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/ >