Instructions for HACH Free and Total Chlorine Analysis

Chlorine, Free and Total, TNTplus, 10231 and 10232
Chlorine, Free and Total TNTplus
DOC316.53.01248
DPD Method 1
Free Chlorine: Method 10231
(0.05 to 2.00 mg/L Cl 2 ) Total Chlorine: Method 10232
Scope and Application: For drinking water, wastewater and pool water. TNTplus 866/866T
1 Adapted from Standard Methods for the Examination of Water and Wastewater.
Test preparation
How to use instrument-specific information
The Instrument-specific information table displays requirements that may vary between
instruments. To use this table, select an instrument then read across to find the corresponding
information required to perform this test.
Table 1 Instrument-specific information
Instrument Light shield Adapter
DR 5000 — —
DR 2800 LZV646 —
Before starting the test:
DR 2800: Install the light shield in Cell Compartment #2.
Read the safety information and expiration date on the package label.
Analyze samples immediately. Do not preserve samples for later analysis.
Color or turbidity in the sample can cause incorrect results. To correct for color or turbidity, measure a Sample blank.
Perform this test at 15–25 °C (59–77 °F) and store reagents at 2–8 °C (35–46 °F) for best results.
The recommended sample pH is 3–10.
To sequentially measure free and total chlorine, measure free chlorine and then complete steps 2–4 and 6 of the total
chlorine procedure.
Potassium iodide Solution A for total chlorine is included with the TNT866T reagent set but is not packaged inside the box.
A Zero vial is included in the TNT866 reagent set. The same vial is used to zero the instrument for the entire lot of reagents.
TNTplus methods are activated from the Main Menu when a vial is inserted into the sample cell holder.
Collect the following items:
Description
Quantity
Light Shield (see Instrument-specific information) 1
Chlorine TNT866 Reagent Set 1
Potassium iodide Solution A (for total chlorine only) 1
Beaker, 50 mL 1
Disposable wipes 1
See Consumables and replacement items for reorder information.
Chlorine, Free and Total TNTplus
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Chlorine, Free and Total TNTplus
Free Chlorine TNTplus method
1. Insert the Zero vial
into the sample cell holder.
The instrument reads the
barcode, then selects the
method and sets the
instrument to zero. The
instrument shows L1 when
zeroing is complete.
2. Fill the sample vial
with sample to the neck of
the vial.
3. Cap the vial and
carefully invert it 2 or 3
times while rotating to
remove any air bubbles
from the sides of the vial.
Do not shake.
4. Within one minute of
adding the sample, wipe
the sample vial and insert
it into the cell holder.
Results are in mg/L Cl 2 .
Total Chlorine TNTplus method
1. Fill the sample vial
with sample to the neck of
the vial.
2. Immediately add 3
drops of potassium iodide
Solution A.
3. Cap the vial and
carefully invert it 2 or 3
times while rotating to
remove any air bubbles
from the sides of the vial.
Do not shake.
4. Wait 3 minutes.
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Chlorine, Free and Total TNTplus
Total Chlorine TNTplus method (continued)
5. Insert the Zero vial
into the sample cell holder.
The instrument reads the
barcode, then selects the
method and sets the
instrument to zero. The
instrument shows L1 when
zeroing is complete.
6. After the timer expires,
wipe the sample vial and
insert it into the cell holder.
Results are in mg/L Cl 2 .
Interferences
Table 2 Interfering substances and levels
Interfering substance
Color
Interference levels and treatments
Can cause high results. To make a correction for the interference, measure a Sample blank.
All oxidizing agents, e.g. ozone, iodine, chlorine dioxide, manganese dioxide and chromate
react with the indicator and are included in the results.
Oxidizing agents
If a large excess of oxidizing agents is present, some or all of the indicator changes to a
colorless form. The test result will appear to be negative or within the range of the test.
pH The sample pH should be between pH 3 and pH 10.
Turbidity
Can cause high results. To make a correction for the interference, measure a Sample blank.
Sample blank
If the sample has color or turbidity, measure a sample blank to correct the test result for the
interference.
Required:
• TNTplus 919 sample blank vial
Procedure
1. Complete the test procedure for free or total chlorine.
2. Fill a TNTplus 919 sample blank vial with sample to the neck of the vial.
3. Wipe the vial and insert it into the cell holder. The instrument will read the barcode of the
sample blank vial and subtract the value from the original test result.
Chlorine, Free and Total TNTplus
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Chlorine, Free and Total TNTplus
Sample collection, preservation and storage
Accuracy check
• Analyze samples for chlorine immediately after collection. Free chlorine is a strong oxidizing
agent and it is unstable in natural waters. It reacts rapidly with various inorganic compounds
and more slowly oxidizes organic compounds. Many factors, including reactant
concentrations, sunlight, pH, temperature and salinity influence decomposition of free chlorine
in water.
• Avoid plastic containers since these may have a large chlorine demand.
