Automated solid phase extraction of theophylline by sequential injection on renewable column

A miniaturized and fully automated solid phase extraction system was developed based on sequential injection onto a renewable microcolumn of an ion exchanger. Extraction of theophylline from caffeine solutions was used as an example of sample preparation. An important feature, compared to commercial sorbent extraction systems, was the elimination of prepackaged sorbent cartridges by using an automatically renewable microcolumn. The method has evolved from recent innovations in sequential injection analysis using a jet ring cell that entraps ion exchanger beads and discards them after completion of the monitoring cycle.