Print

Print


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
http://www.soest.hawaii.edu/GG/isotope_biogeochem/