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

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

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GB/T 11275-2007: Surface active agents -- Determination of water content

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.
GB/T 11275-2007
GB
NATIONAL STANDARD OF THE
PEOPLE 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, add a small amount of anhydrous alkane or oleic acid to the flask to eliminate the foam. Let stand until the water has been completely separated, without residual emulsified layer. Read off the volume of water in the collecting cylinder at the reference temperature of 20??C.
7.2.3 Results presentation
The mass fraction of water content is expressed in x. The value is expressed in %, calculated according to formula (4):
Where,
V - the volume of the water layer in the collecting cylinder, in milliliters (mL); m - the mass of the specimen, in grams (g).
7.2.4 Reproducibility
The difference between the results of the same specimen measured in two different laboratories should not be greater than 1% (mass fraction).
8 Test report
The test report should include the following:
a) all the information required for complete identification of the sample; b) the reference method used, the type of solvent, the type of Karl Fischer reagent; c) the obtained results and presentation methods;
d) test conditions;
e) persons and operational details that are optional for all operational details not included in this Standard and referenced standards that could affect the results.

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