ASTM D6304-20

Standard Test Method for Determination of Water in Petroleum Products, Lubricating Oils, and Additives by Coulometric Karl Fischer Titration

SIGNIFICANCE AND USE
5.1 A knowledge of the water content is important in the manufacturing, purchase, sale, or transfer of petroleum products to help in predicting their quality and performance characteristics.  
5.2 The presence of moisture could lead to premature corrosion and wear, an increase in the debris load resulting in diminished lubrication and premature plugging of filters, an impedance in the effect of additives, and undesirable support of deleterious bacterial growth.
SCOPE
1.1 This test method covers the direct determination of entrained water in petroleum products and hydrocarbons using automated instrumentation. This test method also covers the indirect analysis of water thermally removed from samples and swept with dry inert gas into the Karl Fischer titration cell. Mercaptan, sulfide (S– or H2S), sulfur, and other compounds are known to interfere with this test method (see Section 6). The precision statement of this method covers the nominal range of 20 mg/kg to 25 000 mg/kg for Procedure A, 30 mg/kg to 2100 mg/kg for Procedure B, and 20 mg/kg to 360 mg/kg for Procedure C.  
1.2 This test method is intended for use with commercially available coulometric Karl Fischer reagents and for the determination of water in additives, lube oils, base oils, automatic transmission fluids, hydrocarbon solvents, and other petroleum products. By proper choice of the sample size, this test method may be used for the determination of water from mg/kg to percent level concentrations.  
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 30-Nov-2020
• ICS: 71.040.50 - Physicochemical methods of analysis
• ICS: 75.080 - Petroleum products in general
• ICS: 75.100 - Lubricants, industrial oils and related products
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.06 - Analysis of Liquid Fuels and Lubricants

Relations

• Refers: ASTM D6300-24 - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 01-Mar-2024
• Refers: ASTM E203-24 - Standard Test Method for Water Using Volumetric Karl Fischer Titration
• Effective Date: 01-Jan-2024
• Refers: ASTM E1064-24 - Standard Test Method for Water in Organic Liquids by Coulometric Karl Fischer Titration
• Effective Date: 01-Jan-2024
• Refers: ASTM D4175-23a - Standard Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 15-Dec-2023
• Refers: ASTM D6299-23a - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 01-Dec-2023
• Refers: ASTM D6300-23a - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 01-Dec-2023
• Refers: ASTM D4175-23e1 - Standard Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 01-Jul-2023
• Refers: ASTM D6300-19a - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products and Lubricants
• Effective Date: 01-Dec-2019
• Refers: ASTM D6299-17b - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 15-Dec-2017
• Refers: ASTM D6299-17a - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 15-Nov-2017
• Refers: ASTM D6299-17 - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 01-Jan-2017
• Refers: ASTM D6300-16 - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products and Lubricants
• Effective Date: 01-Apr-2016
• Refers: ASTM D6300-15 - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products and Lubricants
• Effective Date: 01-Jun-2015
• Refers: ASTM D6300-14ae1 - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products and Lubricants
• Effective Date: 01-Jun-2014
• Refers: ASTM D6300-14a - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products and Lubricants
• Effective Date: 01-Jun-2014

Overview

ASTM D6304-20 is the internationally recognized standard test method for determining water content in petroleum products, lubricating oils, and additives using coulometric Karl Fischer titration. Published by ASTM International, this standard ensures precise and reliable quantification of water, crucial for assessing product quality, performance, and stability. The presence of water in petroleum-based products can cause corrosion, degradation, and malfunction in mechanical systems, making accurate water measurement essential for manufacturers, suppliers, and end users.

Key Topics

• Water Determination: The standard offers both direct and indirect test procedures for measuring water in a wide range of petroleum products and hydrocarbons, including lubricating oils, base oils, additives, automatic transmission fluids, and hydrocarbon solvents.
• Test Range: Procedure A targets water concentrations from 20 mg/kg to 25,000 mg/kg, Procedure B from 30 mg/kg to 2,100 mg/kg, and Procedure C from 20 mg/kg to 360 mg/kg.
• Sample Types: Suitable for both low viscosity samples and more complex, viscous, or interfering matrices via water vaporization accessories.
• Interference Management: Highlights interference from compounds such as mercaptans, sulfides (S– or H₂S), and certain organometallic substances. The document provides best practices and references for minimizing bias or false results.

Applications

ASTM D6304-20 is valuable in various sectors where water presence in petroleum products impacts product quality and equipment reliability:

• Manufacturing and Blending: Accurate water determination supports the formulation of high-performance lubricating oils and fuel additives, ensuring product efficacy and stability.
• Quality Control in Refineries: Verification of water content before shipping, receiving, or transferring petroleum products helps prevent corrosion, filter plugging, and microbial contamination.
• Automotive and Industrial Maintenance: Routine monitoring of water in lubricating oils and transmission fluids extends machinery life and reduces maintenance costs.
• Research and Development: Essential for developing new oil formulations, fuel blends, and understanding water interaction with petroleum matrices.
• Regulatory Compliance: Enables adherence to industry, safety, and environmental standards that govern maximum allowable water content in fuels and oils.

Related Standards

For optimal laboratory practice and holistic petroleum product analysis, consider these related ASTM standards:

• ASTM D1193 - Specification for Reagent Water
• ASTM D1298 - Test Method for Density, Relative Density, or API Gravity by Hydrometer
• ASTM D4052 - Test Method for Density, Relative Density, and API Gravity by Digital Meter
• ASTM D4057 / D4177 - Practices for Manual/Automatic Sampling of Petroleum and Petroleum Products
• ASTM D5854 - Practice for Mixing and Handling Petroleum Samples
• ASTM D6299 - Practice for Statistical Quality Assurance
• ASTM E203 / E1064 - Karl Fischer Titration Methods for water in organic liquids
• ASTM D4175 - Terminology Relating to Petroleum Products

Practical Value

By implementing ASTM D6304-20, organizations benefit from:

• Accurate, Repeatable Water Content Measurement across a spectrum of petroleum products
• Reduced Risk of Equipment Failure from corrosion and wear related to excess moisture
• Enhanced Product Performance through improved process and quality control
• Support for Regulatory Compliance and Product Claims, building customer trust and reliability

