pH Study and Partition of Riboflavin in an Ethyl Lactate-Based Aqueous Two-Phase System with Sodium Citrate

Abstract

Antioxidants neutralize reactive oxygen species in excess in animal bodies, ensuring a proper reduced state of the cells and avoiding the appearance of diseases. Since antioxidants are very reactive, they are heavily affected by changes in pH, which may influence partition and hamper solute quantification due to chemical structure and conformation modification. Natural antioxidants are present, for example, in fruit pomaces, and could be extracted for food supplementing purposes, contributing to a more circular economy. Aqueous Two-Phase Systems (ATPS) constitute a liquid-liquid extraction technique which has been applied with success in the recovery of bioproducts due to its sustainability and biocompatibility. Ethyl lactate and organic saltsbased ATPS are considered very eco-friendly because of their high biodegradability and low toxicity. In this work, the extraction of riboflavin (vitamin B2) was successfully performed in the ATPS {ethyl lactate (1) + sodium citrate (2) + water (3)} at 298.15 K and 0.1 MPa. This was accomplished after a careful study of the influence of pH in the UV-vis spectra and allowed to obtain a maximum partition coefficient (K) of 6.61 and a maximum extraction efficiency (%E) of 87.6% for the longest tie-line (TLL = 69.68) with antioxidant losses below 3%.