Hello Jennifer,
Sorry to hear you are struggling with your MultiPrep.
If I may add a few words to the discussion I'd say be very careful
before dismantling the MultiPrep valve system. As Georges said, it is
not exactly straightforward so you really have to make sure this is
where the problem comes from.
As I already said on the list, our experience here is that acid delivery
is usually a good candidate when problem occurs on a MultiPrep. First,
as Li Huang said you have to make sure the acid delivery is working OK.
We have experienced a few problems here with acid delivery with some of
our batches of acid although we always make it with the same protocole.
Different batch of initial H3PO4, overheating of one of our old hetaing
plate, overheating when outgassing the acid, all this can contribute to
make it a bit too viscous and alter the acid delivery. Li Huangs
suggested test is a good one. If you deliver acid in 10 vials in a row,
make sure you get the same amount of acid every time. If not take the
acid delivery system appart, clean it including the acid pump mechanism,
change or clean the peek tubing, make a new batch of acid and re-try. If
the acid delivery is OK.
A second good candidate for troubleshooting is the external cold finger
and/or its thermocouple. Like us I think you've been through that a few
times in Montreal. It can happen that the thermocouple breaks That is
easy as you have no reading. That is obviously not your case. But it has
happenned to us that the white cement which is at the bottom of the cold
finger cracks, then condensation comes inside the hole where the
thermocouple is and gives you erratic temperature readings. Depending on
how erratic they are, this is not always easy to detect. A good sign can
be the presence of a large pack of ice around the cold finger and a cold
finger which is constantly sucking liquid nitrogen. Have a look at how
your cold finger operates and make sure its behaviour is normal, during
the trapping phase as well as during the releasing phase. When ours did
that we kept the thermocouple in place with a drop of araldite, trying
to carry on our analyses until the replacement part arrived, it has
worked like that for 5 months now and we haven't installed the
replacement one.
If it's neither the acid delivery nor the external cold finger, then you
should very carefully test your MultiPrep valves for cross seat leakage
and make sure they are the source of the problem.
The water trap is surely not the problem. In fact you could run
carbonates with your water trap at room temperature as if your acid is
water free, which it should be, you get virtually no water when running
carbonates. And if you do, the external cold finger releasing CO2 at
-70°C, water is kept in this cold finger which is baked between samples.
A few more points. The modified scripts to flush the MultiCarb needle
was written mainly to help when running fine carbonate powders as some
grains might get stuck inside the needle and block it. It was not meant
to eliminate acid as acid should never get there.
I don't personally use filters on the MultiPrep lines but I know others do.
And to answer Georges' question, we have not noticed any leakage problem
with our laser welded needle and have recently run successfully small
carbonates with it. I have to add that if this new needle seems better
than the previous one and especially more reliable in terms of quality,
all the initial work done with the MultiCarb was done successfully with
the original one.
Sorry to have been a bit long.
--
François FOUREL
UMR CNRS 5125 PEPS
Université Claude Bernard Lyon 1
2 rue Raphaël Dubois - Bât. Géode
F-69622 VILLEURBANNE Cedex - FRANCE
Tél : +33 (0) 4 72 44 62 42
FAX : +33 (0) 4 72 43 16 88
Email : [log in to unmask]
Jennifer McKay a écrit :
> Hi Georges,
>
> In an attempt to avoid leaks we will be replacing the seats, as well as
> the diaphrams and buttons, but not the valve blocks because, as you
> noted, they are welded together. I'm keeping my fingers crossed because
> I don't want to have to rebuild the entire thing at the moment. So many
> samples .... so little time. However, putting together a new valve
> assembly will probably happen sometime in the near future because
> Swagelok no longer sells our type of valves and getting replacement
> seats/diaphrams will eventually be impossible. So if you could send me
> your part list that would be great.
>
> I normally blow a bit of N2 gas through the needle after every batch of
> samples. If acid comes out it is time to clean. However, it would be
> ideal to do this after every sample. I think it is time to contact the
> software guys at GV and have the multicarb method tweaked a bit. They
> have made similar small modifications to Masslynx for us in the past.