• Pretreat glass sample containers to remove any chlorine demand by soaking in a dilute bleach
solution (1 mL commercial bleach to 1 liter of deionized water) for at least 1 hour. Rinse
thoroughly with deionized or distilled water. If sample containers are rinsed thoroughly with
deionized or distilled water after use, only occasional pre-treatment is necessary.
• A common error in testing for chlorine is not obtaining a representative sample. If sampling
from a tap, let the water flow for at least 5 minutes to ensure a representative sample. Let the
container overflow with the sample several times, then cap the sample containers so there is
no headspace (air) above the sample. Perform the chlorine test immediately.
To validate the method, use a standard solution in place of the sample. The standard solution must
be prepared by dilution.
Required for accuracy check * :
• Chlorine Standard Solution Ampule, 50–75 mg/L Cl 2 (exact concentration shown on label)
• Ampule breaker
• Volumetric Flask, 100-mL glass
• Pipet, variable volume
• Pipet tip
• Deionized water
Standard solution method
1. Add approximately 50 mL of deionized water into a clean 100-mL volumetric flask.
2. Open a chlorine standard solution ampule, 50–75 mg/L Cl 2 .
3. Use a pipet to add 2.0 mL of the standard solution into the flask.
4. Dilute to the 100-mL mark with deionized water. Stopper and invert several times to mix.
5. Follow the test procedure to measure the concentration of the diluted standard.
6. Find the expected concentration of the diluted standard solution from the following equation:
( C 1
)( V 1
) = ( C 2
)( V 2
)
where C = concentration and V = volume
* See Optional reagents and apparatus.
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Chlorine, Free and Total TNTplus
Example: The concentration that is shown on the chlorine ampules package is 65.0 mg/L Cl 2 .
The expected concentration of the diluted standard is:
C 1 = concentration of standard solution ampule as printed on the package = 65.0 mg/L
V 1 = volume of standard solution before dilution = 2 mL (step 3)
C 2 = concentration after dilution = expected concentration
V 2 = final volume of the diluted standard = 100 mL (step 4)
( 65.0 mg/L) ( 2.0 mL) = ( C 2
)( 100 mL)
C 2 = 1.3 mg/L Cl 2
Summary of method
The expected concentration of the diluted standard solution is 1.3 mg/L Cl 2 .
7. Compare the expected concentration to the measured concentration. Acceptable results are
typically within 10% of the expected.
Chlorine can exist in water as free chlorine and as combined chlorine. Both free and combined
chlorine can be measured together as total chlorine. Free chlorine exists as hypochlorous acid or
hypochlorite ion. Combined chlorine exists as monochloramine, dichloramine, nitrogen trichloride
and other chloro derivatives.
Combined chlorine oxidizes iodide in the reagent to iodine. The iodine and free chlorine react with
DPD (N,N-diethyl-p-phenylenediamine) to form a magenta color, which is proportional to the
chlorine concentration. Test results are measured at 515 nm.
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Chlorine, Free and Total TNTplus
Consumables and replacement items
Required reagents
Description Quantity/Test Unit Catalog number
Free Chlorine TNT 866 Reagent Set 1 39/pkg TNT866
Chlorine TNT 866T Reagent Set, total/sequential
Includes potassium iodide Solution A
1
1
39/pkg
each
TNT866T
TNT866A
Required apparatus
Description Unit Catalog number
Beaker, 50 mL glass each 50041H
Light Shield (DR2800) each LZV646
Wipes, disposable, 11 x 22 cm 280/pkg 2097000
Recommended standards and apparatus
Description Unit Catalog number
Chlorine Standard Solution, 50–75 mg/L, 2-mL PourRite ® Ampule 20/pkg 1426820
Chlorine Standard Solution, 50–75 mg/L, 10-mL Voluette ® Ampule 16/pkg 1426810
Chlorine Standard Solution, 25–30 mg/L, 2-mL PourRite ® Ampule 20/pkg 2630020
Ampule breaker, 10-mL Voluette each 2196800
Ampule breaker, 2-mL PourRite each 2484600
Water, deionized 4L 27256
Optional reagents and apparatus
Description Unit Catalog number
Flask, volumetric, Class A, glass, 100 mL, w/ stopper each 1457442
Pipet, variable volume, 1.0–5.0 mL each BBP065
Pipet Tips, for variable volume pipet 75/pkg BBP068
TNTplus 919 sample blank vials 5/pkg TNT919
FOR TECHNICAL ASSISTANCE, PRICE INFORMATION AND ORDERING:
In the U.S.A. – Call toll-free 800-227-4224
Outside the U.S.A. – Contact the HACH office or distributor serving you.
On the Worldwide Web – www.hach.com; E-mail – techhelp@hach.com
HACH COMPANY
WORLD HEADQUARTERS
Telephone: (970) 669-3050
FAX: (970) 669-2932
© Hach Company, 2008. All rights reserved. Printed in the U.S.A. Updated May 2008 Edition 1