SOLID-PHASE EXTRACTION CONDITIONS FOR THE SELECTIVE ISOLATION OF DRUGS FROM BIOLOGICAL-FLUIDS PREDICTED USING LIQUID-CHROMATOGRAPHY

A new method to predict the most suitable conditions for the solid phase extraction of 1,4-benzodiazepines and related compounds using C18 Sep-Pak cartridges is proposed. The composition of the washing and elution solvents for the solid phase extraction of a test compound can be obtained from its capacity factor on a C18 HPLC column and an equation which relates capacity factors and solid phase extraction data of other similar compounds. The solid phase extraction data given in this paper can be used by others, there by saving considerable time and effort in the development of sample preparation methods. The suitability of the method was checked with two test compounds, showing good results.