Optoacoustic determination of analytical parameters and physicochemical constants in highly concentrated solutions of chromophores

Determination of chromophores of various classes—rosaniline (fuchsine), cyanidin-3-O-glucoside, tris(1,10-phenanthroline) iron(II), and phenol red — in their concentrated solutions near their solubility limits is performed with the optoacoustic technique for optically dense solutions; light-absorption coefficients of samples range from 0.5 to 500cm–1. The assessment of these substances in organo-aqueous and organic solvents is possible up to ca. 0.1molL–1. Characteristic stability and rate constants of the chelation of iron(II) with 1,10-phenanthroline are determined. It was found that turbidities up to 200 FTU and dynamic viscosities up to 20mPas do not affect the determination. The determination of total anthocyanins (as cyanidin-3-O-glucoside) in bilberry and sweet-cherry juices agrees with the reference spectrophotometric method and demonstrates the possibilities of the optoacoustic technique for the analysis of real samples without dilution and with almost no sample preparation. [Display omitted] •Substances at their solubility limits are determined by the optoacoustic technique.•Light-absorption coefficients of samples range from 0.5 to 500cm–1.•Stability and rate constants for iron(II) with 1,10-phenanthroline are determined.•Turbidities up to 200 FTU and dynamic viscosities up to 20mPas do not interfere.•Total anthocyanins in real samples without dilution were determined.