These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Spectrophotometric determination of sulfur dioxide in air, using thymol blue.
    Author: Gayathri N, Balasubramanian N.
    Journal: J AOAC Int; 2001; 84(4):1065-9. PubMed ID: 11501906.
    Abstract:
    A simple and sensitive spectrophotometric method was developed for the determination of trace amounts of sulfur dioxide. The method is based on the reaction of SO2 with a known excess of ICI as the oxidant. The unreacted ICI iodinates thymol blue under acidic conditions. The lambdamax of thymol blue is at 545 nm under acidic conditions, and on lodination lambdamax shifts to 430 nm. This shift results in a decrease in the absorbance at 545 nm. The amount of uniodinated thymol blue present depends on the concentration of unreacted ICI, which in turn depends on the SO2 concentration. The system obeys Beer's law in the range 0-30 microg SO2 in a final volume of 25 mL, having a molar absorptivity of 3.2 x 10(4) L/mol cm with a relative standard deviation (RSD) of 2% at 24 microg SO2 (n = 10). The uniodinated dye can be extracted into 5 mL isoamyl alcohol under acidic conditions for measurement of absorbance. The extraction method obeys Beer's law in the range 0-5 microg SO2, having a molar absorpitivity of 4.16 x 10(4) L/mol x cm with an RSD of 1.9% at 4 microg SO2 (n = 10). The method has been successfully applied to the determination of atmospheric SO2.
    [Abstract] [Full Text] [Related] [New Search]