Capillary electrophoresis with on-line sample pretreatment for the analysis of biological samples with direct injection

Abstract A method of capillary electrophoresis (CE) using on-line sample pretreatment was developed. The system utilized on-line solid-phase extraction and capillary column switching. To explore the advantages of the method, propranolol in serum was determined by direct injection. lie pretreatment part of the system consisted of an injection capillary including a small bed of protein-coated ODS. The protein-coated ODS concentrated the analyte by hydrophobic interactions, and the serum proteins were allowed to flow into a drain capillary. As samples up to ca . 1 μl could be loaded without a decrease in resolution, the detection limit was improved by two orders of magnitude (0.15 μg/ml). Propranolol was detected in a separation capillary by UV absorbance measurement without any interfering peaks. A linear response was obtained between 100 fg and 2 ng per injection. This method provides novel possibilities for extending the application of capillary electrophoresis.