Aldrin has left the building

[montucky1]

Aldrin, hexachlorocyclopentadiene, heptachlor and hexachlorobenzene have all plummeted in recoveries... un-extracted std.s and cal checks are fine... endrin breakdown is <20% DDT Breakdown is <20%... the IS Abundances for all extracted samples are out of the continuing Cal range (I am recalibrating as i write this). Just performed PM. cleaned inlet, new liner (Agilent focus which i baked out for an hour at 100C) squeaky clean source and new filaments. Tuned great no noticable changes when compared to previous tune.
I use glass c-18 cartridges with a supelco vacuum manifold...
i extract with as little ambient light as possible and watch the blowdown like a hawk and usually get the concentrator tubes out right at 1.0 mL...HELP!!!
This has happened before and magically fixed itself after a couple months... i would like to know what causes this... i have half a notebook of notes if you want more info.

Thank you for any and all help

[tlahren]

What type of GC are you using? What type of injection (I assume splitless)? When you say you did a "PM," what all did you clean and how? I have seen a similar issue in the past and after trying "everything" (to the best of my knowledge at the time) I found that the problem was a dirty split-vent line and trap. On Agilent 6890 and 7890 it's the copper tube at the top-left of the inlet that is connected with a Swagelok fitting. Remove this copper tube and replace it (or solvent clean it) if you haven't already. Let me know what else you have done as far as maintenance.

[dischiessel]

Obviously there are a gazillion potential issues. I will try to give a few ideas.

I will assume you've checked the obvious by now:
-Checked your LCS **AND** IS (unextracted) spike against your cal standards. If they match, forget about the instrument; it's not it.
Even if there's severe tailing or breakdown, the two mixes will "match".

Since your breakdown limits are <=20% and your doing hexachlorocyclopentadiene it sounds like you are doing EPA method 508 or 508.1 as opposed to 8081. A major loss of Aldrin is in the sodium sulfate drying step. HCB and HCCPD get lost in the vap down if your pressure(N2 flow) is too high. Lower pressure is better for recovery; we were forced to spend an hour vapping down 508's at 5psig because the analytes were being lost from the blowing of nitrogen. Remember, these analytes are SEMI-volatile which means they WILL go into the gas phase if you heat them or blow nitrogen on them (as in a Turbovap). This includes Decachlorobiphenyl as heavy as it is!!! I've seen it happen when pressures in the turbovap are up at 15-20 psig.

Dave

[montucky1]

the split-vent trap was replaced, the copper tubing was solvent rinsed as part of the PM...
i was having issues with the turbo-vap... someone else had used it prior to me and unbeknownst to me... the thing was cranked... darn me...
i'm replacing the copper line since it is old and will check the turbovap pre blow down from now on.

thanks guys.

[tlahren]

Quick question about your Turbo-Vap:

Is it a Turbo-Vap II? And if so, are you using 1/8" or 1/16" copper tube from the N2 tank to the Turbo-Vap? If you are, your problem may not be too much N2 but too little. You would get a normal or high pressure reading but too little mass flow out of a standard instrument copper tube.

I used 1/16" before (as it was already connected to the tank) and had problems splitting the flow to 2 machines. I may not have noticed if I was only using one turbo-vap. The vendor recommends their Bev-a-line tubing. I think it's 1/4" ID × 3/8" OD and it makes a huge difference in recoveries. It's quite expensive so shop around for it. I had to order 200' of it to go 125' distance. On http://www.coleparmer.com/Product/Bev_A ... W-06491-15 it's about $91/50ft. Or you could find some alternative tubing at 1/4" ID that will be inert and withstand the input pressure required.

[montucky1]

I'm running a teflon line from my hood nozzle to the turbovap... i set the pressure at 20 psi with at least 2 rows running and then back it down to 3-4 using the black knob... I'm getting enough pressure... i can blow water and extract all over the place. bad recoveries on that set as well...
update... HCPD has shown back up and brought the rest with it, Aldrin is still MIA... i'm thinking the drying step is the next step... i blew down with 5psi N2 yesterday for about an hour...
keep the ideas coming!!\

Thank you very much

[Bigbear]

Are you certain the loss is in the turbovap? A quick check would be to inject your standard stock into the volume of solvent that goes into the turbovap and blow it down.
I blowdown for 525 ( EA and MeCl ) at 11 psi at 56C. It usually takes me 10-15 min.

Use the same check for the drying. Run the volume of extract containing your std stock through the sulfate and blow down.

[tlahren]

I'm running a teflon line from my hood nozzle to the turbovap...

How big is the supply to the Hood nozzle? Everything from the N2 tank/generator must be at least 1/4" ID. Double check this as well.

As Bigbear said, I'm inclined to believe that it's not the Turbo-Vap at this point. If you are running EPA methods they require you to use a second source standard (different lot # or vendor) correct? If so, do what Bigbear said with blowing down both standards. They should be very comparable.

I blowdown for 525 ( EA and MeCl ) at 11 psi at 56C. It usually takes me 10-15 min.

I seem to remember about the same for my 8270 prep. I think it was 180 mL MeCl2 @ 12 psi or so at 52°C for about 20 min. Something like that...