Raman, IR, and GC–MS Analysis of Nutritional Supplements Discussed at New York–New Jersey Meeting of Society for Applied Spectroscopy

Oct 13, 2017

At the September 27, 2017, meeting of the New York–New Jersey chapter of the Society for Applied Spectroscopy, Gene Hall, a professor of analytical chemistry at Rutgers, the State University of New Jersey, shared some of his recent work using Raman spectroscopy, mid-infrared (IR) spectroscopy, and gas chromatography–time-of-flight mass spectrometry (GC–TOF-MS) to analyze omega-3 fatty acid supplements marketed for pets. The attendees appreciated the opportunity to learn details about the methods used, which can take only minutes for analysis after very simple sample preparation, and to hear the surprising results.

“Our data also show that numerous companion pet nutritional supplements have false labels and do not contain the contents in the capsules or bottles as listed,” said Hall.

In the studies, Hall and his group used a molecular modeling program to investigate the correlation between molecular structure and the corresponding Raman and mid-IR spectra. Those calculations have shown that omega-3 fatty acid derivatives can have multiple stable conformers. The predicted theoretical spectral bands can be compared to the experimental bands to determine the correct molecular structure. Hall and his team have taken this approach to interpret the complex spectra of omega-3 fatty acid sourced nutritional supplements specifically marketed for dogs and cats. Their data have shown that there are unique differences in both the Raman and mid-IR spectra that allow them to distinguish between the free fatty acid (unesterified), fatty acid ethyl esters, and the natural triacyl-sn-glycerol (nTAG) chemical forms of the supplements. In the studies, mid-IR spectroscopy was used in combination with GC–TOF-MS to corroborate the findings.

In the presentation, Hall demonstrated how he employed a software program to use band assignments to interpret spectra and correlate molecular bond vibrations to bands. He also discussed other software for doing this type of analysis.

The results of the studies showed that the contents of many of the pet nutritional supplements tested did not match the contents listed on the packaging and that some of those contents are 100% synthetic, despite being advertised as 100% natural. Hall mentioned that fatty acid supplements of this type, if truly 100% natural,  should have a no-observed-adverse-effect level (NOAEL), whereas 100% synthetic fatty acids can have serious adverse effects.

The legal requirements for labeling food, as well as animal feed, which includes products marketed as supplements for pets, have recently been revised and are very strict. The U.S. Food and Drug Administration (FDA) has specific labeling requirements for these products and if a manufacturer does not follow the rules, the product is considered to be misbranded or adulterated, or both. Surprisingly, state commercial feed laws trump FDA laws and many states require that all pet food manufacturers register their products before they are sold in the state. If not registered, a supplement marketed for use in pets (which is considered animal feed under FDA rules) cannot be legally sold in the state. Therefore, based on Hall’s analyses of more than 30 nutritional supplements for companion animals, more than 95% are being illegally sold in New Jersey because the manufacturer has not registered the product based on “New Jersey Commercial Feed Law,” (NJSA 4:4-20.1).


Hall further illustrated his work on fatty acid analysis using an example of the analysis of a fish sample. He showed an image of a salmon filet taken directly from a package and placed on an attenuated total reflectance mid-IR (ATR MIR) spectrometer. He  explained how he could determine, in just a few minutes, whether the salmon were farm-bred or wild caught, and how fresh it was. Such information is important because the location where fish oil comes from must be carefully documented and tracked.

Hall’s presentation prompted interest and questions from the meeting attendees, who also had a chance to meet and network before the talk over dinner. “The advantages of having face-to-face meetings include the additional information and insights the experts in the audience can share,” Ali Virani from Sun Chemical,  who attended the meeting.  “The value of the networking and making friends includes getting help solving our work problems and getting new ideas.”

Analysis of the fatty acids in fresh salmon using infrared spectroscopy

The New York–New Jersey chapter of SAS holds monthly meetings, and most meetings include a guest speaker, a simple dinner, and time for networking. Students are always welcome. The next meeting will be held on Wednesday, October 25, and will include a presentation by Emil Ciurczak, "Thinking Outside the Plane: 3-D Printing and Chemical Imaging," and will be held at Fairleigh Dickinson University.

More information about the chapter and the schedule of meetings can be found at www.nysas.org.

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