engleski

Application of numerical taxonomy in the investigation of benzodiazepines

Identification and separation of structurally similar substances, as well as evaluation of chromatographic systems and choice of optimal combination of mobile phase for identification of certain group of substances are one of the major problems in chromatographic analysis. On a set of twelve benzodiazepines (alprazolam, diazepam, medazepam, oxazepam, triazolam, prazepam, lorazepam, chlordiazepoxide, clonazepam, acetoxylorazepam, bromazepam and carbamazepine) optimal mobile phase was selected using numerical taxonomy methods. Plates coated with aluminum oxide 60 F254 were used as stationary phase and detection was done using CAMAG TLC Scanner 3 and Reprostar 3 system under UV light  = 254 nm. For the evaluation of efficacy and selection of the most suitable mobile phase (out of forty used) three numerical methods were used: calculation of information content (I), determination of discriminating power (DP) and the methods of numerical taxonomy. Comparison of the efficacy of chromatographic separation of examined substances regarding development time was also evaluated. Presuming the error range of 2% (E = 0.02) optimal mobile phase is heptane : ethyl acetate : ethanol = 30 : 70 : 10 (v/v/v) having the highest DP = 0.9848 and midrange I = 3.418, development time being 78 minutes. Error range of 3% allows usage of additional mobile phase trichlorethylene : ethanol = 9 : 1 for discrimination of analyzed benzodiazepines, although the development time was slightly higher 88 min. For the combination of mobile phases all 9 combinations tested in error range 2 and 3% had DP and T values of 1.000 which means that all analyzed substances can be distinguished. Results obtained in this work show that numerical approaches for qualitative identification of structurally similar compounds present good mathematical for precise identification of the mentioned compounds.

TLC; benzodiazepines

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