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GB/T 14571.4-2022 English PDF (GBT14571.4-2022)

GB/T 14571.4-2022 English PDF (GBT14571.4-2022)

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GB/T 14571.4-2022: Test method of ethylene glycol for industrial use -- Part 4???Determination of ultraviolet transmittance -- Ultraviolet spectrophotometric method

This document specifies the method for determination of the UV light transmittance of ethylene glycol for industrial use in the wavelength range of 200nm~350nm. This document is applicable to the determination of the UV light transmittance of ethylene glycol for industrial use.
GB/T 14571.4-2022
NATIONAL STANDARD OF THE PEOPLE REPUBLIC OF CHINA
ICS 71.080.60
CCS G 16
Replacing GB/T 14571.4-2008
Test method of ethylene glycol for industrial use - Part 4:
Determination of ultraviolet transmittance - Ultraviolet
spectrophotometric method
ISSUED ON: APRIL 15, 2022
IMPLEMENTED ON: NOVEMBER 01, 2022
Issued by: State Administration for Market Regulation;
Standardization Administration of the People's Republic of China.
Table of Contents
Foreword ..... 3
Introduction .... 5
1 Scope ..... 6
2 Normative references ..... 6
3 Terms and definitions .... 6
4 Method summary ..... 7
5 Reagents or materials .... 7
6 Instruments ..... 7
7 Sampling ... 8
8 Test steps ..... 8
9 Test data processing ... 11
10 Precision ... 11
11 Quality control and assurance ... 12
12 Report ... 12
Annex A (normative) Method for determination of absorbance of reference water .... 13 Test method of ethylene glycol for industrial use - Part 4:
Determination of ultraviolet transmittance - Ultraviolet
spectrophotometric method
WARNING: This document is not intended to address all safety issues related to its use. Users are responsible for taking appropriate safety and health measures to ensure compliance with relevant national laws and regulations.
1 Scope
This document specifies the method for determination of the UV light transmittance of ethylene glycol for industrial use in the wavelength range of 200nm~350nm. This document is applicable to the determination of the UV light transmittance of ethylene glycol for industrial use.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. GB/T 3723, Sampling of chemical products for industrial use - Safety in sampling GB/T 6680, General rules for sampling liquid chemical products
GB/T 6682, Water for analytical laboratory use - Specification and test methods GB/T 8170, Rules of rounding off for numerical values and expression and judgement of limiting values
JJG 178-2007, Verification Regulation of Ultraviolet, Visible, Near-Infrared Spectrophotometers
3 Terms and definitions
This document does not have terms and definitions that need to be defined. 4 Method summary
Place the specimen in a 10mm quartz absorption cell. Use water as a reference. Directly determine the UV transmittance at 220nm, 250nm, 275nm and 350nm. The absorbance at the above wavelengths can also be determined. Calculate the UV transmittance. If necessary, nitrogen can be introduced to remove the dissolved oxygen in the specimen. Then determine its UV transmittance.
5 Reagents or materials
5.1 Unless otherwise specified, all reagents used are analytically pure. 5.2 Holmium oxide wavelength calibration filter: qualified after calibration. 5.3 Transmittance filter in the ultraviolet region: qualified after calibration. 5.4 Cut-off filter.
5.5 Isooctane: spectrally pure.
5.6 Naphthalene solution (1mg/L): commercially available or dissolve 1mg of naphthalene in 1000mL of spectroscopically pure isooctane.
5.7 Holmium oxide standard solution (40g/L): commercially available or prepared according to C.4 in JJG 178-2007.
5.8 Potassium dichromate standard solution (60.00mg/L): commercially available or prepared according to C.3 in JJG 178-2007.
5.9 Sodium iodide standard solution (10g/L): prepare according to C.1 in JJG 178-2007. 5.10 Nitrogen: purity ??? 99.99% (volume fraction); without oil.
5.11 Reference water: grade one water in compliance with GB/T 6682; the absorbance at 220nm is not greater than 0.01. The absorbance of water shall be tested in accordance with Annex A.
6 Instruments
6.1 UV spectrophotometer
Double beam. Determination wavelength is 200nm~400nm. The absorbance accuracy is better than 0.001. The working wavelength of the instrument is divided into two sections, namely section A (190nm~340nm) and section B (340nm~400nm). The wavelength accuracy of section A is ??0.5nm; the wavelength repeatability is ???0.2nm. 8.1.1 Start-up preparation
The instrument starts up and enters the hardware self-inspection. After a period of stability, set the instrument parameters. A bandwidth of 2.0nm is used. 8.1.2 Instrument verification
8.1.2.1 Wavelength accuracy
