Endrin breakdown

Hi, I am running a 7890A with dual ECD's for multiple methods including 504, 505, 515, 552, 8081, and 8082. We got a super inert splitless injection port and weldment because we were having a lot of Endrin breakdown problems, and it seems to help but not eliminate the Endrin breakdown. I replaced our gas trap in January ( triple trap for oxygen, moisture and hydrocarbons ) using Nitrogen as our carrier and make-up gas. Seems like I almost always have to cut 1/2 loops off each analytical column and 1/2 loop off the guard column to have any chance of getting < 15% Endrin breakdown. Usually DDT breakdown is OK. I have frequently been cooling the injection port down to rinse and swab with MeCL2, Acetone, MeOH and Hexane, with some success. But it is not unusual to see 40-50% Endrin breakdown after a PCB run or 515 Herbicide run.

  Any ideas? We are using a pulsed splitless injection, Have lowered the injection port temp to 180, and use a drilled hole uniliner (Topaz from Restek). Not sure if there is something I am missing.

  Thanks, DaveD

  • Is switching to a split injection possible? We run 608/8081 on our 6890. We used to run splitless with the drilled hole uniliners and I frequently had trouble passing the endrin degradation check. I ended up switching to the Restek topaz precision liner with wool and a 10:1 split. My peak shape improved significantly and I haven't had difficulty passing a degradation check since then. In fact, I find I can run for a lot longer without doing maintenance than I used to be able to. Plus, I change my gold seal much less frequently. I know using wool seems like the worst thing for passing a degradation check, but it works for us. I don't know how "dirty" your sample matrices are as compared to ours, but it might be worth a try if you have enough response/signal-to-noise to try a split injection (my lowest calibration standards for 608/8081 are 5 ppb for pesticides, 50 ppb for toxaphene and 20 ppb for chlordane and I have acceptable responses at those levels).


    For reference: We are using the same RTX-CLP column with no guard column, but we use helium as carrier gas. When I do find it necessary to do inlet maintenance I rarely cut more than ~8" from the column. We are also running 552 on the same instrument and I am usually able to pass a degradation check even after running a batch of 552 samples. Primarily, the instrument runs industrial waste samples for PCB/Tox/Chl screening and I am also usually able to pass degradation checks after running those samples (which are frequently quite dirty). I've also been doing some method development on a 7890/7000 triple quad for running pesticides by 625. I am using a Restek single taper gooseneck liner w/wool, HP-5MS UI column and a pulsed splitless injection. I have a bit more difficulty passing degradation tests on that instrument (maintenance is needed about every two extraction batches or any time I've run a raw influent extract). This suggests to me that the split vs splitless potentially makes a pretty big difference in the degradation.


    (As an aside, if you're interested, I did a pretty comprehensive study of different liner types for our pesticides analysis when I switched from the uniliner to the precision liner. I wasn't evaluating endrin degradation, just peak shape and reproducibility. I'd be happy to send you my conclusions.)

  • We have started doing pulsed split injections with a 5:1 split and are getting much lower Endrin breakdown.  That seems to be a game changer as we still have been battling with Endrin breakdown for some time. Thanks for the feedback.

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