Utilize ASTM D6304-20 to ensure robust, compliant, and high-quality operations within the petroleum and lubricants industry.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D6304 − 20
Standard Test Method for
Determination of Water in Petroleum Products, Lubricating
Oils, and Additives by Coulometric Karl Fischer Titration
This standard is issued under the fixed designation D6304; 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 U.S. Department of Defense.
1. Scope* 2. Referenced Documents
1.1 This test method covers the direct determination of 2.1 ASTM Standards:
entrained water in petroleum products and hydrocarbons using D1193 Specification for Reagent Water
automated instrumentation. This test method also covers the D1298 Test Method for Density, Relative Density, or API
indirect analysis of water thermally removed from samples and Gravity of Crude Petroleum and Liquid Petroleum Prod-
swept with dry inert gas into the Karl Fischer titration cell. ucts by Hydrometer Method
–
Mercaptan, sulfide (S or H S), sulfur, and other compounds D4052 Test Method for Density, Relative Density, and API
are known to interfere with this test method (see Section 6). Gravity of Liquids by Digital Density Meter
The precision statement of this method covers the nominal D4057 Practice for Manual Sampling of Petroleum and
rangeof20 mg⁄kgto25 000mg/kgforProcedureA,30 mg⁄kg Petroleum Products
to 2100 mg⁄kg for Procedure B, and 20 mg⁄kg to 360 mg⁄kg D4175 Terminology Relating to Petroleum Products, Liquid
for Procedure C. Fuels, and Lubricants
D4177 Practice for Automatic Sampling of Petroleum and
1.2 This test method is intended for use with commercially
Petroleum Products
available coulometric Karl Fischer reagents and for the deter-
D5854 Practice for Mixing and Handling of Liquid Samples
mination of water in additives, lube oils, base oils, automatic
of Petroleum and Petroleum Products
transmission fluids, hydrocarbon solvents, and other petroleum
D6299 Practice for Applying Statistical Quality Assurance
products. By proper choice of the sample size, this test method
and Control Charting Techniques to Evaluate Analytical
may be used for the determination of water from mg/kg to
Measurement System Performance
percent level concentrations.
D6300 Practice for Determination of Precision and Bias
1.3 The values stated in SI units are to be regarded as
Data for Use in Test Methods for Petroleum Products,
standard. No other units of measurement are included in this
Liquid Fuels, and Lubricants
standard.
E203 Test Method for Water Using Volumetric Karl Fischer
1.4 This standard does not purport to address all of the Titration
safety concerns, if any, associated with its use. It is the E1064 Test Method for Water in Organic Liquids by Coulo-
responsibility of the user of this standard to establish appro- metric Karl Fischer Titration
priate safety, health, and environmental practices and deter-
3. Terminology
mine the applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accor-
3.1 For general terminology, refer to Terminology D4175.
dance with internationally recognized principles on standard-
4. Summary of Test Method
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
4.1 This method uses Karl Fischer titration to determine the
mendations issued by the World Trade Organization Technical
amount of water in a sample. A coulometric apparatus is used
Barriers to Trade (TBT) Committee.
to generate iodine for the Karl Fischer reaction at the anode.
When all the water has been titrated, excess iodine is detected
by an electrometric end point detector and the titration is
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
Subcommittee D02.06 on Analysis of Liquid Fuels and Lubricants. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Dec. 1, 2020. Published January 2021. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
ɛ1
approved in 1998. Last previous edition approved in 2016 as D6304 – 16 . DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D6304-20. the ASTM website.
*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
D6304 − 20
terminated. Based on the stoichiometry of the reaction, 1 mole significance of the mercaptan and sulfide interference on the
of iodine reacts with 1 mole of water; thus, the quantity of Karl Fischer titration for water in the 10 mg⁄kg to 200 mg⁄kg
waterisproportionaltothetotalintegratedcurrentaccordingto range has not been determined experimentally. At these low
Faraday’s Law. water concentrations, however, the interference may be ex-
pected to be significant for mercaptan and sulfide concentra-
4.2 In Procedure A, a representative portion of the test
tions of greater than 500 mg⁄kg as sulfur.
specimen is injected directly into the titration cell. This
procedure is recommended only for low viscosity samples
6.3 The indirect analysis using a water vaporizer accessory
without expected interferences (Section 5).
(Procedure B and C) may minimize interferences.
6.3.1 Ahigher than appropriate extraction temperature may
4.3 Procedures B and C can be used to analyze samples
cause sample decomposition resulting in chemical interfer-
appropriate for ProcedureA, those that do not readily dissolve
ences. These interferences may cause erroneously high results.
in Karl Fischer reagent, viscous samples, or samples with
components that are expected to interfere with the Karl Fischer
6.4 Helpful hints in obtaining reliable results are given in
reaction.Theseproceduresuseeitherawaterovenaccessoryor
Appendix X1.
water evaporator accessory.
4.3.1 In Procedure B, a representative portion of the sample
7. Apparatus
is placed into a sealed glass vial and heated in an oven to
extract any water present into the headspace of the vial. The 7.1 Coulometric Automatic Titrator, consisting of a control
vaporized water in the headspace is carried into the Karl unit,titrationvessel,dualplatinumsensingelectrode,generator
Fischertitrationcellbyadrynon-reactivecarriergaswherethe electrode assembly, and magnetic stirrer. The instrument is
water is titrated. Co-solvents may be used to enhance water designed to coulometrically generate iodine that reacts stoi-
extraction from the sample. chiometrically with the water present in the sample solution.
4.3.2 In Procedure C, a representative portion of the test Thecoulombsofelectricityrequiredtogeneratethereagentare
specimen is injected into a heated solvent or mineral oil in the convertedtomicrogramsofwater,whichisobtainedasadirect
water vaporizer accessory and the vaporized water is carried to digital readout. Measuring cells with and without diaphragms
may be used.
theKarlFischercellbyadrynon-reactivecarriergaswherethe
water is titrated.
7.2 Water Oven Accessory—A standalone or automated
4.4 For samples that can be analyzed by all procedures, the
devicewheresamplesareweighedintovial,sealedwithasepta
referee procedure is A.
cap, and inserted into an oven where the sample is heated. The
volatilized water is transferred using a dry carrier gas via a
5. Significance and Use
transfer line to a coulometric titration cell where it is titrated
5.1 A knowledge of the water content is important in the
for water content. See Appendix X2, Fig. X2.1.
