Applicability of the Universal Mixture for describing system suitability and quality of analytical data in routine normal phase High Performance Thin Layer Chromatography methods

•Discussion of the origin of RF shifts between repetitions of analyses.•Usage of the UHM for assessing chromatographic results and plate quality.•Comparison of RF values of the UHM substances with SST's and samples of official pharmacopeia methods.•Towards computer-supported standardization of HPTLC analysis. The Universal HPTLC Mixture (UHM) consists of eight substances (guanosine, sulisobenzone, thymidine, paracetamol, phthalimide, 9-hydroxyfluorene, thioxanthen-9-one, and 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol) and yields separated zones over the whole RF range for a multitude of developing solvents. Therefore, it could be used in a generic system suitability test (SST) as well as for the verification of quality of HPTLC data. In this work, changes caused by ±10% variation of the volume fractions of the developing solvent components were tested on three developing solvents, to investigate the RF shifts of the UHM zones in comparison to established SSTs and results described for test samples in selected pharmacopeia monographs for identification of herbal drugs. Additionally, one of the developing solvents was investigated with different stationary phases. The components of the UHM showed similar prediction intervals as the substances of established SSTs and specific markers. The UHM could, therefore, be considered for use in an alternative SST. Because it covers the whole RF range, the UHM can detect changes in developing solvent gradients or saturation effects, whereas many established SSTs generally describe only a limited RF range. The use of the UHM can help facilitate automation of HPTLC. Furthermore, it can potentially be used for correlating RF shifts across HPTLC plates. The circumstances, under which this is possible, are discussed.