Hi everyone,
currently I'm using 7890 agilent GCMS for pesticides identification in water sample. However, I always get a sharp peak around 7.3min in the blank (methanol/acetone) during the process and this peak is still there in the sample. I've changed to newly opened solvent, vial but the peak is still there. Is it contamination from other source that i didn't look at? how to overcome this problem?
Thanks everyone
1. Replace the liner. (The liner may be contaminated.)
2. Cut both ends of the column about 10 cm.
3. Make enough column aging to remove all contaminants.(Raise to near the column's limit temperature and make conditioning until the signal is stabilized.)
4. Wash the syringe with fresh solvent.
5. If there is a wash vial, fill the vial with fresh solvent.
Follow the steps above to see if the same problem occurs.
thanks. i will try to do 1-3.. i have tried 4-5 but didnt work
I think you should change the solvent system. Then check the peak again, it is still at 7.3 min or not (with other mobile phase) for clearance the problem associated with mobile phase or column.
yes,
First I try to run with acetone. That is the first time we saw the peak. WE taught of solvent contamination. So we changed to newly opened acetone. But the peak is still there.
Then we changed to new solvent; methanol. We used new solvent and bottle (washer vial). Still do difference.
We try to 'bake' the column to 320dec for 25 min. The peak is still there however the peak is smaller compared to before (half of the reading before). Can we say something wrong with the column?
With that result I would try baking the column for longer: a couple of hours maybe. Keep track of how long it takes to bake the column until it is clean. Your next task is to determine how the column became contaminated. Was it one of your samples, and if so how do you clean/dilute the sample so that you do not have this problem again.
If the ghost peak was reduced compared to previous experiments, it is likely to be a contaminant in the column. In this case, ghost peak could be removed by column baking. Overnight baking can be performed at column limit temperature - 5~10 dec to burn all the contaminants in your column. Also I recommend you to replace the liner.
thank you everyone..
i am pretty sure the contaminants came from our sample because previously we did run a high concentration of samples. since that we keep on getting the ghost peak at the same RT for our sample
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