Determination of free fatty acids in pharmaceutical lipids by 1H NMR and comparison with the classical acid value

•An 1H NMR approach to determine the acid value is described.•The reliability of the method is demonstrated by a comprehensive in-house validation.•The method is applied to pharmaceutical oils and fats, oleyloleat, and various waxes. Indices like acid value, peroxide value, and saponification value...

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Bibliographic Details
Published in:Journal of pharmaceutical and biomedical analysis 2014-05, Vol.93, p.43-50
Main Authors: Skiera, Christina, Steliopoulos, Panagiotis, Kuballa, Thomas, Diehl, Bernd, Holzgrabe, Ulrike
Format: Article
Language:English
Subjects:
Acid value
Fatty Acids, Nonesterified - chemistry
Free fatty acids
Lipids - chemistry
Models, Theoretical
Oils - chemistry
Pharmaceutical lipids
Plant Oils - chemistry
Proton Magnetic Resonance Spectroscopy - methods
qNMR
Reproducibility of Results
Saponification value
Solvents - chemistry
Waxes - chemistry
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Summary:•An 1H NMR approach to determine the acid value is described.•The reliability of the method is demonstrated by a comprehensive in-house validation.•The method is applied to pharmaceutical oils and fats, oleyloleat, and various waxes. Indices like acid value, peroxide value, and saponification value play an important role in quality control and identification of lipids. Requirements on these parameters are given by the monographs of the European pharmacopeia. 1H NMR spectroscopy provides a fast and simple alternative to these classical approaches. In the present work a new 1H NMR approach to determine the acid value is described. The method was validated using a statistical approach based on a variance components model. The performance under repeatability and in-house reproducibility conditions was assessed. We applied this 1H NMR assay to a wide range of different fatty oils. A total of 305 oil and fat samples were examined by both the classical and the NMR method. Except for hard fat, the data obtained by the two methods were in good agreement. The 1H NMR method was adapted to analyse waxes and oleyloleat. Furthermore, the effect of solvent and in the case of castor oil the effect of the oil matrix on line broadening and chemical shift of the carboxyl group signal are discussed.
ISSN:0731-7085
1873-264X
DOI:10.1016/j.jpba.2013.04.010