LaMotte SMART Spectro Spectrophotometer - Manual (Page 84)

IODINE
Like chlorine and bromine, iodine is an effective germicidal agent employed in
drinking water treatment, pool and spa water sanitation, food service
sanitation, and other public health applications.
APPLICATION: Drinking, surface, and saline waters; swimming pool water;
domestic and industrial wastes.
RANGE: 0.00–14.00 ppm Iodine
METHOD: In a buffered sample iodine reacts with
diethyl-p-phenylene-diamine (DPD) to produce a pink-red
color in proportion to the concentration of iodine present.
SAMPLE
HANDLING &
PRESERVATION: Iodine in aqueous solutions is not stable, and the iodine
content of samples or solutions, particularly weak solutions,
will rapidly decrease. Exposure to sunlight or agitation will
accelerate the reduction of iodine present in such solutions.
For best results start analysis immediately after sampling.
Samples to be analyzed for iodine 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 iodine present so that the degree of
interference can be measured.
Chlorine and bromine can give a positive interference, but
these are not normally present unless they have been added
as sanitizers.
SMART SPECTRO TEST PROCEDURES 04.08 Chlorine–Bromine–Iodine 7/8