ASTM D3590-02(2006)
(Test Method)Standard Test Methods for Total Kjeldahl Nitrogen in Water
Standard Test Methods for Total Kjeldahl Nitrogen in Water
SIGNIFICANCE AND USE
These test methods are useful for measuring organic nitrogen and ammoniacal nitrogen, which are essential growth nutrients.
Nitrogen compounds are widely distributed in the environment. Sources of nitrogen include surface-applied fertilizers, cleaning products, and drinking water treatment aids. Because nitrogen is a nutrient for photosynthetic organisms, it may be important to monitor and control discharge into the environment.
SCOPE
1.1 These test methods cover the determination of total Kjeldahl nitrogen. The following test methods are included:SectionsTest Method A-Manual Digestion/Distillation8 to 14Test Method B-Semiautomated Colorimetric Bertholt15 to 23
1.2 The analyst should be aware that precision and bias statements included may not necessarily apply to the water being tested.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:D3590–02 (Reapproved 2006)
Standard Test Methods for
Total Kjeldahl Nitrogen in Water
This standard is issued under the fixed designation D3590; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* which are converted to ammonium sulfate [(NH ) SO ] under
4 2 4
the specified digestion conditions.
1.1 These test methods cover the determination of total
Kjeldahl nitrogen. The following test methods are included:
4. Significance and Use
Sections
4.1 These test methods are useful for measuring organic
Test Method A—Manual Digestion/Distillation 8 to 14
Test Method B—Semiautomated Colorimetric Bertholt 15 to 23
nitrogen and ammoniacal nitrogen, which are essential growth
nutrients.
1.2 The analyst should be aware that precision and bias
4.2 Nitrogen compounds are widely distributed in the envi-
statements included may not necessarily apply to the water
ronment. Sources of nitrogen include surface-applied fertiliz-
being tested.
ers, cleaning products, and drinking water treatment aids.
1.3 This standard does not purport to address all of the
Because nitrogen is a nutrient for photosynthetic organisms, it
safety concerns, if any, associated with its use. It is the
may be important to monitor and control discharge into the
responsibility of the user of this standard to establish appro-
environment.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
5. Interferences
2. Referenced Documents 5.1 Nitrateisknowntocauseaseriousnegativeinterference
in the test. Reportedly, a concentration of 250 mg/L NO
2.1 ASTM Standards:
results in zero recovery of some level of N added as some N
D1129 Terminology Relating to Water
compound.
D1193 Specification for Reagent Water
5.2 The analyst is cautioned that ammonia in the laboratory
D1426 Test Methods for Ammonia Nitrogen In Water
may easily become an interference in these test methods from
D2777 Practice for Determination of Precision and Bias of
contamination of reagents, caps, or from the laboratory atmo-
Applicable Test Methods of Committee D19 on Water
sphere. Care should be taken that ammonium hydroxide, either
D3370 Practices for Sampling Water from Closed Conduits
as a reagent or as a cleaning substance, is not used in the same
D5810 Guide for Spiking into Aqueous Samples
room.
D5847 Practice for Writing Quality Control Specifications
for Standard Test Methods for Water Analysis
6. Purity of Reagents
3. Terminology 6.1 Reagent-grade chemicals shall be used in all tests.
Unless otherwise indicated, it is intended that all reagents shall
3.1 Definitions—For definitions of terms used in these test
conform to the specifications of the Committee on Analytical
methods, refer to Terminology D1129.
Reagents of the American Chemical Society, where such
3.2 Definitions of Terms Specific to This Standard:
specifications are available. Other grades may be used,
3.2.1 total Kjeldahl nitrogen—the sum of the nitrogen
provided it is first ascertained that the reagent is of sufficient
contained in the free ammonia and other nitrogen compounds
high purity to permit its use without lessening the accuracy of
the determination.
