QUANTITATIVE C-13 NMR METHOD USING THE DEFT PULSE SEQUENCE FOR THE DETECTION OF OLIVE OIL ADULTERATION WITH SOYBEAN OIL

The polarization transfer method DEPT (distortionless enhancement by p olarization transfer) was employed to set up a quantitative method to detect olive oil adulteration by seed oils, in particular soybean oil. The DEPT pulse sequence promotes the transfer of polarization from 'c oncentrate spins = H-1' to 'dilute spins = C-13' via scalar coupling i nteraction. This improves the signal-to-noise ratios in the C-13 NMR s pectra which would have to be acquired for quantitative purposes, unde r conditions of NOE suppression that reduce dramatically the carbon-13 resonance intensities, The resonance intensities of unsaturated carbo ns, C-9 for oleyl and C-10 for linoleyl and linolenyl chains, were use d to detect olive oil adulteration by addition of soya ail at differen t levels. Calibration graphs based on a linear relationship between re sonance intensities and soybean oil concentration were obtained. The l imits of detection of the method were determined for each acyl chain. (C) 1997 John Wiley & Sons, Ltd.