manufacturing, purchase, sale, or transfer of petroleum prod-
7.3 Water Evaporator Accessory—An apparatus where a
ucts to help in predicting their quality and performance
measured sample aliquot is transferred to a heated vessel of
characteristics.
mineraloilorothersuitablesolventwherethevolatilizedwater
5.2 The presence of moisture could lead to premature
is transferred using a dry carrier gas via a transfer line to a
corrosion and wear, an increase in the debris load resulting in
coulometric titration cell where it is titrated for water content.
diminished lubrication and premature plugging of filters, an
See Appendix X2, Fig. X2.2.
impedanceintheeffectofadditives,andundesirablesupportof
7.4 Gas-tight Syringe, fitted with a cannula needle of
deleterious bacterial growth.
appropriate length and gauge for introducing sample into the
6. Interferences
titration chamber or removing excess solution from titration
chamber (see Note 1). The volume of the syringe will depend
6.1 A number of substances and classes of compounds
on the sample size and is recommended the sample to occupy
associated with condensation or oxidation-reduction reactions
at least 25 % of the syringe volume. If using plastic syringes
interferes in the determination of water by Karl Fischer
the material must be compatible with the sample matrix.
titration.
6.1.1 The following types of chemicals are known to
NOTE 1—If using glass syringes it is suggested that all parts of the glass
interfere in Karl Fischer type analyses: mercaptans, sulfides,
syringes and needles be rinsed with dry methanol or ethanol after
cleaning, then dried in an oven and stored in a desiccator
amines,ketones,aldehydes,oxidizingandreducingagents,and
some organometallic compounds.
7.5 Oven, suitable for drying glassware.
6.1.2 For more information on substances that interfere in
7.6 Desiccator, standard laboratory type with color change
thedeterminationofwaterbytheKarlFischertitrationmethod,
indicator.
see Test Method E203. Some interferences, such as ketones,
may be overcome if the appropriate reagents are used.
7.7 Analytical Balance, capable of weighing to 60.0001 g.
6.2 In petroleum products, the most common interferences
7.8 Glass Vials,forusewithovenaccessoryinProcedureB.
are mercaptans and sulfides. At levels of less than 500 mg⁄kg
as sulfur, the interference from these compounds is insignifi- 7.9 Septa Caps (Crimp or Screw Caps with Septa), for use
cant for water concentrations greater than 0.02 % by mass.The with oven accessory in Procedure B.
D6304 − 20
8. Reagents and Materials 8.6 White Mineral Oil—Also called paraffin oil or mineral
oil.
8.1 Purity of Reagents—Unless otherwise indicated, it is
intended that all reagents shall conform to the specifications of 8.7 Molecular Sieve or other suitable drying agent.
theCommitteeonAnalyticalReagentsoftheAmericanChemi-
8.8 Toluene—Reagent Grade, less than 200 mg⁄kg water
cal Society, where such specifications are available. Other
(Warning—Flammable. Vapor harmful).
grades may be used, provided it is first ascertained that the
8.9 Nitrogen—Used as a carrier for transferring moisture
reagent is of sufficiently high purity to permit its use without
into the Karl Fischer titration vessel in Procedure B and C.
lessening the accuracy of the determination.
Other dry gasses may be used.
8.2 Purity of Water—Unless otherwise indicated, references
to water shall be understood to mean Type II or Type III
9. Safety Precautions
reagent water, conforming to Specification D1193, or better.
9.1 The reagents contain one or more of the following:
8.3 Karl Fischer Reagents—Commercial coulometric Karl
iodine, organic base, sulfur dioxide, and methanol or other
Fischer (KF) reagents and reagent systems of various types are
alcohol. Wear chemically resistant gloves when mixing the
available for use with autotitrators for water determination.
reagents and removing solution from the titration chamber.
Traditionally, pyridine was the organic base used in KF
Exercise care to avoid inhalation of reagent vapors or direct
reagents. Pyridine-free formulations are available and are
contact of the reagent with the skin.
preferred by most KF instrument manufacturers for use with
their equipment. The pyridine-free reagents are less toxic, less
10. Sampling
odorous, and more stable than those containing pyridine. The
10.1 Sampling is defined as all the steps required to obtain
use of pyridine-free reagents is recommended whenever pos-
an aliquot representative of the contents of any pipe, tank, or
sible. Coulometric titrations normally require two reagent
other system and to place the sample into a container for
solutions: an anolyte and a catholyte or generator solution.
analysis by a laboratory or test facility.
However, with the use of an integrated or diaphragm-less cell,
a single solution that contains all of the reagents needed for a
10.2 Laboratory Sample—The sample of petroleum product
KF titration may be used.
presented to the laboratory or test facility for analysis by this
8.3.1 Catholyte Solution—Contains ammonium salts and
test method. Only representative samples obtained as specified
methanol.
in Practices D4057 and D4177 and handled and mixed in
8.3.2 Anolyte Solution—Contains iodide, sulfur dioxide and accordance with Practice D5854 shall be used to obtain the
a buffer in a suitable solvent. laboratory sample.
8.3.3 One Component Solution—Contains iodide, sulfur
NOTE 3—Examples of laboratory samples include bottles from a
dioxide, a buffer, and bases in a suitable solvent. This solution
manual sampling, receptacles from automatic samplers, and storage
may be used as the only solution in a coulometric system with
containers holding a product from a previous analysis.
a diaphragm-less generator cell or as the anolyte solution in a
10.3 Test Specimen—Arepresentative aliquot obtained from
diaphragm cell if specified by the manufacturer
the laboratory sample for analysis by this test method. Irre-
8.3.4 If the sample to be analyzed contains ketone, use
spective of the type of sample a homogenization step is
commercially available reagents that have been specially
recommended.
modified for use with ketones.
NOTE 4—Homogenization may be necessary to measure a representa-
NOTE 2—Some laboratories add the ketone suppressing reagent as part
tive analytical sample.
of their standard analytical procedure since often the laboratory does not
10.3.1 Exercise care at all times to avoid contaminating the
know whether the sample contains ketone.
sample with moisture from the sample container, the
8.4 Water Standards, 0.1 % by mass and 1 % by mass,
atmosphere, or transfer equipment.
commercially prepared in organic solvent are recommended.
10.3.2 Verify that samples are single phase before taking an
Other concentrations of prepared standards may be used. Oven
aliquot to test. Water can separate from hydrocarbon if the
accessory standards containing up to 5 % water are acceptable
solubility limit is exceeded.The solubility limit depends on the
for use. Consult with oven accessory manufacturer in the
makeup of the sample, concentration levels, and the tempera-
selection of standards.
ture. If phase separation occurs after mixing, sample is not
