PASCO EZ-2339 Chlorine ezSample - Manual (Page 2)

® 2
012-10113C
Test Method Description
The ezSample test method employs the DPD chemistry. 1 Free chlorine oxidizes DPD (N,N-diethyl-p-
phenylenediamine) to form a pink colored species in direct proportion to the chlorine concentration. Total chlorine, the
sum of free and combined chlorine, is determined by adding an excess of potassium iodide to the sample. Chloramines
(combined chlorine) oxidize the iodide to iodine. The iodine then oxidizes DPD to the pink colored species. Results are
expressed in ppm (mg/Liter) Cl
2 . Halogens, ozone and halogenating agents will produce high test results. Chlorine,
at >500 ppm may prevent color development .
Accuracy and practical detection limit (PDL)
The lower limit of the stated test range is the “Practical Detection Limit (PDL).” Accuracy may be compromised if test
results are outside of the test range. Test results obtained at or below the PDL should be further confirmed for best
accuracy.
References
1. APHA Standard Methods, 20th ed., p. 4-63, method 4500-CI G (1998)
2. EPA Methods for Chemical Analysis of Water and Wastes, method 330.5 (1983)