Naphthalene solution (5.6) can be used to check the wavelength accuracy of the photometer at 220nm. Use spectrally pure isooctane as a reference. Use the 10mm absorption cell to measure the maximum absorption wavelength of naphthalene (shall be 220.6nm). The measured value shall be within the range of 220.6nm??0.3nm. Otherwise, the absorbance of the ethylene glycol specimen shall be measured at a wavelength 0.6 nm lower than the measured value.
It can also use holmium oxide standard solution (5.7) or holmium oxide wavelength calibration filter (5.2) to check the wavelength accuracy, which shall meet the requirements of 6.1.
NOTE: The absorbance of ethylene glycol varies greatly around 220nm. The wavelength accuracy of the photometer at 220nm has a great influence on the detection results. 8.1.2.2 Transmittance accuracy
Use the potassium dichromate standard solution (5.8) or the ultraviolet region transmittance filter (5.3) to test the accuracy of the light transmittance of the photometer, which shall meet the requirements of 6.1.
8.1.2.3 Stray light
Use sodium iodide standard solution (5.9), or cut-off filter (5.4) to measure the transmittance of the photometer at 220nm (i.e., stray light), which shall meet the requirements of 6.1.
8.1.3 Glassware preparation
Use hydrochloric acid-water-methanol solution (1:3:4, volume ratio) or chromic acid washing solution to thoroughly clean the absorption cell and other glassware. 8.2 Specimen pretreatment
8.2.1 For the fresh ethylene glycol specimens collected directly from the production device, the UV light transmittance or absorbance of the collected specimens can be measured according to 8.3.1 and 8.3.2. Ethylene glycol specimens that have been stored and transported, or the specimens of which the light transmittance at 220nm is lower than the specified limit value (such as product index), can be pretreated according to the requirements of 8.2.2.
8.2.2 Use nitrogen to thoroughly purge lines. Add about 20mL of ethylene glycol sample into a 25mL volumetric flask or Erlenmeyer flask. Use a clean closed glass tube (6.6) to access nitrogen gas at a flow rate of 150mL/min to the bottom of the specimen for 10min. Plug and save.
NOTE: Ethylene glycol has an absorption peak at 180nm in the far ultraviolet region. When there is dissolved oxygen (air) in the specimen, the dissolved oxygen will associate with ethylene glycol. It will cause the absorption peak of ethylene glycol to shift to the long-wave direction and reduces the light transmittance of ethylene glycol at 220nm. Therefore, injecting nitrogen gas into the specimen can eliminate the influence of dissolved oxygen on the light transmittance of ethylene glycol at 220nm.
8.3 Specimen analysis
8.3.1 Direct method
Fill the reference water (5.11) into two paired 10mm quartz absorption cells. Place the absorption cell in the cell holder of the photometer. Pay attention to the direction of the absorption cell. Calibrate the transmittance at 220nm, 250nm, 275nm and 350nm as 100%. Pour out the water in the sample cell. Dry with nitrogen. Load the specimen to be tested in the sample cell. Take reference water (5.11) as reference. Measure and record the UV transmittance of the specimen at each wavelength. Note that the direction of the absorption cell in the cell holder shall remain the same. The water in the reference cell shall be replaced with each set of measurements. After the measurement, empty the specimen. Use water to clean the absorption cell. Soak in water.
NOTE: Be very careful when transferring the specimen so as not to generate air bubbles and affect the test results.
8.3.2 Absorbance method
Fill the reference water (5.11) into two paired 10mm quartz absorption cells. Place the absorption cell in the cell holder of the photometer. Pay attention to the direction of the absorption cell. Measure the absorbance at the wavelengths of 220nm, 250nm, 275nm and 350nm. The absorption cell with higher absorbance value is used as the sample cell, and the other is used as the reference cell. Record the absorbance values as the calibration values for the cell at different wavelengths. Pour out the water in the sample cell. Dry with nitrogen. Load the specimen to be tested in the sample cell. Take reference water (5.11) as reference. Measure and record the absorbance value of the specimen at each wavelength. Note that the direction of the absorption cell in the cell holder shall remain the same. When carrying out each set of measurements, the water in the reference cell shall be replaced. After the measurement, empty the specimen and clean the absorption cell with water. Soak in water.
NOTE: Avoid air bubbles when transferring the specimen, which will affect the test results.

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