Bioequivalence and Bioavailability Forum

Hi Selwa,

» I would like to know if we are called …

Nobody calls you to use anything. You can use any stationary phase (normal or reversed phase, diol, amino, ion-exchange, …) you like. As long as the method passes validation, all is good.*

» … to use HPLC or UPLC MS columns in normal phase in bioanalysis?

I would avoid normal phase if ever possible, since strongly non-polar mobile phases (e.g., hexane) in analytical grade are rather expensive and environmentally problematic.

I suggest HILIC instead, i.e., an RP column and a mobile phase consisting of a moderately non-polar (e.g., acetonitrile) component modified by adding <20% water. Pretty old approach.^3,4
In my CRO we used it for amitriptyline/nortriptyline, clobutinol, and doxepin.

• Pros
  • Much better suitable for (highly) polar compounds than RP.
    
  • Sometimes better for basic compounds than RP.
    
  • Mobile phase substantially cheaper than for normal phase LC.
    
  • Mobile phase more volatile than in RP → nice for MS.
• Cons
  • Mobile phase more expensive than for RP.
    
  • Method development might be more difficult; somewhat steeper learning curve.

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• Do you know GC-O¹ or even GC/MS-olfactometry?²

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1. Acree TE, Barnard J, Cunningham G. A procedure for the sensory analysis of gas chromatographic effluents. Food Chem. 1984; 14(4): 273–86. doi:10.1016/0308-8146(84)90082-7.
   
2. Song H, Liu J. GC-O-MS technique and its applications in food flavor analysis. Food Res Int. 2018; 114: 187–98. doi:10.1016/j.foodres.2018.07.037.
   
3. Schmid RW, Wolf C. Use of unmodified silica with buffered aqueous mobile phase mixtures for selective chromatography of basic drugs. Chromatographia. 1987; 24: 713–9. doi:10.1007/BF02688574.
   
4. Alpert AJ. Hydrophilic-interaction chromatography for the separation of peptides, nucleic acids and other polar compounds. J Chromatogr A. 1990; 499:177–96. doi:10.1016/s0021-9673(00)96972-3.