> Its a great service.
>
> Free filters! Who could say no to such an offer...especially after
> spending $500 on valve repair kits. My postal address is below.
>
> Thanks again for the help.
>
> Jennifer
>
>> Hi Jennifer,
>>
>> Yes. The solder connection at both ends of the needle are a weak
>> link. Apparently many users have had success with these solder
>> connection needles for years, but of late, the quality is
>> unpredictable. GVI developed the new laser welded needle (four
>> hole). There must be a reason for this, even though it's hard to get
>> anyone to come clean at GVI regarding this issue.
>>
>> There are two ways acid gets into the prep line and beyond. The first
>> is from the solder connection cracking, which can result in a large
>> amount of acid moving quickly. The resulting droplets can cause
>> partial physical blockage which results in fractionation and
>> incomplete transfer of the gas to the cold finger. The other
>> mechanism is accumulation of acid droplets from routine use. There
>> are users blowing N2 gas through the needle after every sample. This
>> has resulted in keeping the prep line and needle free of acid blockage.
>>
>> Good luck cleaning out your multiprep valve block. These valves are
>> not servicable, meaning that to replace the seat, you must replace the
>> valve block in addition to replacing the diaphram. When we cleaned
>> out our multiprep valve block after needle failure, we did the same as
>> you by replacing the diaphrams only. Cross seat leaks developed on
>> these cleaned valves. This can mess things up, especially valves FC
>> and FH that have one atmosphere on the other side. Since the
>> multiprep valve block is a pre-welded assembly, replacing valves is
>> problematic. We have since replaced the multiprep valve block with
>> individual valves connected using VCR fittings. Any future servicing
>> will be one valve at a time. Let me know and I can shoot you a parts
>> list.
>>
>> I recommend using the filters in the 1/4" to 1/16" union. GVI part
>> #T3602810. I just realized that I have extra filters because they
>> don't fit in my VCR to 1/16" swage union. I need a different filter.
>> If your interested, I'll send you a few.
>>
>> Happy cleaning,
>> Georges
>>
>>
>>
>>
>> ----- Original Message ----- From: "Jennifer McKay"
>> <[log in to unmask]>
>> To: <[log in to unmask]>
>> Sent: Friday, April 21, 2006 3:27 PM
>> Subject: Re: [ISOGEOCHEM] Multicarb problem
>>
>>> Hello Georges,
>>>
>>> Thanks for the advice.
>>>
>>> I did check the 1/4 to 1/16 union for acid as part of my needle and
>>> stainless (ss) tubing. It looked OK. However, there is no filter in
>>> the union. If the missing filter is designed to keep acid from
>>> reaching the dual inlet valves I could have bigger problems. That
>>> said, we are now in the process of taking apart and cleaning the
>>> valves and replacing the valve diaphrams.
>>>
>>> Now, I've noticed that acid gets into the system (i.e., needle side
>>> hole and ss tubing) when there is a leaky vial or leaky needle. Have
>>> you observed the same?
>>>
>>> Jennifer
>>>
>>>> Hi Jennifer,
>>>>
>>>> Although you mentioned that the needle and prep line don't have acid
>>>> blockage, it may be worth pulling the 1/4" to 1/16" union that
>>>> attaches the prep line to the multiprep valve block. We've had acid
>>>> migrate to the filter in the union. This resulted in very strange
>>>> performance, including no gas getting to the cold finger. Swab the
>>>> inside of the 1/4" tubing with a kimwipe and inspect for acid. Also
>>>> look closely at the filter in the union. A quick boiling in DI
>>>> followed by a good bake will clean the union (filter).
>>>>
>>>> I'm glad to hear you installed the new four holed laser welded
>>>> needle. Maybe GVI would consider a recall of the old design needle,
>>>> or possibly offer a reasonable trade-in.
