Development of Transparent Film Having Functions of Separation, Concentration, and Sensing

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A new, highly sensitive, and simple sensing method by the use of plasticized PVC film has been developed. The analyte is concentrated on the surface of the transparent film containing 20-30 % of plasticizer such as di-n-octylphthalate (DOP), which serves as a water immiscible second phase for extraction. The resulting film is measured by visual colorimetry or spectrophotometry. Extraction-fluorphotometry can be also adopted for this system. When a colored species is used as the counter ion in the ion-pair extraction colorimetry, marked enhancement of the sensitivity can be realized by the large molar absorptibity of the counter ion and by the color combination of the counter ion, the metal chelate, and the excess reagent, which is effective for discrimination by human eyes. While, adsorption of mono color species, such as the ion-pair of zephiramine (Z^+) and cupper (I) -neocuproin chelate, [CuL_2]^-, on PVC film also offers a high sensitivity without any problem of blank absorption. The detection limit for cupper is 4X10^<-7> mol dm^<-3> by visual colorimetry. The depth profile of the extracted species in the film phase has been investigated. Further, both of the soft PVC containing more than 70 wt% of plasticizer and the solvent without PVC have proved to be useful as new medium for ultra-concentration (3X10^4 hold), separation, and sensing of trace species.