Title page for ETD etd-07242002-111511

Type of Document Master's Thesis
Author Desai, Unmesh Jeetendra
Author's Email Address udesai@vt.edu
URN etd-07242002-111511
Title Comparative Analytical Methods for the Measurment of Chlorine Dioxide
Degree Master of Science
Department Environmental Engineering
Advisory Committee
Advisor Name Title
Dietrich, Andrea M. Committee Co-Chair
Hoehn, Robert C. Committee Co-Chair
Edwards, Marc A. Committee Member
Little, John C. Committee Member
  • Analytical Methods
  • Chlorate
  • Chlorite
  • Chlorine Dioxide
Date of Defense 2002-06-10
Availability unrestricted
Four commercially available methods used for the analysis of low-level Chlorine Dioxide (ClO2) concentrations in drinking water were evaluated for accuracy and precision and ranked according to cost, efficiency and ease of the methods under several conditions that might be encountered at water treatment plants.

The different analytical methods included:

1.The DPD (N, N-diethyl-p-phenylenediamine) method

2.Lissamine Green B (LGB) wet-chemical method

3.Palintest® kit LGB

4.Amperometric titration

All these tests were performed with standard 1.0 mg/L ClO2 either alone or in the presence of different chlorine species, including chlorite ion (ClO2-, 0.5 mg/L), chlorate ion (ClO3-, 0.5 mg/L) and chlorine (Cl2, 1.0 mg/L). The tests were performed with four different matrices, with different concentrations of 0.1 mg/L ClO2, 0.5 mg/L ClO2 and 1.0 mg/L ClO2 at a constant temperature of 20oC and at different temperatures of 0oC, 10oC and 20oC at a fixed ClO2 concentration of 1.0 mg/L.

None of the four methods produced the desired level of either accuracy or precision. For all four methods, interference to the measured ClO2 concentration from the addition of ClO2-, ClO3-, and Cl2 was minimal when the methods were performed according to specifications. The Palintest® was the best all-round method because it was easy to perform, performed well at all concentrations tested, and its colored product was stable. The HACH® DPD method was also easy to perform and gave the best results when measuring concentrations of 1.0 mg/L ClO2.

The DPD method was less accurate than the Palintest® at lower concentrations. The DPD colored product that formed upon reaction of ClO2 and DPD was unstable, making it necessary to measure the intensity of the colored product at exactly 1 minute. The amperometric titration and lissamine green methods were more cumbersome and time-consuming to perform than either the DPD or Palintest® methods; for this reason they are less desirable for routine use.

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