Expert system for the selection of high-performance liquid chromatographic methods in pharmaceutical analysis. Validation of the rules for the selection of the mobile phase.

The rules for the selection of the mobile phase and the validation performed on 44 pharmaceutical preparations, containing one to five active compounds, are described. These rules are incorporated into an expert system, called LABEL, for the selection of high-performance liquid chromatographic methods in pharmaceutical analysis. A single stationary phase type is used, namely a nitrile or cyanopropyl (CN) column, which can be used in both normal-phase (NP) and reversed-phase (RP) chromatography. Three mobile phase systems were evaluated on this column type: NP, RP with water and RP with buffer. LABEL selects one of these three systems on the basis of the rules incorporated for the mobile phase selection, checks if the addition of ion-suppressing agents to the eluting agent is necessary and finally gives the starting composition of the mobile phase in each of the three systems. For this selection the number of compounds in the sample, the acid-base properties and the hydrophobicity of the solutes are the more important factors. The validation of the rules on 44 pharmaceutical preparations resulted in an immediate success in 82% of all cases. In half of the remaining cases, the system proposed can be adapted with a minor change in conditions, so that it can also be used in practice.