MEASUREMENT SYSTEMS FOR DETERMINATION OF VITAMINS IN FOODS AND DIETARY SUPPLEMENTS
Location: Food Composition and Methods Development Lab
Title: Ultraviolet and mass spectrometric analysis of vitamin D in retail fortified orange juice
Submitted to: Journal of Food Composition and Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 10, 2010
Publication Date: December 7, 2010
Citation: Byrdwell, W.C., Exler, J., Gebhardt, S.E., Harnly, J.M., Holden, J.M., Horst, R., Patterson, K.K., Phillips, K., Wolf, W.R. 2010. Ultraviolet and mass spectrometric analysis of vitamin D in retail fortified orange juice. Journal of Food Composition and Analysis. 24:299-306.
Interpretive Summary: Vitamin D is important for maintaining bone health, and adequate levels have been shown to lower the risk of some cancers and other diseases. The American public gets much of its requirement for vitamin D from dietary sources, primarily in foods that are fortified with the nutrient. One such source is orange juice that is fortified with vitamin D3 and calcium. The FDA has approved fortification of orange juice at a level of 100 IU/240 mL (2.5 µg/8 oz.), and many producers now make a retail fortified product available. This study describes the analysis of retail orange samples from half-gallon cartons purchased across the United States. An example is given to demonstrate how problematic vitamin D analysis can be, and to show that our analytical approach used multiple techniques to confirm that our data were reliable. The results indicated that that the average content of retail orange juice that a consumer might buy was 3.4 ± 0.3 µg (136 ± 12 IU) per 8 oz. glass. All samples except one contained more than the amount stipulated by the FDA, indicating that under-fortification was not a widespread problem, and that orange juice represents a generally reliable source of vitamin D3 in the diet.
Samples of vitamin D fortified orange juice obtained from retail food stores were analyzed for vitamin D3 content using a method developed by combining the best features of two AOAC officially approved methods. The ether/petroleum ether extraction from AOAC 992.26 was combined with the high performance liquid chromatography (HPLC) methods and internal standard from AOAC 2002.05. Detection by ultraviolet absorption at 265 nm was compared to detection by selected ion monitoring (SIM) using atmospheric pressure chemical ionization (APCI) mass spectrometry (MS). Furthermore, an ion trap (IT) mass spectrometer was employed in a ‘dual parallel MS’ arrangement to simultaneously obtain qualitative APCI-ITMS data. The method was applied to 33 samples of 3 national orange juice brands and 7 samples of 5 other brands collected using a statistically designed national sampling plan as part of the National Food and Nutrient Analysis Program to provide values for the USDA National Nutrient Databank for Standard Reference. The levels determined were compared to the label values, which corresponded to FDA allowed levels. There was a high degree of compliance with all but one brand exceeding the label amounts. Vitamin D3 values ranged from 1.075 µg (43 IU)/100g to 1.675 (67 IU)/100g, with an average value across 55 samples analyzed, including duplicates, of 1.433 ± 0.114 µg (57.31 ± 4.58) IU/100g. The average content of the 38 uniquely identified samples, using the averages of duplicate sets, was 1.416 ± 0.122 µg (56.62 ± 4.88 IU)/100g, indicating that a typical 8 oz. glass of orange juice provided 3.4 ± 0.3 µg (136 ± 12 IU) vitamin D3. Only one store brand out of 39 fortified retail samples was labeled as fortified, but found not to contain vitamin D3.