The great advantage of TLC’s is its flexibility. Understanding the effects of each parameter on the outcome of the final chromatogram allows adjustments to the methodology in order to obtain the desired result. However, that degree of freedom can become a problem for reproducing a method, especially if not all parameters were documented and adhered to.
For obtaining predictable and reproducible HPTLC results, it is essential to establish a standardized methodology in the form of an SOP.
The United States Pharmacopoeia (USP-NF 2015) and the European Pharmacopoeia (Ph. Eur. 2017) published HPTLC general chapters on HPTLC, which are the basis for HPTLC methods of identification as part of monographs on herbal materials. All parameters are based on an SOP adopted by the HPTLC Association in 2012.
References:
United States Pharmacopeial Convention, “Chapter 203: High-performance thin-layer chromatography procedure for identification of articles of botanical origin,” in The United States Pharmacopoeia, 40th–NF 35 ed., Rockville, 2017, pp. 258–260.
European Directorate for the Quality of Medicines and Healthcare (EDQM), “Chapter 2.8.25: High-performance thin-layer chromatography of herbal drugs and herbal preparations,” in European Pharmacopoeia, 9.0., 2017, pp. 295–296.