APPLICATION OF MIXED-MODE, SOLID-PHASE EXTRACTION IN ENVIRONMENTAL AND CLINICAL-CHEMISTRY - COMBINING HYDROGEN-BONDING, CATION-EXCHANGE AND VANDERWAALS INTERACTIONS

Silica- and styrene-divinylbenzene-based mixed-mode resins that contain C-8, C18 and sulphonated cation-exchange groups were compared for their efficiency in isolation of neutral triazine compounds from water and of the basic drug, benzoylecgonine, from urine. The triazine compounds were isolated by a combination of Van der Waals and hydrogen-bonding interactions, and benzoylecgonine was isolated by Van de Waals interactions and cation exchange. All analytes were eluted with a polar organic solvent containing 2% ammonium hydroxide. Larger recoveries (95%) were achieved on copolymerized mixed-mode resins where C18 and sulfonic acid are in closer proximity than on ''blended'' mixed-mode resins (60-70% recovery).