Title: Performance evaluation criteria for preparation and measurement
of macro and microfabricated ion-selective electrodes
Chairman: Yoshio Umezawa
Member: Erno Lindner
Completion Date: 2008 - project completed
During 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 ionophore based liquid
membrane ISEs has now entered the arena of trace analysis and precision
science due to the latest updated and upgraded R/D 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.
There are more or less generally accepted evaluation criteria for ISEs.
Some of those are summarized in Pure Appl. Chem. documents (PAC
1994, 66, 2527; PAC 1995; 67, 507).
In this 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 is of the
same importance. Items we will discuss includes
- Conditioning of the multi-layered sensor system (sensing membrane,
underlying hydrogel and eventually biocompatible coating) before use
to reach high stability readings, due to water transport through the
- Conditioning overnight or store in humid atmosphere. Conditioning
and calibration before and after the measurement
- Effect of osmotic pressure (give a procedure, how to measure)
- Shelf and use life time (effect of storage); estimation of the residual
life time in vivo and in vitro
- Added-site optimization for selectivity and as requisite for Nernstian
- Electrode construction including microfabrication, FET covered with
membranes, and Ppy electrode covered with membranes
- Response time as well as detection limit
- Microfabricated inner and outer reference electrodes
We will 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.
The darft report includes: 1. Introduction, 2. Ionophore based liquid
membrane ion-selective electrodes, 3. Trace analysis with ion-selective
electrodes, 4. Consequences of improved detection on limits on the selectivity
coefficients, 5. Conditioning of ion selective electrodes for optimal
performance, and 6. Inconsistencies in the recommended procedures for
presenting a calibration plot for pH
and other ion selective electrodes.
The manuscript is 70% completed, and it is projected that the document
will be ready for external review around March 2005.
> Nov 2004 report update (pdf
file - 12KB)
> May 2006 report update (pdf
file - 11KB)
> June 2007- Manuscript completed; minor revisions are necessary.
> Jan 2008 - Project completed - IUPAC Technical report published
80(1), 85-104, 2008.
Last Update: 15 January 2008
<project announcement published in