Endrin Degradation Problems

[cgwinner]

So I have been fighting this endrin degradation problem for over a month now and feel like I have gotten no where. Endrin breakdown is hovering between 15-20% and needs to be less than 15% for me. I am running pesticides and PCBs on an Agilent 5890 with dual ECD detectors. Doing dual injection with 2 towers at the moment. I have ordered new Degradation check standard, replaced the columns, replaced liners (Agilent ultra inert goosneck (no wool)), replaced gold seals (Agilent ultra inert gold seals), replaced inlet body, replaced inlet weldments, replaced purge lines, replaced chemical traps, and the best it has gotten has only been like 14%.

Should I try to play with the method and adjust the temperatures? I don't know what to try and do next to be honest

[rb6banjo]

I don't do any pesticide analysis but I did a quick google search to learn a little about the degradation of your analytes. I assume that you know about this but just in case, here's an app note from Agilent describing how their inert flow path minimizes the difficulty.

https://www.chem.agilent.com/Library/ap ... 1862EN.pdf

Apparently even the most herculean efforts won't eliminate it. They recommend equipment that you might consider putting in your GC to make the analysis better.

I observed a webinar on their inert flow path efforts in regard to PAH analysis and the differences measured were pretty amazing.

Good luck!

[Steve Reimer]

From back a few years so the details have gotten elusive:
Endrin and DDT degradation can be lessened by keeping the time in the inlet as short as possible, so increasing the flow helps, I used to run a splitter into two columns. On an instrument with a pair of 0.25mm columns degradation would be much worse than a similar instrument with 0.32 columns. Also the endrin degradation would be worse when new liners were installed, improve with sample dirt for a while before getting bad again. DDT degrade would start off great and get worse with dirty samples. Your milage may vary, I was often analyzing fish or sediments.

[BHolmes]

At our lab we analyze Endrin with no problem, we have just started to analyze DDT o,p and no degradation issues so far. We work really hard to get it that way though, inlet maintenance is done after every 100 injections, sometimes less depending on matrix (i.e. after 50 injections of Milk or Fish matrix, maintenance is required). Maintenance includes trimming the guard column (we install a 1 meter section of the analysis column to act as guard column before actual column), changing out gold seal, ultra inert double tapered liner, and septa.

Our standards are a mixture of about 50 analytes that is made every 6 months. The neat standards used to make the mixture are made fresh every year. All standards are stored in freezer at 0 degree C. Solvent is acetone, sometimes MeOH depending on solubility of analyte. LOD is 10ppb for Endrin and 1ppb for DDT.

Hope this helps.

[Yama001]

If you can drop your inlet temperature to 200 it may help out.

[Hornet]

Restek Sky liners.

[cgwinner]

Have Dropped the temp to 250 on the inlet and it helped a little but it seems to vary from run to run floating between 17 & 20%. Will try playing with the method some more to see if I can bring it down some more.

Do the Sky liners prove to work better than the Agilent Ultra inert? Really hard to tell when its usually the manufacturer comparing theirs to the others to get the real truth.

Thank you for all the help so far.

[Turret_Error]

At my old job we did pesticide analysis on 5890/ECDs as well. We found that our issue was in the liners. We had little to no breakdown when we ran our DDT/Endrin standard at the beginning of a sequence but we knew that if we tried to run another sequence afterwards that there was no way the breakdown would pass. So we sucked it up and started ordering more liners and replacing them before every pesticide sequence. Worked well. We used some pretty simple Phenomenex straight liners with glass wool.

My coworker did have problems at her previous job when they tried to do split injections from one autosampler onto 2 columns. The breakdown can occur at any place that can create active sites and that split tubing junction did just that.