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- Posts: 8
- Joined: Mon Jan 29, 2018 2:47 am
We have been crushing in a problem of weird hunches (I dont know which name it should be) and we truly hope all of you can help us to solve:
1. When we used mobile phase containing acetonitrile - water (70:30) or acetonitrile - water - acid phosphoric (700:300:0,2), C18 column, DAD 215 nm, with the sample was mobile phase or tacrolimus solution (prepared in acetonitrile-water 10:1), there was a hunch repeatly with retention time (80 mins) about 10 times of the main peak (8 mins).
When we sent this sample and the same method to an other laboratory, the hunch appeared, too, but retention times were not repeat among peaks.
2. The same problem happened with mobile phase containing acetonitril - tetrabutyl ammonium dihydrogenphosphate 0,01 M (66:34), C18 column, DAD 214 nm, in different days, the chromatograph of blank (acetonitrile - water 50:50) had a hunch at different retention times (the first day: 120 mins (25-27 degree celcius), the second day: 60 mins (27 degree celcius), the third day: 120 mins at 27 degree celcius, 90 mins at 40 degree celcius and 127 mins at 24,5 degree celcius) (using the same column for 3 days). The chromatograph of mobile phase was the same but the hunch is higher (~10 mAu) (the hunch of blank: ~5 mAu). We tried with different degas time but nothing different.
3. We have some other mobile phases having the same rate of acetonitrile (ex: Acetonitrile - phosphate buffer pH 2,2 67:33, DAD 214 nm) but there has been not any hunches.
4. We have a mobile phase containg acetonitrile - tetrabutylammonium hydroxide 0,01 M buffer with acid phosphoric (pH 6,5) (25:75), there was no problem.
The hunch area has the width about 8-10 mins. Spectrum of it had max absortion at about 190-200 nm, and min at about 200 and almost horizon after that.
We are very confused and we put all believe in your help!
Thank you so muchhhhhh!