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ARS Home » Research » Publications at this Location » Publication #66055


item Byrdwell, William
item Emken, Edward
item Neff, William
item Adlof, Richard

Submitted to: Lipids Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: There continues to be a great amount of interest in the types and amount of fat consumed in the diet. To characterize the main components in fats, called triglycerides, a technique called high performance liquid chromatography (HPLC) is used to separate the triglycerides. Then, the amounts of the triglycerides are counted (quantitated) as they pass by a detector. Unfortunately, in complex fats even the best HPLC separation cannot separate all of the triglycerides, so some of them are over-counted, and some are missed altogether. To solve this problem, we have used a technique for detection called mass spectrometry, which is a method of breaking molecules into pieces and analyzing the weights of the pieces to determine what triglycerides they came from. By using mass spectrometry, even when triglycerides are not separated by HPLC, they can be differentiated, so they can be counted separately. Since triglycerides are elarge molecules, a new method of introduction called Atmospheric Pressure Chemical Ionization was used to spray the triglycerides into the mass spectrometer for detection. The combination of HPLC for separation with atmospheric pressure chemical ionization mass spectrometry for detection allowed us to determine what triglycerides were present (qualitative analysis), and how much of each one was present (quantitative analysis) in a complex mixture. This method will be very useful by food producers for determining the types of triglycerides present in seed oils and animal fats. The method can also be used to examine human blood and tissues to determine how the fat in the diet has affected the types of fat in the body.

Technical Abstract: Atmospheric pressure chemical ionization mass spectrometry (APCI-MS) was used for qualitative analysis of mixtures of heterogeneous triglycerides (TGs) separated by reverse-phase high performance liquid chromatography. APCI-MS was further used for quantitative analysis of homogeneous (mono acid) triglyceride standards containing deuterated internal standard and for quantitative analysis of a model synthetic mixture of heterogenoeous TGs. A factor termed the triglyceride quotient was developed and used to characterize the appearance of TG spectra and to produce response factors which allowed approximation of percentage composition. Quantitation of the TGs in a synthetic mixture by three approaches are compared. These methods are based on interpolation of response factors obtained from six homogeneous TG standards, based on response factors obtained from the synthetic mixture of heterogeneous TGs, and based on response factors calculated from the triglyceride quotient. The least relative error was obtained when quantitation was based on a mixture of TGs which were similar in composition to the analyte.