2007 Annual Report
1a.Objectives (from AD-416)
1) Develop robust multi-element methods and quality control materials for trace and ultratrace elements important to human health,.
2)develop method for total vitamin B12 in foods,.
3)develop elemental speciation methods for vitamin B12 (cobalamin),.
4)develop analytical methods for the determination of hemeprotein and heme Fe in meats, and.
5)develop elemental fingerprinting method for food and botanical materials.
1b.Approach (from AD-416)
Analytical methods for the accurate determination of trace elements in foods will be developed using inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS) and graphite furnace atomic absorption spectrometry (GFAAS). The appropriate method will depend on the metal concentration in the foods. Elements of interest include: Mn, Zn, Fe, Cu, Mg, Ca and P (ppm levels) as well as Co, Cr, Ni and V (ppb levels). Methods developed will be evaluated by commercial labs through collaborative studies. We will be involved in the preparation and characterization of a range of trace element control materials. Elemental speciation methods will be developed by combining microseparation methods with ICP-MS detection focusing on cobalamins (Vitamin B12 species). Species specific cobalamin data will be important for studying absorption and bioavailabilitly and the current official AOAC method is a time consuming, microbiological method which can measure only cyanocobalamin - not all the naturally occurring cobalamin species. Finally, iron species will be measured using size exclusion chromatography and UV/Vis and flame atomic absorption spectrometry. Total iron will be measured in meat samples as well as hemeprotein and heme iron. Appropriate speciation control materials will be developed and characterized to facilitate technology transfer. Preliminary elemental speciation food composition data speciation data tables will be prepared.
Activities related to this project have been dramatically curtailed as a result of the early and unexpected retirement of the lead scientist. Most of the research to be conducted in the original proposal has been modified or delayed. The research that is continuing is described below under the direction of the Research Leader.
Naturally occurring levels of Vitamin B12 are extremely low and difficult to detect even by mass spectrometry. A project was initiated to determine B12 based on detection of cobalt (Co) that is incorporated in the porphyrin ring of the vitamin, using inductively coupled plasma-mass spectrometry (ICP-MS). Direct analysis of a digested ready-to-eat dry cereal gave results approximately five-fold higher than the Nutrition Facts label value, indicating the possible presence of Co in a form other than B12. An acidified acetone extraction similar to that used for heme-iron, a metal also present in a porphyrin ring, initially gave results that were approximately 20% high compared to the label value. This research will continue using both Co detection and liquid chromatography-MS methods.
The levels of calcium (Ca) in soy milk that are associated with the solids were investigated. It was demonstrated that after moderate centrifugation, 90% of the Ca was found in the solid cake. This suggested that there would be little Ca in the liquid phase of soy milk products that had sat on the shelf for some time. The level of Ca in the liquid phase would strongly depend on how vigorous the consumer shook the milk container prior to use. These results suggest that the next step is to determine the extent of settling in soy milk products and ability of users to re-mix the Ca with shaking.
Trace metals (calcium, copper, iron, magnesium, manganese, phosphorous, potassium, and zinc) were analyzed in the multivitamin/multielement tablet Standard Reference Material (SRM) 3280 being developed by the National Institutes of Standards and Technology (NIST). These data were submitted to NIST for use in establishing the reference values.
The Food Composition and Methods Laboratory (FCML) also participated in the National Marine Analytical Quality Assurance Program for the determination of trace metals in marine mammal tissue sponsored by NIST and the National Oceanic and Atmospheric Administration. Values for cadmium, copper, iron, manganese, and zinc were reported to NIST.
Studies were initiated to develop a method for profiling the elemental content of samples using the full scan mode of the inductively coupled plasma-mass spectrometer (ICP-MS). This method determines semi-quantitative values for all elements from mass 6 to 238 based on internal standardization. The method was first used to determine the elemental profile of dry bean samples. The semi-quantitative values of the scanning method were compared to values determined using a routine analytical method based on ICP-atomic emission spectrometry for 15 elements.
This research addresses National Program 107, Human Nutrition, Action Plan Component 1, Composition of Foods.
5.Significant Activities that Support Special Target Populations