A multivariate curve resolution-alternating least-squares approach for the resolution and quantification of phenolic acids in a complex real olive oil sample

M.P. GODOY-CABALLERO; M.J. CULZONI; M.I. ACEDO-VALENZUELA; T. GALEANO-DÍAZ

Budapest

Congreso; XIII Chemometrics in Analytical Chemistry; 2012

This work presents the development of a non-aqueous capillary electrophoresis method coupled to UV detection (NACE-DAD) combined with multivariate curve resolution-alternative least-squares (MCR-ALS) approach to carry out the resolution and quantification of a complex mixture of six phenolic acids in real extra virgin olive oil (EVOO) samples. Phenolic compounds are part of the minority fraction of compounds in olive oil, which constitutes approximately 2 % by weight of total. The interest in the study and analysis of these compounds is related with the fact that they act as natural antioxidants and may contribute to the prevention of human disease. The modeling strategy involves the building of a single MCR-ALS model composed of matrices augmented in the temporal mode, namely spectra remain invariant while time profiles may change from sample to sample. p-Coumaric (p-CUM), caffeic (CAF), ferulic (FER), 3,4-dihydroxyphenylacetic (DOPAC), vanillic (VAN) and 4-hydroxyphenilacetic (4-HP) acids have been chosen as a representative group of phenolic compounds. All of them present different absorption spectra and overlapped time profiles with the olive oil matrix interferences and between them. So MCR-ALS is used to cope the coeluiting intereferences, on account the second order advantage inherent to this algorithm which, in addition is able to handle data sets deviating from linearity, like the NACE data analized in the present comunication. Initially, a set of 13 calibration samples were randomly prepared, in a concentration range from 3.00 to 9.00 μg?mL-1 for all phenolic acids. The validation was firstly carried out using standard mixtures of these phenols in 1-propanol and, sencondly, with real EVOO samples getting very good results. The importance of this methodoly relies that the combination of the non-aqueous technique with the second-order data and MCR-ALS algorithm allow perfoming the resolution of all of these compounds by simplifing the previous sample pretreatment stages. Only a simple preconcentration by a liquid-liquid extraction with ethanol has been employed and the direct injection of the extracting solvent was carried out obtaining good results, despite of the low selectivity of the UV detection.