COMPARISON BETWEEN PHENYLBORONIC ACID AND IRON LOADED SILICAS TO SELECTIVELY PRECONCENTRATE CATECHOLAMINES ONLINE COUPLED WITH HPLC

The use of the on-line preconcentration of catecholamines on small precolumns packed with iron loaded and phenylboronic acid silicas was investigated. For both preconcentration materials, parameters which can influence the retention of catecholamines on the support such as pH, ionic strength, polarity and flow rate of the sample solution are described to predict the mechanism of retention on these silicas. On-line coupling with an ion-pair chromatography column is presented. Combined with amperometric detection, these methods hav been applied to the quantitative determination of catecholamines in urine samples, using 1,2-dihydroxybenzylamine as an internal standard.