IMMOBILIZED PHENYLBORONIC ACIDS FOR THE SELECTIVE EXTRACTION OF BETA-BLOCKING DRUGS FROM AQUEOUS-SOLUTION AND PLASMA

The use of phenylboronic acid (PBA) solid-phase extraction cartridges for the extraction of a range of beta-blockers from aqueous buffer and plasma has been investigated and compared with other phases commonly used for solid-phase extraction. PBA was found to provide an efficient means for the extraction of this class of compound from simple aqueous buffer systems. Extraction from buffers was pH-dependent and gave optimum results at approximately pH 8. Extraction from plasma was less efficient for some of the test compounds; this matrix effect was probably due to protein binding. Chromatography showed that plasma extracts were free of major sources of interference.