LaMotte SMART3 Colorimeter - Manual (Page 114)

APPLICATION: Drinking, surface, and saline waters; swimming pool
water; domestic and industrial wastes.
RANGE: 0.00–4.00 ppm Chlorine
MDL: 0.03 ppm
METHOD: In the absence of iodide, free available chlorine reacts
instantly with DPD to produce a red color. Subsequent
addition of potassium iodide evokes a rapid color
response from the combined forms of chlorine
(chloramines).
SAMPLE HANDLING
& PRESERVATION:
Chlorine in aqueous solutions is not stable, and the
chlorine content of samples or solutions, particularly weak
solutions, will rapidly decrease. Exposure to sunlight
or agitation will accelerate the reduction of chlorine
present in such solutions. For best results, start analysis
immediately after sampling. Samples to be analyzed for
chlorine cannot be preserved or stored.
INTERFERENCE: The only interfering substance likely to be encountered
in water is oxidized manganese. The extent of this
interference can be determined by treating a sample with
sodium arsenite to destroy the chlorine present so that
the degree of interference can be measured.
Iodine and bromine can give a positive interference, but
these are not normally present unless they have been
added as sanitizers.
CHLORINE, DPD Liquid SMART3 Test Procedures 11.10
Test P
rocedures