[Liquid-liquid extraction for the quantitative determination of sorbed drugs in polyethylene. Part 40: Contributions to the problems of the use of plastic containers for liquid dosage forms (author's transl)].

Salicylic acid was used as a model substance to establish the conditions under which liquid-liquid extraction will yield reproducible results when applied in sorption studies. As the low-density polyethylene used is soluble in toluene only at a temperature above 80 degrees C, an extraction apparatus was developed for transferring salicylic acid from the hot lipophil phase to an appropriate aqueous phase. After optimization of the experimental conditions, the recovery rate was 82.6% with a standard deviation of +/- 2.9%. The procedure is suited for routine determinations of water-extractable sorbed substances.