Vol. 24, No. 6
Evaluation Criteria for Preparation and Measurement of Macro- and Microfabricated
the past several years, the application of microfabrication technologies
of practical microsensor devices has entered the field of biology and
medicine and is beginning to serve as the driving force for discoveries
in cell biology, neurobiology, pharmacology, and tissue engineering.
In parallel, the methodology of ionophorebased liquid membrane ion-selective
electrodes (ISEs) has now entered the arena of trace analysis and precision
science due to the latest updated and upgraded research and development
of this method. This circumstance has made it necessary to also upgrade
and update the evaluation criteria for the preparation and measurements
of ISEs, primarily microfabricated ISEs and potentiometric cells. This
is in fact the purpose of this project.
are more or less generally accepted evaluation criteria for ISEs. Some
of those are summarized in Pure and Applied Chemistry documents
(PAC 1994, 66, 2527; PAC 1995, 67, 507).
new document, we will deal with the specialities of macro- and microfabricated
ISE sensors; standard procedures for the microfabricated devices are
much more critical compared to macroelectrodes. In addition, some evaluation
criteria for the micro reference electrodes are of the same importance.
Items we will discuss include the following:
of the multilayered sensor system (sensing membrane, underlying hydrogel;
and eventually biocompatible coating) before use to reach high stability
readings, due to water transport through the membrane
overnight or storage in humid atmosphere
and calibration before and after the measurement
of osmotic pressure (give a procedure, how to measure)
and use lifetime (effect of storage); estimation of the residual lifetime
in vivo and in vitro
optimization for selectivity and as requisite for Nernstian response
construction including microfabrication, FET covered with membranes,
and Ppy electrode covered with membranes
time as well as detection limit
inner- and outer-reference electrodes
correct the inconsistencies in the previous document (PAC 1994,
66, 2527) (e.g., the definition of the calibration plot, which
contradicts the convention related to the determination of pH). Finally,
we will discuss the latest results concerning the lower detection limit,
true selectivity coefficients, and twice Nernstian slopes, etc.
more information, contact the Task Group Chairman Yoshio
Umezawa <[email protected]>.