Determination of Polyphenol Content by Formation of Unstable Compound Using a Mini-Pump Multicommutation System
This article describes a multicommuted flow procedure for photometric determination of the polyphenol content in wines and teas, exploiting the formation of unstable intermediate products, by the reaction of sodium hypochloride with gallic acid. Because the lifetime of the formed compound is very short, a special flow cell was designed in order to enable mixing of sample and reagent solution within the flow cell, thus allowing signal monitoring, while compound formation proceeded. The flow system manifold comprised three solenoid mini-pumps to propel sample, reagent solution, and carrier fluid. The photometer consisted of a photodiode and a light emitting diode (LED) with maximum emission at 490 nm. Under the selected operational conditions, useful features including a linear response ranging from 62 to 1000 mg L−1 gallic acid solution (R = 0.9987), a detection limit of 21 mg L−1 gallic acid, a sampling rate of 120 determinations per hour, a relative standard deviation of 1.9 % (n = 20) for a typical solution containing 400 mg L−1 gallic acid, and a waste generation of 1.0 mL per determination were also achieved. Medium recovery values of 96.2 ± 10.4 and 101.9 ± 7.3 % for wines and teas, respectively, were achieved.
KeywordsMulticommuted flow analysis Gallic acid Wine Tea LED-based photometer
The authors acknowledge the financial support from Programa CAPES/Pesquisador Visitante Especial - Projeto 093/2012, CNPq and FACEPE. The English text has been revised by Sidney Pratt, Canadian, MAT (The Johns Hopkins University), RSAdip-TEFL (University of Cambridge).
Compliance with Ethical Standards
Conflict of Interest
Suelle Gisian Farias de Assis declares that she has no conflict of interest. Marcelo Farias de Andrade declares that he has no conflict of interest. Ana Paula Silveira Paim declares that she has no conflict of interest. Boaventura Freire dos Reis declares that he has no conflict of interest. Maria Conceição B. S. M. Montenegro declares that she has no conflict of interest.
This article does not contain any studies with human or animal subjects.
Informed consent was obtained from all individual participants included in the study.
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