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GB/T 14571.3-2008 English PDF (GBT14571.3-2008)

GB/T 14571.3-2008 English PDF (GBT14571.3-2008)

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GB/T 14571.3-2008: Ethylene glycol for industrial use -- Determination of content total aldehydes present -- Spectrophotometric method

This Part specifies spectrophotometric method for determination of content of total aldehydes present in ethylene glycol for industrial use. This Part is applicable to determination of content of total aldehydes present in ethylene glycol for industrial use. The determination range is 0.00001%~0.005% (mass fraction).
GB/T 14571.3-2008
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 71.080.60
G 16
Replacing GB/T 14571.3-1993
Ethylene glycol for industrial use -
Determination of content of total aldehydes present -
Spectrophotometric method
ISSUED ON: FEBRUARY 26, 2008
IMPLEMENTED ON: AUGUST 01, 2008
Issued by: General Administration of Quality Supervision, Inspection and Quarantine;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Method summary ... 5
4 Reagents and materials ... 6
5 Apparatus ... 6
6 Sampling ... 6
7 Analysis steps ... 7
8 Calculation of results ... 7
9 Repeatability ... 8
10 Report ... 8
Annex A (informative) Contrast on Clause No. between this Part and ASTM E2313-2004 ... 9
Foreword
GB/T 14571 consists of the following parts:
- Part 1: Test method of ethylene glycol for industrial use - Determination of acidity - Titration method
- Part 2: Test method of ethylene glycol for industrial use - Determination of purity and impurities - Gas chromatography
- Part 3: Ethylene glycol for industrial use - Determination of content of total aldehydes present - Spectrophotometric method
- Part 4: Ethylene glycol for industrial use - Determination of ultraviolet transmittance - Ultraviolet spectrophotometric method
This Part is Part 3 of GB/T 14571.
The meditation of this Part uses ASTM E 2313-2004 ?€?Standard Test Method for Aldehydes in Mono-, Di-, and Triethylene Glycol (Spectrophotometric Method)?€? (English version). See Annex A for structural differences between this Part and ASTM E 2313-2004. The main technical differences between this Part and
ASTM E 2313 are:
- modified the measuring wavelength from 635nm to 620nm;
- modified the colorimetric capacity from 100mL to 50mL;
- modified the diluent from acetone or methanol to water;
- used the self-determined repeatability limit (r);
- used the current national standards in normative references.
This Part replaces GB/T 14571.3-1993 ?€?Ethylene glycol for industrial use. Determination of content of total aldehydes present. Spectrophotometric method?€?. Compared with GB/T 14571.3-1993, the main changes in this Part are as follows:
- modified 3-methyl-2-benzothiazolone oxime (MBTH) reagent from 0.20%
(mass fraction) to 0.30% (mass fraction), colorimetric capacity from 25mL to 50mL, determination range from 0.00001%~0.003% (mass fraction) to
0.00001%~0.005 % (mass fraction);
- re-determine the repeatability limit (r).
Annex A of this Part is informative.
Ethylene glycol for industrial use -
Determination of content of total aldehydes present -
Spectrophotometric method
1 Scope
This Part specifies spectrophotometric method for determination of content of total aldehydes present in ethylene glycol for industrial use. This Part is applicable to determination of content of total aldehydes present in ethylene glycol for industrial use. The determination range is 0.00001%~0.005% (mass fraction).
This Part is not intended to describe all security issues related to its use. It is the responsibility of the user to take appropriate safety and health measures to ensure the compliance with relevant national regulations.
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 6680-2003, General rules for sampling liquid chemical products
GB/T 6682-1992, Water for laboratory use - Specifications (neq ISO
3639:1987)
GB/T 8170-1987, Rules for rounding off of numerical values
GB/T 9009-1998, Formaldehyde solution for industrial use
3 Method summary
Aliphatic aldehyde in the sample, in the presence of ferric chloride, reacts with 3-methyl-2-benzothiazolone oxime (MBTH) to generate blue-green fused
cation. Use spectrophotometer to measure absorbance at a wavelength of
7 Analysis steps
7.1 Drawing of working curve
In 6 50mL volumetric flasks, respectively add 0 mL, 1.0 mL, 2.0 mL, 3.0 mL, 4.0 mL, 5.0 mL of standard solutions (4.5). Then add 5.0 mL, 4.0 mL, 3.0 mL, 2.0 mL, 1.0 mL, 0 mL of water in sequence respectively. Shake well. Then
respectively add 5.0mLof MBTH solution (4.2). Shake well completely. Perform action at room temperature for 30min. Then separately add 5.0mL of oxidizer solution (4.3). Shake well completely. Place for 20min. At last, use distilled water to dilute to the scale. At 620nm, use water as reference solution. Use 10mm absorption pool to determine absorbance.
Use the mass of formaldehyde (??g) as abscissa, corresponding net absorbance (the absorbance of the reagent blank is deducted) as Y-axis to draw the working curve. The equation of the working curve is expressed by C=K??A+B. The
related coefficient shall be greater than 0.99.
NOTE: Avoid exposure to direct sunlight in the operation place. The absorbance of the reagent blank shall be less than 0.070. If the absorbance of the blank solution exceeds the upper limit of the control, the glassware must be re-cleaned before re-calibration is performed.
7.2 Sample determination
Weigh an appropriate amount of sample (to the nearest of 0.0002g) into a 50mL volumetric flask. Add 4.0mL of water. The rest steps are same with 7.1. Perform the blank test of one reagent at the same time.
8 Calculation of results
8.1 Calculation
On the working curve equation (7.1), according to the net absorbance, calculate the mass of aldehydes (??g). Then according to equation (1), calculate the mass fraction of aldehydes in sample (in formaldehyde):
Where,
w - Mass fraction of aldehydes in sample, %;

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