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Chlorine, Total
Sample Collection, Storage and Preservation
Accuracy Check
Chlorine, Total
Page 4 of 6
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 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 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.
Do not use the same sample cells for free and total chlorine. If trace iodide from
the total chlorine reagent is carried over into the free chlorine determination,
monochloramine will interfere. It is best to use separate, dedicated sample cells
for free and total chlorine determinations.
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 headspace (air) above the sample. If
sampling with a sample cell, rinse the cell several times with the sample, the
carefully fill to the 10-mL mark. Perform the chlorine analysis immediately.
Standard Additions Method (Sample Spike)
1. After reading test results, leave the sample cell (unspiked sample) in the
instrument.
2. Touch
. Touch
Options
average chlorine concentration shown on the certificate enclosed with the
Chlorine Voluette® Ampules. Touch
3. A summary of the Standard Additions procedure will appear. Touch
accept the values for standard concentration, sample volume, and spike
volumes as shown. Touch
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
25–30 mg/L Cl
.
2
5. Prepare three sample spikes. Fill three mixing cylinders (Cat. No. 1896-40)
with 10 mL of sample. Use the TenSette
0.3 mL of standard, respectively to three 10-mL samples and mix each
thoroughly.
®
Note: For AccuVac
Ampuls, fill three mixing cylinders (Cat. No. 1896-41) with 50-mL of sample
and spike with 0.4 mL, 0.8 mL, and 1.2 mL of standard. Transfer 40 mL from each of the
three mixing cylinders to three 50-mL beakers (Cat. No. 500-41H). Analyze each standard
addition sample as described in the procedure above. Accept each standard additions
reading by touching Read. Each addition should reflect approximately 100% recovery.
6. Analyze each sample spike as described in the procedure above, starting with
the 0.1 mL sample spike. Accept each standard additions reading by touching
. Each addition should reflect approximately 100% recovery.
Read
. A keypad will appear. Enter the
Standard Additions
.
OK
to change these values. After values are
Edit
®
Ampule Standard,
®
Pipet to add 0.1 mL, 0.2 mL and
OK
ChlorineTot_AVPP_Other_DPD_Eng_Ody.fm
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