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Validation of spectrophotometric methods for the determination of total polyphenol and total flavonoid content

The aim of this study was to validate spectrophotometric methods for the measurement of total polyphenol (Folin-Ciocalteu method) and total flavonoid content (aluminum chloride method). Validation parameters of these methods were determined, including linearity, sensitivity, precision (intra-assay, intermediate precision), accuracy, limit of detection and limit of quantification. For the validation process, groups of polyphenols standards were used, including phenolic acids (gallic-, p-coumaric-, caffeic-, chlorogenic acid), flavan-3-ols ((+)-catechin, procyanidin B1, procyanidin B2), flavonols (quercetin, quercetin-3-rutinoside) and dihydrochalcones (phloretin, phloretin-2-glucoside). Obtained validation parameters were in acceptable ranges with high determination coefficients, reasonably low limits of detection and quantification and high slopes of calibration curves for both methods, except for phloretin and phloretin-2-glucoside for which the aluminum chloride method showed low slopes of calibration curves. In order to evaluate the differences in polyphenol content, the validated spectrophotometric methods were used for the determination of total polyphenol and total flavonoid content in wines (Plavac, Graševina, Vranac) and juices (blueberry, strawberry, blackcurrant juice) according to the polyphenol calibration curves. Polyphenol contents were different for both methods in all wines and juices.

Polyphenols, Flavonoids, Validation parameters, Method validation

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