Derivatization-free GC Method to Analyze Oleic Acid Excipient

Researchers from the USA have developed a simple and derivatization-free gas chromatography (GC) method for the quantitative analysis of oleic acid and related fatty acids.¹

A common pharmaceutical excipient, oleic acid is widely used for long-term stabilization, solid formation bulking, and for the therapeutic enhancement of active ingredients including serving as an emulsion agent in topical pharmaceutical formulations and a solubility enhancer for gastrointestinal tract delivery.

The importance of oleic acids to the pharmaceutical industry has led to a variety of analytical methods being developed with high performance liquid chromatography (HPLC) the most common.¹ However, HPLC separation of fatty acids is not perfect. The absence of chromophores or fluorescent functional groups² means the majority of HPLC methods in the literature require a derivatization process prior to analysis; those without a derivatization process suffer from poor sensitivity.³

Gas chromatography offers an alternative for the analysis of fatty acids and is commonly used. Unfortunately, GC methods suffer from a similar issue to HPLC, requiring a derivatization process
because of the high boiling points of fatty acids.⁴

A laborious, tedious, and time-consuming process, derivatization, while effective, often results in lower accuracy and precision⁵ - two undeniably unwanted side effects. The aim of this study was to develop a simple method for oleic acid and related fatty acid analysis, free from a derivatization process, but capable of accurate and robust analysis suitable for use in a quality controlled laboratory.

The method developed used a nitroterephthalic acid modified polyethylene glycol (PEG) capillary GC column as well as a flame ionization detector (FID). The sample preparation procedure was simple and straightforward requiring no derivatization. The method successfully separated 15 fatty acids in a total run time of 20 min. This was validated and proved to be specific, precise, and accurate for the analysis of oleic acid and related fatty acids. - L.B.

References

1. H. Zhang et al., J. Pharm. Anal. 5, 223–230 (2015).
2. Y. Tsuyama et al., J. Chromatogr. A596, 181–184 (1992).
3. H. Guo et al., J. Am. Oil Chem. Soc.89, 183–187 (2012).
4. T.S. Laakso et al., Anal. Chim. Acta.465, 39–62 (2002).
5. M. Mizumoto et al., J. Anal. Appl. Pyrolysis87,163–167 (2011).