title: Determination of folic acid in milk, milk powder and energy drink by an indirect immunoassay.
abstract: BACKGROUND
  Folic acid (FA) is essential for healthy people (reference daily intake 400 µg day⁻¹) and pregnant women (600 µg day⁻¹). Insufficient intake of FA will increase the risk of neural tube defects in newborns. In this study an indirect enzyme-linked immunosorbent assay was developed for rapid and convenient detection of FA in vitamin-fortified foods.
  
  
  RESULTS
  A carbodiimide-modified active ester method was used to synthesise the immunogen (FA-bovine serum albumin (BSA) conjugate) to raise polyclonal antibodies for FA. The coupling ratio of FA with BSA was determined to be 14:1 (molar ratio). The detection limit of the immunoassay was 3.0 ng mL⁻¹ in buffer, 3.52 ng mL⁻¹ in energy drink, 11.91 ng mL⁻¹ in milk and 16.50 ng mL⁻¹ in milk powder. Intra- and inter-assay variability ranged from 6.6 to 15.1%. Analytical recoveries of FA-spiked samples were 88.3-108.9%.
  
  
  CONCLUSIONS
  The immunoassay developed in this study can be used as a simple, rapid and accurate method for fast semi-quantitative and quantitative on-site analysis of FA in food products.
authors.affiliation: College of Pharmacy and Tianjin Key Laboratory of Molecular Drug Research, Nankai University, Tianjin, China.
authors.forename: Taichang
authors.initials: T
authors.lastname: Zhang
authors.forename: Huyin
authors.initials: H
authors.lastname: Xue
authors.forename: Bo
authors.initials: B
authors.lastname: Zhang
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhang
authors.forename: Pei
authors.initials: P
authors.lastname: Song
authors.forename: Xi
authors.initials: X
authors.lastname: Tian
authors.forename: Yue
authors.initials: Y
authors.lastname: Xing
authors.forename: Peng
authors.initials: P
authors.lastname: Wang
authors.forename: Meng
authors.initials: M
authors.lastname: Meng
authors.forename: Rimo
authors.initials: R
authors.lastname: Xi
mesh_terms: D000818:Animals; D000918:Antibody Specificity; D001628:Beverages / Q000032:analysis*; D003429:Cross Reactions; D005492:Folic Acid / Q000031:analogs & derivatives / Q000032:analysis* / Q000737:chemistry; D005513:Food Inspection / Q000379:methods*; D005527:Food, Fortified / Q000032:analysis*; D057141:Food, Preserved / Q000032:analysis*; D006241:Haptens / Q000737:chemistry; D007118:Immunoassay; D057230:Limit of Detection; D008892:Milk / Q000737:chemistry*; D015203:Reproducibility of Results
chemical_list: D006241:Haptens; D005492:Folic Acid