ASTM D3401-97(2012)
(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.
Water can cause corrosion and spotting when solvents are used for metal cleaning.
Water can reduce the shelf life of aerosol formulations.
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 Titrator—The coulometric test method is known for its high degree of sensitivity (typically 10 μg H2O) 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 Titrator—The 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.
1.4 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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D3401 − 97 (Reapproved 2012)
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
2.1 ASTM Standards:
1.1 These test methods describe the use of the Karl Fischer
E203 Test Method for Water Using Volumetric Karl Fischer
(KF) titration for determination of water in halogenated or-
Titration
ganicsolventsandmixturesthereof.Waterconcentrationsfrom
2 to 1000 ppm can be determined in these solvents. Two test
3. Summary of Test Methods
methods are covered as follows:
1.1.1 Test Method A, Water Determination Using a Coulo-
3.1 In the Karl Fischer reaction, water will react with iodine
metricKFTitrator—The coulometric test method is known for in the presence of sulfur dioxide, alcohol, and an organic base
its high degree of sensitivity (typically < 10 µg H O) and according to the following equation:
should be the test method of choice if water concentrations are
H O1I 1SO 1CH OH13RN→~RNH!SO CH 12~RNH!I (1)
2 2 2 3 4 3
typically below 50 ppm or if only small amounts of sample are
where RN = organic base.
available for water determinations. This test method requires
the use of equipment specifically designed for coulometric
3.2 When the volumetric titration test method is used for
titrations.
this determination, the halogenated sample is added to a KF
1.1.2 TestMethodB,WaterDeterminationUsingaVolumet-
solvent that usually consists of sulfur dioxide and an amine
ric KF Titrator—The volumetric test method is a more tradi- dissolved in anhydrous methanol. This solution is titrated with
tional approach to KF water determinations.Although titrators an anhydrous solvent containing iodine. The iodine titrant is
first standardized by titrating a known amount of water.
are specifically designed for KF volumetric determinations,
many automatic titrators on the market can be adapted to
3.3 In the coulometric titration test method, the sample is
perform KF titrations.
injected into an electrolytic cell where the iodine required for
the reaction with water is produced by anodic oxidation of
1.2 Either of these test methods can be used to determine
iodide. With this technique, no standardization of reagents is
typical water concentrations (15 to 500 ppm) found in haloge-
required.
nated solvents.
3.4 In both test methods, the end point is determined
1.3 These test methods recommend the use of commercially
amperometrically with a platinum electrode that senses a sharp
available Karl Fischer titrators and reagents.
change in cell resistance when the iodine has reacted with all
1.4 This standard does not purport to address all of the
of the water in the sample.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
4. Significance and Use
priate safety and health practices and determine the applica-
4.1 High water concentrations can have a detrimental effect
bility of regulatory limitations prior to use. For specific
on many uses of halogenated solvents.
precautionary statements, see Sections 11 and 15.
4.1.1 Water can cause corrosion and spotting when solvents
are used for metal cleaning.
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 March 1, 2012. Published June 2012. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1975. Last previous edition approved in 2006 as D3401 – 97(2006). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/D3401-97R12. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D3401 − 97 (2012)
ableandpreferredbymostKFinstrumentmanufacturersforusewiththeir
4.1.2 Water can reduce the shelf life of aerosol formula-
equipment. Pyridine-free reagents are said to be less toxic, less odorous,
tions.
and more stable than pyridine types.
4.1.3 Water can inhibit desired reactions when solvents are
used in formulations.
8. Sampling
5. Interferences
8.1 Since halogenated solvents normally contain low con-
centrations of water, care must be taken to eliminate the
5.1 Certain compounds or classes of compounds interfere
introduction of water from sampling equipment and atmo-
with the accurate determination of water by the Karl Fischer
spheric moisture.
test method. They include aldehydes, ketones, free halogens,
ferric salts, and strong oxidizing and reducing agents.
8.2 Without taking the proper sampling precautions, more
5.2 Free halogens can oxidize the iodate in the KF reagents error is typically introduced into the determination of water
through sampling techniques than in the titration process itself.
to form iodine; this causes erroneously low water values.
