posted on 1999-12-23, 00:00authored byEtsuko Hirayama, Tsunemi Sugiyama, Hideaki Hisamoto, Koji Suzuki
A new optical analytical method, “Digital Color Analysis
(DCA)”, is proposed based on a digital color analyzer
instead of the conventional optical methodology, “Spectrophotometry”. The digital color analyzer is a hand-held-size instrument for measuring “colors”, and it can transform the color information into numerical values, color
library data, etc., that can be treated as analytical information. DCA gives us a more informative analytical method
than spectrophotometry by treating colors as digital
information. In addition, DCA can also simulate the
optimum color variations for optimization of the visual
sensor with computer assistance. By utilizing colors as
digital information, colorimetric analysis that has been
used for only semiquantitative analysis can serve as an
accurate determination method. On the basis of DCA, we
developed a plasticized PVC film optode and a paper
optode for Li+ determination in saliva. After the optimization of color variation and the detection range for the Li+
measurements, the optode membrane gives colorless gray
in the Li+ therapeutic range (at 10-3 M) in saliva.
Consequently, whether or not the optimum therapeutic
Li+ concentration is maintained can be easily evaluated
with these optodes. Especially, the sensing paper optode
can be easily handled within a short measurement time
(∼80 s) which is suitable for home use. Using the digital
color analyzer with QxQy coordinates, a linear relation
calibration curve can be obtained over the range from
10-5 to 10-1 M Li+, in which the analyzer can detect a
concentration difference of ∼0.1 mM Li+. For the near
future, an accurate and simple analysis is needed for a
health check at home that does not require going to a
hospital. The optode based on DCA has great potential
for this analytical purpose.