Completely agree Jenny,

We’ve changed tanks, changed reactors, baked out the EA column and heated the source/inlet for 48hrs. I think I will take your advice and heat the source, with the valve close for ~a week. Additionally, I will check to see if there is an issue with the O2 valve on the EA by checking the copper wires after a few more days of the new reactor being in place. I recently clean the source (about 3 months ago), and I really don’t want to do that again considering all the problems that can arise from misalignment. When you take a hairdryer to the components, how long are you heating it for? And is it literally just holding the dryer a few inches away from the component with it set to high heat?

I’ll keep the community updated with our progress as it seems like this is something many folks would benefit from.

Thanks again,
TEA

> On Sep 17, 2019, at 2:15 PM, Carlson, Jenny Louise <[log in to unmask]> wrote:
>
>
> EXTERNAL EMAIL: Exercise caution with links and attachments.
>
>
>
>
> Hi All,
>
> Very interested in this string as we just fought what sounds like exact same issue which resolved, but still not totally sure how.
>
> Also hoping for clarification on some of the ideas put forth; how could EA factors like old copper, saturated water trap, or GC column needing bakeout influence the 30 increase whether gas is directed through EA or not? We would also see the rise in 30 during a variable number of std on/off cycles each day, whether flow path was through the EA or the EA was vented to room, i.e. the Conflo was isolated. Seemed like an effect of basically re-introducing N2 each morning.
>
> For the record my issue now seems resolved, however hard to offer solution as we fixed within a huge string of repairs. We did do a full source disassembly and cleaning (source was way more tarnished than suspected), then pumped with all heaters on and inlet closed for almost a full week. During pumpdown, took a hairdryer to all suspicious components while scanning mass 18 to watch for suspicious behavior. For us, inlet region (valve + heater block) showed lots of mass 18 change when heated.
>
> On my system at least, did not seem to be wet tanks as we saw same issue on multiple tanks, and now is resolved without a further tank swap. Also didn't seem to be oil/turbo cartridge as it resolved without changing either of those this cleaning (both were very fresh pre-shutdown for major issues). My best bet here is dirtier-than-suspected source that was super sticky to H2O and making NO, and took major cleanout and cookout to resolve? Please keep us posted as you go TEA!
>
> Jenny
>
>
> -----Original Message-----
> From: Stable Isotope Geochemistry <[log in to unmask]> On Behalf Of gerard olack
> Sent: Thursday, September 12, 2019 11:19 AM
> To: [log in to unmask]
> Subject: Re: [ISOGEOCHEM] Mass 30 instability on Delta V
>
> HI All--
>
> Yeah, NOx's tend to be "sticky" and not pump out quickly.
>
> Something a little different--it might be getting time to change the oil (oil pads) on the turbo pumps--especially if water is high in the mass spec. And double check the roughing pumps too--if the rotor seal leaks, you can still run it for a while, but with increased backstreaming.
>
> It doesn't sound like you can get away with conditioning the source, and I'd guess the source is fairly clean.
>
> take care,
>
> gerry
>
> On 9/12/2019 9:23 AM, Arnold,Thomas E wrote:
>> As a follow up -
>>
>> I baked out the EA oven, closed the valve to the IRMS and baked that out for 24hrs. We still have the same issue with mass 30 increasing within a single on/off run and across multiple on/off runs. Today I will switch out our He tank for a new one, and change the water trap (even though it show no sign on water consumption).
>>
>> Not sure if there are any other suggestions beyond what has already been put forth. The standard deviations look fine after the 4th (or so) N2 on/off run, so maybe I am making too much of an issue out of this, but it is frustrating that such an issue would suddenly appear and be difficult to fix.
>>
>> Thanks for the help,
>> -TEA
>>
>>> On Sep 10, 2019, at 2:08 PM, Harlow, Benjamin <[log in to unmask]> wrote:
>>>
>>>
>>> EXTERNAL EMAIL: Exercise caution with links and attachments.
>>>
>>>
>>>
>>>
>>> Tom, it works nice to install a 3 way valve at the exit of the EA. That way you can quickly vent to the room (or a flow meter) instead of the conflo. You can also use this valve to block off all flow out of the EA for gas savings or a leak down test.
>>>
>>> I would turn off the HF on your conflo and vent the EA whenever you do maintenance such as chemical changes and GC bake out. Then restore the EA to work mode and let it get up to flow and temperature for an hour or so before switching the 3 way back to the conflo. This allows any contaminants introduced during the maintenance to bake off and flow somewhere other than the IRMS.
>>>
>>> Have your helium or O2 tanks been changed recently?
>>>
>>> Cheers, Ben
>>>
>>> -----Original Message-----
