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GB/T 14571.3-2022 PDF in English


GB/T 14571.3-2022 (GB/T14571.3-2022, GBT 14571.3-2022, GBT14571.3-2022)
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GB/T 14571.3-2022: PDF in English (GBT 14571.3-2022)

GB/T 14571.3-2022
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 71.080.60
CCS G 16
Replacing GB/T 14571.3-2008
Test method of ethylene glycol for industrial use - Part 3:
Determination of content of aldehydes
ISSUED ON: JULY 11, 2022
IMPLEMENTED ON: FEBRUARY 01, 2023
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 Spectrophotometry ... 7
5 Liquid chromatography ... 9
6 Presentation of analysis results ... 13
7 Precision ... 14
8 Quality assurance and control ... 14
9 Report ... 14
Test method of ethylene glycol for industrial use - Part 3:
Determination of content of aldehydes
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 spectrophotometric and liquid chromatographic methods for
the determination of aldehydes in ethylene glycol for industrial use.
This document applies to the determination of aldehyde content in industrial ethylene
glycol. The determination range is 0.10mg/kg~50mg/kg.
If the ethylene glycol sample contains ketones, the liquid chromatography analysis
results will be high. Therefore, when applying this document to the quality control of
the aldehyde content of ethylene glycol products, relevant parties shall negotiate to
determine the analytical method to be used.
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
3 Terms and definitions
This document does not have terms and definitions that need to be defined.
4.3.3 Analytical balance
Accuracy is 0.1mg.
4.4 Sampling
Take samples according to the requirements of GB/T 3723 and GB/T 6680.
4.5 Analysis steps
4.5.1 Inspection of MBTH solution absorbance
Take the MBTH solution (4.2.2) in the 10mm absorption cell. Use water as reference
solution. Measure the absorbance value of the solution at 350nm, 375nm and 400nm.
Record this value. It shall not be greater than 0.020, 0.010, 0.010.
4.5.2 Drawing of working curve
Add 0mL1.0mL, 2.0mL, 3.0mL, 4.0mL, 5.0mL of formaldehyde standard solution
(4.2.5) into six 50mL volumetric flasks. Then add 5.0mL, 4.0mL, 3.0mL, 2.0mL, 1.0mL,
0mL of water respectively. Shake well. Then add 5.0mL of MBTH solution (4.2.2).
Shake well. React at room temperature for 30min. Then add 5.0mL of oxidant solution
(4.2.3). Shake well. Leave it for 20min. Finally use water to dilute to the scale. At
620nm, with water as the reference solution, use the 10mm absorption cell to measure
the absorbance.
Take the mass of formaldehyde (μg) as the abscissa, and the corresponding net
absorbance (deducting the absorbance of the reagent blank) as the ordinate to draw a
working curve. The linear correlation coefficient shall be greater than 0.99.
The operating place shall avoid direct sunlight. The absorbance of the reagent blank
shall not be greater than 0.070. If the absorbance of the blank solution exceeds the upper
limit of the control, the glassware shall be cleaned again. Do the calibration again.
4.5.3 Specimen determination
Weigh an appropriate amount of specimen in a 50mL volumetric flask. The mass is m
(accurate to 0.1mg). Add 4.0mL of water. Subsequent steps are the same as 4.5.2.
Simultaneously do a reagent blank test. The net absorbance of the specimen is its
absorbance minus the absorbance of the blank.
4.6 Calculation
On the working curve drawn according to 4.5.2, check the mass m1 (μg) of aldehyde
according to the net absorbance. Then calculate the aldehyde content (as formaldehyde)
in the specimen according to formula (1).
5.2.4 2,4-Dinitrophenylhydrazine (DNPH)
Purity is ≥99%. It shall not contain phenylhydrazone that affects the determination
results of this method. If there is, it shall be deducted from the measurement.
5.2.5 Aldehyde-2,4-dinitrophenylhydrazone mixed standard solution (15μg/mL)
Aldehyde-2,4-dinitrophenylhydrazone mixed standard solution, includes
formaldehyde-2,4-dinitrophenylhydrazone, acetaldehyde-2,4-dinitrophenylhydrazone.
The solvent is acetonitrile. The corresponding mass concentrations of formaldehyde
