Hach DR2400 - Page 189

Chlorine, Total
Chlorine, Total
ChlorineTot_AVPP_Other_DPD_Eng_Ody.fm Page 5 of 6
7. After completing the sequence, touch Graph to view the best-fit line through
the standard additions data points, accounting for matrix interferences. Touch
View: Fit, then select Ideal Line and touch OK to view the relationship between
the sample spikes and the “Ideal Line” of 100% recovery.
See Section 3.2.2 Standard Additions on page 32 for more information.
Method Performance
Precision
Standard: 1.07 mg/L Cl
2
See Section 3.4.3 Precision on page 44 for more information, or if the standard
concentration did not fall within the specified range.
Sensitivity
See Section 3.4.5 Sensitivity on page 44 for more information.
Summary of Method
Chlorine can be present in water as free chlorine and as combined chlorine. Both
forms can exist in the same water and be determined together as the total
chlorine. Free chlorine is present as hypochlorous acid or hypochlorite ion.
Combined chlorine exists as monochloramine, dichloramine, nitrogen
trichloride and other chloro derivatives. The combined chlorine oxidizes iodide
in the reagent to iodine. The iodine and free chlorine reacts with DPD
(N,N-diethyl-p-phenylenediamine) to form a red color which is proportional to
the total chlorine concentration. To determine the concentration of combined
chlorine, run a free chlorine test. Subtract the results of the free chlorine test from
the total chlorine test to obtain the combined chlorine concentration. Test results
are measured at 530 nm.
Required Reagents
Quantity Required
Description per test Unit Cat. No.
DPD Total Chlorine Reagent AccuVac
®
Ampuls ..........................1 ampul........... 25/pkg...............25030-25
or DPD Total Chlorine Reagent Powder Pillows, 10-mL ..................1 pillow........... 100/pkg.............21056-69
Water, deionized ................................................................................................................. 4 liters ....................272-56
Required Apparatus
Beaker, 50-mL............................................................................................1 ....................... each.................... 500-41H
Sample Cells, 10-mL, w/cap...................................................................2 ....................... 6/pkg.................24276-06
Required Standards
Chlorine Standard Solution, 2-mL Voluette
®
Ampule, 20–30 mg/L .......................... 20/pkg...............26300-20
Program 95% Confidence Limits of Distribution
80 1.05–1.09 mg/L Cl
2
85 1.03–1.11 mg/L Cl
2
Program Portion of Curve ∆Abs ∆Concentration
80 Entire range 0.010 0.02 mg/L Cl
2
85 Entire range 0.010 0.02 mg/L Cl
2