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.