Applicability of the Universal Mixture for describing system suitability and quality of analytical data in routine...

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 R_F 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 R_F 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 R_F range, the UHM can detect changes in developing solvent gradients or saturation effects, whereas many established SSTs generally describe only a limited R_F range. The use of the UHM can help facilitate automation of HPTLC. Furthermore, it can potentially be used for correlating R_F shifts across HPTLC plates. The circumstances, under which this is possible, are discussed.