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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 500 cm –1 . The assessment of these substances in organo-aqueous and organic solvents is possible up to ca. 0.1 mol L –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 20 mPa s 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. [ABSTRACT FROM AUTHOR]

Abstract: As a primary aim, several approaches to photothermal (thermal-lens) and optoacoustic determination of exogenous pyrogens (lipopolysaccharides) based on photometric procedures for their determination at the microgram level and below are compared. The limits of detection of lipopolysaccharides by thermal-lens spectrometry and optoacoustic spectroscopy are at a level of 2–100ng/mL, and the conditions of optoacoustic and photothermal procedures are the same. Optoacoustic spectroscopy is advantageous in determining suspensions, while thermal lensing is superior in determining lipopolysaccharides from homogenous aqueous solutions. As a secondary aim, photometric procedures for lipopolysaccharides by the formation of their ion pairs with several dyes and by the reaction of 2-keto-3-deoxyoctulosonic acid as a part of a lipopolysaccharide molecule with thiobarbituric acid are optimized. In the case of the 2-keto-3-deoxyoctulosonic acid reaction, the sampling stage time is decreased twofold, and the possibility of substitution of the toxic metaarsenite for sulfite with better sensitivity is shown. [Copyright &y& Elsevier]