Comparison of analytical methodologies based on 1h and 31p NMR spectroscopy with conventional methods of analysis for the determination of some olive oil constituents.
The present study was designed to assess the agreement between analytical methodologies based on 1H and 31P NMR spectroscopy and conventional analytical methods (titration, gas chromatography, and high performance liquid chromatography) for measuring certain minor and major constituents (free acidity, fatty acids, iodine value, and phenolic compounds) of olive oil. The standard deviations of the NMR method were comparable to those of the conventional methods, except perhaps those of the total hydroxytyrosol and total tyrosol. Linear regression analyses showed strong correlations between NMR and conventional methods for free acidity, total hydroxytyrosol, total tyrosol, total diacylglycerols, (+)-pinoresinol, (+)-1-acetoxypinoresinol, and apigenin; good correlations for linoleic acid, free hydroxytyrosol, and free tyrosol; and weak correlations for oleic acid, linolenic acid, saturated fatty acids, and luteolin. Furthermore, a method comparison study was conducted and the agreement between NMR and conventional methods was evaluated by using the Bland and Altman statistical analysis. The distribution of the data points in the bias plot showed that 96.4% and 100% of the measurements of free acidity and iodine value, respectively, were within the limits of agreement of the two methods. For the remaining constituents of olive oil, the percentage of measurements, located within the limits of agreement, ranged from 94% to 98.5%.
Dais
Photis
P
NMR Laboratory, Department of Chemistry, University of Crete, P.O. Box 2208, Voutes, 71003 Heraklion, Crete, Greece. dais@chemistry.uoc.gr
Spyros
Apostolos
A
Christophoridou
Stella
S
Hatzakis
Emmanuel
E
Fragaki
Georgia
G
Agiomyrgianaki
Alexia
A
Salivaras
Emmanuel
E
Siragakis
George
G
Daskalaki
Despina
D
Tasioula-Margari
Maria
M
Brenes
Manuel
M
D002849:Chromatography, Gas; D002851:Chromatography, High Pressure Liquid; D005227:Fatty Acids / Q000032:analysis; D006859:Hydrogen; D006863:Hydrogen-Ion Concentration; D016014:Linear Models; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D000069463:Olive Oil; D010636:Phenols / Q000032:analysis; D010758:Phosphorus; D010938:Plant Oils / Q000737:chemistry*
D005227:Fatty Acids; D000069463:Olive Oil; D010636:Phenols; D010938:Plant Oils; D010758:Phosphorus; D006859:Hydrogen