Assessment of the European pharmacopoeia method for fatty acid composition of hydrogenated castor oil using gas chromatography

Background: Hydrogenated castor oil is widely used as a pharmaceutical excipient due to its emulsifying and solubilizing properties [1, 5]. The quality and consistency of this excipient are critically dependent on its fatty acid composition, which must comply with the specifications outline in the European Pharmacopoeia (Ph. Eur.) [1, 5]. This study presents an assessment of the European Pharmacopoeia gas chromatography (GC) method for the determination of fatty acid composition in hydrogenated castor oil intended to pharmaceutical manufacturing. Key performance activities including specificity, precision and system suitability, were evaluated in accordance with pharmacopoeia and ICH guidelines [4, 6]. The GC method demonstrated adequate resolution of major saturated fatty acids characteristic of hydrogenated castor oil, with reproducible retention times and consistent quantitative results.
Purpose: The aim of this study is to verify a gas chromatographic method for the identification and quantification of fatty acids presents in castor oil namely Methyl Myristate, Methyl Palmitate, Methyl Stearate, Methyl Oleate, Methyl Arachidate, Methyl Eicosenoate, Methyl Behenate, 12-Oxostearic acid, Methyl 12-Hydroxystearate, Methyl Lignocerate. The challenge of this EP method was to find the Exact GC column mention by monograph. This method will be able to identify and quantify the fatty acid composition within a single gas chromatographic procedure using a specific brand column.
The findings confirm that the European Pharmacopoeia GC method is suitable for routine quality control and regulatory compliance testing of hydrogenated castor oil in pharmaceutical products.
Method: A gas chromatography (GC) equipped with a liquid injector and a flame ionization detector [2, 7], and a column InertCap Wax, Material: Fused Silica, Size: l = 30m, Ø = 0.32 mm, Film thickness 0.25μm, Brand-GL Science was used to develop this method. The GC oven temperature was 215 °C over the run time 55 min. Nitrogen was used as a carrier gas at a flow rate of 0.9 mL per minute. 1, 1- dimethyl ethyl methyl ether was selected as sample solvent. N-heptane used as blank. 
Fatty acid methyl ester analysis by GC-FID is a widely accepted approach for the determination of fatty acid composition [2, 3, 7].
Results: The developed method is precise and specific. The percent RSD for the areas of six replicate injections of this gas chromatographic method was within 5%.