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Advisor(s)
Abstract(s)
A new flow-injection analytical procedure is
proposed for the determination of the total amount of
polyphenols in wines; the method is based on the formation
of a colored complex between 4-aminoantipyrine and
phenols, in the presence of an oxidizing reagent. The oxidizing
agents hexacyanoferrate(III), peroxodisulfate, and
tetroxoiodate(VII) were tested.
Batch trials were first performed to select appropriate
oxidizing agents, pH, and concentration ratios of reagents,
on the basis of their effect on the stability of the colored
complex. Conditions selected as a result of these trials
were implemented in a flow-injection analytical system in
which the influence of injection volume, flow rate, and reaction-
coil length, was evaluated. Under the optimum conditions
the total amount of polyphenols, expressed as gallic
acid, could be determined within a concentration range of
36 to 544 mg L–1, and with a sensitivity of 344 L mol–1 cm–1
and an RSD <1.1%. The reproducibility of analytical
readings was indicative of standard deviations <2%. Interference
from sugars, tartaric acid, ascorbic acid, methanol,
ammonium sulfate, and potassium chloride was negligible.
The proposed system was applied to the determination
of total polyphenols in red wines, and enabled analysis of
approximately 55 samples h–1. Results were usually precise
and accurate; the RSD was <3.9% and relative errors,
by the Folin–Ciocalteu method, <5.1%.
Description
Keywords
Total polyphenols Photometry Wines Flow injection and FIA
Citation
Publisher
Springer-Verlag