I need to scale up from a tlc pattern from RP-TLC (W) to semi prep RP column (50 mm length X 20 mm ID x 5 um part. size). The mobile phase is 75:25 (Methanol: water).
There is a formula to scale up from analytical to semi prep scale-up, but its applicable to columns. How to modify it for tlc to semi prep scale-up. Loading will be determined by the column, but I am particularly interested in flow rate determination.
There are scale up methods for certain equipments like analytical to prep/semiprep HPLC, TLC to HPTLC anfd flsha chromatography. in your case I suppose you need to develop the method by repeated runs using different variables.
As I can understand there are only two things you can figure out from TLC separation: efficiency of separation as ΔRf (plus tailing) and column volume (CV) calculated from Rf (CV=1/Rf). Higher Rf - less volume of mobile phase you need. The efficiency of separation for the same sorbent will depend on sorbent size, column diameter, flow rate and amount of sample you are loading. But you can predict that with good separation (higher ΔRf) you can use higher flow rates.
If you are going to predict if there will be satisfactory separation between say 2 compounds with different Rf you can use the following formula and empirical rule:
ΔCV=1/Rf1-1/Rf2
If ΔCV is between1,5 and 4,0 the separation will be good, if ΔCV is less than 1,0 – 1,5 it will be insufficient. This rule is for preparative columns with particle size of 10-50 um. It could happen that for your 5 um column this difference could be less. But once again we are not discussing sample size that is so important for preparative separation.
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