The Interaction between Mobile and Stationary Phase

The separation results from the combination of mobile and stationary phases (and of course temperature). Some combinations are not practicable and, therefore. 

The following is the most important basic principle here  

For the chromatography of basic compounds on nonpolar stationary phases (classical reversed phase), use preferably aprotic solvents (e.g., acetonitrile) as the mobile phase and on polar stationary phases (reversed phase with embedded polar groups) preferably protic solvents (e.g., methanol). 

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