Hi Natalie,
Are you sure the old columns were still 60m? By that, I mean did anyone
clip them during maintenance (it would have to be a big clip, but still)?
That would impact any calculations that lead to figuring out the column
pressure. If you havn't already, it would be a god idea to check the flows
from the old and new columns to be sure they match.
If you're looking for oversights, you can start with this checklist from
Restek:
http://www.restek.com/techtips/Installation-Checklist-for-GC-Columns
But I think if you're overlooking one thing on the new columns, you would
be likely to repeat that same error when re-installing the old. Are other
acids also broader, or is it just the two showing reduced performance?
Cheers,
Robert
Robert
On Thu, Apr 6, 2017 at 2:33 PM, Natalie Wallsgrove <[log in to unmask]> wrote:
> Thanks for the suggestion - I wish that was the fix. I've done the column
> eval/auto leak check routine with each column installation, to no avail.
>
> This is exactly the type of oversight that I am trying to eliminate as the
> culprit, so it would be great to know if anyone else has recently replaced
> a similar column?
>
> Thanks! Natalie
>
> On Thu, Apr 6, 2017 at 7:14 AM, Mike Elefante, Elf Analytical Services <
> [log in to unmask]> wrote:
>
>> Natalie,
>>
>> The Trace GC has a leak check and column characterization built in. If
>> these are not done correctly the flow through the GC will not be correct.
>> After any column change or maintenance both need to be done. The flow
>> controller has no way to measure the column flow. It calculates what the
>> pressure should be for the column last characterized. It can only measure
>> the Spilt, Purge and Total flow. So it gives a column flow readback that is
>> a calculation based on characterization not measured flow. I just worked
>> on a Trace that said the flow was 1 mil/min and actual flow was measured at
>> 5 mil/min.
>>
>>
>> Mike Elefante, President
>> Elf Analytical Services, Inc
>> 732-922-8400 <(732)%20922-8400>
>>
>>
>>
>>
>> -----Original Message-----
>> From: Natalie Wallsgrove <[log in to unmask]>
>> To: ISOGEOCHEM <[log in to unmask]>
>> Sent: Wed, Apr 5, 2017 9:31 pm
>> Subject: Re: [ISOGEOCHEM] AA CSIA peak separation problems with new
>> column(s)
>>
>> Thanks for all the response!
>>
>> This issue is with our d15N AA CSIA set up, and we use the TFAA
>> derivatization method. I've been testing the system with a suite if 14
>> pure AA's that have been derivitized, and the same suite injected on the
>> old column separated tyr/lys well, but not on the newer columns. I swap the
>> old column back in and I am able to get decent separation again. One of the
>> BPx5 columns has slightly better separation than any of the other columns.
>> Seemingly endless futzing with temp program and flow rate has not yielded a
>> satisfactory separation to date. Sge and I went back and forth for ages,
>> and they even sent me a new column in the efforts. They assured me that
>> nothing has changed in the manufacturing, etc. In the end they just
>> suggested that I try something other than the BPx5 (which is when we tried
>> the DB5). Both the BPx5 and the DB5 show the same problem. I was kind of
>> hoping that perhaps I was doing something stupid at the installation. With
>> one of the columns I even tried a 12 hour initial conditioning instead of
>> the 3 hour - same results.
>>
>> There is an observed broadening of the peaks, especially compared to the
>> nice sharp peaks we were getting when the old column was newly installed
>> back in 2011. Perhaps its the supply chain or something.
>>
>> Thanks for all the suggestions and food for thought!
>>
>>
>> On Wed, Apr 5, 2017 at 1:50 PM, Robert Panetta <[log in to unmask]>
>> wrote:
>>
>> Aloha Natalie,
>>
>> To understand, you install a new column and it fails. So you put the old
>> one back and it works when injecting the exact same sample, correct? Is the
>> bad seperation just overlap, or do they exhibit broadening/tailing?
>>
>> If it's overlap then the new columns probably have slightly different
>> dimensions or backpressure characteristics so playing with temperature or
>> flows would do the trick. If it's broadening and/or tailing, then odds are
>> you suffer from more active sites in the new column (could be due to a new
>> manufacturing method, a change in the supply chain, relaxed QC, bad batch,
>> etc.). Sigma used to sell an HDMS/BSA/TMSI cocktail for recovering packed
>> columns, but I'm not sure if it worked for capillary columns. You could
>> make your own cocktail and pray it fixes things, but I'd put more research
>> into that one. Restek has the Rxi, which they advert as the "most inert
>> column in the market". Could be worth a shot if it's an active site issue
>> that's been introduced.
>>
>> What does SGE have to say about the change in performance, anyway?
>>
>> Malama pono,
>> Robert
>>
>> p.s. chromforum.org/ is a great resource for this one
>>
>>
>>
>>
>>
>> Robert
>>
>> On Wed, Apr 5, 2017 at 5:08 PM, Natalie Wallsgrove <[log in to unmask]> wrote:
>>
>> Aloha All,
>> I was wondering if anyone else has observed trouble with separation
>> between tyrosine and lysine on newly purchased columns? Our aging column in
>> one of our Trace GCs is starting to show its age, but we've tried several
>> new columns and consistently get bad separation between tyr and lys (all
>> other AAs look fine). We have historically used SGE BPx5 (60m x 0.32mm x
>> 1.0um) columns with success, but we've tried multiple new BPx5 columns as
>> well as an Agilent DB5 (also 60m x 0.32mm x 1.0 um) with the same results.
>>
>> Has anyone else had this trouble? The old columns were purchased in
>> 2011/2012, and all the troublesome columns have been purchased since late
>> 2015.
>>
>> Thanks! Natalie
>>
>> --
>>
>>
>> Isotope Biogeochemistry Laboratory
>> University of Hawai'i at Mānoa
>> Lab Manager
>> [log in to unmask]
>> (808) 956 5362 <(808)%20956-5362>
>> http://www.soest.hawaii.edu/GG/isotope_biogeochem/
>>
>>
>>
>>
>>
>> --
>>
>>
>> Isotope Biogeochemistry Laboratory
>> University of Hawai'i at Mānoa
>> Lab Manager
>> [log in to unmask]
>> (808) 956 5362 <(808)%20956-5362>
>> http://www.soest.hawaii.edu/GG/isotope_biogeochem/
>>
>
>
>
> --
>
>
> Isotope Biogeochemistry Laboratory
> University of Hawai'i at Mānoa
> Lab Manager
> [log in to unmask]
> (808) 956 5362 <(808)%20956-5362>
> http://www.soest.hawaii.edu/GG/isotope_biogeochem/
>
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