8.5 Xylene, Reagent Grade, less than 200 mg⁄kg water, suitable for testing.
dried over a molecular sieve (Warning—Flammable. Vapor
NOTE 5—Once the sample is drawn from the original container, either
harmful).
usetheentireportionofthetestspecimenfortheanalysisordisposeofthe
excess. It should not be reintroduced back into the original sample
container for future use.
ACS Reagent Chemicals, Specifications and Procedures for Reagents and
11. Preparation of Apparatus
Standard-Grade Reference Materials, American Chemical Society, Washington,
DC. For suggestions on the testing of reagents not listed by theAmerican Chemical
11.1 Follow the manufacturer’s directions for preparation
Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset,
and operation of the coulometric automatic titrator and acces-
U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharma-
copeial Convention, Inc. (USPC), Rockville, MD. sories.
D6304 − 20
TABLE 1 Recommended Test Sample Size Based on Expected
11.2 Seal all joints and connections to the vessel following
Water Content
manufacturer’srecommendationstopreventatmosphericmois-
ture from entering the apparatus.
NOTE 1—This table includes expected water concentrations that exceed
the scope of Procedure B and Procedure C.
11.3 Add the Karl Fischer anode solution to the anode
Expected Water Sample Size Water Titrated
(outer) compartment. Add the solution to the level recom-
Concentration, % g or mL µg
mended by the manufacturer.
0.001 to <0.01 5 50 to 500
0.01 to <0.03 3 300 to 900
11.4 Add the Karl Fischer cathode solution to the cathode
0.03 to <0.07 1 300 to 700
(inner) compartment when using generator electrodes with 0.07 to <0.1 0.5 350 to 500
0.1 to <0.5 0.25 250 to 1250
diaphragm. Add the solution to a level 2 mm to 3 mm below
0.5 to 2.5 0.1 500 to 2500
the level of the solution in the anode compartment.
NOTE 6—There is no need of cathode solution when using diaphragm-
less generator electrodes.
13.2 Add the test specimen to the coulometric titration
11.5 Conditioning of the Coulometric Titration Apparatus:
vessel as follows:
11.5.1 Turnontheapparatusandstartthemagneticstirrerof
13.2.1 Using a clean, dry syringe of suitable capacity (see
the titration cell for a smooth stirring action. Condition the
Table 1 and Note 5), withdraw and discard to waste a portion
titration vessel by pre-titrating any moisture in the vessel until
ofthetestspecimen.Immediatelywithdrawafurtherportionof
a baseline is achieved that is less than the maximum recom-
the test specimen, wipe the needle to remove excess sample,
mended by the manufacturer of the instrument.
and weigh the syringe and either record the weight of the
sample and syringe to the nearest 0.1 mg or tare the balance to
11.6 Conditioning of the Water Vapor Accessory—
Additionally to 11.5, the water vaporizer accessory is condi- zero.
tioned as follows:
13.3 Start the titration, insert the needle through the inlet
11.6.1 Adjust temperature and gas flow according to the
port septum, taking care that the test specimen is transferred to
manufacturer’s recommendations and sample requirements.
the titration reagent and not to parts of the titration vessel
11.6.2 Allow the residual water from the vaporizer acces-
outside of contact with the liquid. Withdraw the syringe and
sory in the titration cell to be titrated until the end-point is
record the weight to the nearest 0.1 mg. If the syringe and
reached and the baseline is less than the manufacturer’s
sample were tared to zero before sample introduction, the
recommended value.
negative weight displayed on the balance is the sample weight.
If the syringe and sample weight before injection were
12. Verification of System Performance
recorded, subtract the weight of the sample and syringe after
12.1 Coulometric automatic titrators may vary in verifica-
sample introduction as the sample weight.
tionproceduresbymanufacturer.Consulttheoperatingmanual
13.4 Aftertheendpointisreached,recordthemicrogramsof
for the coulometer and oven accessory or water vaporizer if
water titrated or the mg/kg (or %) water calculated by the
used. Stable, prepackaged water standards are commercially
titrator
available and suitable for use. It is desirable to verify system
performance with a standard solution that approximates the
NOTE 8—If the concentration of water in the sample is completely
same level of water expected to be in the samples. unknown, it is advisable to start with a small trial portion of sample to
avoid excessive titration time and depletion of the reagents. Further
12.2 Because reagent performance deteriorates with use, it
adjustment of the aliquot size may then be made as necessary.
shouldberegularlymonitoredbycommerciallyavailablewater
13.4.1 When the titration is complete and a stable baseline
standards as recommended by the equipment manufacturer. In
is achieved additional test specimens may be added as per
the absence of this, the recommended intervals are initially
13.2.1.
withfreshreagent,eachdaytestsamplesareanalyzedandafter
every ten determinations. If the measured value exceeds 65% 13.5 When problems with sample analysis or verification
occur, or the titration cell becomes fouled, clean the coulomet-
of the known amount, take appropriate corrective action to
return the value of the verification sample into the acceptable ric titration vessel and generator electrode, replace the reagents
as suggested in X1.2.7, prepare the apparatus as described in
range before proceeding with sample analysis (see Note 7).
Section 11, and verify system performance as described in
NOTE 7—Follow manufacturer’s instructions for possible causes of
Section 12.
poor recovery of standards. This may require replacing the reagent
solutions or identifying and correcting issues with the oven accessory
14. Procedure B (Oven Accessory)
(Procedure B) or water vaporizer accessory (Procedure C) if used.
14.1 Prepare the coulometric automatic titrator as described
12.2.1 It is recommended that a control chart be established
in Section 11 and adjust the nitrogen or other dry, non-reactive
and maintained according to generally accepted guidelines.
carrier gas flow according to the manufacturer’s instructions.
Practice D6299 may be used for this purpose.
Heat evaporation chamber to the temperature appropriate for a
13. Procedure A (Direct Injection)
particular product type. The minimum recommended oven
13.1 Prepare the coulometric automatic titrator as described temperature is 90 °C. Co-solvents such as toluene may be used
in Section 11 and verify system performance as described in to assist in the recovery of water. Follow manufacturer’s
Section 12. instructions and take appropriate safety precautions. Ensure
D6304 − 20
that the oven temperature chosen is high enough to remove the ric titration vessel and generator electrode, replace the reagents
water without degrading the sample. Refer to X1.5.3 for more as suggested in X1.2.7, prepare the apparatus as described in
informationonselectinganappropriateextractiontemperature. Section 11 and verify system performance as described in
Section 12.
NOTE 9—The 2019 ILS used to determine the precision for Procedure
B used an extraction temperature of 150 °C for the following sample
15. Procedure C (Water Evaporator or Oil Vaporizer
