Ultrasound-assisted conversion of tannic acid to gallic acid as a strategy to obtain value-added products.

Autor: Santos D; Departamento de Química, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS, Brazil., Hagemann Cauduro V; Departamento de Química, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS, Brazil., Wohlmann W; Departamento de Química, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS, Brazil., Bizzi CA; Departamento de Química, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS, Brazil., Mello PA; Departamento de Química, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS, Brazil., Flores EMM; Departamento de Química, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS, Brazil. Electronic address: ericommf@gmail.com.
Jazyk: angličtina
Zdroj: Ultrasonics sonochemistry [Ultrason Sonochem] 2021 Apr; Vol. 72, pp. 105442. Date of Electronic Publication: 2020 Dec 24.
DOI: 10.1016/j.ultsonch.2020.105442
Abstrakt: In this work, ultrasound was applied for the conversion of tannic acid into gallic acid using only diluted H 2 O 2 as reagent. Experiments were carried out using several types of ultrasonic horns operating at 20 kHz (VC750W processor). The following experimental conditions were evaluated: H 2 O 2 concentration (0.2 to 8.5 mol L -1 ), horn type (10 to 25 mm of diameter), ultrasound amplitude (20 to 70%), sonication time (10 to 45 min), tannic acid concentration (170 to 1360 mg L -1 ), and reaction temperature (50 to 90 °C). Gallic acid production was monitored with ultra-performance liquid chromatography with high-resolution time-of-flight mass spectrometry (UPLC-ToF-MS). The isolated gallic acid was confirmed with nuclear magnetic resonance ( 1 H and 13 C NMR). It is important to emphasize that this study was developed as a proof of concept to demonstrate the potential of ultrasound for tannic acid conversion into gallic acid using just diluted H 2 O 2 . Under selected conditions gallic acid production yield was 128 ± 4 mg g -1 of initial tannic acid (using 170 mg L -1 of tannic acid as starting material). Reaction time was set as 30 min, which was carried out using 1 mol L -1 H 2 O 2 and ultrasound amplitude of 50% at 90 °C. At silent conditions (mechanical stirring, from 100 to 1000 rpm), gallic acid production was halved (less than 78 ± 4 mg g -1 of initial tannic acid).
(Copyright © 2020 The Authors. Published by Elsevier B.V. All rights reserved.)
Databáze: MEDLINE
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