and acetaldehyde are both 15μg/mL. This solution is a commercially available standard
solution. Store it prior to use in accordance with the storage instructions provided by
the supplier.
5.2.6 Aldehyde-2,4-dinitrophenylhydrazone mixed standard solution A (0.6μg/mL)
Transfer 1.0mL of aldehyde-2,4-dinitrophenylhydrazone mixed standard solution (5.2.5)
into a 25mL volumetric flask. Dilute to constant volume with acetonitrile (5.2.2). Shake
well.
5.2.7 Dilute hydrochloric acid (1mol/L)
Pipette 9mL of hydrochloric acid (5.2.3) into a 100mL volumetric flask. Use grade one
water to set constant volume. Prepare dilute hydrochloric acid solution of which its
concentration is about 1mol/L.
5.2.8 DNPH solution [0.036% (mass fraction)]
Accurately weigh 0.0180g of DNPH (5.2.4), accurate to 0.1mg. Place in a 50mL
volumetric flask. Add dilute hydrochloric acid (5.2.7) to near the mark. Ultrasound
20min. After the solid dissolves, dilute to constant volume with dilute hydrochloric acid
(5.2.7).
5.3 Instruments and equipment
5.3.1 High performance liquid chromatograph: equipped with ultraviolet detector. The
peak height produced by formaldehyde with the minimum determination content
(0.1mg/kg) specified in this document shall not be lower than 10 times the noise level.
5.3.2 Analytical balance: accuracy is 0.1mg.
5.3.3 Ultrasonic cleaner.
5.3.4 Chromatographic column: see Table 1 for recommended chromatographic
columns.
5.4 Instrument operating conditions
Recommended typical operating conditions are shown in Table 1. A typical
Turn on the chromatograph and make necessary adjustments. Set the instrument
parameters according to the typical operating conditions shown in Table 1 or other
suitable conditions that can obtain the same separation. After the baseline is stable, the
sample can be measured.
NOTE: It takes about 4h~6h for the new chromatographic column to reach equilibrium. Activate
according to the instructions before use.
5.6.2 Drawing of working curve
Transfer 0.5mL, 1.0mL, 2.5mL, 5.0mL of aldehyde-2,4-dinitrophenylhydrazone mixed
standard solution A (5.2.6) into four 10mL volumetric flasks. Then use acetonitrile
(5.2.2) to set to the constant volume in sequence. Shake well. Form a series of standard
solutions together with aldehyde-2,4-dinitrophenylhydrazone mixed standard solution
A (5.2.6). The corresponding mass concentrations of formaldehyde and acetaldehyde
are 0.03μg/mL, 0.06μg/mL, 0.15μg/mL, 0.30μg/mL, and 0.60μg/mL, respectively.
Inject the prepared series of standard solutions into the liquid chromatograph in
sequence. Record its chromatogram and peak areas of formaldehyde-2,4-
dinitrophenylhydrazone and acetaldehyde-2,4-dinitrophenylhydrazone. Take the peak
area as the ordinate, and the corresponding mass concentration of formaldehyde and
acetaldehyde as the abscissa, to respectively draw working curves of formaldehyde and
acetaldehyde.
5.6.3 Specimen determination
Weigh (1±0.02)g or an appropriate amount of ethylene glycol specimen and place it in
a 25mL volumetric flask. Weigh accurately to 0.1mg. Add 5.0mL of DNPH solution
(5.2.8). Shake well. Ultrasound 10min. Use acetonitrile (5.2.2) to set to the constant
volume. If the aldehyde content in the specimen exceeds the linear range of the working
curve, the specimen amount can be appropriately reduced.
Inject the derivatized specimen solution into the chromatograph under the same
chromatographic conditions as the working curve preparation for separation and
determination. Record chromatograms and peak area values for formaldehyde-2,4-
dinitrophenylhydrazone, acetaldehyde-2,4-dinitrophenylhydrazone, and another
aldehyde-2,4-dinitrophenylhydrazone. Check the mass concentration value of
formaldehyde in the specimen solution through the formaldehyde working curve.
Check the mass concentration value of acetaldehyde and other aldehydes in the
specimen solution through the acetaldehyde working curve.
5.7 Calculation
The content of formaldehyde, acetaldehyde and other aldehydes calculated as
acetaldehyde in the specimen is calculated according to formula (2).
......
 
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.