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Quantitative analysis of partial acylglycerols and free fatty acids in palm oil by 13 C nuclear magnetic resonance spectroscopy
Author(s) -
Ng Soon
Publication year - 2000
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/s11746-000-0120-7
Subject(s) - glyceride , chemistry , glycerol , relaxation (psychology) , nuclear magnetic resonance spectroscopy , analytical chemistry (journal) , carbon 13 nmr , fatty acid , organic chemistry , nuclear magnetic resonance , psychology , social psychology , physics
The chemical shifts, spin‐lattice relaxation times ( T 1 ), and one‐bond C−H coupling constants of the glycerol carbons of mono‐, di‐, and triacylglycerols in CDCI 3 solution are presented and discussed. The glycerol carbons have low T 1 values (<1.0 s) and full nuclear Overhauser effect and also exhibit broader linewidths than the aliphatic carbons, suggesting that the glycerol carbons are at or near the T 1 minimum for the dipole‐dipole relaxation mechanism. Therefore, for quantitative measurement of the composition of partial acylglycerols (relative to the triacylglycerols) in palm oil, the nuclear magnetic resonance (NMR) spectrum of the β‐carbons, which lie exclusively in the region δ68.3–72.1 ppm, should preferably be acquired at medium or low magnetic fields and at an elevated temperature in order to ensure that the condition for extremely narrow spectral lines is satisfied. The chemical shifts and spinlattice relaxation times of the aliphatic C‐2 and C‐3 carbons and of the carbonyl carbons (C‐1) of acyl groups present in palm oil are also presented and discussed. The presence of free fatty acid in the palm oil is easily detected and quantified in the spectrum of the aliphatic carbons. The presence of partial acylglycerols in palm oil can also be detected and/or quantified in the NMR spectra of the C‐2 and the carbonyl carbons. The quantitative analysis of the glycerol carbons of a known mixture of acylglycerols obtained by using this method is presented.