This article describes a new design for a paper-based
electrochemical system for flow-injection analysis. Capillary wicking facilitates
a gravity-driven flow of buffer solution continuously through paper and
nitrocellulose, from a buffer reservoir at one end of the device to a sink at the
other. A difference in height between the reservoir and the sink leads to a
continuous and constant flow. The nitrocellulose lies horizontally on a working
electrode, which consists of a thin platinum layer deposited on a solid support.
The counter and reference electrodes are strategically positioned upstream in
the buffer reservoir. A simple pipetting device was developed for reliable
application of (sub)microliter volumes of sample without the need of
commercial micropipets; this device did not damage the nitrocellulose
membrane. Demonstration of the system for the determination of the
concentration of glucose in urine resulted in a noninvasive, quantitative assay
that could be used for diagnosis and monitoring of diabetes. This method does
not require disposable test strips, with enzyme and electrodes, that are thrown away after each measurement. Because of its low
cost, this system could be used in medical environments that are resource-limited.