6.2 Purity of Water—Unless otherwise indicated, reference
These test methods are under the jurisdiction of ASTM Committee D19 on
Water and are the direct responsibility of Subcommittee D19.05 on Inorganic
towatershallbeunderstoodtomeanreagentwaterconforming
Constituents in Water.
Current edition approved Dec. 15, 2006. Published February 2007. Originally
approved in 1977. Last previous edition approved in 2002 as D3590 – 02. DOI: Reagent Chemicals, American Chemical Society Specifications, American
10.1520/D3590-02R06. Chemical Society, Washington, DC. For suggestions on the testing of reagents not
For referenced ASTM standards, visit the ASTM website, www.astm.org, or listed by the American Chemical Society, see Analar Standards for Laboratory
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
Standards volume information, refer to the standard’s Document Summary page on and National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,
the ASTM website. MD.
*A Summary of Changes section appears at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D3590–02 (2006)
to Specification D1193, Type I. Other reagent water types may 10.4 Electrometer (pH Meter), with expanded millivolt
be used provided it is first ascertained that the water is of scale, or a specific ion meter.
sufficiently high purity to permit its use without adversely 10.5 Ammonia Selective Electrode.
affecting the precision and bias of the test method. Type III 10.6 Magnet Stirrer, thermally insulated.
water was specified at the time of round-robin testing of this
11. Reagents and Materials
test method.
11.1 Ammonia Solution Stock, (1.0 mL = 1.0 mg ammonia
7. Sampling and Preservation
nitrogen)—Dissolve 3.819 g of ammonium chloride (NH Cl)
in water and dilute to 1 L in a volumetric flask with water.
7.1 Collect the sample in accordance with applicable Prac-
11.2 Ammonia Solution, Standard (1.0 mL = 0.01 mg am-
tices D3370.
monia nitrogen)—Dilute 10.0 mL of the stock solution (see
7.2 Samples may be preserved up to 28 days by adding
11.1) with water to 1 L in a volumetric flask.
concentrated sulfuric acid to adjust to pH 2 or less and storing
11.3 BoricAcid Solution (2 %)—Dissolve20gofboricacid
at 4°C. The preserved sample should be analyzed as soon as
(H BO ) in water and dilute to 1 L with water in a volumetric
possible; data on decomposition are not available. 3 3
flask.
TEST METHOD A—MANUAL DIGESTION/
11.4 Mercuric Sulfate Solution—Dissolve8gofredmer-
DISTILLATION
curic oxide (HgO) in a mixture of 10 mL of sulfuric acid
(H SO , sp gr 1.84) and 40 mLof water, and dilute solution to
2 4
8. Scope
100 mL.
8.1 This test method covers the determination of total
NOTE 1—Mercury is a toxic metal and requires special diposal require-
Kjeldahl nitrogen in water. It measures free ammonia or
ments. See Occupational Health and Safety Act (OSHA) regulations for
ammonia formed from the conversion of nitrogen components
specific instructions on handling and disposal of mercury compounds.
of biological origin such as amino acids and proteins. How-
Alternate catalysts may be used but it is the users responsibility to
ever, the procedure may not convert the nitrogenous com- determine the validity of other catalysts.
pounds of some wastes to ammonia. Examples of such com-
11.5 Mixed Indicator Solution—Mix 2 volumes of 0.2 %
pounds that may not be measured are nitro compounds,
methyl red in 95 % ethanol with 1 volume of 0.2 % methylene
hydrozones, oximes, nitrates, semicarbazones, pyridines, and
blue in ethanol. Prepare fresh every 30 days.
some refractory tertiary amines.
11.6 Methyl Purple Indicator Solution (1 g/L)—Dissolve
8.2 Three alternatives are described for the final determina-
0.4 g of dimethyl-aminoazobenzene-o-carboxylic acid, sodium
tion of the ammonia: a titrimetric method, which is applicable
salt, in approximately 300 mL of water. To this solution add
to concentrations above 1 mg N/L; a Nesslerization method, 6
0.55 g of a water-soluble blue dyestuff, Color Index No. 714,
which is applicable to concentrations below 1 mg N/L; and a
dissolve, and dilute to 1 L with water. This indicator is
potentiometric method which is applicable to the range from 7
available commercially in a prepared form.
