Aplicação de MCR-ALS em calibração pseudo univariada para determinação de ácido ascórbico em sucos industrializados

Abstract

Ascorbic acid (vitamin C) is used as an additive in many foods due to their antioxidant capacity, increasing the quality of processed juices. In the determination of vitamin C, the titration method of Tillmans is used on samples with low vitamin C concentration and demand a considerable period of analysis. Alternatively, the use of spectroscopy in the ultraviolet region combined with the chemometric method of multivariate curve resolution with alternating least squares (MCR-ALS) in developing a model of pseudo-univariate calibration has been proposed. A total of 123 samples were used and the model was built with the values of the relative concentration, obtained from the MCR-ALS, as a function of the vitamin C concentration obtained through the Tillmans method. The results showed the possibility of employer spectroscopy in the ultraviolet region associated with the pseudo-univariate calibration for quantification of vitamin C in industrialized juices. An advantage associated with this calibration type is that the measurement can be performed in the presence of unknown interferents, without the need to perform physical separations. The proposed methodology was validated by figures of merit calculation, in which case of the pseudo-univariate calibration can be calculated identically to the univariate calibration. This can also be considered an advantage since the calculation of figures of merit for the univariate calibration is considered simple and well established. Moreover, once the model has been developed, prediction of the vitamin C concentration in future samples can be performed using the UV spectra by the value of relative concentration, obtained by applying MCR-ALS and the equation of the line. Thus, other benefits associated with the proposal are speed, cost and non-employment of reagents/solvents and the non-generation of waste that need to be properly designed.