A ninety-six well plate as headspaces with moist starch indicator paper as a cover for the determination of ascorbic acid by iodate oxidation and formation of volatile iodine
Issued Date
2022-02-21
Resource Type
ISSN
17599660
eISSN
17599679
Scopus ID
2-s2.0-85124850511
Pubmed ID
35108716
Journal Title
Analytical Methods
Volume
14
Issue
7
Start Page
741
End Page
749
Rights Holder(s)
SCOPUS
Bibliographic Citation
Analytical Methods Vol.14 No.7 (2022) , 741-749
Suggested Citation
Nawalohakul T., Charoenjiraroj P., Chantiwas R., Wilairat P., Praditweangkum W. A ninety-six well plate as headspaces with moist starch indicator paper as a cover for the determination of ascorbic acid by iodate oxidation and formation of volatile iodine. Analytical Methods Vol.14 No.7 (2022) , 741-749. 749. doi:10.1039/d1ay02050a Retrieved from: https://repository.li.mahidol.ac.th/handle/20.500.14594/84104
Title
A ninety-six well plate as headspaces with moist starch indicator paper as a cover for the determination of ascorbic acid by iodate oxidation and formation of volatile iodine
Author's Affiliation
Other Contributor(s)
Abstract
This work presents the use of a 96-well plate as headspaces for the determination of ascorbic acid in samples loaded in the 96-well plate. Ascorbic acid in the sample is oxidized to iodide by the addition of excess acidic iodate solution into the well. The iodide is further oxidized by the remaining iodate to molecular iodine. A single sheet of moist starch indicator paper is immediately placed over the 96-well plate after the addition of the iodate with the moisture forming a gas seal. The iodine gas in each well diffuses through the headspace to react with the starch paper producing circular areas of a colored starch-iodine complex. After 15 min the indicator paper is scanned, and the digital images of the complex are analyzed by using ImageJ software to obtain blue intensity values. The precision of the intensity values from 12 wells containing 20 μL of 2.84 mM standard ascorbic acid is <2% relative standard deviation. Optimal conditions for detection were investigated, including the starch concentration, the acidic iodate reagent, and the measurement time. The linear calibration range of ascorbic acid is 0.284-2.84 mM, based on the plot of concentration vs. -log(reflectance). The coefficient of determination (r2) is >0.998. Samples of fruit juice and dietary supplements were analyzed for their ascorbic acid contents. The results obtained from the headspace reflectance method are not statistically different from values obtained from the titration method using paired t-tests (α = 0.05). This journal is