THIN-LAYER CHROMATOGRAPHY UNDER TROPICAL CONDITIONS - IMPACT OF HIGH-TEMPERATURES AND HIGH HUMIDITIES ON SCREENING SYSTEMS FOR ANALYTICAL TOXICOLOGY

The impact of high temperatures (33-38 degrees C) and high relative hu midities (80-100%) on the applicability of TLC systems for drug identi fication was studied during a six month climatologic cycle in Jakarta, Indonesia. In general, the R(F) values as observed on the plates were substantially affected in comparison to values obtained at moderate c limates: most substances gave higher R(F) values under the tropical co nditions, although exceptions may occur as well. The deviations tended to increase with increasing humidities and could amount easily to 20- 30 R(F) units. On the other hand, some TLC systems were more affected than others. Tropical conditions also had a negative effect on the rep roducibility of the R(F) values. However, when an R(F) correction proc edure was applied, using reference mixtures of standard drugs on each plate, accuracies as well as reproducibilities of the resulting R(F)(c ) values were drastically improved and data thus corrected were found to be compatible with existing TLC data bases developed under moderate climatic conditions. These results are in line with earlier studies c arried out in a relatively dry tropical climate. In the latter the obs erved R(F) values tended to be lower than the ones published in the li terature, but the R(F) correction procedure was able to correct for th is phenomenon.