types: Lubricant Additives, Automatic Transmission Fluids, Base Oil,
Biodiesel, Compressor Lubricant, Ultra-Low Sulfur Diesel, Gear Oil,
Accessory)
Hydraulic Oil and Turbine Oil.
15.1 Prepare the coulometric automatic titrator as described
14.2 A vial blank determin
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation: D6304 − 16 D6304 − 20
Standard Test Method for
Determination of Water in Petroleum Products, Lubricating
Oils, and Additives by Coulometric Karl Fischer Titration
This standard is issued under the fixed designation D6304; 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 U.S. Department of Defense.
ε NOTE—Reference to a Summary of Changes was removed editorially in September 2016.
1. Scope Scope*
1.1 This test method covers the direct determination of water in the range of 10 mg⁄kg to 25 000 mg⁄kg entrained water in
petroleum products and hydrocarbons using automated instrumentation. This test method also covers the indirect analysis of water
−–
thermally removed from samples and swept with dry inert gas into the Karl Fischer titration cell. Mercaptan, sulfide (S or H S),
sulfur, and other compounds are known to interfere with this test method (see Section 56). The precision statement of this method
covers the nominal range of 20 mg ⁄kg to 25 000 mg/kg for Procedure A, 30 mg ⁄kg to 2100 mg ⁄kg for Procedure B, and 20 mg ⁄kg
to 360 mg ⁄kg for Procedure C.
1.2 This test method is intended for use with commercially available coulometric Karl Fischer reagents and for the determination
of water in additives, lube oils, base oils, automatic transmission fluids, hydrocarbon solvents, and other petroleum products. By
proper choice of the sample size, this test method may be used for the determination of water from mg/kg to percent level
concentrations.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D1193 Specification for Reagent Water
D1298 Test Method for Density, Relative Density, or API Gravity of Crude Petroleum and Liquid Petroleum Products by
Hydrometer Method
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.06 on Analysis of Liquid Fuels and Lubricants.
Current edition approved July 1, 2016Dec. 1, 2020. Published July 2016January 2021. Originally approved in 1998. Last previous edition approved in 20072016 as
ɛ1
D6304 – 07D6304 – 16 , which was withdrawn in April 2016 and reinstated in July 2016. DOI: 10.1520/D6304-16. DOI: 10.1520/D6304-20.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*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
D6304 − 20
D4052 Test Method for Density, Relative Density, and API Gravity of Liquids by Digital Density Meter
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
D4177 Practice for Automatic Sampling of Petroleum and Petroleum Products
D5854 Practice for Mixing and Handling of Liquid Samples of Petroleum and Petroleum Products
D6299 Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measure-
ment System Performance
D6300 Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products, Liquid Fuels, and
Lubricants
E203 Test Method for Water Using Volumetric Karl Fischer Titration
E1064 Test Method for Water in Organic Liquids by Coulometric Karl Fischer Titration
3. Terminology
3.1 For general terminology, refer to Terminology D4175.
4. Summary of Test Method
4.1 An aliquot is injected into the titration vessel of a coulometric Karl Fischer apparatus in which This method uses Karl Fischer
titration to determine the amount of water in a sample. A coulometric apparatus is used to generate iodine for the Karl Fisher
reaction is generated coulometrically Fischer reaction at the anode. When all of the water has been titrated, excess iodine is
detected by an electrometric end point detector and the titration is terminated. Based on the stoichiometry of the reaction, 1 mol
1 mole of iodine reacts with 1 mol 1 mole of water; thus, the quantity of water is proportional to the total integrated current
according to Faraday’sFaraday’s Law.
4.2 The sample injection can be done either by mass or volume.In Procedure A, a representative portion of the test specimen is
injected directly into the titration cell. This procedure is recommended only for low viscosity samples without expected
interferences (Section 5).
4.3 The viscous samples can be analyzed by using a water vaporizer accessory that heats the sample in the evaporation chamber,
and the vaporized water is carried into the Karl Fischer titration cell by a dry inert carrier gas.Procedures B and C can be used
to analyze samples appropriate for Procedure A, those that do not readily dissolve in Karl Fischer reagent, viscous samples, or
samples with components that are expected to interfere with the Karl Fischer reaction. These procedures use either a water oven
accessory or water evaporator accessory.
4.3.1 In Procedure B, a representative portion of the sample is placed into a sealed glass vial and heated in an oven to extract any
water present into the headspace of the vial. The vaporized water in the headspace is carried into the Karl Fischer titration cell by
a dry non-reactive carrier gas where the water is titrated. Co-solvents may be used to enhance water extraction from the sample.
4.3.2 In Procedure C, a representative portion of the test specimen is injected into a heated solvent or mineral oil in the water
vaporizer accessory and the vaporized water is carried to the Karl Fischer cell by a dry non-reactive carrier gas where the water
is titrated.
4.4 For samples that can be analyzed by all procedures, the referee procedure is A.
5. Significance and Use
5.1 A knowledge of the water content of lubricating oils, additives, and similar products is important in the manufacturing,
purchase, sale, or transfer of such petroleum products to help in predicting their quality and performance characteristics.
5.2 For lubricating oils, the The presence of moisture could lead to premature corrosion and wear, an increase in the debris load
resulting in diminished lubrication and premature plugging of filters, an impedance in the effect of additives, and undesirable
support of deleterious bacterial growth.
6. Interferences
6.1 A number of substances and classes of compounds associated with condensation or oxidation-reduction reactions interferes in
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the determination of water by Karl Fischer titration. In petroleum products, the most common interferences are mercaptans and
sulfides. At levels of less than 500 mg⁄kg as sulfur, the interference from these compounds is insignificant for water concentrations
greater than 0.02 % by mass. For more information on substances that interfere in the determination of water by the Karl Fischer
titration method, see Test Method E203. Some interferences, such as ketones, may be overcome if the appropriate reagents are
used.
6.1.1 The following types of chemicals are known to interfere in Karl Fischer type analyses: mercaptans, sulfides, amines, ketones,
aldehydes, oxidizing and reducing agents, and some organometallic compounds.
6.1.2 For more information on substances that interfere in the determination of water by the Karl Fischer titration method, see Test
