Identification power of thin-layer chromatographic colour reactions and integration of colour codes in a database for computerized identification in systematic toxicological analysis

A system has been developed that makes colour reactions on thin-layer chromatographic (TLC) plates amenable to computer handling. As a result, correctedRF values and colour reactions can now be used for the identificationof unknown substances by means of computerized retrieval from large databases. The system is based on a series of four colour reactions carried out in sequence on the same spot and by numeric encoding of the observed colour by means of a colour reference chart. Other identification parameters such as retention indices in gas chromatography (GC) and UV absorption maxima can also be introduced in the identification program. The utilization of colour reactions in combination with correctedRF values considerably increased the identification power of TLC in that the so-called Mean List Length parameter could be reduced byca. 50–70% compared with using correctedRF values alone. The application of a single TLC system with colour reactions now provides about the same identification power as a single GC system and can be further increased by using two or three different TLC systems in parallel.