Determination of Electroactive Organic Acids in Sugarcane Vinasse by High Performance Anion-Exchange Chromatography with Pulsed Amperometric Detection Using a Nickel Nanoparticle Modified Boron-Doped Diamond

Ethanol production process generates a huge quantity of vinasse. A suitable destination for this byproduct may be its utilization as source of chemical substances, by recovery within the biorefinery process. Vinasse is rich in organic acids, which present value-added due to their many industrial applications. In this context, the present work aimed the development of an anion-exchange chromatographic method with pulsed amperometric detection, using oxidized nickel nanoparticle modified boron-doped diamond electrode, to determine industrially interesting electroactive organic acids, such as lactic acid, malic acid, and tartaric acid, in sugarcane vinasse. The chromatographic separation was carried out in a CarboPac PA 1 column under gradient elution employing different proportions of 0.10 mol L–1 NaOH in 0.25 mol L–1 CH3COONa and deionized water. Under these conditions, lactic acid, malic acid, and tartaric acid were separated in 27 min. The limits of detection were 1.2 × 10–4 mol L–1 for lactic acid, 6.1 × 10–5 mol L–1 for malic acid, and 2.8 × 10–5 mol L–1 for tartaric acid. The concentration of each organic acid in sugarcane vinasse was determined to be (1.2 ± 0.3) × 10–1 mol L–1 lactic acid, (2.7 ± 0.6) × 10–3 mol L–1 malic acid, and (9.9 ± 1.0) × 10–4 mol L–1 tartaric acid. The values of recovery between 97.4 and 107.6% indicated the method has excellent accuracy. Our results showed the present method is attractive for routine analysis during the ethanol production process because of the not costly and not time-consuming sample preparation, no need for organic solvent, rapid run time, and satisfactory separation. Thus, it can contribute to the process of utilization of sugarcane vinasse as a source of value-added chemical substances.