I got write a short, boring book on the Isolink system, leaks and
blockages. No one wants to read something like that.
Seriously, wečve learned that owing to all the linked flows, if there is a
problem in one system, check both of them.
Glad yours is up and running again.
On 12/11/18, 11:39 AM, "Stable Isotope Geochemistry on behalf of Lane,
Chad S." <[log in to unmask] on behalf of [log in to unmask]> wrote:
>Just an update regarding our pyrolysis issues on our Isolink (described
>below) just in case anyone ever sees a similar problem. Our sincerest
>thanks to Henry Holmstrand, Patrick Griffin, and Paul Eby who all replied
>with very helpful suggestions.
>Based on our symptoms of changing delta values with successive injections
>and improvement in delta value accuracy following reconditioning of the
>reactor, we were all on the same general reasoning path that something
>had to be oxidizing the graphite out of the pyrolysis reactor. My first
>(easiest) move was to swap the He carrier gas tank (Henry Holmstrand's
>idea) to see if it was contaminated and introducing an oxidant to the
>reactor. Unfortunately, that had no effect, but a great idea! Patrick
>and Paul both suspected a leak. I had searched the pyrolysis reactor
>path NUMEROUS times with Ar and never saw a hint of a leak.
>The key to that sentence is that I had ONLY searched the pyrolysis
>reactor pathway and had ignored my combustion reactor. As well as I
>thought I understood the Isolink, I clearly do not, because apparently a
>leak on the combustion reactor can find its way to the pyrolysis
>reactor...I still do not understand how this is possible unless the Valco
>valve is a bit leaky internally or the flow paths via the MCD are not
>what I thought they were. Well, in any case, isolating the combustion
>reactor solved the problem and our standards are now looking normal again
>(knocking on wood as I write this).
>Thanks again for your suggestions Henry, Paul, and Patrick. Next time
>any of you are at the same conference with me please print this e-mail as
>your free beer coupon and I shall honor it.
>I know listserv's are (or have?) largely gone out of vogue, but thank
>goodness for this one!!!!!
>From: Stable Isotope Geochemistry <[log in to unmask]> On Behalf Of
>Sent: Saturday, December 8, 2018 6:29 AM
>To: [log in to unmask]
>Subject: Re: [ISOGEOCHEM] GC-IRMS Odd Behavior with dD
>How about air impurity in the carrier gas?
>Ute pć vift
>> 8 dec. 2018 kl. 02:37 skrev Patrick Griffin <[log in to unmask]>:
>> My first reaction is an air leak somewhere upstream from the TC that is
>>degrading the graphitization. I'm sure you see why that would fit, and
>>so you have troubleshot around it with He sniffer and Ar overpressure on
>>every conceivable fitting. The second is the magnet current regulator,
>>which I know nothing about in the V but is straightforward to diagnose
>>on the software side. The other explanations are harder to pin down...
>>shitty for you, fun for us puzzles obsessives.
>> How closely have you monitored the high temperature conversion device?
>>My imagination has concocted a elaborate scenario where everything
>>you've seen matches a nearly-but-not-quite dead heating element with a
>>hairline fracture somewhere. That could either be the wise and helpful
>>voice of experience or the bitterness and resentment of someone who has
>>PTSD from a silicon carbide heating element (Roxanne, Seth, Marilyn?).
>> I don't know about your device at all, but if you crack it open and
>>find a variable resistor, it may be worthwhile to move it up a step. If
>>you find the time to fully power down (unplug!) your device, checking
>>the resistance along the element when cold will be definitive.
>> An overnight trace of standard gas that bypasses the thermal conversion
>>can rule out the magnet current regulator. I would also monitor the
>>injection volume as a function of intensity and d2H since conversion
>>efficiency is dependent on temperature and bond strength is a function
>>of redox conditions.
>> If conditioning returns the B4 standard to good values and good peak
>>heights, consider overloading your injections with a fast-eluting
>>compound that conditions the reactor on each run. Works a charm for me.
>> Keep us updated.