0.04 to 1000 mg N/L.
11.7 Nessler Reagent—Dissolve 100 g of mercuric iodide
8.3 This test method is described for micro and macro
(HgI ) and 70 g of potassium iodide (KI) in a small volume of
systems. Micro determination can be made on sample aliquots
water. Add this mixture slowly, with stirring, to a cooled
containing up to 10 mg of nitrogen.
solution of 160 g of sodium hydroxide (NaOH) in 500 mL of
water. Dilute the mixture to 1 L. This solution is stable for at
9. Summary of Test Method
least one year if stored in a thick amber polyethylene bottle out
9.1 The sample is heated in the presence of concentrated
of direct sunlight.
H SO,K SO , and HgSO , and is digested until SO fumes
2 4 2 4 4 3
NOTE 2—Mercury is a toxic metal and requires special diposal require-
are obtained and the solution becomes colorless or pale yellow.
ments. See Occupational Health and Safety Act (OSHA) regulations for
The residue is cooled, diluted, and is treated and alkalized with
specific instructions on handling and disposal of mercury compounds.
a hydroxide-thiosulfate solution. The ammonia is distilled into
Alternate reagents may be used but it is the users responsibility to
a boric acid solution and total Kjeldahl nitrogen is determined
determine the validity of other reagents.
by colorimetry, titrimetry, or potentiometry.
11.8 Phenolphthalein Indicator Solution—Dissolve5gof
phenolphthalein in 500 mL of 95 % ethyl alcohol or isopro-
10. Apparatus
panol and add 500 mL of water.Add NaOH (0.8 g/L) solution
10.1 Digestion Apparatus—A Kjeldahl digestion apparatus
dropwise until a faint pink color appears.
with 800 to 100-mL flasks and suction takeoff to remove SO
fumes and water.
EIL Model 8002-2 of Electronics Instruments Ltd. (U. S. Representative:
10.2 Distillation Apparatus —Amacro Kjeldahl flask con-
Cambridge Instrument Co., 73 Spring St., Ossining, NY 10562) has been found
nected to a condenser and an adaptor so that the distillate can
satisfactory for this purpose. Also, Orion Model 95-12 has been found satisfactory
for this purpose.
be collected.
Refers to compounds, bearing such number, as described in “Color Index,”
10.3 Spectrophotometer or Colorimeter, for use at 425 nm
Society of Dyers and Colourists, Yorkshire, England (1924). American Cyanamid
with a spectral band path of not more than 6 20 nm and a light
Company’s “Calcocid Blux AX Double” has been found satisfactory for this
path of 1 cm or longer.
purpose.
TM Fleisher Methyl Purple indicator, U. S. Patent No. 241699, is available
from Fleisher Chemical Co., P. O. Box 616, Ben Franklin Station, Washington, DC
Micro Kjeldahl steam distillation apparatus is commercially available. 20004, or from any chemical supply company handling Fleisher Methyl Purple.
D3590–02 (2006)
11.9 Sodium Hydroxide Solution (400 g/L)—Dissolve 400 g 12.2.4 Connect the Kjeldahl flask to the condenser with the
ofNaOHin800mLofwater,cool,anddiluteto1Lwithwater. tip of the condenser (or an extension of the condenser tip)
11.10 Sodium Hydroxide Solution (0.8 g/L)—Dilute2mLof below the level of 50 mL of 2 % boric acid solution (see 11.3)
NaOH solution (400 g/L) (see 11.9) with water to 1 L. contained in a 500-mL Erlenmeyer flask. Distill 300 mL at the
11.11 Sodium Hydroxide-Sodium Thiosulfate Solution— rate of 6 to 10 mL/min.
Dissolve 500 g of NaOH and 25 g of Na S O ·5H O in water 12.2.5 Transfer the distillate to a 500-mL volumetric flask,
2 2 3 2
and dilute to 1 L.
