DW-WAX column - analyse methanol in water:isopropanol (95:5). UNEXPECTED peak!!!

Hello, Im using DW-WAX column (30m, 0,53mm, 1um). I was trying to analyse methanol in water:isopropanol (95:5). I have huge problem, in my desorbent always is methanol peak and it is big.. the weidrest is that this peak in 1st inj has area about 10, next inj - peak is bigger, sometimes area 200.. then 3rd inj peak has area about 25 and over and over again.
What could be the problem? Any idea how can I remove it? The program is isotermal - 50*C for 5 min, detector temp=250*C and injector temp=200*C.

Please heeeelp!

  • Additionally, the client samples usually contain dissolved minerals that elute before the methanol peak. When the injection flashes in the inlet port liner it will stay there until you do maintenance (change liners every day) clip the guard column as needed to get back to baseline. We know the methanol "rides" the interference peak so we set the base line at the valley.

  • yes.. in client samples of course could be some junk, but i am on validation etap, so as I said i injected only desorbent (water:IPA - 95:5) and methanol in my desorbent..

    unfortunately I dont understand second part of your answer - this about flash in inlet port and something about the baseline, could you explain, please? :) 

  • He means when is it vaporized in the hot inlet (250C).  He means the methanol peak is on top of another as they coelute.  

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