Antioxidant Activity II

We did a series of two experiments on antioxidants in the Introduction to Organic Chemistry laboratory this spring. We chose to use TPTZ (2,4,6-tripyridyl-s-triazine) as our indicator in the ferric reducing antioxidant power (FRAP) assay. As far as I could tell the original article for this assay is a 1996 Analytical Chemistry paper by Benzie and Strain. This assay turns blue/purple as Fe(III) ions in the assay buffer are to converted to Fe(II) ions by antioxidants in the sample. The assay media has to be made fresh for best results. The first day of the lab, students worked with one of three standard solutions made up of gallic acid, ascorbic acid, and Trolox. They did both the FRAP and Folin-Ciocalteu with a series of dilutions. In this way, the student became familiar with making serial dilutions, performing the assay technique, and making Beer’s Law plots. We did the volume measurements in 4 mL square cuvettes with graduated plastic pipettes. The students entered their results on a spreadsheet before leaving the lab. The students also ran a sample of unknown concentration, which is typical for these Beer’s Law labs. The student compiled data from the three standards was compared. The data for gallic acid looked the most consistent over the two class sections.

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One Comment

  1. Posted May 31, 2010 at 9:20 am | Permalink

    Very cool experiment for your students!


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