dilute to volume with water, and mix. Transfer 250 mL to an
11.12 SulfuricAcid Solution, Standard (0.02 N, 1 mL = 0.28 Erlenmeyer flask and titrate with H SO (see 12.4.1). If the
2 4
mg ammonia nitrogen)—Prepare a stock solution of approxi-
concentrationisfoundtobebelow1mg/L,determinethevalue
mately 0.1 N acid by diluting 3 mL of concentrated H SO (sp colorimetrically. Use the remaining 250 mL for this determi-
2 4
gr 1.84) to 1 L with water. Dilute 200 mL of this solution to 1 nation.
L with water. Standardize the approximately 0.02 N H SO 12.3 Micro Kjeldahl System:
2 4
solution against 0.0200 N Na CO solution. This last solution
12.3.1 Place 50.0 mL of sample or an aliquot in a 100-mL
2 3
is prepared by dissolving 1.060 g of anhydrous Na CO , oven
Kjeldahl flask and add 10 mLof digestion solution (see 11.13).
2 3
dried at 140°C, and diluting to 1 L with water.
At the same time start a reagent blank. Evaporate the mixture
11.13 Digestion Solution—Dissolve 267 g of K SO in
in the Kjeldahl apparatus until SO fumes are given off and the
2 4
1300 mL water and 400 mL of concentrated H SO . Add 50
solution turns colorless or pale yellow. Digest for an additional
2 4
mL of mercuric sulfate solution (see 11.4) and dilute to 2 L
30 min. Cool the residue and add 30 mL of water.
with water. A digestion packet may be used in place of the
12.3.2 Alkalizethedigestatebycarefuladditionof10mLof
digestion solution in the macro Kjeldahl system.
sodium hydroxide-thiosulfate solution (see 11.11). Do not mix
until the digestion flask has been connected to the distillation
12. Procedure
apparatus (see Note 4).
12.1 Clean the distillation apparatus with steam before use 12.3.3 Connect the Kjeldahl flask to the condenser with the
tip of the condenser (or an extension of the condenser tip)
by distilling a 1 + 1 mixture of water and sodium hydroxide-
thiosulfate solution (see 11.11) until the distillate is ammonia- below the level of 5 mL of 2 % H BO solution (see 11.3)
3 3
contained in a small Erlenmeyer flask. Distill 30 mLat the rate
free. Repeat this operation each time the apparatus is out of
service long enough to accumulate ammonia (usually4hor of 6 to 10 mL/min.
more). 12.3.4 Transfer to a 50-mL volumetric flask, dilute to
12.2 Macro Kjeldahl System: volume with water, and mix. Pipet 25 mL to an Erlenmeyer
12.2.1 Place a measured sample into an 800-mL Kjeldahl flask and titrate with H SO (see 12.4.1). If the concentration
2 4
flask and dilute to 500 mL. The sample size can be determined is found to be below 1 mg/L determine the value colorimetri-
using the following table: cally. Use 20 mL of the remaining solution for this determina-
tion.
Kjeldahl Nitrogen in Sample,
mg/L Sample Size, mL
12.4 Determination of Ammonia Distillate—Determine the
0to5 500
ammonia content of the distillate titrimetrically, colorimetri-
5to10 250
10 to 20 100 cally, or potentiometrically.
20 to 50 50.0
12.4.1 Titrimetric Determination—Add 3 drops of the
50 to 500 25.0
mixed indicator (see 11.5) to the distillate and titrate the
Prepare a 500-mL reagent water blank.
ammonia with 0.02 N H SO (see 11.12), matching the end
2 4
12.2.2 Add 100 mL of digestion solution (see 11.13) (see
point against a blank containing the same volume of water and
Note 3) and digest the mixture in the Kjeldahl apparatus until
H BO solution (see 11.3). If a pH meter is preferred, titrate to
3 3
SO fumesaregi
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.