>>>>
>>>> I've observed that the laser welded needles don't seal as well to
>>>> the blue septa/kel-f disk combo. I was wondering if anyone had any
>>>> experience with the new laser welded needles running small carbonate
>>>> samples. This extra leaking may affect small samples.
>>>>
>>>> Good luck,
>>>> Georges
>>>>
>>>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>> Georges L. Paradis
>>>> ICPMS Lab Manager
>>>> Department of Earth Science, Marine Science Institute
>>>> University of California Santa Barbara
>>>> Santa Barbara, CA 93106
>>>> 805-893-7182
>>>> [log in to unmask]
>>>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>>
>>>>
>>>> ----- Original Message ----- From: "Jennifer McKay"
>>>> <[log in to unmask]>
>>>> To: <[log in to unmask]>
>>>> Sent: Friday, April 21, 2006 9:25 AM
>>>> Subject: [ISOGEOCHEM] Multicarb problem
>>>>
>>>>> Hello Everyone,
>>>>>
>>>>> I have a rather interesting/annoying problem with my
>>>>> Isoprime-Multicarb system. Essentially, during a run no gas is
>>>>> getting from the reaction vial to the first coldfinger (CF2). At
>>>>> first we thought it was a problem with CF2 (e.g., either it was
>>>>> plugged or not cooling properly) but the problem still persisted
>>>>> after changing to a new coldfinger. If we simply inject CO2 into
>>>>> the vial (bypassing the calcite-phosphoric acid reaction) we are
>>>>> able to get CO2 from the vial to CF2 and trap it correctly.
>>>>> However, this works only if we are using a lot of CO2 gas. If we
>>>>> use only a small amount (as if we reacted 100 ug calcite) it does
>>>>> not work. I have confirmed that CO2 gas is being produced (i.e.,
>>>>> no problem with the addition of acid to the vial). So essentially,
>>>>> it appears that CF2 does not have the ability to "pull" the CO2
>>>>> from the reaction vial or the CO2 gas is being trapped / lost
>>>>> somewhere along the way. I have considered the possibility that
>>>>> the water trap is too cold (and that the thermocouple is reading
>>>>> incorrectly) and will check this today.
>>>>>
>>>>> Here are a few more details. I've checked the system for leaks
>>>>> with Argon and everything looks OK. The needle and stainless steel
>>>>> tubing leading from the needle to the inlet system are not plugged
>>>>> with acid (...those of you with the multicarb know this is a common
>>>>> problem). We have confirmed that the heated rack is at about
>>>>> 90°C. We are using a new batch of acid, but it worked fine for a
>>>>> few runs so I don't think this is the problem. We also have the
>>>>> re-designed multicarb needle, but again we used this for a few runs
>>>>> without problem.
>>>>>
>>>>> Any suggestions would be greatly appreciated.
>>>>>
>>>>> Jennifer
>>>>>
>>>>>
>>>>> --
>>>>> Post-doctoral Researcher
>>>>> Centre GEOTOP, Universite du Quebec a Montreal
>>>>> C.P. 8888, succursale Centre-Ville
>>>>> Montreal, Quebec, Canada
>>>>> H3C 3P8
>>>>>
>>>>> GEOTOP: 514-987-4080
>>>>> Office: 514-987-3000 (1718)
>>>>> Lab: 514-987-3000 (7028)
>>>>> Fax: 514-987-3635
>>>>>
>>>>> E-mail: [log in to unmask] (or [log in to unmask])
>>>
>>>
>>>
>>> --
>>> Post-doctoral Researcher
>>> Centre GEOTOP, Universite du Quebec a Montreal
>>> C.P. 8888, succursale Centre-Ville
>>> Montreal, Quebec, Canada
>>> H3C 3P8
>>>
>>> GEOTOP: 514-987-4080
>>> Office: 514-987-3000 (1718)
>>> Lab: 514-987-3000 (7028)
>>> Fax: 514-987-3635
>>>
>>> E-mail: [log in to unmask] (or [log in to unmask])
>
>
>
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