ABSTRACT
Quantitative thin-layer chromatography (QTLC) measured by direct photometric scanning has been performed for nearly 50 years. Despite its long history, this procedure has not achieved the reputation of being a very reliable quantitative analytical technique. Relatively large standard deviation has often been mentioned as one reason that QTLC was not acceptable as a reliable quantitative technique. The most important drawbacks were problems in sample application, development, scanning, and data processing. The opposition was unjustified (1). TLC is an openbed technique with many not precisely controllable parameters, which on the one hand contributes to a large dispersion of measurements but on the other hand eliminates systematic errors. High accuracy can easily be obtained by using a large number of applications of the same sample and statistical methods. In addition, certain steps in the procedure can be strictly controlled and even automated. Major improvements in reproducibility, simplicity, and speed are obtained with automatic sample applicators, controlled development and drying conditions, and sophisticated computer-controlled scanning modes with the use of image processing.
