title: Determination of free fatty acids in pharmaceutical lipids by ¹H NMR and comparison with the classical acid value.
abstract: 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. (1)H NMR spectroscopy provides a fast and simple alternative to these classical approaches. In the present work a new (1)H 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 (1)H 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 (1)H 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.
authors.affiliation: Institute of Pharmacy and Food Chemistry, University of Würzburg, Am Hubland, 97074 Würzburg, Germany; Chemisches und Veterinäruntersuchungsamt Karlsruhe, Weißenburger Str. 3, 76187 Karlsruhe, Germany. Electronic address: christina.skiera@cvuaka.bwl.de.
authors.forename: Christina
authors.initials: C
authors.lastname: Skiera
authors.affiliation: Chemisches und Veterinäruntersuchungsamt Karlsruhe, Weißenburger Str. 3, 76187 Karlsruhe, Germany.
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Steliopoulos
authors.affiliation: Chemisches und Veterinäruntersuchungsamt Karlsruhe, Weißenburger Str. 3, 76187 Karlsruhe, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Kuballa
authors.affiliation: Spectral Service, Emil-Hoffmann-Str. 33, 50996 Köln, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Diehl
authors.affiliation: Institute of Pharmacy and Food Chemistry, University of Würzburg, Am Hubland, 97074 Würzburg, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Holzgrabe
mesh_terms: D005230:Fatty Acids, Nonesterified / Q000737:chemistry*; D008055:Lipids / Q000737:chemistry*; D008962:Models, Theoretical; D009821:Oils / Q000737:chemistry; D010938:Plant Oils / Q000737:chemistry*; D066244:Proton Magnetic Resonance Spectroscopy / Q000379:methods*; D015203:Reproducibility of Results; D012997:Solvents / Q000737:chemistry; D014885:Waxes / Q000737:chemistry
chemical_list: D005230:Fatty Acids, Nonesterified; D008055:Lipids; D009821:Oils; D010938:Plant Oils; D012997:Solvents; D014885:Waxes
keywords: Acid value; Free fatty acids; Pharmaceutical lipids; Saponification value; qNMR