title: Assessing analytical variability of measurement of vitamin A in corn-soy blend.
abstract: Two multilaboratory investigations were conducted by SUSTAIN to assess variability in the measurement of vitamin A, the marker used to verify levels of vitamin premix addition to enriched/fortified food aid products, including the widely distributed corn-soy blend (CSB). CSB specifications identify AACC Approved Method 86-06 or equivalent methods for vitamin A analysis, however there is no requirement to demonstrate equivalency. CSB samples with known and blinded levels of vitamin A and a reference standard were analyzed by 16 laboratories using their respective methods. Calculated coefficients of variation across all laboratories and methods for unknown samples and reference standard were 35 and 7.1%, respectively, suggesting the largest source of variation is the vitamin extraction procedure. Laboratories generally overestimated low levels and underestimated high levels of vitamin A within the range of 6000 and 16 000 IU/lb. Only two laboratories demonstrated excellent internal precision (+/- 300 IU vitamin A/lb) and reported values within 95% confidence interval for all blinded samples. Results of this study have implications both for quality control in food aid products (due to the use of vitamin A as a marker) and for regulatory oversight of vitamin A content in commercial food products.
authors.affiliation: SUSTAIN, 2000 P St, NW, Suite 300, Washington, DC 20036, USA. wmoore56@verizon.net
authors.forename: Wayne R
authors.initials: WR
authors.lastname: Moore
authors.forename: Jonathan
authors.initials: J
authors.lastname: DeVries
authors.forename: John
authors.initials: J
authors.lastname: MacDonald
authors.forename: Lynne
authors.initials: L
authors.lastname: Hare
authors.forename: J
authors.initials: J
authors.lastname: Carson
authors.forename: P
authors.initials: P
authors.lastname: Chaudhari
authors.forename: J
authors.initials: J
authors.lastname: DeVries
authors.forename: J
authors.initials: J
authors.lastname: Fontana
authors.forename: P
authors.initials: P
authors.lastname: Golz
authors.forename: J
authors.initials: J
authors.lastname: King
authors.forename: J
authors.initials: J
authors.lastname: MacDonald
authors.forename: C
authors.initials: C
authors.lastname: McCullough
authors.forename: S
authors.initials: S
authors.lastname: Noggle
authors.forename: E
authors.initials: E
authors.lastname: Rasgorshek
authors.forename: S
authors.initials: S
authors.lastname: Schorn
authors.forename: L
authors.initials: L
authors.lastname: Skogerson
authors.forename: D
authors.initials: D
authors.lastname: Sullins
authors.forename: D
authors.initials: D
authors.lastname: Sullivan
authors.forename: M
authors.initials: M
authors.lastname: Sussman
authors.forename: M
authors.initials: M
authors.lastname: Weibel
mesh_terms: D002623:Chemistry Techniques, Analytical; D005504:Food Analysis / Q000379:methods*; D005527:Food, Fortified / Q000032:analysis*; D009753:Nutritive Value; D011786:Quality Control; D012015:Reference Standards; D015203:Reproducibility of Results; D013025:Glycine max / Q000378:metabolism*; D014481:United States; D016885:United States Department of Agriculture; D014801:Vitamin A / Q000032:analysis / Q000737:chemistry*; D003313:Zea mays / Q000378:metabolism*
chemical_list: D014801:Vitamin A