Method E203. Some interferences, such as ketones, may be overcome if the appropriate reagents are used.
6.2 In petroleum products, the most common interferences are mercaptans and sulfides. At levels of less than 500 mg ⁄kg as sulfur,
the interference from these compounds is insignificant for water concentrations greater than 0.02 % by mass. The significance of
the mercaptan and sulfide interference on the Karl Fischer titration for water in the 10 mg ⁄kg to 200 mg ⁄kg range has not been
determined experimentally. At these low water concentrations, however, the interference may be expected to be significant for
mercaptan and sulfide concentrations of greater than 500 mg ⁄kg as sulfur.
6.3 The indirect analysis using a water vaporizer accessory (Procedure B and C) may minimize interferences.
6.3.1 A higher than appropriate extraction temperature may cause sample decomposition resulting in chemical interferences. These
interferences may cause erroneously high results.
6.4 Helpful hints in obtaining reliable results are given in Appendix X1.
7. Apparatus
7.1 Coulometric Karl Fischer Apparatus (using electrometric end point)—Automatic Titrator, A number of automatic coulometric
Karl Fischer titration assemblies consisting of titration cell, platinum electrodes, magnetic stirrer, and a control unit are available
on the market. Instructions for operation of these devices are provided by the manufacturers and are not described herein.
consisting of a control unit, titration vessel, dual platinum sensing electrode, generator electrode assembly, and magnetic stirrer.
The instrument is designed to coulometrically generate iodine that reacts stoichiometrically with the water present in the sample
solution. The coulombs of electricity required to generate the reagent are converted to micrograms of water, which is obtained as
a direct digital readout. Measuring cells with and without diaphragms may be used.
6.1.1 Water Vaporizer Accessory—A number of automatic water vaporizer accessories are available on the market. Instructions for
the operation of these devices are provided by the manufacturers and are not described herein.
7.2 Water Oven Accessory—A standalone or automated device where samples are weighed into vial, sealed with a septa cap, and
inserted into an oven where the sample is heated. The volatilized water is transferred using a dry carrier gas via a transfer line to
a coulometric titration cell where it is titrated for water content. See Appendix X2, Fig. X2.1.
7.3 Water Evaporator Accessory—An apparatus where a measured sample aliquot is transferred to a heated vessel of mineral oil
or other suitable solvent where the volatilized water is transferred using a dry carrier gas via a transfer line to a coulometric titration
cell where it is titrated for water content. See Appendix X2, Fig. X2.2.
7.4 Syringes—Gas-tight Syringe, Samples are most easily added to the titration vessel by means of accurate glass or disposable
plastic syringes with luer fittings and hypodermic needles of suitable length to dip below the surface of the anode solution in the
cell whenfitted with a cannula needle of appropriate length and gauge for introducing sample into the titration chamber or removing
excess solution from titration chamber (see Note 1inserted through the inlet port septum. The bores of the needles used shall be
kept as small as possible, but large enough to avoid problems arising from back pressure or blocking while sampling. Suggested
syringe sizes are as follows: ). The volume of the syringe will depend on the sample size and is recommended the sample to occupy
at least 25 % of the syringe volume. If using plastic syringes the material must be compatible with the sample matrix.
6.2.1 Ten microlitres, with a needle long enough to dip below the surface of the anode solution in the cell when inserted through
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TABLE 1 Test Sample Size Based on Expected Water Content
Expected Water Sample Size μg Water
Concentration g or mL Titrated
10 mg⁄kg to 100 mg/kg or μg/mL 3.0 30 to 300
10 mg⁄kg to 500 mg/kg or μg/mL 2.0 200 to 1000
0.02 % to 0.1 % 1.0 200 to 1000
0.1 % to 0.5 % 0.5 500 to 2500
0.5 % to 2.5 % 0.25 1250 to 6250
TABLE 1 Recommended Test Sample Size Based on Expected
Water Content
NOTE 1—This table includes expected water concentrations that exceed
the scope of Procedure B and Procedure C.
Expected Water Sample Size Water Titrated
Concentration, % g or mL μg
0.001 to <0.01 5 50 to 500
0.01 to <0.03 3 300 to 900
0.03 to <0.07 1 300 to 700
0.07 to <0.1 0.5 350 to 500
0.1 to <0.5 0.25 250 to 1250
0.5 to 2.5 0.1 500 to 2500
the inlet port septum and graduated for readings to the nearest 0.1 μL or better. This syringe can be used to accurately inject a small
quantity of water to check reagent performance as described in Section 10.
NOTE 1—If using glass syringes it is suggested that all parts of the glass syringes and needles be rinsed with dry methanol or ethanol after cleaning, then
dried in an oven and stored in a desiccator
6.2.2 As identified in Table 1, syringes of the following capacities: 250 μL accurate to the nearest 10 μL; 500 μL accurate to the
nearest 10 μL; 1 mL accurate to the nearest 0.01 mL; 2 mL accurate to the nearest 0.01 mL; and 3 mL accurate to the nearest
0.01 mL. A quality gas-tight glass syringe with a TFE-fluorocarbon plunger and luer fitting is recommended.
7.5 Oven, suitable for drying glassware.
7.6 Desiccator, standard laboratory type with color change indicator.
7.7 Analytical Balance, capable of weighing to 60.0001 g.
7.8 Glass Vials, for use with oven accessory in Procedure B.
7.9 Septa Caps (Crimp or Screw Caps with Septa), for use with oven accessory in Procedure B.
8. Reagents and Materials
8.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, Unless otherwise indicated,
it is intended that all reagents shall conform to the specifications of the Committee on Analytical Reagents of the American
Chemical SocietySociety, where such specifications are available. , where such specifications are available. Use other grades,
provided Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use
without lessening the accuracy of the determination.
8.2 Purity of Water—Unless otherwise indicated, references to water shall be understood to mean reagent water as defined by Type
II of Type II or Type III reagent water, conforming to Specification D1193., or better.
Reagent Chemicals, American Chemical Society Specifications,ACS Reagent Chemicals, Specifications and Procedures for Reagents and Standard-Grade Reference
Materials, American Chemical Society, Washington, DC. For Suggestionssuggestions on the testing of reagents not listed by the American Chemical Society, see
AnnualAnalar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharmacopeial
Convention, Inc. (USPC), Rockville, MD.
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7.3 Xylene, Reagent Grade, less than 100 mg ⁄kg to 200 mg ⁄kg water, dried over a molecular sieve (Warning—Flammable. Vapor
harmful).
8.3 Karl Fischer Reagent, Reagents—standard commercially available reagents for Commercial coulometric Karl Fischer
titrations.(KF) reagents and reagent systems of various types are available for use with autotitrators for water determination.
