Nitrogen, Free Ammonia, 10201
Nitrogen, Free Ammonia DOC316.53.01084
Indophenol Method1 Method 10201
(0.01 to 0.50 mg/L NH3–N) Powder Pillows
Scope and Application: For controlling free ammonia levels during the production of chloramines, at booster
stations and for monitoring free ammonia levels in potable distribution system waters.
1 U.S. Patent 6,315,950
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 Program Sample Cell Cell Orientation Adapter
DR 5000 261 4864302 1-cm path facing user A23618
DR 2800 261 5940506 1-cm path in line with adapter arrow LZV585 (B)
DR 2700 261 5940506 1-cm path in line with adapter arrow LZV585 (B)
Before starting the test:
Use Method 10200, Nitrogen, Free Ammonia and Chloramine (Mono) to determine free ammonia and monochloramine
simultaneously on the same sample.
In bright light conditions (e.g. direct sunlight) it may be necessary to close the DR 2800 cell compartment with the protective
cover during measurements.
Description Quantity
Free Ammonia Reagent Set —
Free Ammonia Reagent Solution 1 drop
Monochlor F Reagent Pillows 2
Sample Cell (see Instrument-specific information) 2
See Consumables and replacement items for reorder information.
Nitrogen, Free Ammonia
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Nitrogen, Free Ammonia
Indophenol method for powder pillows
Stored Programs
388 N, Ammonia Free
Start
1. Select the test. 2. Fill two cells to the 3. Prepared Sample: 4. Cap the reagent bottle
Insert an adapter if 10-mL line with sample. Add one drop of Free to maintain reagent
required (see Instrument- Label one cell ‘sample’ Ammonia Reagent performance and stability.
specific information). and one cell ‘blank’. Solution to the sample.
Refer to the user manual
for orientation.
5. Cap and invert the 6. Start the instrument 7. When the timer 8. Cap and shake both
sample to mix. timer. expires, add the contents cells about 20 seconds to
If the sample becomes A 5-minute reaction period of one MonoChlor F dissolve the reagent.
cloudy by the end of the will begin. powder pillow to each cell. A green color will develop
reaction period, pretreat Color development time if monochloramine is
the sample and retest. See depends on sample present.
Interferences. temperature. For accurate
results allow the full
reaction period to occur.
See Color development
based on sample
temperature.
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Nitrogen, Free Ammonia
Indophenol method for powder pillows (continued)
Zero
9. Start the instrument 10. When the timer 11. ZERO the instrument. 12. Insert the sample into
timer. expires, insert the vial into The display will show: 0.00 the cell holder.
A 5-minute reaction period the cell holder. mg/L NH3–N f
will begin. Remove the blank.
Color development time
depends on sample
temperature. For accurate
results allow the full
reaction period to occur.
See Color development
based on sample
temperature.
Read
13. READ the results in
mg/L NH3–N f.
Interferences
This method is intended for finished, chloraminated drinking water samples that have a
measurable combined (total) chlorine disinfectant residual. Samples where the disinfectant
residual has disappeared and samples which exhibit a chlorine demand may produce low
ammonia test results. Blanks and ammonia standards analyzed without a disinfectant residual
must be prepared using high quality, reagent grade water.
The following do not interfere in the free ammonia determination at or below the stated
concentration.
Table 2 Interfering substances
Interfering substance Interference level
Aluminum 0.2 mg/L
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Nitrogen, Free Ammonia
Table 2 Interfering substances (continued)
Interfering substance Interference level
Chloride 1200 mg/L Cl-
Copper 1 mg/L Cu
Iron 0.3 mg/L Fe
Manganese 0.05 mg/L Mn
Nitrate 10 mg/L NO3–N
Nitrite 1 mg/L NO2–N
Phosphate 2 mg/L o–PO4
Silica 100 mg/L SiO2
Sulfate 1600 ppm as CaCO3
Zinc 5 ppm Zn
Samples containing high levels of both Total Hardness and Alkalinity may become cloudy after the
addition of the Free Ammonia Reagent Solution. If this occurs by the end of the first reaction
period, the sample for Free Ammonia measurement must be pretreated as follows:
Note: The blank does not need pretreatment.
1. Measure 10 mL of sample into the cell for the labeled sample.
2. Add the contents of one Hardness Treatment Reagent Powder Pillow to the sample.
3. Cap the cell and invert until the reagent is dissolved.
4. Remove the cap.
5. Continue with the analysis at step 2 using the pretreated sample as the sample cell.
Color development time
Test results are strongly influenced by sample temperature. Both reaction periods in the
procedure are the same and depend on the temperature of the sample. The reaction periods
indicated in the procedure are for a sample temperature of 18–20 °C (64–68 °F). Adjust both
reaction periods (see Color development based on sample temperature).
Table 3 Color development based on sample temperature
Sample Temperature
Development Time (minutes)
°C °F
5 41 10
7 45 9
9 47 8
10 50 8
12 54 7
14 57 7
16 61 6
18 64 5
20 68 5
23 73 2.5
25 77 2
greater than 25 greater than 77 2
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Nitrogen, Free Ammonia
Sample collection, preservation and storage
Collect samples in clean glass bottles. Most reliable results are obtained when samples are
analyzed as soon as possible after collection.
Accuracy check
Dilution water is required when testing a diluted sample and preparing standard solutions. Dilution
water must be free of ammonia, chlorine and chlorine demand. A convenient source is a
recirculating, deionizer system with carbon filtration which produces 18 megohm-cm water.
