COMPARATIVE ANALYTICAL METHODS FOR THE MEASURMENT OF CHLORINE DIOXIDE
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
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.
Advisor:Dr. Robert C Hoehn; Dr.Marc Edwards; Dr. Andrea M Dietrich; Dr. John C Little
School:Virginia Polytechnic Institute and State University
School Location:USA - Virginia
Source Type:Master's Thesis
Date of Publication:07/30/2002