Traditionally, pyridine was the organic base used in KF reagents. Pyridine-free formulations are available and are preferred by most
KF instrument manufacturers for use with their equipment. The pyridine-free reagents are less toxic, less odorous, and more stable
than those containing pyridine. The use of pyridine-free reagents is recommended whenever possible. Coulometric titrations
normally require two reagent solutions: an anolyte and a catholyte or generator solution. However, with the use of an integrated
or diaphragm-less cell, a single solution that contains all of the reagents needed for a KF titration may be used.
8.3.1 Catholyte Solution—Contains ammonium salts and methanol.
8.3.2 Anolyte Solution—Contains iodide, sulfur dioxide and a buffer in a suitable solvent.
8.3.3 Anode One Component Solution—Mix six parts of commercial Karl Fischer anode solution with four parts of reagent grade
xylene on a volume basis. Newly made Karl Fischer anode solution shall be used. Other proportions of anode solution and xylene
Contains iodide, sulfur dioxide, a buffer, and bases in a suitable solvent. This solution may be used and determined for a particular
reagent, apparatus, and sample tested. Some samples may not require any xylene, whereas others will require the solvent effect
of the xylene (as the only solution in a coulometric system with a diaphragm-less generator cell or as the anolyte solution in a
diaphragm cellWarning—Flammable, toxic if inhaled, swallowed, or absorbed through skin). if specified by the manufacturer
NOTE 1—Toluene may be used in place of xylene. However, the precision data in Section 17 were obtained using xylene.
7.4.2 Cathode Solution—Use standard commercially available cathode Karl Fischer solution. Newly made solution shall be used
(Warning—Flammable, may be fatal if inhaled, swallowed, or absorbed through skin. Possible cancer hazard.).
8.3.4 If the sample to be analyzed contains ketone, use commercially available reagents that have been specially modified for use
with ketones.
NOTE 2—Some laboratories add the ketone suppressing reagent as part of their standard analytical procedure since often the laboratory does not know
whether the sample contains ketone.
8.4 Water Standards, 0.1 % by mass and 1 % by mass, commercially prepared in organic solvent are recommended. Other
concentrations of prepared standards may be used. Oven accessory standards containing up to 5 % water are acceptable for use.
Consult with oven accessory manufacturer in the selection of standards.
8.5 Hexane,Xylene, Reagent Grade, less than 100 mg⁄kg to 200 mg ⁄kg water water, dried over a molecular sieve (Warning—
Flammable. Vapor harmful). Dried over molecular sieve.
8.6 White Mineral Oil—Also called paraffin oil or mineral oil. Reagent grade.
8.7 Molecular Sieve 5Å—8 to 12 mesh.or other suitable drying agent.
8.8 Toluene—Reagent Grade, less than 200 mg ⁄kg water (Warning—Flammable. Vapor harmful).
8.9 Nitrogen—Used as a carrier for transferring moisture into the Karl Fischer titration vessel in Procedure B and C. Other dry
gasses may be used.
9. Safety Precautions
9.1 The reagents contain one or more of the following: iodine, organic base, sulfur dioxide, and methanol or other alcohol. Wear
chemically resistant gloves when mixing the reagents and removing solution from the titration chamber. Exercise care to avoid
inhalation of reagent vapors or direct contact of the reagent with the skin.
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10. Sampling
10.1 Sampling is defined as all the steps required to obtain an aliquot representative of the contents of any pipe, tank, or other
system and to place the sample into a container for analysis by a laboratory or test facility.
10.2 Laboratory Sample—The sample of petroleum product presented to the laboratory or test facility for analysis by this test
method. Only representative samples obtained as specified in Practices D4057 and D4177 and handled and mixed in accordance
with Practice D5854 shall be used to obtain the laboratory sample.
NOTE 3—Examples of laboratory samples include bottles from a manual sampling, receptacles from automatic samplers, and storage containers holding
a product from a previous analysis.
10.3 Test Specimen—The A representative aliquot obtained from the laboratory sample for analysis by this test method. Once
drawn, use the entire portion of the test specimen in the analysis. Irrespective of the type of sample a homogenization step is
recommended.
NOTE 4—Homogenization may be necessary to measure a representative analytical sample.
10.3.1 Exercise care at all times to avoid contaminating the sample with moisture from the sample container, the atmosphere, or
transfer equipment.
10.3.2 Verify that samples are single phase before taking an aliquot to test. Water can separate from hydrocarbon if the solubility
limit is exceeded. The solubility limit depends on the makeup of the sample, concentration levels, and the temperature. If phase
separation occurs after mixing, sample is not suitable for testing.
NOTE 5—Once the sample is drawn from the original container, either use the entire portion of the test specimen for the analysis or dispose of the excess.
It should not be reintroduced back into the original sample container for future use.
8.4 Select the test specimen size as indicated in Table 1 based on the expected water concentration.
11. Preparation of Apparatus
11.1 Follow the manufacturer’smanufacturer’s directions for preparation and operation of the titration apparatus.coulometric
automatic titrator and accessories.
11.2 Seal all joints and connections to the vessel following manufacturer’s recommendations to prevent atmospheric moisture
from entering the apparatus.
11.3 Add the Karl Fischer anode solution to the anode (outer) compartment. Add the solution to the level recommended by the
manufacturer.
11.4 Add the Karl Fischer cathode solution to the cathode (inner) compartment. compartment when using generator electrodes
with diaphragm. Add the solution to a level 2 mm to 3 mm below the level of the solution in the anode compartment.
NOTE 6—There is no need of cathode solution when using diaphragm-less generator electrodes.
11.5 Turn on the apparatus and start the magnetic stirrer for a smooth stirring action. Allow the residual moisture in the titration
vessel to be titrated until the end point is reached. Do not proceed beyond this stage until the background current (or background
titration rate) is constant and less than the maximum recommended by the manufacturer of the instrument.Conditioning of the
Coulometric Titration Apparatus:
NOTE 4—High background current for a prolonged period may be due to moisture on the inside walls of the titration vessel. Gentle shaking of the vessel
(or more rigorous stirring action) will wash the inside with electrolyte. Keep the titrator on to allow stabilization to a low background current.
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11.5.1 Turn on the apparatus and start the magnetic stirrer of the titration cell for a smooth stirring action. Condition the titration
