Determination of underivatized long chain fatty acids using RP-HPLC with capacitively coupled contactless conductivity detection

A reversed-phase high-performance liquid chromatographic method with capacitively coupled contactless conductivity detector (C4D) has been developed for the separation and the simultaneous determination of five underivatized long chain fatty acids (FAs), namely myristic, palmitic, stearic, oleic, and linoleic acids. An isocratic elution mode using methanol/1 mM sodium acetate (78:22, v/v) as mobile phase with a flow rate of 0.6 mL min−1 was used. The separation was effected by using a Hypersil ODS C18 analytical column (250 mm × 4.6 mm × 5 μm) and was operated at 45 °C. Calibration curves of the five FAs were well correlated (r2 > 0.999) within the range of 5– 200 μg mL−1 for stearic acid, and 2–200 μg mL−1 for the other FAs. The proposed method was tested on four vegetable oils, i.e., pumpkin, soybean, rice bran and palm olein oils; good agreement was found with the standard gas chromatographic (GC) method. The proposed method offers distinct advantages over the official GC method, especially in terms of simplicity, faster separation times and sensitivity.