Method 552.3 UCMR4

Discussions about GC-MS, LC-MS, LC-FTIR, and other "coupled" analytical techniques.

8 posts Page 1 of 1
Good morning,
We are currently trying to get Method 552.3 MDLs to work and are having trouble with Tribromoacetic acid, Chlorodibromo acetic acid and Bromodichloroacetic acid. Does anyone have any suggestions to try?
Thanks,
Lisa
lisalimke wrote:
Good morning,
We are currently trying to get Method 552.3 MDLs to work and are having trouble with Tribromoacetic acid, Chlorodibromo acetic acid and Bromodichloroacetic acid. Does anyone have any suggestions to try?
Thanks,
Lisa


Is this the MRL study?

If so, are you using the primary source standard or the secondary source (QCS) standard to spike the MRL extractions?

We are seeing that the second source is slightly different from the primary and gives us some trouble with percent recovery, so we will try again using the primary source to spike with.
The past is there to guide us into the future, not to dwell in.
We are using the primary source and aren't getting a decent enough response at the MRL to be reproducible.
What column are you using and what conditions?
The past is there to guide us into the future, not to dwell in.
We are using the columns stated in the method and we tried the temperature program stated. We are now trying different temperature programs. We are making one injection onto a guard column which is then put in a y-splitter that has the two columns attached. We have tried injecting more volume since it is split between two columns but we just aren't getting very good reproducible sensitivity.
When you said you tried injecting more volume because of the split....did you calculate the vapor volume? Because if the vapor volume exceeds the capacity of your liner (i guess you are using a SSL-Injector?) you get a backflush and the sample will get stuck in the non-heated gas pipes. Even if you don't experience weird peaks in the next runs i would strongly recommend to change the liner and clean at least the injector chamber since it is very easy to use to much volume. So if you used a 2 mm quartz liner like in the method you can just inject tiny ammounts to get reproducible results. Use a solvent expansion calculator to check if everything is ok.
http://www.restek.com/chromatogram/view/GC_EV01006

This is the column setup we are using, but we switched to hydrogen carrier gas to get better sensitivity. Using the same cyclo liner listed in the link.

You will need to experiment with the flows and temp program just a little to get complete separation.

If using and Agilent, it should be able to calculate the proper head pressure to deliver the needed flow to both columns connected to a single inlet.
The past is there to guide us into the future, not to dwell in.
Just curious, what is your calibration range?
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