Chlorine, Total
Chlorine, Total
ChlorineTot_MP_High_DPD_Eng_2400.fm Page 3 of 4
Sampling and Storage
Analyze samples for chlorine immediately after collection. Free and combined
chlorine are strong oxidizing agents and react rapidly with various compounds.
Many factors such as sunlight, pH, temperature and sample composition will
influence decomposition of free chlorine in water.
Avoid plastic containers since these may have a large chlorine demand. Pretreat
glass sample containers to remove any chlorine demand by soaking in a dilute
bleach solution (1 mL commercial bleach to 1 liter of deionized water) for at least
1 hour. Rinse thoroughly with deionized or distilled water. If sample containers
are rinsed thoroughly with deionized or distilled water after use, only occasional
pre-treatment is necessary.
Do not use the same sample cells for free and total chlorine. If trace iodide from
the total chlorine reagent is carried over to the free chlorine test,
monochloramine could interfere. It is best to use separate, dedicated sample cells
for free and total chlorine determinations.
A common error in testing for chlorine is 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 container 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 5-mL mark. Proceed with the chlorine test immediately.
Method Performance
Precision
Standard: 5.6 mg/L Cl
2
See Section 3.4.3 Precision for more information, or if the standard concentration
did not fall within the specified range.
Sensitivity
See Section 3.4.5 Sensitivity for more information.
Use Method 8167 to test chlorine concentrations at levels typically less than
2 mg/L or Method 8370 to test chlorine concentrations at levels typically less
than 500 µg/L. For more information on determining precision data and method
detection limits, refer to Section 3.4 Method Performance.
Program 95% Confidence Limits of Distribution
88 5.5–5.7 mg/L Cl
2
Portion of Curve ∆Abs ∆Concentration
Entire range 0.010 0.1 mg/L Cl
2
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