Direct measurement of lithium in whole blood using a capillary electrophoresis microchip

Receiving clinically relevant blood parameters even for off-chip cleaned up sample is a nontrivial analytical problem. Few devices have been developed that fully exploit combining multiple functions in socalled micro total analysis systems (1, 2). Instead of advanced component integration on chip, here we demonstrate that the measurement of alkali metals can be performed in a drop of whole blood using an established type of capillary electrophoresis microchip (3-7) by applying the principles of moving boundary electrophoresis. The emphasis will be on the determination of lithium, which is used in the treatment of manic-depressive mood disorders. The low therapeutic index of lithium in blood is critical throughout the treatment and is therefore an ideal candidate for the demonstration of a microchip for self-testing.