GB/T 19941.2-2019 PDF English
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Leather and fur -- Determination of formaldehyde content -- Part 2: Colorimetric method
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GB/T 19941.2-2019: PDF in English (GBT 19941.2-2019) GB/T 19941.2-2019
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 59.140.30
Y 46
Partially replacing GB/T 19941-2005
Leather and fur - Determination of formaldehyde
content - Part 2: Colorimetric method
(ISO 17226-2:2018, Leather - Chemical determination of formaldehyde
content - Part 2: Method using colorimetric analysis, MOD)
ISSUED ON: DECEMBER 31, 2019
IMPLEMENTED ON: JULY 01, 2020
Issued by: State Administration for Market Regulation;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 6
2 Normative references ... 6
3 Principle ... 7
4 Reagents and materials ... 7
5 Instruments and equipment... 8
6 Test steps ... 8
7 Result representation ... 12
8 Test report ... 12
Annex A (informative) Structural changes in this Part compared with ISO 17226-
2:2018 ... 14
Annex B (informative) Technical differences between this Part and ISO 17226-
2:2018 and their reasons ... 15
Annex C (normative) Determination of formaldehyde content in standard stock
solution ... 17
Foreword
GB/T 19941 “Leather and fur - Determination of formaldehyde content” consists
of the following 3 parts:
- Part 1: High performance liquid chromatography method;
- Part 2: Colorimetric method;
- Part 3: Formaldehyde emissions.
This Part is Part 2 of GB/T 19941.
This Part was drafted in accordance with the rules given in GB/T 1.1-2009.
This Part replaces colorimetric method in GB/T 19941-2005 “Leather and fur-
Chemical tests - Determination of formaldehyde content”.
Compared with GB/T 19941-2005, the main technical changes in this Part are
as follows:
- added references of QB/T 1273, QB/T 2717, GB/T 19941.1; deleted
references of QB/T 1266 and QB/T 2707 (see Clause 2 of this Edition,
Clause 2 of Edition 2005);
- modified “3 Principle” (see Clause 3 of this Edition, 5.1 of Edition 2005);
- added "sodium lauryl sulfate" as extraction solution (see 4.2 of this Edition);
- modified expiry date of Nessler's reagent (see 4.3 of this Edition, 5.2.2 of
Edition 2005);
- deleted air conditioning requirements before weighing in the preparation of
samples (see 5.4.2.3 of Edition 2005);
- modified types and specifications of glassware in instruments and
equipment (see Clause 5 of this Edition, 5.3 of Edition 2005);
- modified composition of blank solution in "Inspection of other compounds
that develop color with acetylacetone"; added the processing method when
the absorbance value is higher than 0.05 (see 6.5 of this Edition, 5.4.6 of
Edition 2005);
- added regulations for the direct preparation of formaldehyde standard
solutions from commercially available reference materials (see 6.6 of this
Edition);
Leather and fur - Determination of formaldehyde
content - Part 2: Colorimetric method
1 Scope
This Part of GB/T 19941 specifies the method for determination of free and
hydrolyzed formaldehyde content in leather and fur by colorimetric method.
This Part is applicable to determination of formaldehyde content in various
leathers, furs and their products.
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 6682, Water for analytical laboratory use - Specification and test
methods (GB/T 6682-2008, ISO 3696:1987, MOD)
GB/T 19941.1, Leather and fur - Determination of formaldehyde content -
Part 1: High performance liquid chromatography method (GB/T 19941.1-
2019, ISO 17226-1:2018, MOD)
QB/T 1267, Fur - Chemical, physical and mechanical and fastness tests -
Sampling location (QB/T 1267-2012, ISO 2418:2002, MOD)
QB/T 1272, Leather - Chemical tests - Preparation of chemical test samples
(QB/T 1272-2012, ISO 4044:2008, MOD)
QB/T 1273, Fur - Chemical Tests - Determination of Volatile Matter (QB/T
1273-2012, ISO 4684:2005, MOD)
QB/T 2706, Leather - Chemical physical and mechanical and fastness tests
- Sampling location (QB/T 2706-2005, ISO 2418:2002, MOD)
QB/T 2716, Leather - Preparation of chemical test samples (QB/T 2716-2018,
ISO 4044:2008, MOD)
QB/T 2717, Leather - Chemical tests - Determination of volatile (QB/T 2717-
5 Instruments and equipment
5.1 Volumetric flasks: 10mL, 50mL, 1000mL.
5.2 Erlenmeyer flasks: 25mL, 100mL, 250mL.
5.3 Glass fiber filter: GF8 (or glass filter G3, diameter is 70mm~100mm).
5.4 Constant temperature water bath oscillator: oscillation frequency is (50±10)
times/min.
5.5 Thermometer: range is 10°C~50°C, accuracy is 0.1°C.
5.6 Analytical balance: accuracy is 0.1mg.
5.7 Spectrophotometer: wavelength is 412nm, equipped with suitable cuvette.
It is recommended to use 20mm cuvette; 40mm or 50mm cuvette can also be
used.
