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Asked 14 November 2024

Job in postdoc electrical chemistry?

I'm looking for postdoc position

All Answers (3)

Imane Ait Bouabdallah
Université de Biskra
I'm looking for postdoc position too
Dmitriy Berillo
Kozybayev North Kazakhstan State University
Imane Ait Bouabdallah
Université de Biskra
Dmitriy Berillo thank you for sharing the links

Similar questions and discussions

Piperidine derivatives - extra peak in pure compounds. Why and how to change it?
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1 answer
  • Radosław ZanRadosław Zan
Welcome I need help with solving a certain problem. Maybe someone had the same problem as mine and have a tip. I have to prepare a calibration curves and make pharmacokinetic analize piperidine derivatives, which were synthesied. Purity all this compounds at least is 98%. They are free basis, acids or their hydrochlorid salts. During the preparation of the calibration curves compounds as a free form basis/acids, I noticed the appearance of two peaks (new in the dead volume and second in appropriate elution time). Peaks area of new peak increase with injected volume. All hydrochlorid salts eluted as a one peak in adequate elution time. Concentration probes: less than 0,2 mg/ml. Solvent used: for salts: water or water/ACN 1:1; for free: MeOH (they don’t disolve in water or water/MeOH mix and water/ACN mix) Injection volume: 1-10 µl. Column: Kinetex 2.6µm PS C18 100A, 100×2,1 mm Solvent A: water with 0,2% TFA (initial TFA concentration was 0,1%) Solvent B: ACN with 0,2% TFA (initial TFA concentration was 0,1%) Flow rate: 0,5 ml/min Also i tried on other column: Accucore RP-MS 100×2,1 mm (changing column helps a little, but many of free forms still have two peaks in chromatogram) Solvent A: 5% water/ACN with 0,2% TFA Solvent B: ACN with 0,2% TFA Flow rate: 0,5 ml/min Probabilities: - add buffer - solvent is so strong - altering the colmun but I don’t know which one will be better.
For me, the most interesting thing is when the same compound as a hydrochlorid salt elute as one peak, and as a free basic/acid elute in two peaks. Why some molecules, of the same compound have retention and interact with stationary phase and other moleculse say: "I dont like you, i'm out". Column isn't overloaded. I thought that additions in firts column have impact on retention and are saturating, but when i changed a column on "typical" C18 I observed two peaks. Please help.

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