Microchip capillary electrophoresis for point-of-care analysis of lithium

Background: Microchip capillary electrophoresis (CE) is a promising method for chemical analysis of complex samples such as whole blood. We evaluated the method for point-of-care testing of lithium. Methods: Chemical separation was performed on standard glass microchip CE devices with a conductivity detector as described in previous work. Here we demonstrate a new sample-to-chip interface. Initially, we took a glass capillary as a sample collector for whole blood from a finger stick. In addition, we designed a novel disposable sample collector and tested it against the clinical standard at the hospital (Medisch Spectrum Twente). Both types of collectors require < 10 mu L of test fluid. The collectors contain an integrated filter membrane, which prevents the transfer of blood cells into the microchip. The combination of such a sample collector with microchip CE allows point-of-care measurements without the need for off-chip sample treatment. This new on-chip protocol was verified against routine lithium testing of 5 patients in the hospital. Results: Sodium, lithium, magnesium, and calcium were separated in < 20 s. The detection limit for lithium was 0.15 mmol/L. Conclusions: The new microchip CE system provides a convenient and rapid method for point-of-care testing of electrolytes in serum and whole blood. (c) 2007 American Association for Clinical Chemistry