Desenvolvimento de método analítico para quantificação de adulteração de óleo-resina de copaíba com óleo de soja

Abstract

Copaiba oil-resin has remarkable importance in the phytotherapic context due to its pharmacologic properties; it is a basic material whose added value increasing is an obstacle for the northern region of Brazil, the biggest producer of this natural product. In this regard, TD-NMR stands out as an alternative technique for the quality control of the copaiba oil-resin by detecting and quantifying adulteration of this matrix with soybean oil. This work aimed to develop a quantitative TD-NMR method for the assessment of copaiba oil-resin adulteration with soybean oil using the CPMG pulse sequence and partial least squares regression. The figures of merit of the proposed method were evaluated. The limits of detection and of quantification values found were respectively 11,0 ± 2,5 and 36,1 ± 8,4 %SO; the analytical sensitivity value was found to be 0,32 ± 0,08 %SO-1 ; the linearity was assessed by the coefficient of determination (R2 > 0,99) and the analysis of residuals and by the test of homogeneity of variances in each one of the calibration curve levels; the precision was verified by studying the method’s repeatability, intermediate precision and reproducibility and was found to be satisfactory; the test of accuracy of the proposed method was achieved by comparing its results with those obtained by usual methods (NIR, MIR and 1H NMR spectroscopies). Additionally, TD-NMR was used to explore the temperature dependence of 𝑇2 and was found capable of discriminating pure copaiba oil-resin samples of the adulterated ones. Therefore, this work shows the potential applicability of TD-NMR in the processing chain of the copaiba oil-resin with respect to detecting and quantifying TAG adulterants.