GB/T 22807-2019 English PDF (GBT22807-2019)

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GB/T 22807-2019: Leather and fur -- Chemical tests -- Determination of chromium Ⅵ content
GB/T 22807-2019
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 59.140.30
Y 46
Replacing GB/T 22807-2008
Leather and fur - Chemical tests - Determination
of chromium (VI) content: Colorimetric method
[ISO 17075-1:2017, Leather - Chemical determination of chromium (VI)
content in leather - Part 1: Colorimetric method, 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 ... 5
2 Normative references ... 5
3 Principle ... 6
4 Reagents and materials ... 6
5 Apparatus and equipment ... 7
6 Sampling and preparation of samples ... 8
7 Test procedure ... 8
8 Calculation and expression of results ... 11
9 Test report ... 13
Annex A (informative) Structural changes of this Standard compared with ISO
17075-1:2017 ... 15
Annex B (informative) Technical differences between this Standard and ISO
17075-1:2017 and their reasons ... 16
Annex C (informative) Comparison of colorimetric method (GB/T 22807) and
chromatographic method (GB/T 38402) ... 19
Leather and fur - Chemical tests - Determination
of chromium (VI) content: Colorimetric method
1 Scope
This Standard specifies the colorimetric method for the determination of
chromium content in leather and fur.
This Standard applies to the determination of chromium content in various
leather, fur 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 38402 Leather and fur - Chemical tests - Determination of chromium
(VI) content: Chromatographic method (GB/T 38402-2019, ISO 17075-
2:2017, 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 Fur - 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 matter (QB/T
6 Sampling and preparation of samples
6.1 Sampling
For leather, it is carried out according to the provisions of QB/T 2706.
For fur, it is carried out according to the provisions of QB/T 1267.
If the sampling is not possible according to the requirements of QB/T 2706 or
QB/T 1267 (such as shoe uppers, leather on leather clothing), the sampling
process shall be indicated in the report.
6.2 Preparation of samples
Leather: according to the provisions of QB/T 2716.
Fur: according to the provisions of QB/T 1272. It shall avoid damaging the fur
during the sample preparation process and keep the fur intact.
REMOVE the glue and attachments on the sample as cleanly as possible, MIX
the sample evenly, and PUT it into a clean sample bag for test.
7 Test procedure
7.1 Preparation of analytical solution
WEIGH (2.0 ± 0.1) g of cut sample, to the nearest 0.001 g.
PIPETTE 100 mL of degassed phosphate buffer (4.2) into a 250 mL conical
flask (5.2); INSERT an aeration tube (5.3) (the aeration tube must not touch the
liquid surface); PASS argon or nitrogen into the conical flask (4.8) at a flow rate
of (50 ± 10) mL/min. After 5 min, REMOVE the aeration tube; ADD the sample
and COVER with a ground stopper; PLACE it in an oscillator (5.1) at room
temperature (18 °C ~ 26 °C) for water bath extraction for (180 ± 5) min, and the
oscillation frequency is (100 ± 10) times/min.
NOTE 1: Take care to avoid the sample sticking to the flask wall above the liquid surface during
the oscillation.
NOTE 2: The extraction conditions have a direct impact on the test results of this method. The
results obtained by using different extraction conditions (such as extraction solvent, pH value,
extraction time, etc.) are not comparable to the results obtained by this method.
After the extraction is completed, filter with filter paper (5.7), and then check the
pH value of the extract, which shall be between 7.0 and 8.0. If it exceeds this
range, it needs to reduce the mass of the sample and carry out the extraction
and the absorbance is determined by the same method, and denote it as E2.
7.3 Blank solution
TAKE a 25 mL volumetric flask; ADD phosphate buffer (4.2) to three-quarters
of the volumetric flask; ADD 0.5 mL of phosphoric acid solution (4.4) and 0.5
mL of 1,5-diphenylcarbazide solution (4.3); USE phosphate buffer (4.2) to make
the volume constant and SHAKE well. The solution shall be prepared for
immediate use and placed in a dark place before use.
7.4 Plotting of standard working curve
In the range of 0.5 mL ~ 15 mL of chromium standard solution (4.7), PREPARE
at least 6 standard working solutions, and PLOT a suitable standard working
curve, ensuring that the range of the standard working curve is within the linear
measurement range of the spectrophotometer. PIPETTE a certain amount of
chromium standard solution (4.7) into 25 mL volumetric flasks; ADD 0.5 mL of
phosphoric acid solution (4.4) and 0.5 mL of 1,5-diphenylcarbazide solution (4.3)
to each volumetric flask; DILUTE with buffer solution (4.2) and make the volume
constant; LET STAND for (15 ± 5) min.
Taking the blank solution (7.3) as a reference, use a 2 cm cuvette to determine
the absorbance of the standard working solutions at 540 nm.
PLOT a standard working curve with absorbance as the Y axis and the mass
concentration of chromium (μg/mL) as the X axis.
NOTE: Tests have proved that 2 cm cuvettes are the most suitable. The above standard
working solutions are for testing with 2 cm cuvettes. In some cases, it may be suitable to use
cuvettes with a longer or shorter optical path.
7.5 Determination of recovery rate
7.5.1 Influence of matrix
PIPETTE 10 mL of the analytical solution obtained in 7.1, ADD an appropriate
amount of chromium standard solution, so that the content of chromium is close
to 2 times (±25 %) of the content of chromium in the original analytical solution
(7.1). The final volume of the solution after adding the chromium standard
solution does not exceed 11 mL. Then use the same method as the sample to
process and determine the absorbance (see 7.2), and denote them as E1s and
E2s respectively.
The absorbance shall be within the range of the standard working curve,
otherwise it shall reduce the pipetting volume of the analytical solution and
repeat the test. The recovery rate shall be greater than 80 %.
E1 - the absorbance of analytical solution with diphenylcarbazide solution;
E2 - the absorbance of analytical solution without diphenylcarbazide solution;
ρ - the mass concentration of the chromium added, in micrograms per
milliliter (μg/mL);
F - the gradient of the standard working curve.
8.4 Expression of results
For the chromium content in the sample, it takes the arithmetic mean value of
th...