6 Test steps
6.1 Sampling and sample preparation
6.1.1 Sampling
Leather is sampled in accordance with QB/T 2706. Fur is sampled in
accordance with QB/T 1267.
If it is not possible to sample according to the requirements of QB/T 2706 or
QB/T 1267 (such as shoe uppers, leather on leather clothing), it shall be noted
in the report.
6.1.2 Sample preparation
The preparation of leather samples is carried out in accordance with QB/T 2716.
The preparation of fur samples is carried out in accordance with QB/T 1272.
During the sample preparation process, try to keep the coat intact to avoid
damage to the coat.
6.2 Extraction
Accurately weigh (2.0±0.1) g of sample, to the nearest of 0.01g. Put into a
100mL Erlenmeyer flask (5.2). Add 50mL of extraction solution (4.2) that has
been preheated to 40°C. Tighten the stopper. In a constant temperature water
bath oscillator (5.4) at (40±1)°C, gently oscillate (60±2) min. The warm extract
determined absorbance value shall be less than 0.05 (use 20mm cuvette).
When the absorbance value is higher than 0.05, it shall be tested in accordance
with the method in GB/T 19941.1. If it cannot be tested in accordance with GB/T
19941.1, it shall be stated in the test report. Other compounds detected during
the analysis may cause a positive reaction to formaldehyde.
6.6 Drawing of standard working curve
Prepare formaldehyde standard stock solution according to Annex C. Transfer
5mL of formaldehyde standard stock solution into a 1000mL volumetric flask
containing 100mL of distilled water. After oscillating well, use distilled water to
dilute to the scale. This solution is the formaldehyde standard solution (the
mass concentration of formaldehyde in the standard solution is about 10μg/mL).
Commercially available standard materials can also be used to directly prepare
formaldehyde standard solution.
NOTE: At present, there are "standard substances of formaldehyde solution in water" as
standard samples on the market.
Respectively pipette 1mL, 5mL, 10mL, 15mL and 20mL of formaldehyde
standard solution into a 50mL volumetric flask. Use distilled water to dilute to
the scale. The mass concentration of formaldehyde in this series of standard
working solutions ranges from 0.2μg/mL to 4.0μg/mL (Under the given
conditions, it is equivalent to the range of formaldehyde content in the sample
from 5mg/kg to 100mg/kg. For samples with higher formaldehyde mass
concentration, less filtrate shall be taken for testing).
From the above 5 solutions, respectively pipette 5mL. Separately transfer them
into 25mL conical flasks (5.2). Add 5mL of acetylacetone solution (4.3). Mix. At
(40±1)°C, conduct constant temperature oscillation (30±1) min. Cool to room
temperature in the dark. Take a mixture of 5mL of acetylacetone solution (4.3)
and 5mL of distilled water as a blank. Use a spectrophotometer to determine
the absorbance value at 412nm. Before determination, use the blank solution
(5mL of acetylacetone solution and 5mL of distilled water) to conduct zero
adjustment to the spectrophotometer (5.7). The blank solution and standard
working solution shall be processed under the same conditions.
Plot the mass concentration-absorbance standard curve. X axis is mass
concentration (μg/mL). Y axis is absorbance.
NOTE: The standard working curve is drawn using a 20mm cuvette. It may also use 40mm
or 50mm cuvette.
6.7 Calculation of formaldehyde content in samples
Calculate the formaldehyde content in the sample according to formula (1):
Annex C
(normative)
Determination of formaldehyde content in standard stock solution
C.1 Reagents and materials
C.1.1 Formaldehyde solution: mass fraction is about 37%.
C.1.2 Iodine solution: 0.05mol/L, that is 12.68g/L.
C.1.3 Sodium hydroxide solution: 2.0mol/L.
C.1.4 Sulfuric acid solution: 2.0mol/L.
C.1.5 Sodium thiosulfate solution: 0.1mol/L.
C.1.6 Starch solution: 1%, that is, 1g of starch is dissolved in 100mL of distilled
water.
C.2 Instruments and equipment
C.2.1 Volumetric flask: 1000mL.
C.2.2 Erlenmeyer flask: 250mL.
C.2.3 Pipettes: 5mL, 10mL.
C.3 Determination methods
C.3.1 Preparation of formaldehyde standard stock solution
Transfer 5.0mL of formaldehyde solution (C.1.1) into a 1000mL volumetric flask
(C.2.1) filled with about 100mL of distilled water. Use distilled water to dilute to
the scale. This solution is formaldehyde standard stock solution.
C.3.2 Determination
Pipette 10mL of formaldehyde standard stock solution into a 250mL conical
flask (C.2.2). Add 50mL of iodine solution (C.1.2). After mixing well, add sodium
hydroxide solution (C.1.3) until it turns yellow. Place and react at a temperature
of 18°C~26°C for (15±1) min. Then add 15mL of sulfuric acid solution (C.1.4).
Oscillate.
Then add 2mL of starch solution (C.1.6). Use sodium thiosulfate solution (C.1.5)
to titrate the excess iodine until the blue color disappears. Conduct three
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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