Standard additions method (sample spike)
Required for accuracy check:
• Ammonium Nitrogen Standard, 10 mg/L as NH3-N
• Ampule breaker
• TenSette Pipet and Pipet Tips
• Mixing cylinders, 50 mL (3)
1. After reading test results, leave the sample cell (unspiked sample) in the instrument.
2. Select standard additions from the instrument menu:
Instrument Navigate to:
DR 5000 OPTIONS>MORE>STANDARD ADDITIONS
DR 2800 OPTIONS>MORE>STANDARD ADDITIONS
DR 2700 OPTIONS>MORE>STANDARD ADDITIONS
3. Accept the default values for standard concentration, sample volume and spike volumes. After
the values are accepted, the unspiked sample reading will appear in the top row. See the user
manual for more information.
4. Open the standard solution.
5. Use the TenSette Pipet to prepare spiked samples: add 0.3 mL, 0.6 mL and 1.0 mL of
standard to three 50-mL portions of fresh sample.
6. Follow the Indophenol method for powder pillows test procedure for each of the spiked
samples, starting with the 0.3 mL sample spike. Measure each of the spiked samples in the
instrument.
7. Select GRAPH to view the results. Select IDEAL LINE (or best-fit) to compare the standard
addition results to the theoretical 100% recovery.
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Nitrogen, Free Ammonia
Standard solution method
Note: Refer to the instrument user manual for specific software navigation instructions.
Required for accuracy check:
• Ammonia Nitrogen Standard Solution, 10 mg/L NH3–N
• Deionized water
• Volumetric Pipet, 2 mL or Tensette Pipet and Pipet tips, 100 mL
• Volumetric flask, 100 mL
1. Prepare a 0.20 mg/L ammonia nitrogen standard solution as follows:
• Dilute 2.00 mL of Ammonia Nitrogen Standard Solution, 10 mg/L to 100 mL with deionized
water.
• Or, use the TenSette Pipet to dilute 0.4 mL of a Ammonia Nitrogen Voluette Standard
Solution, 50 mg/L as NH3–N, to 100 mL with dilution water.
2. Use this solution in place of the sample. Follow the Indophenol method for powder pillows test
procedure.
3. To adjust the calibration curve using the reading obtained with the standard solution, navigate
to Standard Adjust in the software.
Instrument Navigate to:
DR 5000 OPTIONS>MORE>STANDARD ADJUST
DR 2800 OPTIONS>MORE>STANDARD ADJUST
DR 2700 OPTIONS>MORE>STANDARD ADJUST
4. Turn on the Standard Adjust feature and accept the displayed concentration. If an alternate
concentration is used, enter the concentration and adjust the curve to that value.
Method performance
Precision—95% Confidence Sensitivity—ΔConcentration
Program Instrument Standard
Limits of Distribution per 0.010 ΔAbs
DR 5000 0.20 mg/L NH3–N 0.19–0.21 mg/L NH3–N 0.01 NH3–N
388 DR 2800 0.20 mg/L NH3–N 0.19–0.21 mg/L NH3–N 0.01 NH3–N
DR 2700 0.20 mg/L NH3–N 0.19–0.21 mg/L NH3–N 0.01 NH3–N
Summary of method
Monochloramine (NH2Cl) and free ammonia (NH3 and NH4+) can exist in the same water sample.
Added hypochlorite combines with free ammonia to form more monochloramine. In the presence
of a cyanoferrate catalyst, monochloramine in the sample reacts with a substituted phenol to form
an intermediate monoimine compound. The intermediate couples with excess substituted phenol
to form a green-colored indophenol, which is proportional to the amount of monochloramine
present in the sample. Free ammonia is determined by comparing the color intensities, with and
without added hypochlorite. Test results are measured at 655 nm.
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Nitrogen, Free Ammonia
Consumables and replacement items
Required reagents
Description Quantity/Test Unit Catalog number
Free Ammonia Reagent Set (50 tests), includes: — — 2879700
(1) 2802299, (1) 2877336
Free Ammonia Reagent Solution 1 drop 4 mL SCDB 2877336
Monochlor F Reagent Pillows 2 100/pkg 2802299
Recommended standards
Description Unit Catalog number
Hardness Treatment Reagent Pillows (1 per test) 50/pkg 2882346
Nitrogen Ammonia Standard Solution, 10 mg/L as NH3–N 500 mL 15349
Nitrogen Ammonia Standard Ampule, 50 mg/L as NH3–N, 10 mL 16/pkg 1479110
Water, organic-free water 500-mL 2641549
Optional reagents and apparatus
Description Unit Catalog number
Ampule Breaker Kit each 2196800
Flask, volumetric, Class A, 100 mL each 1457442
Pipet Filler, Safety Bulb each 1465100
Pipet, TenSette®, 0.1 to 1.0 mL each 1970001
Pipet Tips, for TenSette Pipet 1970001 50/pkg 2185696
Thermometer, –10 to 110 °C each 187701
Wipers, Disposable Kimwipes®, 30 x 30 cm, 280/box box 2097000
Pipe, Volumetric, 2 mL each 1451536
Cylinder, graduated mixing, 50 mL each 189641
Nitrogen, Free Ammonia
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On the Worldwide Web – www.hach.com; E-mail – techhelp@hach.com FAX: (970) 669-2932
© Hach Company, 2007. All rights reserved. Printed in the U.S.A. Updated February 2008, Edition 5