5.3 A more detailed discussion of KF interferences can be 8.3 Dry sample bottles and closures in an oven at 110°C for
3,4
found in Test Method E203 and other sources. several hours. Place caps on the bottles immediately after
removing from the oven.
6. Apparatus
8.4 Transfer solvent to the bottles as quickly as possible.
6.1 Coulometric Titrator, (for Test Method A only) con-
Adjust the liquid level to come within 1 in. of the top of the
sisting of a single or dual bath electrolytic cell, dual platinum
bottle. Immediately place the cap on the bottle and tighten.
electrode, magnetic stirrer, and control unit.
8.5 When removing a portion of sample from the bottle for
6.2 Volumetric Titrator, (for Test Method B only) consist-
KF analysis, use pipets or syringes that have been thoroughly
ing of a titration cell, dual platinum electrode, magnetic stirrer,
dried. Replace the cap on the bottle immediately.
dispensing buret, and control unit.
8.6 If more than one portion of sample is to be taken from
6.3 Syringes, 2, 5, 10, or 20-mL sizes.
the bottle or if the sample is to be retained for further water
6.4 Syringe, 5-µL size.
analysis, it is a good practice to blanket the top of the bottle
with dry nitrogen when removing the sample. If septum cap
6.5 Silicon Rubber Blocks or Silicon Rubber Septa.
closures are being used, dry nitrogen can be introduced with a
6.6 Drying Oven, air circulating.
syringe at the same time a portion of the sample is being
6.7 Desiccator.
removed with a second syringe.
6.8 Analytical Balance, capable of weighing to 60.01 g.
TEST METHOD A—WATER DETERMINATION
USING A COULOMETRIC KF TITRATOR
7. Reagents
7.1 Anode Reagent, for dual bath titration (for Test Method
9. Summary of Test Method
Aonly), use reagent recommended by manufacturer of titrator.
9.1 The dual bath coulometric titration cell consists of a
7.2 Cathode Reagent, for dual bath titration (for Test
sealed vessel containing both an anode and cathode compart-
MethodAonly), use reagent recommended by manufacturer of
ment. The anodic compartment usually contains a solution
titrator.
consisting of sulfur dioxide, iodide, and an amine in a
7.3 Single Bath Reagent, (for Test Method A only), use
methanol/chloroform solvent. The cathodic compartment con-
reagent recommended by manufacturer of titrator.
tains similar reagents optimized for cathodic reduction.
7.4 Karl Fischer Volumetric Titrant, (for Test Method B
9.2 When a sample containing water is injected into the
only)typicallyconsistsofamixtureofanorganicamine,sulfur
anode compartment, the electrolytic cell generates its own
dioxide, and iodine dissolved in a non-hydroscopic solvent(s).
supply of iodine from the iodide present. The iodine reacts
Reagents with titers of 1.00, 2.00, and 5.00 mg of H O/mLcan
2 stoichiometrically with the water and the completion of the
be commercially obtained.
reaction is detected with a platinum sensing electrode. The
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.
NOTE 1—Pyridine was the organic amine that was traditionally used in
Karl Fisher reagents, however, pyridine-free formulations are now avail- 9.3 The single bath coulometric titration cell consists of a
sealed vessel filled with single bath reagent and dual platinum
electrodes.When a sample containing water is injected into the
Mitchell, J., Jr. and Smith, D. M., Aquametry—A Treatise on Methods for the
vessel, the electrolytic cell generates its own supply of iodine
Determination of Water, Part III—The Karl Fischer Reagent, 2nd ed., J. Wiley and
Sons, Inc., New York, NY, 1977.
from the iodide present in the single bath reagent. The iodine
Hydranal—Eugen Scholz Reagents for Karl Fischer Titration, 4th ed., by
reacts stoichiometrically with the water and the completion of
Riedel-deHaen Aktiengesellschaft (US Distributor—Cresent Chemical Co., Inc.).
the reaction is detected by a platinum sensing electrode. The
Automatic coulometric and volumetric titrators are manufactured by many
differentcompanies. coulombs of electricity required to generate the necessary
D3401 − 97 (2012)
amounts of iodine is then translated by the microprocessor in Following the procedure recommended by the instrument
thecontrolunitintotheamountofwaterthatwaspresentinthe manufacturer is suggested.
sample.
