GB/T 11275-2007 English PDF (GBT11275-2007)

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GB/T 11275-2007: Surface active agents -- Determination of water content
GB/T 11275-2007
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 71.100.40
G 72
Replacing GB/T 7380-1995, GB/T 11275-1995
Surface active agents - Determination of water content
(ISO 4317:1991, Surface active agents and detergents - Determination of water
content - Karl Fischer method, MOD)
ISSUED ON: AUGUST 13, 2007
IMPLEMENTED ON: FEBRUARY 01, 2008
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine of the People's Republic of China;
Standardization Administration of the People's Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Terms and definitions ... 5
4 Principle ... 6
5 Reagents and materials ... 6
6 Instruments and equipment ... 6
7 Determination ... 7
8 Test report ... 10
Annex A (normative) Preparation of Karl Fischer reagent (containing pyridine) ... 11
Annex B (informative) Comparison on clause and subclause numbers between this
Standard and ISO 4317:1991 ... 12
Surface active agents - Determination of water content
1 Scope
This Standard specifies the method for the determination of the water content of surface
active agents. Xylene azeotropic distillation can be used for powdery, slurry and liquid
products with water content (mass fraction) greater than 5%. However, the azeotropic
distillation method is not suitable for products containing water-soluble volatiles, such
as products containing ethanol. The Karl Fischer method is the only applicable method
for powdery, slurry and liquid products with water content (mass fraction) less than 1%.
However, the specimen contains basic compounds such as silicate, carbonate,
hydroxide and borate, which will affect the measured value, so the basic compounds in
the specimen should be analyzed before measurement.
2 Normative references
The provisions in following documents become the provisions of this Standard through
reference in this Standard. For dated references, the subsequent amendments (excluding
corrigendum) or revisions do not apply to this Standard, however, parties who reach an
agreement based on this Standard are encouraged to study if the latest versions of these
documents are applicable. For undated references, the latest edition of the referenced
document applies.
GB/T 6372, Surface active agents and detergents - Methods of sample division
(GB/T 6372-2006, ISO 607:1980, IDT)
GB/T 6682, Water for analytical laboratory use - Specification and test methods
(GB/T 6682-1992, neq ISO 3696:1987)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
water content
The amount of free water, crystallization water, adsorbed water or occluded water in
the specimen is calculated according to the amount of Karl Fischer reagent consumed
and expressed in mass fraction.
4 Principle
4.1 Karl Fischer method
Water in the specimen reacts with iodine and sulfur dioxide in the Karl Fischer reagent.
The Karl Fischer reagent is previously calibrated by titration with an accurately known
amount of water. The mass fraction of water content is calculated from the amount of
reagent used.
4.2 Azeotropic distillation method
Water in the specimen is azeotropically distilled with boiling xylene or petroleum. The
water content is expressed in mass fraction.
5 Reagents and materials
5.1 Distilled water: grade II water specified in GB/T 6682.
5.2 Anhydrous methanol: analytically pure.
5.3 Karl Fischer reagent.
NOTE: Pyridine-free reagents may be used if shown to be suitable (stated in test report).
5.3.1 Pyridine-containing Karl Fischer reagent.
5.3.2 Pyridine-free Karl Fischer reagent.
5.4 Sodium tartrate or oxalic acid: analytically pure.
5.5 Xylene or petroleum (boiling range is180°C~220°C): analytically pure.
NOTE: Xylene is a toxic solvent and must be handled according to safety regulations for toxic
solvents.
6 Instruments and equipment
6.1 Trace moisture analyzer, fully automatic or semi-automatic, consists of the
following parts:
6.1.1 Double platinum electrode titration device;
Fischer reagent used.
Calculate the value of water equivalent T according to formula (1) or formula (2):
Or
Where,
m1 - the mass of water, in grams (g);
V1 - the volume of Karl Fischer reagent used for titration, in milliliters (mL);
T - the water equivalent of Karl Fischer reagent, in milligrams per milliliter (mg/mL);
m0 - the mass of sodium tartrate or oxalic acid, in milligrams (mg);
w - the water content of sodium tartrate is 15.66 or the water content of oxalic acid is
28.57, expressed in mass fraction.
7.1.2 Specimen preparation
If the water content (mass fraction) of the specimen is less than 1%, weigh 5 g ~ 10 g
(accurate to 0.001 g) equivalent to the specimen that contains 10 mg to 50 mg of water.
If the water content (mass fraction) in the specimen is higher than 1%, weigh 1 g ~ 5 g
(accurate to 0.001 g) and place it in a volumetric flask. Add anhydrous methanol and
dilute to scale. Shake vigorously to dissolve the water in the sample. Let stand to allow
insoluble salts to settle to the bottom of the flask. Use a pipette to draw the upper layer
of methanol solution equivalent to 10 mg ~ 50 mg of water.
When the water content (mass fraction) of the specimen is higher than 1%, the water in
anhydrous methanol must be titrated with Karl Fischer reagent, and then deducted.
7.1.3 Determination of water content
Add a certain volume (submerging the electrode by 2 mm ~ 3 mm) of anhydrous
methanol into the reaction bottle. Titrate to the end point with Karl Fischer reagent
under stirring (do not record the volume of Karl Fischer reagent consumed). Quickly
add the specimen to the reaction bottle. Stir to dissolve. Titrate to the endpoint. Record
the volume of Karl Fischer reagent used.
7.1.4 Expression of results
The mass fraction of water content is expressed in X. The value is expressed in %,
calculated according to formula (3):
Where,
m2 - the mass of the specimen, in grams (g);
V2 - the volume of Karl Fischer reagent used for titration, in milliliters (mL);
T - the water equivalent of the Karl Fischer reagent, in milligrams per milliliter (mg/mL).
7.1.5 Repeatability
For the same specimen, the difference between two successive measurements by the
same analyst should not exceed 6% (mass fraction) of the average value.
7.1.6 Reproducibility
For the same specimen, the difference between the results measured in two different
laboratories should not be greater than 10% (mass fraction) of the average value.
7.2 Azeotropic distillation method
If xylene is used, this operation must be carried out in a fume hood.
7.2.1 Specimen weighing
Weigh 10 g ~ 50 g of specimen, accurate to 0.01 g. Put in a flask. Select the specimen
size so that the collecting cylinder is at least 50% (volume fraction) full at the end of
the test.
7.2.2 Determination
Add 100 mL ~ 300 mL of xylene or petroleum and an anhydrous anti-knock agent to
the specimen, such as porcelain chips. Connect the flask to the rest of the apparatus.
Gradually heat to boil. Continue boiling until the xylene or petroleum distillate becomes
clear (reflux 2 or 3 drops per second) and no more water separates out.
If water droplets adhere to the tube wall, drive them away with a spiral wire. Wash them
down with 5 mL of xylene or petroleum during or after distillation.
If foam interferes with the determination, a...