User Guide

14
HOW TO COLLECT THE SAMPLE
Free chlorine is a strong oxidizing agent and in natural wa-
ters reacts with various inorganic and organic compounds,
its decomposition being influenced by parameters like reac-
tant concentrations, pH, temperature, salinity and sunlight.
Combined chlorine (chloroamines) is more stable and per-
sistent in the environment.
For best results, the delay between sample collection and
analysis should be minimized.
Plastic sample containers have a high chlorine demand, thus
collect sample in glass bottles. If possible rinse the container
with a portion of the sample otherwise rinse with deionized
water.
Fill the bottle up to the rim and keep it tightly closed.
Avoid excess agitation and exposure to sunlight when sam-
pling.
If the back titration method is used for total chlorine determi-
nation, preserve the sample on site. Add 2.00 mL of 0.00564N
standard PAO solution and 1.0 mL pH 4 Acetate Buffer to a
clean dry glass container with at least 150 mL capacity. At
the sampling site, measure 100 mL of sample and carefully
transfer it to the sample container. Swirl to mix.
It is important that the entire contents of the sample container
be transferred to the beaker used in the titration. Rinse the
bottle a few times with a small amount of chlorine free water.