Polymethacrylate optodes: A potential for chemical digital color analysis

• Colorimetric polymethacrylate sensors can be a base for digital color analysis. • Optodes allow determinations with solid-phase spectrophotometer or naked eye. • One may measure visible color changes using digital imaging of the optode. • The digital images then can be represented as basic color (e.g. RGB) data. • Colorimetric data enable effective computer implementation of analytic method. The paper describes results of implementing a new kind of optical analytical method, digital color analysis (DCA), in which colorimetric polymethacrylate sensors (optodes) are used. The optodes are made of optically transparent polymethacrylate matrix with physically immobilized analytical reagent which is responsible for the extraction of the analyte into the sensing material and changing its color. The developed optodes can be used in determination of various analytes using both solid-phase spectrophotometer and naked eye. In order to improve accuracy and sensitivity of the naked-eye determination, it is possible to measure visible color changes using digital imaging of the polymethacrylate optode. The digital images then can be represented as basic color (e.g. RGB) data. The DCA determinations of Cu (II), Ag (I) and Co (II) have indicated that the developed optodes are linear in concentration ranges 0.02–0.30; 0.02–0.20 and 0.05–0.25 mg L −1 appropriately with corresponding practical detection limits of 0.01; 0.02 and 0.07 mg L −1 .