Rapid Screening of Fatty Acids in Oil Supplements Using Ambient Ionization (DART) and Mass Detection

Importance of the topic

A balanced intake of polyunsaturated fatty acids (PUFAs), especially omega-3 and omega-6, is critical for cardiovascular health and inflammation control. Dietary supplements rich in fish or plant oils are widely used to correct common imbalances in the Western diet. Ensuring authenticity and correct labeling of these products is essential to protect consumers and maintain regulatory compliance.

Objectives and overview

This study demonstrates a rapid, low-complexity approach using Direct Analysis in Real Time (DART) ambient ionization coupled to a single quadrupole mass detector (ACQUITY QDa) for the direct screening and authentication of fatty acids in oil supplements. Key goals include:

• Identification of major omega-3 and omega-6 fatty acids
• Assessment of method speed, reproducibility, and minimal sample preparation
• Comparison of experimental fatty acid profiles with label claims

Methodology and instrumentation

Samples of standard PUFA mixes and commercial oil capsules (fish, safflower, flax seed) were diluted in toluene and applied to disposable QuickStrip cards. The card passed through a 200 °C helium DART source, generating deprotonated fatty acid ions [M–H]–. Ions entered the ACQUITY QDa detector operating in Selected Ion Recording (SIR) mode, monitoring m/z values from 255 to 331.3 for target fatty acids. Minimal sample prep and no chromatographic separation were required.

Main results and discussion

Method development showed temperature-dependent ionization efficiency; 200 °C provided balanced response for C16–C22 PUFAs. Ten replicate analyses of the standard mix yielded experimental percentages within ±2 % of expected values (except stearidonic acid, which ionized less efficiently). Three commercial supplements were analyzed in triplicate. Experimental fatty acid distributions closely matched label claims:

• Fish oil: 59 % EPA vs. expected 60 %, 41 % DHA vs. 40 %
• Safflower oil: 55 % linoleic vs. 63 % label, 33 % oleic vs. 22 %
• Flax seed oil: 57 % ALA vs. 67 %, 21 % linoleic vs. 16 %

Unexpected oleic acid in fish oil was attributed to soy oil used as a preservative, while minor DHA in flax oil suggested possible cross-contamination or adulteration.

Benefits and practical applications

The DART-MS approach enables:

• Analysis of up to 12 samples in 6–7 minutes total
• Elimination of derivatization and chromatography
• Compact setup suitable for in-line quality control during manufacturing
• Rapid authenticity testing of dietary supplements

Future trends and potential uses

Advances in ambient ionization and compact mass detectors may expand this technique to:

• Routine quality assurance in food and nutraceutical production
• On-site screening of raw materials and finished products
• Detection of adulterants and contaminants in complex matrices
• Integration with automated sampling for high-throughput monitoring

Conclusion

Ambient DART coupled with ACQUITY QDa mass detection provides a fast, reproducible, and user-friendly platform for direct screening of fatty acids in oil supplements. The method delivers results comparable to traditional GC-based assays without extensive preparation, supporting rapid authenticity checks and quality control outside the central laboratory.

References

1. AOAC Official Method 991.39. Fatty Acids in Encapsulated Fish Oils and Fish Oil Methyl and Ethyl Esters. 1995.
2. Cody RB, Laramee JA, Durst HD. Versatile New Ion Source for the Analysis of Materials in Open Air Under Ambient Conditions. Analytical Chemistry. 2005;77:2297–2302.