ASTM D3401-97(2006)
(Test Method)Standard Test Methods for Water in Halogenated Organic Solvents and Their Admixtures
Standard Test Methods for Water in Halogenated Organic Solvents and Their Admixtures
SIGNIFICANCE AND USE
High water concentrations can have a detrimental effect on many uses of halogenated solvents.
4.1.1 Water can cause corrosion and spotting when solvents are used for metal cleaning.
4.1.2 Water can reduce the shelf life of aerosol formulations.
4.1.3 Water can inhibit desired reactions when solvents are used in formulations.
SCOPE
1.1 These test methods describe the use of the Karl Fischer (KF) titration for determination of water in halogenated organic solvents and mixtures thereof. Water concentrations from 2 to 1000 ppm can be determined in these solvents. Two test methods are covered as follows:
1.1.1 Test Method A, Water Determination Using a Coulometric KF TitratorThe coulometric test method is known for its high degree of sensitivity (typically 10 g H 2O) and should be the test method of choice if water concentrations are typically below 50 ppm or if only small amounts of sample are available for water determinations. This test method requires the use of equipment specifically designed for coulometric titrations.
1.1.2 Test Method B, Water Determination Using a Volumetric KF TitratorThe volumetric test method is a more traditional approach to KF water determinations. Although titrators are specifically designed for KF volumetric determinations, many automatic titrators on the market can be adapted to perform KF titrations.
1.2 Either of these test methods can be used to determine typical water concentrations (15 to 500 ppm) found in halogenated solvents.
1.3 These test methods recommend the use of commercially available Karl Fischer titrators and reagents.
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. For specific precautionary statements, see Sections 11 and 15.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:D3401–97(Reapproved 2006)
Standard Test Methods for
Water in Halogenated Organic Solvents and Their
Admixtures
This standard is issued under the fixed designation D3401; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope 2. Referenced Documents
1.1 These test methods describe the use of the Karl Fischer 2.1 ASTM Standards:
(KF) titration for determination of water in halogenated or- E203 Test Method forWater UsingVolumetric Karl Fischer
ganicsolventsandmixturesthereof.Waterconcentrationsfrom Titration
2 to 1000 ppm can be determined in these solvents. Two test
3. Summary of Test Methods
methods are covered as follows:
3.1 In the Karl Fischer reaction, water will react with iodine
1.1.1 Test Method A, Water Determination Using a Coulo-
metricKFTitrator—The coulometric test method is known for in the presence of sulfur dioxide, alcohol, and an organic base
according to the following equation:
its high degree of sensitivity (typically < 10 µg H O) and
should be the test method of choice if water concentrations are
H O 1 I 1 SO 1 CH OH 1 3RN→ ~RNH!SO CH 1 2~RNH!I
2 2 2 3 4 3
typically below 50 ppm or if only small amounts of sample are
(1)
available for water determinations. This test method requires
the use of equipment specifically designed for coulometric
where RN = organic base.
titrations.
3.2 When the volumetric titration test method is used for
1.1.2 TestMethodB,WaterDeterminationUsingaVolumet-
this determination, the halogenated sample is added to a KF
ric KF Titrator—The volumetric test method is a more
solvent that usually consists of sulfur dioxide and an amine
traditional approach to KF water determinations. Although
dissolved in anhydrous methanol. This solution is titrated with
titrators are specifically designed for KF volumetric determi-
an anhydrous solvent containing iodine. The iodine titrant is
nations, many automatic titrators on the market can be adapted
first standardized by titrating a known amount of water.
to perform KF titrations.
3.3 In the coulometric titration test method, the sample is
1.2 Either of these test methods can be used to determine
injected into an electrolytic cell where the iodine required for
typical water concentrations (15 to 500 ppm) found in haloge-
the reaction with water is produced by anodic oxidation of
nated solvents.
iodide. With this technique, no standardization of reagents is
1.3 These test methods recommend the use of commercially
required.
available Karl Fischer titrators and reagents.
3.4 In both test methods, the end point is determined
1.4 This standard does not purport to address all of the
amperometrically with a platinum electrode that senses a sharp
safety concerns, if any, associated with its use. It is the
change in cell resistance when the iodine has reacted with all
responsibility of the user of this standard to establish appro-
of the water in the sample.
priate safety and health practices and determine the applica-
4. Significance and Use
bility of regulatory limitations prior to use. For specific
precautionary statements, see Sections 11 and 15.
4.1 High water concentrations can have a detrimental effect
on many uses of halogenated solvents.
These test methods are under the jurisdiction of ASTM Committee D26 on
Halogenated Organic Solvents and Fire Extinguishing Agents and are the direct
responsibility of Subcommittee D26.04 on Test Methods. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved June 1, 2006. Published June 2006. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1975. Last previous edition approved in 2001 as D3401 – 97(2001). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/D3401-97R06. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D3401–97 (2006)
equipment. Pyridine-free reagents are said to be less toxic, less odorous,
4.1.1 Water can cause corrosion and spotting when solvents
and more stable than pyridine types.
are used for metal cleaning.
