Digital-image photometry and salting-out assisted liquid-liquid microextraction for determination of flavonols in berries

• Published in: Journal of food composition and analysis 2023-10, Vol.123, p.105515, Article 105515
• Main Authors: Martins, Luís Claudio, Soares, Samara, Rocha, Fábio R.P.
• Format: Article
• Language: English
• Subjects: Bioactive compounds; Colorimetry; Green analytical chemistry; Microextraction; Quercetin
• ISSN: 0889-1575; 1096-0481
• DOI: 10.1016/j.jfca.2023.105515

The metal-chelating ability of flavonols is exploited in spectrophotometric screening methods, but the content is often overestimated due to interferences by anthocyanins and phenolic acids. In order to circumvent this drawback, liquid-liquid microextraction with acetonitrile is proposed for the separation of flavonols from anthocyanins and further partitioning to the aqueous phase as Al(III) complexes with the working pH adjusted to 3.5 to avoid the interference of phenolic acids. The standard addition method circumvented the matrix effects in photometric measurements by digital-image photometry. A linear response was achieved up to 10 mg L-1 quercetin, with coefficient of variation (n = 10) and limits of detection and quantification estimated at 3.1%, 0.5 and 1.7 mg L-1, respectively. Accurate results were achieved in comparison to the spectrophotometric reference procedure. The proposed procedure is a simple and cost-effective approach, with low reagent and solvent consumption (105 µg of Al(III), 15 mg of NaCl, and 1.2 mL of acetonitrile) and waste generation (1.5 mL) per determination. [Display omitted] •A novel approach for fast and selective determination of flavonols.•A green and cost-effective approach exploiting smartphone-based digital images.•Salting-out assisted LLME to avoid interferences from anthocyanins.•Simple, practical, and selective strategy for extraction of flavonols from berries.•Improved detectability vs spectrophotometric and chromatographic procedures.