Received on May 23, 2006
Accepted on October 26, 2006

Point-of-Care Testing

Microchip Capillary Electrophoresis for Point-of-Care Analysis of Lithium

¹ MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands
² Department of Clinical Chemistry, Medisch Spectrum Twente, Hospital Group, Enschede, The Netherlands

^* To whom correspondence should be addressed. E-mail: a.vandenberg{at}ewi.utwente.nl.

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 µL 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.