Comparison of SPB-PUFA and Omegawax Capillary Columns for FAMEs Analysis by GC

Importance of the Topic

Gas chromatography analysis of fatty acid methyl esters (FAMEs) is a cornerstone technique in food, beverage and nutritional oil quality control. Precise separation of saturated and polyunsaturated FAMEs allows accurate profiling of dietary fats, verification of product labels and monitoring of industrial processes. Comparing novel and established capillary columns is critical to improving resolution, run time and reproducibility in routine and research laboratories.

Objectives and Study Overview

This study evaluates two polyethylene glycol–based capillary GC columns: the established Omegawax™ 320 and the newly developed SPB™-PUFA. The aim was to compare their selectivity, elution patterns and equivalent chain length (ECL) behavior in the analysis of two FAME standards: a 37-component mix representing common food fatty acids and a PUFA-rich mix simulating marine oil profiles.

Methodology and Instrumentation

Gas chromatographic analyses were performed using the following conditions:

• Columns: Omegawax 320 (30 m × 0.32 mm ID, 0.25 µm film) and SPB-PUFA (30 m × 0.32 mm ID, 0.20 µm film).
• Carrier gas flow set to 25 cm/sec (linear velocity).
• Detector: flame ionization at 260 °C.
• Injection: 1 µL, split 100:1, injector 250 °C.
• Temperature programs: 50 °C (2 min) ramped at 4 °C/min to 210 °C for the 37-component mix; isothermal at 200 °C (Omegawax) and 210 °C (SPB-PUFA) for the PUFA mix.

Main Results and Discussion

Both columns successfully separated the 37 FAME components, but differed in elution order for long-chain polyunsaturated species. SPB-PUFA, with slightly lower polarity, provided a more consistent carbon-number-based elution, avoiding overlap of C22:6n3 with C24:0 observed on Omegawax. Equivalent chain length measurements at 200 °C revealed increasing ECL divergence with higher unsaturation: ΔECL ranged from ~0.09 units for monoenes to ~0.55 units for hexaenes. Temperature sensitivity (ΔECL/°C) also rose with double bond count, indicating stronger selectivity changes for highly unsaturated FAMEs.

Benefits and Practical Applications

• Enhanced resolution of polyunsaturated FAMEs improves quantitation accuracy in fish oils and nutritional products.
• Truer chain-length separation on SPB-PUFA reduces coelution issues in complex matrices.
• SPB-PUFA can serve as a confirmatory column or primary choice when unique separations are required.

Future Trends and Applications

Advancements in stationary phase chemistry and column dimensions will continue to refine FAME analysis. Ultra-high-efficiency columns and multidimensional GC techniques promise faster run times and superior separation of positional and geometric isomers. Integration with mass spectrometric detection may further enhance identification of trace and novel fatty acids in emerging food and biotech applications.

Conclusion

The SPB-PUFA column demonstrates lower polarity and improved carbon-number resolution compared to the Omegawax 320, particularly for highly unsaturated fatty acids. Equivalent chain length data confirm greater selectivity differences at higher degrees of unsaturation. Laboratories analyzing diverse FAME profiles can benefit from incorporating SPB-PUFA as either a complementary or primary GC column.

References

1. AOAC International. Official Methods of Analysis of AOAC International, 16th Edition, Supplement, 1996. Method 991.39: Fatty Acids in Fish Oils and Methyl/ethyl Esters.
2. Sidisky L.M., Ridley H.R. Temperature Effects on Column Selectivity. HRC & CC. 3 (1991) 191.