Iodine – LaMotte DC1600 Colorimeter User Manual
Page 21
IODINE
APPLICATION:
Drinking, surface, saline waters; swimming pool water; domestic and industrial wastes.
RANGE:
0 - 15.0 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 chlorine 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 disinfectants.
PROCEDURE
1.
Rinse a clean colorimeter tube (0967) with sample water. Fill tube to the 10 mL line with sample.
2.
Select setting 4 on “Select Wavelength” knob and press “30 Second Read” button.
3.
Insert tube into colorimeter chamber and adjust to 100%T with “Set Blank” knob. This is the 100%T blank.
4.
Remove tube from colorimeter. Pour off all but a sufficient amount of sample water to cover a tablet. Add one *DPD
#1 Instrument Grade Tablet (6903). Crush tablet with tablet crusher (0175). Add sample water until tube is filled to
10 mL line. Cap and shake until tablet dissolves. Solution will turn pink if iodine is present.
5.
Press “30 Second Read” button and insert tube into colorimeter chamber. Record %T as soon as reading stabilizes.
6.
Consult calibration chart to determine iodine concentration in parts per million (ppm).
DC1600 IODINE CALIBRATION CHART
%T
9
8
7
6
5
4
3
2
1
0
90
0.13
0.17
0.21
0.25
0.29
0.32
0.36
0.40
0.44
0.49
80
0.53
0.57
0.61
0.66
0.70
0.75
0.79
0.84
0.88
0.93
70
0.98
1.03
1.08
1.13
1.18
1.23
1.29
1.34
1.39
1.45
60
1.51
1.56
1.62
1.68
1.74
1.81
1.87
1.93
2.00
2.07
50
2.13
2.20
2.28
2.35
2.42
2.50
2.58
2.66
2.74
2.82
40
2.91
2.99
3.08
3.17
3.27
3.36
3.46
3.57
3.67
3.78
30
3.89
4.01
4.12
4.25
4.37
4.50
4.64
4.78
4.92
5.08
20
5.23
5.40
5.57
5.74
5.93
6.13
6.33
6.55
6.78
7.02
10
7.27
7.54
7.83
8.14
8.47
8.83
9.22
9.65
10.12
10.64
0
11.23
11.89
12.66
13.56
14.65
21