>>> From: Stable Isotope Geochemistry <[log in to unmask]> On Behalf
>>> Of Arnold,Thomas E
>>> Sent: Tuesday, September 10, 2019 10:33 AM
>>> To: [log in to unmask]
>>> Subject: Re: [ISOGEOCHEM] Mass 30 instability on Delta V
>>>
>>> Hi Ben,
>>>
>>> We have been using the same UHP tank of N2 for some time now (predating the issue at hand).
>>>
>>> I have not baked the GC oven in the EA before. When you say vent the EA away from the conflo, can I do this by simply turning off (in insodat) the high flow capillary that is going into the conflo? If I remove the line in front of our Costech EA that is carrying the gas from the machine to the conflo, the N2 backgrounds skyrocket (as expected). Thus, I’m not sure which is the best way to vent it away from the conflo.
>>>
>>> Thanks,
>>> TEA
>>>
>>>
>>>> On Sep 10, 2019, at 12:37 PM, Harlow, Benjamin <[log in to unmask]> wrote:
>>>>
>>>>
>>>> EXTERNAL EMAIL: Exercise caution with links and attachments.
>>>>
>>>>
>>>>
>>>>
>>>> Hi Tom,
>>>>
>>>> What are your backgrounds? You could have a bad tank as well. Have
>>>> any been changed recently? If 30 is increasing throughout your EA
>>>> sequences it could be that the water scrubbing chemicals are not
>>>> good, or there is a pathway through the trap. When was the last time
>>>> the GC was baked? (Do this with the EA vented away from conflo)
>>>>
>>>> What I meant about instability is that is usually a consequence of excessive water. If you have good N2 on-off stability then I would think the water in your system is manageable. Usually, when we see a strong stair step effect in m/z 30 N2 is not reproducible to 0.06 per mil or better. If N2 is continually flowing into the source you will see 30 rise. But with time it should return down.
>>>>
>>>> It is my understanding that if heaters are off, water is still likely hanging around the source but you may not see a large m/z 18. Compared to leaving heaters on all the time, the water background will be much less.
>>>>
>>>> If your system doesn't seem stable, it may be worth it to close the inlet, turn on all heaters and let the system pump for a day or two then try again.
>>>>
>>>> Ben
>>>>
>>>> -----Original Message-----
>>>> From: Stable Isotope Geochemistry <[log in to unmask]> On
>>>> Behalf Of Arnold,Thomas E
>>>> Sent: Tuesday, September 10, 2019 6:52 AM
>>>> To: [log in to unmask]
>>>> Subject: Re: [ISOGEOCHEM] Mass 30 instability on Delta V
>>>>
>>>> Ben (and others),
>>>>
>>>> Thanks for the quick response, we also assumed water in the system. As a follow-up: why would the m/z 30 signal increase throughout a single run and across multiple runs? You mention instability as a reason. What do you specifically mean by this? That the EA is not properly sealed? It’s also strange because we see this issue when the EA/high flow is disconnected from the IRMS and the on/off runs are through the conflo.
>>>>
>>>> Thanks again,
>>>> TEA
>>>>
>>>>> On Sep 9, 2019, at 5:39 PM, Harlow, Benjamin <[log in to unmask]> wrote:
>>>>>
>>>>> Hi Tom,
>>>>>
>>>>> It is likely elevated water in your system. N from your N2 pulses combines with O from H2O to give you m/z 30. More time will help. We typically run with source and inlet valve heaters on all the time to keep water out. Sometimes a heat gun or hair dryer can be beneficial to drive water off other components. Monitor m/z 18 while heating various components. Watch for the signal to climb, eventually drop and stabilize.
>>>>>
>>>>> Every time you replace reagents or open up the EA more m/z 18 can get in your system. So venting the EA or allowing ample stability time is needed. If water is really bad then close the IRMS inlet and allow it to pump down independently.
>>>>>
>>>>> Usually if m/z 30 does the stair step on std on offs it is not a stable condition for us.
>>>>>
>>>>> Regards, Ben
>>>>>
>>>>> -----Original Message-----
>>>>> From: Stable Isotope Geochemistry <[log in to unmask]> On
>>>>> Behalf Of Arnold,Thomas E
>>>>> Sent: Monday, September 09, 2019 2:04 PM
>>>>> To: [log in to unmask]
>>>>> Subject: [ISOGEOCHEM] Mass 30 instability on Delta V
>>>>>
>>>>> To the great minds of the list serve,
>>>>>
>>>>> Our system: Delta V coupled to a costech EA via conflo IV
>>>>>
>>>>> Our issue: Mass 30 is drifting to higher and higher voltages across multiple N2 on/off runs — more than a 1V increase from our first to fourth on/off. I can send pictures to individual emails if needed.
>>>>>
>>>>> What we've tried thus far: 1)Replaced: the seals on the EA reactors, the copper wires in the reduction reactor, the water trap. 2) We turned on the heater to bake out the source and inlet. I believe this heater operates at a temperature of 50-80C. After the bake out, the amplitude of mass 30 was reduced, but the voltage drift was still there. 3) The problem presents itself in both EA mode and in the conflo only mode.
>>>>>
>>>>> Any suggestions on what to do? Should this even be considered a problem as our standard deviation looks fine after the 3rd series of on/off runs?
>>>>> Thanks,
>>>>> Elliott Arnold
>>>>> Pitt Geology