2006 Annual Report
There is an ever-increasing need for trace element food composition data. Much of the trace element data in the latest National Nutrient Database for Standard Reference was generated many years ago and needs to be updated because foods have changed. Review of the data suggests that in some cases, unsophisticated analytical methodology produced less than accurate results due to problems with contamination, matrix interference effects, or instrumental background correction strategies. Graphite furnace-atomic absorption spectrometry (GF-AAS), inductively coupled plasma-atomic emission spectrometry (ICP-AES) and inductively coupled plasma-mass spectrometry (ICP-MS) are newer instrumental techniques that are readily available to commercial labs. All provide better detection limits for many elements as compared to flame atomic absorption spectrometry and GF-AAS and ICP-AES offer the advantage of multielement determinations, allowing for the generation of accurate data for as many as 15-20 elements simultaneously. This project is organized into four objectives:.
The field of nutrition and public health will benefit, in general, from an improved nutrient database for trace elements and increased knowledge regarding the concentrations and species of trace elements in foods. The field of analytical chemistry will benefit from improved methods for:.
1. Robust Multielement Methods *Develop and circulate a questionnaire to food industry analytical labs on methods for low levels of Mn, Zn, and Cu in foods. *Evaluate responses to questionnaire.
2. Ultratrace Methods *Develop GF-AAS and ICP methods for Co and Cr.
3. Cobalamin Speciation *Develop method for cobalamin species using capillary electrophoresis and ICP-MS. *Start development of sample preparation method for cobalamins focusing on solid phase extraction.
4. Fe Speciation *Acquire standards for Fe species. *Initiate development of an High Performance Liquid Chromatography (HPLC) separation method for Fe species extracted from meat.
Year 2 (FY 2005)
1. Robust Multielement Methods *Complete evaluation of questionnaire. *Develop in-house food control materials for evaluation by food industry labs.
2. Ultratrace Methods *Complete development of GF-AAS and ICP methods for Co and Cr. *Initiate development of GF-AAS and ICP methods for Ni, and V.
3. Cobalamin Speciation *Complete development of sample preparation method for cobalamins.
4. Fe Speciation *Continue development of HPLC method for Fe species extracted from meat. *Determine effect of cooking and acidification on heme Fe. *Set up in vitro digestion system to study heme Fe. *Initiate study of bioavailability of heme Fe.
Year 3 (FY 2006)
1. Robust Multielement Methods *Initiate development of ICP methods for food materials.
2. Ultratrace Methods *Complete development of methods for Ni, and V. *Initiate development of in-house control materials for Co, Cr, Ni, and V.
3. Cobalamin Speciation *Initiate determination of cobalamins in foods and supplements. *Develop fresh-frozen quality control materials.
4. Fe Speciation *Continue study with in vitro digestion system for heme Fe. *Continue study of bioavailability of heme Fe. *Initiate quantification of total Fe and heme Fe in foods for database.
Year 4 (FY 2007)
1. Robust Multielement Methods *Develop Association of Analytical Chemists (AOAC) method(s) for determination of multi-elements in food materials using ICP.
2. Ultratrace Methods *Complete in-house control materials for Co, Cr, Ni, and V. *Initiate determination of Co, Cr, Ni, and V in food materials.
3. Cobalamin Speciation *Initiate development of a dietary supplement quality control material for cobalamins.
4. Fe Speciation *Finish study with in vitro digestion system for heme Fe. *Finish study of bioavailability of heme Fe. *Determine total Fe and heme Fe in foods for database.
Year 5 (FY 2008)
1. Robust Multielement Methods *Complete AOAC method(s) for determination of multi-elements in food materials using ICP.
2. Ultratrace Methods *Complete determination of Co, Cr, Ni, and V in food materials
3. Cobalamin Speciation *Complete development of dietary supplement quality control material for cobalamins.
4. Fe Speciation *Determine total Fe and heme Fe in foods for database.
Completed development of a method for the determination of heme Fe in meats, using an acidified acetone extraction with inductively coupled plasma-atomic emission spectrometridc (ICP-AES) detection. This allows Heme Fe, which is more accessible in foods, to be accurately analyzed. FCL demonstrated that only heme Fe was extracted by the acidified acetone and that Fe was accurately determined by ICP-AES after finding consistent errors with atomic absorption spectrometry. This method can be used routinely for the determination of heme Fe in meats.
Supported development of a new Bovine Serum Standard Reference Material in collaboration with scientist at the National Institutes of Standards and Technology. Helped analyze aluminum (Al), a particularly troublesome element because of its susceptibility to contamination. Showed that the Al concentration was 2.8 ng/mL in the new bovine material and was 2.5 ng/mL in the old material. This was significant, since the previously accepted level for the old standard was 4.0 ng/mL. This new standard will allow standardization of biological analyses.
Developed and circulated a questionnaire to colleagues from the National Food Processor's Analytical Chemists Subcommittee regarding low level trace element methods. Information gathered includes: methods used for trace element determinations, quality control strategies, interest in fresh food QC materials, and interest in participation in a study to improve low level trace element determinations for Mn, Zn, Fe and Cu. All of the laboratories contacted are commercial analytical labs. Many are associated with food producing companies and some are contract labs but all of them generate food composition data. The expected outcome of the study is development and technology transfer of robust methods suitable for industrial labs for the production of multielement food composition data. Another product is the production of much needed in-house food QC materials.
Participated in an inter-laboratory collaborative study determining nine trace elements (Ca, Cu, Fe, Na, K, P, Mg, Zn, and Mn) in a nutritional liquid (similar to Ensure) and a cereal (similar to Cheerios). FCL are 1 of 22 laboratories that participated and FCL data were in good agreement with the mean values from the study.
Developed method for heme Fe in meats that employed the classic Hornsey extraction (acidified acetone) and determined the extracted Fe using atomic absorption spectrometry. Demonstrated that the use of spectrophotometry for the determination of Fe in the Hornsey extract gave results that are biased high by 15% to 40%. Initiated development of HPLC method to separate components extracted by the Hornsey method to verify that all the Fe was heme Fe.