Leading the traditional analysis of fats and oils into the future
In contrast to other fields of scientific research that greatly benefited by modern analytical tools as HR- MS and UHPLC, lipid chemistry is still dominated by traditional techniques. True, fatty acids (FA) and triglycerides (TAG) are no longer identified by counter current distribution (CCD) isolation followed by ozonolysis to produce diagnostic aldehydes. Packed GC columns aren’t anymore used for routine analysis of FA and TAG. However, the TAG composition of olive oil (and other oils) is still determined by HPLC using ancient 5 ❍m high carbon/high surface RP18 columns and refractive index detection. Fatty acids are still analyzed by capillary GC using legacy 100% bis(cyanopropyl siloxane) or PEG phases, and FID detection. Despite this resistance to innovation, multidimensional separation techniques are finally leading lipid chemistry into a new era.
GC×GC and the variant GC-ORxGC (adding a capillary reducer between the two columns) separate almost all the FA contained in the most challenging samples, such as marine oils, and provide analyte identification based on elution patterns. FA and TAG may also be analyzed by offline LC-GC using an RP18 or silver ion loaded column for the first separation (LC), and a capillary GC column for the second separation. More complex LC-GC methodologies may be developed by chemically altering analytes between the two separations. For example, the TAG composing food oils as olive oil may be converted to FA methyl esters after the LC separation, before the introduction in the GC column.
Applying a little creativity, the combination of legacy separations and chemical reactions can provide the multidimensional separations capable of solving the most challenging lipid chemistry problems.
Dr. Pierluigi Delmonte, Research Chemist, Office of Regulatory Science, Division of Chemistry, Bioanalytical Methods Branch, Food and Drug Administration, College Park, MD, Dr. Pierluigi Delmonte earned a Master’s degree in Chemistry from the University of Parma (Italy) and a Doctorate in Food Biotechnology from the University of Bologna. In 2001, Dr. Delmonte joined the Center for Food Safety and Applied Nutrition at the U.S. Food and Drug Administration. His research is primarily focused on fats and oils, dietary supplements and liposoluble vitamins. The lipid research was principally dedicated to the development of analytical methods for measurement of trans fatty acids, conjugated linoleic acid (CLA), and polyunsaturated fatty acids (PUFA) in foods, fats and oils. This work often necessitated the synthesis, purification and structural elucidation of reference fatty acids. While methodologies developed for routine analysis were based primarily on UHPLC and GC-FID, many other applications based on GC×GC, GC×GC with online reduction (GC-OR×GC, and offline LC×GC were developed for research purpose. Current work is dedicated to the detection of olive oil adulteration with other food oils by investigating the triglyceride composition. Dr. Delmonte received the Dutton Award of the American Oil Chemists’ Society (AOCS) in 2016 and has served as vice-chair/scientific program manager of the Analytical Division of AOCS since 2017.