Hach DR2400 - Page 149

Chlorine Dioxide
Chlorine Dioxide
ChlorineDio_None_High_DRM_Eng_Ody.fm Page 3 of 4
demand by soaking in a dilute bleach solution (1 mL commercial bleach to l liter
of deionized water) for at least one hour. Rinse thoroughly with deionized or
distilled water. If sample containers are rinsed thoroughly with deionized or
distilled water after use, only occasional pretreatment is necessary.
A common error in testing for chlorine dioxide is not obtaining a representative
sample. If sampling from a tap, let the water flow for at least 5 minutes to ensure
a representative sample. Let the container overflow with the sample several
times, then cap the sample containers so there is no headspace (air) above the
sample. If sampling with a sample cell, rinse the cell several times with the
sample, then carefully fill to the 10-mL mark. Perform the chlorine dioxide
analysis immediately.
Accuracy Check
Standard Solution Method
Preparing chlorine dioxide standards is difficult and dangerous. In addition,
these standards are both explosive and volatile! Only a trained chemist should
prepare the standards using appropriate safety equipment and precautions.
Hach does not recommend preparation of chlorine dioxide standards. If
independent standard preparation is required, please see the instructions in
Standard Methods for the Examination of Water and Wastewater, 20th ed., under the
headings “Stock chlorine dioxide solution” and “Standard chlorine dioxide
solution” (pp 4–74 and 4–75). Prepare a 500-mg/L chlorine dioxide standard.
Method Performance
Precision
Standard: 500 mg/L ClO
2
See Section 3.4.3 Precision on page 44 for more information, or if the standard
concentration did not fall within the specified range.
Sensitivity
See Section 3.4.5 Sensitivity on page 44 for more information.
Summary of Method
Chlorine dioxide, a yellow gas, can be measured directly in a water solution. Test
results are measured at 445 nm.
Required Reagents
Description Quantity Required Per Test Unit Cat. No
Water, deionized .......................................................................................10 mL .............. 4 liters....................272-56
Required Apparatus
Sample Cells, 10-mL, w/cap...................................................................2 ....................... 6/pkg.................24276-06
Program 95% Confidence Limits of Distribution
75 499–501 mg/L ClO
2
Portion of Curve ∆Abs ∆Concentration
Entire range 0.010 5 mg/L ClO
2