Endrin breakdown

Question

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

daved · Accepted Answer

OK this just in. We have found the cause of my massive Endrin breakdown. Water in my extracts. And have found where that water winds up. In the split vent line. The 505's are extracted in 40ml vials with 35ml water, and 2ml of hexane on top. The extraction is supposed to pull enough Hexane off the top to shoot on the GC and a little extra to save in case re-runs are needed. Water has been getting sucked up with the Hexane and once shot on the GC it vaporizes in the injection port and some makes it way into the split vent line where it condenses and gets stuck. This causes Endrin breakdown to go thru the roof until we 1. cool down the injection port and rinse with MeCl2, Acetone, MeOH and Hexane, 2. replace injection port liner, gold seal, and septa, 3. take 1/2 loop off guard column and each analytical column, 4. replace the split vent line. Yesterday my Endrin breakdown went from 71% to 2% after performing all these steps on my GC. Now we just have to figure out how to keep the water out of my extracts and I think we'll be able to run pesticides without all the headaches. I hope this is helpful to somebody else out there.