4.1.2 Water can reduce the shelf life of aerosol formula-
8. Sampling
tions.
4.1.3 Water can inhibit desired reactions when solvents are 8.1 Since halogenated solvents normally contain low con-
centrations of water, care must be taken to eliminate the
used in formulations.
introduction of water from sampling equipment and atmo-
5. Interferences spheric moisture.
8.2 Without taking the proper sampling precautions, more
5.1 Certain compounds or classes of compounds interfere
error is typically introduced into the determination of water
with the accurate determination of water by the Karl Fischer
through sampling techniques than in the titration process itself.
test method. They include aldehydes, ketones, free halogens,
8.3 Dry sample bottles and closures in an oven at 110°C for
ferric salts, and strong oxidizing and reducing agents.
several hours. Place caps on the bottles immediately after
5.2 Free halogens can oxidize the iodate in the KF reagents
removing from the oven.
to form iodine; this causes erroneously low water values.
5.3 A more detailed discussion of KF interferences can be 8.4 Transfer solvent to the bottles as quickly as possible.
3,4
Adjust the liquid level to come within 1 in. of the top of the
found in Test Method E203 and other sources.
bottle. Immediately place the cap on the bottle and tighten.
6. Apparatus
8.5 When removing a portion of sample from the bottle for
KF analysis, use pipets or syringes that have been thoroughly
6.1 Coulometric Titrator, (for Test Method A only) con-
dried. Replace the cap on the bottle immediately.
sisting of a single or dual bath electrolytic cell, dual platinum
8.6 If more than one portion of sample is to be taken from
electrode, magnetic stirrer, and control unit.
the bottle or if the sample is to be retained for further water
6.2 Volumetric Titrator, (for Test Method B only) consist-
analysis, it is a good practice to blanket the top of the bottle
ing of a titration cell, dual platinum electrode, magnetic stirrer,
with dry nitrogen when removing the sample. If septum cap
dispensing buret, and control unit.
closures are being used, dry nitrogen can be introduced with a
6.3 Syringes, 2, 5, 10, or 20-mL sizes.
syringe at the same time a portion of the sample is being
6.4 Syringe, 5-µL size.
removed with a second syringe.
6.5 Silicon Rubber Blocks or Silicon Rubber Septa.
6.6 Drying Oven, air circulating.
TEST METHOD A—WATER DETERMINATION
6.7 Desiccator.
USING A COULOMETRIC KF TITRATOR
6.8 Analytical Balance, capable of weighing to 60.01 g.
7. Reagents 9. Summary of Test Method
7.1 Anode Reagent, for dual bath titration (for Test Method
9.1 The dual bath coulometric titration cell consists of a
Aonly), use reagent recommended by manufacturer of titrator.
sealed vessel containing both an anode and cathode compart-
7.2 Cathode Reagent, for dual bath titration (for Test ment. The anodic compartment usually contains a solution
MethodAonly), use reagent recommended by manufacturer of
consisting of sulfur dioxide, iodide, and an amine in a
titrator. methanol/chloroform solvent. The cathodic compartment con-
7.3 Single Bath Reagent, (for Test Method A only), use
tains similar reagents optimized for cathodic reduction.
reagent recommended by manufacturer of titrator.
9.2 When a sample containing water is injected into the
7.4 Karl Fischer Volumetric Titrant, (for Test Method B
anode compartment, the electrolytic cell generates its own
only)typicallyconsistsofamixtureofanorganicamine,sulfur
supply of iodine from the iodide present. The iodine reacts
dioxide, and iodine dissolved in a non-hydroscopic solvent(s).
stoichiometrically with the water and the completion of the
Reagents with titers of 1.00, 2.00, and 5.00 mg of H O/mLcan
reaction is detected with a platinum sensing electrode. The
be commercially obtained.
coulombs of electricity required to generate the necessary
7.5 Karl Fischer Solvent, (for Test Method B only)
amountofiodineisthentranslatedbythemicroprocessorinthe
typically consists of a mixture of an organic amine and sulfur
control unit into the amount of water that was present in the
dioxide dissolved in anhydrous methanol.
sample.
9.3 The single bath coulometric titration cell consists of a
NOTE 1—Pyridine was the organic amine that was traditionally used in
sealed vessel filled with single bath reagent and dual platinum
Karl Fisher reagents, however, pyridine-free formulations are now avail-
ableandpreferredbymostKFinstrumentmanufacturersforusewiththeir electrodes.When a sample containing water is injected into the
vessel, the electrolytic cell generates its own supply of iodine
from the iodide present in the single bath reagent. The iodine
3 reacts stoichiometrically with the water and the completion of
Mitchell, J., Jr. and Smith, D. M., Aquametry—A Treatise on Methods for the
the reaction is detected by a platinum sensing electrode. The
Determination of Water, Part III—The Karl Fischer Reagent, 2nd ed., J. Wiley and
Sons, Inc., New York, NY, 1977.
coulombs of electricity required to generate the necessary
Hydranal—Eugen Scholz Reagents for Karl Fischer Titration, 4th ed., by
amounts of iodine is then translated by the microprocessor in
Riedel-deHaen Aktiengesellschaft (US Distributor—Cresent Chemical Co., Inc.).
thecontrolunitintotheamountofwaterthatwaspresentinthe
Automatic coulometric and volumetric titrators are manufactured by many
different companies. sample.
