In general peak fronting may be due overloading so you may decrease conc per spot
Also try drops of acetic acid to make drug in unionized form meanwhile if you use drops of ammonia the drug will be ionized.
If this failed you should try several mobile phases and choose the one which yield good peak shape with good resolution
In general peak fronting may be due overloading so you may decrease conc per spot
Also try drops of acetic acid to make drug in unionized form meanwhile if you use drops of ammonia the drug will be ionized.
If this failed you should try several mobile phases and choose the one which yield good peak shape with good resolution
Adding 1%v/v formic or acetic acid to your mobile phase usually prevents peak tailing (streaking towards the origin) on TLC. Is that what you are referring to?
Dr. Ragab got the gist of it.
Depending on the pH of the silica/solvent system and the pKa of the acid, the acid could exist in an equilibrium between the free acid (less polar since it is uncharged), and its conjugate base which is ionized and more polar. In normal phase chromatography, the less polar form elutes faster. As mentioned above, adding an acid could help as it forces the equilibrium to the free, non-polar, acid. Ammonium hydroxide forces the equilibrium the other way. If using TLC to develop a method for column chromatography, be aware that polar basic solutions dissolve silica.
I've seen people occasionally use the term "fronting" to describe the majority of the compound eluting early such that the there is a spot with a streak behind it - if this is occurring, the spot could be overloaded. The more proper term for a peak which leaves a tail behind it is "tailing"
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