Hach DR2400 - Page 174

Chlorine, Free
© Hach Company, 2003. All rights reserved. Printed in the U.S.A. 3/04 1ed
Page 4 of 4 ChlorineFre_MP_High_DPD_Eng_2400.fm
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6. Analyze each 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 for more information.
Method Performance
Precision
Standard: 5.6 mg/L Cl
2
See Section 3.4.3 Precision for more information, or if the standard concentration
did not fall within the specified range.
Sensitivity
See Section 3.4.5 Sensitivity for more information.
Summary of Method
The range of analysis using the DPD method for free chlorine can be extended by
adding more indicator in proportion to sample volume. Thus, a larger fill
powder pillow of DPD Free Chlorine Reagent is added to a 5-mL
sample portion.
Chlorine in the sample as hypochlorous acid or hypochlorite ion (free chlorine or
free available chlorine) immediately reacts with DPD (N,
N-diethyl-p-phenylenediamine) indicator to form a magenta color which is
proportional to the chlorine concentration.
Required Reagents
Quantity Required
Description Per Test Unit Cat. No.
DPD Free Chlorine Reagent Powder Pillows.......................................1 pillow........... 100/pkg.............14070-99
Required Apparatus
Adapter, multi-pathlength cell ...............................................................1 ....................... each....................59466-00
Cell, sample, multi-pathlength ...............................................................2 ....................... 6/pkg.................59405-06
Required Standards
Chlorine Standard Solution, 2-mL PourRite
®
Ampules, 50–75 mg/L ....................... 20/pkg...............14268-20
Program 95% Confidence Limits of Distribution
88 5.5–5.7 mg/L
Portion of Curve ∆Abs ∆Concentration
Entire range 0.010 0.1 mg/L Cl
2