12.3 The amount of halogenated solvent that is injected into
the cell depends on the quantity of water in the solvent. Table
10. Verification of Instrument Accuracy
1 lists recommended sample sizes for anticipated water con-
10.1 Coulometric titrators do not have a titrant that needs to centrations.
be standardized since the iodine is being generated on demand
12.4 Thoroughly clean and dry the sampling syringe. One
by the titration cell. However, occasional checks of the
method is to dry it in an oven and desiccate before use.
instrument accuracy are recommended. This can be done by
12.5 Fill the syringe to the desired level with sample and
titrating a known amount of water and comparing this amount
draw back the plunger so that no sample remains in the needle.
with the amount of water reported by the titrator.
12.6 Cover the syringe needle with a silicone rubber block
10.2 Use a 5-µL syringe to inject exactly 3.0 µL of water
or piece of silicone rubber septa to further prevent evaporation
into the titration cell. Once the titration is complete, the titrator
or spillage during the weighing process.
should report a value of 3000 µg (3.0 mg) H O. The deviation
12.7 Transfer the filled syringe to an analytical balance and
from this value should not be larger than 10 %. If the value is
larger than 10 %, consult the instrument manual or manufac- weigh the syringe and contents to the nearest 0.01 g.
turer to determine the cause.
12.8 Remove the silicone block and insert the needle into
the titration cell septum. Inject the sample slowly, taking care
10.3 Alternatively, standard solutions containing known
not to touch the needle to the surface of the anode solution.
amounts of water dissolved in either methanol or a non-
While the syringe is still inside the cell, draw any remaining
hydroscopic solvent are available from reagent suppliers for
sample that may remain in the syringe needle back into the
accuracy verification. A known volume of this solution is
titrated and the reported amount of water is compared with the barrel and remove the needle from the cell.
theoretical amount stated by the supplier.
12.9 Place the silicone block back onto the tip of the needle
and reweigh the empty syringe.The weight difference between
11. Precautions
the first and second weighings will be the amount of sample
injected into the titration cell.
11.1 Amounts of coulomatic reagents usually recommended
for addition to the reaction cell typically have the capacity to
12.10 The make and model of the titrator being used will
react with approximately 100 to 200 mg of water. These
determine the actual steps performed to carry out the titration
reagents must be replaced when they are depleted.
process. In most cases, all that is required is pressing a start
titrationorrunkeyontheinstrumentkeyboardeitherjustprior
11.2 Coulomatic reagents are hydroscopic and must be
to or just after the sample injection.
stored in tightly capped containers to reduce the absorption of
atmospheric moisture.
12.11 Once the titration is complete, the amount of water
(µg or mg) that was found in the solvent will appear on the
11.3 Since the titrator automatically generates iodine to
instrument’s digital display. Most instruments will also calcu-
keep the reaction vessel in a dehydrated state, it is important to
late concentrations (ppm or %) if the sample weight is keyed
keep the cell sealed to prevent introduction of excess atmo-
into the instrument’s control panel.
spheric moisture that will decrease reagent life.
11.4 The total amount of solution in the anode compartment 13. Calculation
can affect the KF reaction. Typically, the total volume of
13.1 Calculate the water content of the solvent as follows:
sample liquids that are added to the reaction cell should not
ppm H O 5 µgH O found/grams of solvent injected (2)
2 2
exceed 50 % of the original reagent in the compartment. If the
reagents become too dilute, the stoichiometry and rate of the
Karl Fischer reaction can be adversely affected. This fact
TEST METHOD B—WATER DETERMINATION
should be considered when using large sample sizes.
USING A VOLUMETRIC KF TITRATOR
11.5 Follow the recommended maintenance procedures of
14. Summary of Test Method
the instrument manufacturer.
14.1 The volumetric titration cell consists of a sealed glass
vessel containing a dual platinum electrode. To the cell, a
12. Procedure
12.1 Set up the coulometric titrator according to the manu- TABLE 1 Recommended Sample Amount for Coulometric
Titration
facturer’s instructions, and add the proper amount of coulomat
Water Content, ppm Sample Weight, g
reagentstotheanodeandcathodecompartmentsofthetitration
1000 0.5
cell.
500 0.5
12.2 The cell
...
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