Featured Application: Glycerides (Acylglycerols) in Edible Oils on Rxi-65TG

Robust GC Analysis of Glycerides in Edible Oils

• Good resolution and stable retention times ensure reliable triglyceride profiles.
• Detection of mono- and diglycerides without derivatization.
• High-temperature stability provides consistent results and fewer column changes.

Characterization of edible oils is essential to the food industry because adulteration is common, especially with expensive oils, such as extra virgin olive oil. Reliable GC analysis of glycerides in edible oils is vital to ensure product quality, and testing falls into two primary categories: (1) triglyceride fingerprint profiles are used to verify oil authenticity, and (2) diglyceride ratios (1,2-diacylglycerols to 1,3-diacylglycerols) are used to determine oil freshness. Testing is typically done using 65-type columns, but historically these columns exhibit high column bleed, low inertness, poor resolution of triglycerides, and shifting retention times due to poor thermal stability. Overall, this results in unreliable identification and quantification, as well as short column lifetimes.

These problems can be overcome by using new Rxi-65TG columns, which are made using a modified polymer backbone that increases thermal stability up to 370 °C (compared to 360 °C for most columns). In addition, a new polymerization process is used that results in less column activity. As shown in this analysis of extra virgin olive oil, low column bleed means less interference, good resolution, and more accurate determination of edible oil triglycerides. Low column bleed and high inertness also ensure that mono- and diglycerides are detected when present, even without derivatization. Labs performing GC analysis of glycerides in edible oils will benefit from the reproducible retention times, longer column lifetimes, and consistent performance of low-bleed Rxi-65TG columns.

Peaks tR (min) 1. 1,3-Palmitin-2-olein (POP) 14.592 2. 1,2-Palmitin-3-linolein (PPL) 14.875 3. 1-Palmitin-2-olein-3-stearin (POS) 16.324 4. 1,2-Olein-3-palmitin (POO) 16.649 Peaks tR (min) 5. 1-Palmitin-2-linolein-3-olein (PLO) 17.013 6. 1,2-Linolein-3-palmitin (PLL) 17.397 7. 1,2-Stearin-3-olein (SOS) 18.348 8. Triolein (OOO) 19.065 GC_FF1343 Column Rxi-65TG, 30 m, 0.32 mm ID, 0.10 µm (cat.# 17109) Sample Extra virgin olive oil Diluent: Isooctane Conc.: 5 mg/mL Injection Inj. Vol.: 1 µL split (split ratio 25:1) Liner: Topaz 4.0 mm ID Precision inlet liner w/wool (cat.# 23305) Inj. Temp.: 360 °C Oven Oven Temp.: 200 °C (hold 1.2 min) to 350 °C at 21.7 °C/min to 365 °C at 1.2 °C/min (hold 5 min) Carrier Gas H2, constant flow Flow Rate: 1.28 mL/min Dead Time: 1.4331 min Detector FID @ 365 °C Make-up Gas Flow Rate: 30 mL/min Make-up Gas Type: N2 Hydrogen flow: 40 mL/min Air flow: 370 mL/min Data Rate: 50 Hz Instrument Agilent 7890B GC Notes Sample Preparation: 50 mg of extra virgin olive oil was diluted to 10 mL with isooctane.