vessel by pre-titrating any moisture in the vessel until a baseline is achieved that is less than the maximum recommended by the
manufacturer of the instrument.
11.6 Conditioning of the Water Vapor Accessory—Additionally to 11.5, the water vaporizer accessory is conditioned as follows:
11.6.1 Adjust temperature and gas flow according to the manufacturer’s recommendations and sample requirements.
11.6.2 Allow the residual water from the vaporizer accessory in the titration cell to be titrated until the end-point is reached and
the baseline is less than the manufacturer’s recommended value.
10. Calibration and Standardization
10.1 In principle, standardization is not necessary since the water titrated is a direct function of the coulombs of electricity
consumed. However, reagent performance deteriorates with use and shall be regularly monitored by accurately injecting a known
quantity of water (see 7.2) that is representative of the typical range of water concentrations being determined in samples. As an
example, one may accurately inject 10 000 μg or 10 μL of water to check reagent performance. Suggested intervals are initially
with fresh reagent and then after every ten determinations (see 11.3).
12. Verification of System Performance
12.1 Coulometric automatic titrators may vary in verification procedures by manufacturer. Consult the operating manual for the
coulometer and oven accessory or water vaporizer if used. Stable, prepackaged water standards are commercially available and
suitable for use. It is desirable to verify system performance with a standard solution that approximates the same level of water
expected to be in the samples.
12.2 Because reagent performance deteriorates with use, it should be regularly monitored by commercially available water
standards as recommended by the equipment manufacturer. In the absence of this, the recommended intervals are initially with
fresh reagent, each day test samples are analyzed and after every ten determinations. If the measured value exceeds 65 % of the
known amount, take appropriate corrective action to return the value of the verification sample into the acceptable range before
proceeding with sample analysis (see Note 7).
NOTE 7—Follow manufacturer’s instructions for possible causes of poor recovery of standards. This may require replacing the reagent solutions or
identifying and correcting issues with the oven accessory (Procedure B) or water vaporizer accessory (Procedure C) if used.
12.2.1 It is recommended that a control chart be established and maintained according to generally accepted guidelines. Practice
D6299 may be used for this purpose.
13. Procedure A (by Mass)(Direct Injection)
13.1 Add newly made solvents to the anode and cathode compartments of the titration vesselPrepare the coulometric automatic
titrator as described in Section 11 and bring the solvent to end-point conditions asverify system performance as described in
Section 12described in Section . 9.
13.2 Add the test specimen to the coulometric titration vessel as follows:
13.2.1 Using a clean, dry syringe of suitable capacity (see Table 1 and Note 5), withdraw and discard to waste a portion of the
test specimen. Immediately withdraw a further portion of the test specimen, wipe the needle to remove excess sample, and weigh
the syringe and either record the weight of the sample and syringe to the nearest 0.1 mg or tare the balance to zero.
13.3 Start the titration, insert the needle through the inlet port septum, taking care that the test specimen is transferred to the
titration reagent and not to parts of the titration vessel outside of contact with the liquid. Withdraw the syringe and record the
weight to the nearest 0.1 mg. If the syringe and sample were tared to zero before sample introduction, the negative weight
displayed on the balance is the sample weight. If the syringe and sample weight before injection were recorded, subtract the weight
of the sample and syringe after sample introduction as the sample weight.
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13.4 Add the petroleum product test specimen to the titration vessel using the following method:After the endpoint is reached,
record the micrograms of water titrated or the mg/kg (or %) water calculated by the titrator
11.2.1 Starting with a clean, dry syringe of suitable capacity (see Table 1 and Note 5), withdraw and discard to waste at least three
portions of the sample. Immediately withdraw a further portion of sample, clean the needle with a paper tissue, and weigh the
syringe and contents to the nearest 0.1 mg. Insert the needle through the inlet port septum, start the titration, and with the tip of
the needle just below the liquid surface, inject the test specimen. Withdraw the syringe, wipe clean with a paper tissue, and reweigh
the syringe to the nearest 0.1 mg. After the end point is reached, record the micrograms of water titrated.
NOTE 5—If the concentration of water in the sample is completely unknown, it is advisable to start with a small trial portion of sample to avoid excessive
titration time and depletion of the reagents. Further adjustment of the aliquot size may then be made as necessary.
NOTE 8—If the concentration of water in the sample is completely unknown, it is advisable to start with a small trial portion of sample to avoid excessive
titration time and depletion of the reagents. Further adjustment of the aliquot size may then be made as necessary.
13.4.1 When the background current or titration rate returns to a stable reading at the end of the titration as discussed in titration
is complete and a stable baseline is achieved 9.5, additional test specimens may be added as per 11.2.113.2.1.
13.5 Replace the solutions when one of the following occurs and then repeat the preparation of When problems with sample
analysis or verification occur, or the titration cell becomes fouled, clean the coulometric titration vessel and generator electrode,
replace the reagents as suggested in X1.2.7, prepare the apparatus as described in Section 911, and verify system performance as
described in Section 12.
11.3.1 Persistently high and unstable background current.
11.3.2 Phase separation in the anode compartment or oil coating the electrodes.
11.3.3 The total oil content added to the titration vessel exceeds one quarter of the volume of solution in the anode compartment.
11.3.4 The solutions in the titration vessel are greater than one week old.
11.3.5 The instrument displays error messages that directly or indirectly suggest replacement of the electrolytes—see instrument
operating manual.
11.3.6 The result of a 10 μL injection of water is outside 10 000 μg 6 200 μg.
11.4 Thoroughly clean the anode and cathode compartment with xylene if the vessel becomes contaminated with product. Never
use acetone or similar ketones. Clogging of the frit separating the vessel compartments will cause instrument malfunction.
11.5 For products too viscous to draw into a syringe, add the sample to a clean, dry bottle and weigh the bottle and product.
Quickly transfer the required amount of sample to the titration vessel by suitable means, such as with a dropper. Reweigh the bottle.
Titrate the sample as in 11.2.
14. Procedure B (by Volume)(Oven Acce
...