Chlorine, Total
Chlorine, Total
ChlorineTot_PT2_ULow_DPD_Eng_Ody.fm Page 7 of 10
Sample Collection, Storage and Preservation
Analyze samples for chlorine immediately after collection. Free chlorine is a
strong oxidizing agent and it is unstable in natural waters. It reacts rapidly with
various inorganic compounds and more slowly oxidizes organic compounds.
Many factors, including reactant concentrations, sunlight, pH, temperature and
salinity influence decomposition of 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 l 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.
A common error in testing for chlorine 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 head space (air) above the sample.
Perform the chlorine analysis immediately.
Treating Analysis Labware
Glassware used in this test must be chlorine demand-free. Treat all glassware
with a dilute solution of chlorine bleach prepared by adding 0.5 mL of
commercial bleach to 1 liter of water. Soak glassware in this solution at least one
hour. After soaking, rinse the glassware thoroughly with deionized water and
allow to dry before use.
Treat the Pour-Thru Cell similarly with dilute bleach and let stand for several
minutes and then rinse several times with deionized water.
Cleaning the Pour-Thru Cell
The Pour-Thru Cell may accumulate a buildup of colored reaction products,
especially if the reacted solutions are allowed to remain in the cell for long
periods after measurement. Remove the buildup by rinsing the cell with 5.25 N
Sulfuric Acid (Cat. No. 2449-53) followed by several rinsings with
deionized water.
Accuracy Check
Standard Additions Method (Sample Spike)
1. After reading test results, leave the sample cell (unspiked sample) in
the instrument.
2. Touch
Options. Touch Standard Additions. A keypad will appear. Enter the
average chlorine concentration shown on the certificate enclosed with the
Chlorine Voluette® Ampules. Touch
OK.
3. A summary of the Standard Additions procedure will appear. Touch
OK to
accept the values for standard concentration, sample volume, and spike
volumes as shown. Touch
Edit to change these values. After values are
accepted, the unspiked sample reading will appear in the top row. See
Standard Additions in the instrument manual for more information.
4. Snap the neck off a LR Chlorine Voluette
®
Ampule Standard,
20–30 mg/L Cl
2
.
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