title: A simple and sensitive assay for ascorbate using potassium ferricyanide as spectroscopic probe reagent.
abstract: We have developed a rapid, inexpensive, and reliable assay to determine ascorbate using potassium ferricyanide as spectroscopic probe reagent. In this assay, Fe(III) was deoxidized to Fe(II) by ascorbate at pH 4.0 and then Fe(II) reacted with potassium ferricyanide to form a blue product, soluble Prussian blue (KFe(III)[Fe(II)(CN)6]). The absorbance of this product was monitored over time using a spectrophotometer at an absorption maximum of 735 nm and the amount of ascorbate can be calculated based on absorbance. A good linear relationship of the concentration of ascorbate versus absorbance was observed, and the linear regression equation was A=-0.01911+0.16208C (microg/ml). Moreover, the apparent molar absorption coefficient of indirect determination of ascorbate was 2.85 x 10(4) L/mol x cm. To demonstrate the usefulness of this assay, it was used to determine ascorbate in different samples, and we particularly investigated the uptake of ascorbate and ascorbate phosphate in osteoblasts. We found similar plateau levels of intracellular ascorbate at 24h for ascorbate and ascorbate phosphate. The assay was robust for a variety of samples, including orange juice, fruits, and swine plasma. The assay was quick and very economical and provides results with uncertainties on the order of only 5%.
authors.affiliation: College of Chemistry and Environmental Science, Henan Normal University, Jianshe Road No. 46, Xinxiang, Henan 453007, People's Republic of China.
authors.forename: Hua
authors.initials: H
authors.lastname: Zhang
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.forename: Kui
authors.initials: K
authors.lastname: Wang
authors.forename: Xinzhen
authors.initials: X
authors.lastname: Du
authors.forename: Quanmin
authors.initials: Q
authors.lastname: Li
mesh_terms: D000818:Animals; D001205:Ascorbic Acid / Q000032:analysis* / Q000097:blood / Q000737:chemistry; D001628:Beverages / Q000032:analysis; D002478:Cells, Cultured; D005292:Ferricyanides / Q000737:chemistry*; D005638:Fruit / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D051379:Mice; D010006:Osteoblasts / Q000378:metabolism; D011540:Prussian Blue Reaction; D013053:Spectrophotometry / Q000379:methods*; D013552:Swine
chemical_list: D005292:Ferricyanides; D001205:Ascorbic Acid; C028033:potassium ferricyanide