOGEOCHEM] purifier for He supply for IRMS
>>
>> Great question, I'd appreciate some info on this as well.  I was
>> wondering if
>> there was an inline system capable of purifying 4.0 He (at AUD$45/G
>> bottle) to
>> 99.999% He as 5.0 He is AUD$170/G bottle.
>>
>> Does anyone else do this?
>>
>> Regards
>> Brett
>>
>> -----Original Message-----
>> From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On
>> Behalf
>> Of Shuangquan Zhang
>> Sent: Thursday, 9 June 2011 10:05 AM
>> To: [log in to unmask]
>> Subject: [ISOGEOCHEM] purifier for He supply for IRMS
>>
>> I am looking for the information on the purifier to work best for the He
>> supply
>> line for an IRMS. Any information would be greatly appreciated.
>>
>> Thanks,
>>
>> Shuangquan Zhang
>>
>