Endrin and DDT breakdown?

[chemtexpps]

I was wondering if anyone has problems with endrin/ddt breakdown on Agilent 7890 with micro ECDs? I have had this problem for 2 years and cannot solve it. I have changed inlet body, tried new liners, changed gas lines lowered injection temperature from 250 to 200 and the only thing that works is using new liners. And that only lasts one day maximum before I have to perform maintenence again and I am running relatively clean samples. I tried so many liners.....siltek.... Today i even tried Sky Liner from Restek.My instrument conditions are
instrument 1: Agilent 7890A Gas Chromatograph
Detectors: Electron Capture Detector (ECD)
Auto sampler: Agilent 7683
Column 1: RTX-CL Pesticides 1, 30m x 0.32mm x 0.32µm
Column 2: RTX-CL Pesticides 2, 30m x 0.32mm x 0.25µm

Flow Rate: He @ 4 mL/min.
GC Conditions: Initial Temp: 120C
Initial Time: 0.3min
Injector: 200C
Det:330C
Rate A: 45C/minute
Temp. A: 200C
Time A: 0.0 min.
Rate B: 15C/minute
Temp. B: 230C
Time B: 0 min.
Rate C: 30C/minute
Final Temp: 320C
Final Time: 2.0 min.

It is too expensive to use new liners every day.

Does any one have any other suggestions?

Thanks for your help.

[Don Shelly]

Have you tried taking off a meter of column at the injection port end? These compounds degrade because of active sites. They are usually in the injector, but it sounds like you have that part covered. You may have some activity in that first loop or 2 of column.

Let me know how this works out.

[AICMM]

Wool or no wool? What are you using for carrier and how are you cleaning it? Have you tried a solvent trap injection by any chance. My experience has been a lot of liner changes but not every day. That is a bit much.

Best regards,

AICMM

[Bigbear]

Most likely its your injection port and or seal. I have had this problem with a 6890 and 99% of the time it's the inlet. You can get away with just a liner change but there will come a time where you will have to " gun brush" the inlet or replace it. I have brushed inlets with very good sucess. Visit Agilents web site for instructions. Follow them to the letter.
If you overload the liner durring injection breakdown can be caused by "junk" in the split vent line.

[Robb]

Try reducing your inlet temperature. 180ºC will load both Endrin and DDT (don't know what else you're looking for).

I've had good results cleaning single taper liners with solvent and a cotton swab and reusing for DDT breakdown, not so much with Endrin.

[chemtexpps]

Have you tried taking off a meter of column at the injection port end? These compounds degrade because of active sites. They are usually in the injector, but it sounds like you have that part covered. You may have some activity in that first loop or 2 of column.

Let me know how this works out.

I removed a significant portion of column from injection port side.

[chemtexpps]

Wool or no wool? What are you using for carrier and how are you cleaning it? Have you tried a solvent trap injection by any chance. My experience has been a lot of liner changes but not every day. That is a bit much.

Best regards,

AICMM

No wool. UHP-He is carrier. What is solvent trap injection. Can you please explain how to do it.

[chemtexpps]

Most likely its your injection port and or seal. I have had this problem with a 6890 and 99% of the time it's the inlet. You can get away with just a liner change but there will come a time where you will have to " gun brush" the inlet or replace it. I have brushed inlets with very good sucess. Visit Agilents web site for instructions. Follow them to the letter.
If you overload the liner durring injection breakdown can be caused by "junk" in the split vent line.

I followed the Agilent Cleaning Procedure and performed the above mentioned tasks.I even changed the Split vent trap.

[chemtexpps]

Try reducing your inlet temperature. 180ºC will load both Endrin and DDT (don't know what else you're looking for).

I've had good results cleaning single taper liners with solvent and a cotton swab and reusing for DDT breakdown, not so much with Endrin.

I will try 180C. Can you please explain how you are cleaning liners with Solvent.

[Bigbear]

I see now you are using a dual column set up. How do you split the injection?
Both columns in the inlet? If you are also using a Restek splitter inside the oven, have you changed the splitter and fused silica from the injector to the splitter?