Application of cationic dye pyronin G (Y) for quantitative photometric and fluorimetric determination of higher carboxylic acids in dairy products using extraction

In this work we propose to use a heptane-ethanol extract of the ionic associate of higher carboxylic acids with a cationic dye – pyronin G (Y) for quantitative extraction-photometric and extraction-fluorimetric determination of carboxylic acids in dairy products. The resulting ion associate is characterized by a maximum of optical density at 510 nm and intense of fluorescence with a maximum at 566 nm. The maximum optical density and fluorescence intensity of the ion associate is observed during its extraction with octanol/heptane from aqueous solutions with pH = 11.25. The quantum yield of ionic associates of higher carboxylic acids with pyronine G (Y) relative to the standard solution of fluorescein was calculated. A technique has been developed for the extraction-fluorimetric determination of hydrophobic acids in milk and cheese. The method has been tested in the determination of carboxylic acids content in milk and cheese samples. The content of higher carboxylic acids, determined by the method with pyronin G, in milk was (6.6 ± 0.15) · 10–4 M, in cheese – (1.1 ± 0.10) · 10–3 mol/kg. The obtained results of extraction-photometric and extraction-fluorimetric determination of carboxylic acids in dairy products make it possible to recommend the developed method in the practice of institutions of the corresponding profile.