Status of Mineral Methodology based on SRM 3280 Results for the DSID Project

Authors: ANDREWS, KAREN - Johns Hopkins University; FEINBERG, MATTHEW - Johns Hopkins University; Roseland, Janet; Holden, Joanne

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/20/2009
Publication Date: 3/24/2009
Citation: Andrews, K., Feinberg, M., Roseland, J.M., Holden, J.M. 2009. Status of mineral methodology based on SRM 3280 results for the DSID Project. Dietary Supplement Element Methodology Workshop, March 23-24, 2009, Gaithersburg, Maryland.

Interpretive Summary:

Technical Abstract: The Nutrient Data Laboratory (NDL), Beltsville Human Nutrition Research Center, U.S. Department of Agriculture is working with the Office of Dietary Supplements and other federal agencies to plan and develop a Dietary Supplement Ingredient Database (DSID) to provide levels of ingredients in dietary supplement products. The major product of this research will be a publicly available ingredient database with reliable estimates of nutrients and other bioactive components in dietary supplements. Initial analytical work for the Dietary Supplement Ingredient Database (DSID) focused on multivitamin/minerals (MVMs) due to their high prevalence of use. Pilot studies were initiated to review sample handling procedures and methods of analysis and to qualify laboratories for the analysis of nutrients and other dietary ingredients in supplement products. Preliminary assessments of precision and accuracy for methods and laboratories were established in 2005. These assessments were based on the results of several laboratories’ analyses of 11 minerals in the NIST SRM 3280 MVM material, then under development. These essential elements were measured 5 or 6 times over a period of several weeks or months. After acceptable methods and labs were identified by a federal expert panel, two MVM studies were conducted using NIST SRM 3280 as a control material. This presentation summarizes the ongoing assessments of laboratory method accuracy and variability in the DSID project using SRM 3280 results as an indicator. Mean values (n=19 or 20), standard deviations (sd) and % relative standard deviations (% RSD) were calculated for SRM 3280 results generated by NDL’s contracted laboratory. These data were generated from August, 2006 to May, 2008 during the analysis of adult MVM products. For eight minerals (calcium, copper, iron, magnesium, manganese, phosphorus, potassium, and zinc) analyzed by multi-element inductively coupled plasma spectrometry (ICP), mean values were within the certified NIST ranges and RSDs were < 5%. For selenium, analyzed by hydride generation atomic absorption spectroscopy, and for iodine, analyzed by thiosulfate titration, mean values were within the certified or reference NIST ranges and RSDs were 9.1% and 6.3%, respectively. Chromium analysis by both graphite furnace atomic absorption spectroscopy and by ICP-mass spectrometry showed differences from the certified values that still need to be resolved. These results indicate that of the 11 minerals analyzed for the adult MVM DSID study, 10 are showing good to excellent results with commonly used methods. In the first release of DSID in April, 2009, estimates based on laboratory results for 10 minerals (chromium results will be released at a later time) in adult MVMs will be published. It is important to note that the screening process used in this study identified laboratories applying good quality control practices to these methods and with acceptable precision and accuracy in analyzing the NIST 3280 material under development. The availability of SRM 3280 has been an essential tool for this project. Standard reference materials for other dietary supplement matrices, including children’s products with lower nutrient levels and candy, chewable and liquid forms, would be just as valuable.