Vegetable Oil Analysis

Three different vegetable oil samples were analyzed in another experiment (see Figure 2). In all cases, distinct pro-files and ideal separation were obtain-ed for all oil types when using SFC with ELSD detection.

Separation on a Silver-Loaded Stationary Phase

The separation of the vegetable oils on the silver loaded column is shown in Figure 3. On this column, separation is mainly based on the number of double bonds, resulting in a group type separation of lipids. Within a group of triglycerides with the same number of double bonds, some partial separation could be observed but to a lower degree as compared with separation on C18 (for example, PLL/OLO).

Retention time and peak area repeatability was tested on both columns for a test mixture containing PPP, OOO, and LLL. The RSDs percent on retention times were below 0.2 percent on ODS and around 1 percent on the silver loaded column. Peak area repeatability was around 2 percent on ODS and around 4 percent on the ChromSpher lipid column.

Figure 3: Separation of triglycerides of sunflower seed oil (right), peanut oil (center), and soybean oil (left) on silver loaded ­column.

In Closing

This experiment demonstrated the separation of triglycerides in vegetable oil samples using the Agilent 1260 Infinity Analytical SFC System coupled to ELSD. The ELSD results were reproducible and provided enhanced sensitivity compared to UV detection. The separations obtained on octadecyl silicagel (reversed phase) and on a silver-loaded stationary phase (ChromSpher Lipid) were complementary. Analyzing the three vegetable oils on both column types demonstrated that the combination of both SFC methods creates an ideal quality-control tool for vegetable oil samples.

International standards for the analysis of vegetable oils are evolving. The methods described open the door for continued advances in the assurance of food quality and the fight against food fraud, particularly in regards to vegetable oils like olive oil. In addition, some of the methods, such as SFC separation on a silver-loaded column, could easily be applied to quality-control protocols for other types of food oils, including fish oils.

Dunkle, David, and Sandra work for the Research Institute for Chromatography in Belgium. They can be reached at [email protected]. Vollmer is employed at Agilent Technologies, Inc. in Waldbronn, Germany. Reach him at [email protected].

References Furnished Upon Request