| Abstract
| - A new optical analytical method, “Digital Color Analysis(DCA)”, is proposed based on a digital color analyzerinstead 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, colorlibrary data, etc., that can be treated as analytical information. DCA gives us a more informative analytical methodthan spectrophotometry by treating colors as digitalinformation. In addition, DCA can also simulate theoptimum color variations for optimization of the visualsensor with computer assistance. By utilizing colors asdigital information, colorimetric analysis that has beenused for only semiquantitative analysis can serve as anaccurate determination method. On the basis of DCA, wedeveloped a plasticized PVC film optode and a paperoptode for Li+ determination in saliva. After the optimization of color variation and the detection range for the Li+measurements, the optode membrane gives colorless grayin the Li+ therapeutic range (at 10-3 M) in saliva.Consequently, whether or not the optimum therapeuticLi+ concentration is maintained can be easily evaluatedwith these optodes. Especially, the sensing paper optodecan be easily handled within a short measurement time(∼80 s) which is suitable for home use. Using the digitalcolor analyzer with QxQy coordinates, a linear relationcalibration curve can be obtained over the range from10-5 to 10-1 M Li+, in which the analyzer can detect aconcentration difference of ∼0.1 mM Li+. For the nearfuture, an accurate and simple analysis is needed for ahealth check at home that does not require going to ahospital. The optode based on DCA has great potentialfor this analytical purpose.
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