Breakfast cereal sampling study for nutritional elements.

The National Institute of Standards and Technology (NIST) has established a Dietary Supplement Laboratory Quality Assurance Program (DSQAP) in collaboration with the National Institutes of Health Office of Dietary Supplements (NIH-ODS). The DSQAP invites laboratories twice annually to participate in interlaboratory studies where participants elect to measure concentrations of nutritional and/or toxic elements as well as active and/or marker compounds. One of these studies was designed to determine the effects of material granularity and sample processing techniques on measurement variability (precision) as well as to provide participating laboratories information on their performance relative to the NIST assigned values (bias) and to the other participants (concordance). Participants were asked to determine the mass fractions of Ca, Fe, and Zn, in mg/kg, in six breakfast cereal samples. Cereal samples consisted of three ground materials (homogenized wheat, wheat, and rice), two flake materials (wheat and rice) and a partially crushed material (a wheat/rice mixture). In general, approximately 25% of the laboratories processed and analyzed the suite of six cereal materials with adequate to exemplary measurement precision. Over half of the laboratories (60%) experienced measurement issues related to only a particular type of cereal matrix or for only a single element. A small number (15%) of laboratories experienced significant sample processing or measurement problems. Future studies planned by the DSQAP may be designed to use commercial products to aid laboratories with their sampling and analytical techniques.