Quality Thin layer chromatograph

M. Medic-Saric, G. Stanic and I. Bosnjak, The use of information theory and numerical taxonomy methods for evaluating the quality of thin-layer chromatographic separations of flavonoid constituents of matricariae flos. Pharmazie 56 (2001) 156-159. 

For obtaining reliable analysis results, the (high-performance) thin-layer chromatographic (TLC) method should he validated before using it as a quality control tool. The validation parameters that should he evaluated are stability of the analyte, specificity/selectivity, linearity, accuracy, precision, range, detection limit, quantification limit, and robustness/ruggedness. 

Thin-layer chromatography (TLC), sometimes also called planar chromatography, employ a stationary phase immobilized on a glass or plastic plate and an organic mobile phase. It is a rather old technique whose application in residue analysis has been limited in the past by poor chromatographic resolution, inadequate selectivity, and insufficient sensitivity (49). This was due to inherent problems in the quality of the available stationary phase materials and in the uniformity of the layers prepared. Today, the availability of affordable, precoated plates with acceptable performance and consistency has led to the general acceptance of TLC as an efficient procedure for residue analysis (50). The method is used preferentially when analysts must process large numbers of samples in a short period of time (51). 

Make up thin layer plates as described above. Chromatograph the standards and the unknown(s) in toluene and locate the spots by iodine staining. Calculate the R( values and hence determine which of the five standard compounds the unknown(s) contain. Confirm your conclusions by running a further chromatogram using the unknown mixture as one spot and the suspected mixture as a second spot. (The Rf values may vary with the quality of the TLC plate and hence comparisons between the unknown and the standard must finally be made on the same plate.)... 

Fractionation with the use of filter and glass filter papers has been replaced by the chromatographic procedures described because they are more difficult to perform and the quality of resolution is poorer. If larger samples are to be separated column and thin-layer chromatography may be used as preparative methods. 

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