Chlorine, Total
© Hach Company, 2003. All rights reserved. Printed in the U.S.A. 3/04 1ed
Page 4 of 4 ChlorineTot_TNT_Other_DPD_Eng_Ody.fm
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4. Snap the neck off a HR Chlorine PourRite
®
Ampule Standard, 50-75 mg/L
Cl
2
.
5. Use the TenSette
®
Pipet to add 0.1 mL of standard to a 10-mL sample and mix
thoroughly.
6. Analyze the standard addition sample as described in the procedure above.
Accept each standard additions reading by touching
Read. Each addition
should reflect approximately 100% recovery.
See Section 3.2.2 Standard Additions on page 32 for more information.
Method Performance
Precision
Standard: 2.33 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.
Free or combined chlorine oxidizes iodide in the reagent to iodine. The iodine
and chlorine react with DPD (N,N-diethyl-p-phenylenediamine) to form a
magenta 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.
Test ‘N Tube™ DPD Total Chlorine Reagent........................................1 vial ............... 50/pkg...............21056-45
Required Standards
Chlorine Standard Solution, 2-mL PourRite
®
Ampule, 50–75 mg/L ......................... 20/pkg...............14268-20
Required Apparatus
Adapter, 16-mm Cell ................................................................................1 ....................... each....................59457-00
Program 95% Confidence Limits of Distribution
89 2.27–2.39 mg/L Cl
2
Portion of Curve ∆Abs ∆Concentration
Entire range 0.010 0.09 mg/L Cl
2
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