Determination of Phenolic Acids in Sugarcane Vinasse by HPLC with Pulse Amperometry.

P V Freitas,J L Da Silva,M A Beluomini,D R Da Silva,N R Stradiotto

doi:10.1155/2018/4869487

Abstract

A reversed-phase liquid chromatographic separation with pulsed amperometric detection of phenolic acids at a glassy carbon electrode is described. Chromatographic separation was carried out in isocratic conditions using 0.20 mol·L−1 acetic acid (pH 5.0)/water (80 : 20, v/v) as mobile phase under constant working potential mode of 0.80 V. Chromatographic peaks presented high resolution and separation. Calibration curves exhibited excellent correlation coefficients, above 0.995. Linear ranges of the analytes, in mg L−1, were of 0.018–18 (gallic acid), 0.146–19 (vanillic acid), 0.13–17 (caffeic acid), 0.016–16 (ferulic acid), and 0.008–17 (p-coumaric acid), respectively. Limits of detection ranged from 1.6 to 97 μg·L−1 and precision varied in 1.73–3.78% interval. Concentrations of 19 ± 0.51 mg·L−1 and 7.8 ± 2.5 mg·L−1 were found for vanillic and caffeic acids, respectively, in a sugarcane vinasse sample. Gallic, ferulic, and p-coumaric acids were not detected. Recovery results demonstrated that the proposed method is accurate, and it can be used to detect and quantify phenolic acids in sugarcane vinasse without any influence of interferents.

Highlights

Sugarcane vinasse is an acidic brownish liquid generated after fermentation and distillation of juice for production of ethanol [1, 2]
Considering the lack of studies employing a sensitive, selective, fast, and operated procedure to determine polyphenols in sugarcane vinasse, this work developed a method for detection and quantification of phenolic acids in a vinasse sample by HPLC-ECD with Pulsed amperometric detection (PAD) employing a Glassy carbon electrode (GCE)
For ferulic acid, an anodic peak was observed in NaOH solution. ose results can be explained by analysis of pKa values of studied polyphenols, which range from 4.50 to 9.5, making them weak acids [43]. us, acetate bu er was chosen for subsequent experiments since all phenolic acids exhibited relatively high signals in this supporting electrolyte

Summary

Introduction

Sugarcane vinasse is an acidic brownish liquid generated after fermentation and distillation of juice for production of ethanol [1, 2]. Several reports introduced new approaches to reduce concentration of these compounds, which are toxic to anaerobic microorganisms, responsible for conversion of vinasse into biogas [6, 13, 16, 17, 22] Efficiency of such proposed method is usually evaluated by determination of “total phenolics,” a sum of phenols, and polyphenols concentrations, by employing the spectrophotometric method reported by Folin and Ciocalteu [23, 24]. Considering the lack of studies employing a sensitive, selective, fast, and operated procedure to determine polyphenols in sugarcane vinasse, this work developed a method for detection and quantification of phenolic acids in a vinasse sample by HPLC-ECD with PAD employing a GCE

Experimental

Results and Discussion

Conclusions