DETERMINATION OF VITAMINS IN NIST FOOD MATRIX SRMS
Melissa M. Phillips, Catherine A. Rimmer, Lane C. Sander, Katherine E. Sharpless, and Stephen A. Wise
In 1990, the Nutrition Labeling and Education Act began requiring manufacturers to provide nutrition information on the labels of processed foods sold in the U.S. As a result, authentic reference materials with assigned concentrations of nutrients and potential contaminants are needed to provide a close matrix match for analytical measurements. To support this effort, NIST has made available a number of food-matrix Standard Reference Materials (SRMs), including baking chocolate, peanut butter, and infant/adult nutritional formula.
Several new and updated food-matrix SRMs are under development at NIST to provide additional challenges for measurement of fat- and water-soluble vitamins. Whole milk powder, whole egg powder, and baby food composite SRMs are under development as replacements for currently available materials lacking certified values for vitamins. Fortified breakfast cereal and soy flour SRMs are also under development as new materials. While the measurement of the fortified vitamins in the materials is relatively straightforward, measurement of endogenous vitamins requires careful consideration of plant and animal metabolism and effects of processing.
Separate methods are being developed for determination of B vitamins and fat-soluble vitamins in these materials. Acidic extraction followed by LC-ESI-MS provides exhaustive recovery, sufficient separation, and sensitive detection of the B vitamins from these materials. For high-fat materials, the need for a defatting step such as saponification or gel permeation chromatography prior to MS analysis was evaluated. Extracts were analyzed by LC-APCI-MS for both fortified and endogenous forms of vitamins A, D, E, and K.