D3401–97 (2006)
TABLE 1 Recommended Sample Amount for Coulometric
10. Verification of Instrument Accuracy
Titration
10.1 Coulometric titrators do not have a titrant that needs to
Water Content, ppm Sample Weight, g
be standardized since the iodine is being generated on demand
1000 0.5
by the titration cell. However, occasional checks of the
500 0.5
instrument accuracy are recommended. This can be done by
100 1.0
50 2.0
titrating a known amount of water and comparing this amount
10 5.0
with the amount of water reported by the titrator.
10.2 Use a 5-µL syringe to inject exactly 3.0 µL of water
into the titration cell. Once the titration is complete, the titrator
should report a value of 3000 µg (3.0 mg) H O. The deviation
from this value should not be larger than 10 %. If the value is
12.5 Fill the syringe to the desired level with sample and
larger than 10 %, consult the instrument manual or manufac-
draw back the plunger so that no sample remains in the needle.
turer to determine the cause.
12.6 Cover the syringe needle with a silicone rubber block
10.3 Alternatively, standard solutions containing known
or piece of silicone rubber septa to further prevent evaporation
amounts of water dissolved in either methanol or a non-
or spillage during the weighing process.
hydroscopic solvent are available from reagent suppliers for
12.7 Transfer the filled syringe to an analytical balance and
accuracy verification. A known volume of this solution is
weigh the syringe and contents to the nearest 0.01 g.
titrated and the reported amount of water is compared with the
12.8 Remove the silicone block and insert the needle into
theoretical amount stated by the supplier.
the titration cell septum. Inject the sample slowly, taking care
11. Precautions
not to touch the needle to the surface of the anode solution.
11.1 Amounts of coulomatic reagents usually recommended
While the syringe is still inside the cell, draw any remaining
for addition to the reaction cell typically have the capacity to
sample that may remain in the syringe needle back into the
react with approximately 100 to 200 mg of water. These
barrel and remove the needle from the cell.
reagents must be replaced when they are depleted.
12.9 Place the silicone block back onto the tip of the needle
11.2 Coulomatic reagents are hydroscopic and must be
and reweigh the empty syringe.The weight difference between
stored in tightly capped containers to reduce the absorption of
the first and second weighings will be the amount of sample
atmospheric moisture.
injected into the titration cell.
11.3 Since the titrator automatically generates iodine to
12.10 The make and model of the titrator being used will
keep the reaction vessel in a dehydrated state, it is important to
determine the actual steps performed to carry out the titration
keep the cell sealed to prevent introduction of excess atmo-
process. In most cases, all that is required is pressing a start
spheric moisture that will decrease reagent life.
titrationorrunkeyontheinstrumentkeyboardeitherjustprior
11.4 The total amount of solution in the anode compartment
to or just after the sample injection.
can affect the KF reaction. Typically, the total volume of
12.11 Once the titration is complete, the amount of water
sample liquids that are added to the reaction cell should not
(µg or mg) that was found in the solvent will appear on the
exceed 50 % of the original reagent in the compartment. If the
instrument’s digital display. Most instruments will also calcu-
reagents become too dilute, the stoichiometry and rate of the
late concentrations (ppm or %) if the sample weight is keyed
Karl Fischer reaction can be adversely affected. This fact
into the instrument’s control panel.
should be considered when using large sample sizes.
11.5 Follow the recommended maintenance procedures of
13. Calculation
the instrument manufacturer.
13.1 Calculate the water content of the solvent as follows:
12. Procedure
ppm H O 5 µg H O found/grams of solvent injected (2)
2 2
12.1 Set up the coulometric titrator according to the manu-
facturer’s instructions, and add the proper amount of coulomat
reagentstotheanodeandcathodecompartmentsofthetitration
TEST METHOD B—WATER DETERMINATION
cell.
USING A VOLUMETRIC KF TITRATOR
12.2 The cell solutions must be anhydrous prior to introduc-
tion of the sample. This is accomplished by either pretitrating
14. Summary of Test Method
the cell contents or by adding a small amount of an iodine/
methanol solution until a faint brownish coloration appears. 14.1 The volumetric titration cell consists of a sealed glass
Following the procedure recommended by the instrument vessel containing a dual platinum electrode. To the cell, a
manufacturer is suggested. suitable solvent (usually methanol based) is added.T
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