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GB/T 19941, under the general title of Leather and fur—Determination of formaldehyde content, consists of the following three parts:
—Part 1: Method using high performance liquid chromatography;
—Part 2: Spectrophotometric method;
—Part 3: Formaldehyde emission.
This is Part 1 of GB/T 19941.
This part is drafted in accordance with the rules given in GB/T 1.1-2009.
This part replaces the high performance liquid chromatography method of GB/T 19941-2005 Leather and fur—Chemical tests—Determination of formaldehyde content.
The following main technical changes have been made with respect to GB/T 19941-2005:
—normative references of QB/T 1273, QB/T 2717 and GB/T 19941.2 have been added, and normative references of QB/T 1266 and QB/T 2707 has been deleted (see Clause 2 of this standard and Clause 2 of 2005 Edition);
—"principle" has been modified (see Clause 3 of this standard, and 4.1 of 2005 Edition);
—"sodium dodecylsulfate" has been added as extraction solution (see 4.2 of this standard);
—the requirements for recrystallization of 2,4-dinitrophenylhydrazine have been deleted (see 4.2.2 of 2005 Edition);
—the requirements for acetonitrile purity grade have been added (see 4.4 of this standard);
—volumetric flask and Erlenmeyer flask have been added (see 5.1 and 5.2);
—water bath has been changed to thermostatic water bath oscillator, the temperature requirement has been deleted and the frequency requirement has been added (see 5.4 of this standard and 4.3.2 of 2005 Edition);
—the range of thermometer has been modified (see 5.5 of this standard and 4.3.3 of 2005 Edition);
—the wavelength of UV detector has been modified (see 5.6 of this standard and 4.1 of 2005 Edition);
—the requirements for air conditioning before weighing in sample preparation have been deleted (see 4.4.2.3 of 2005 Edition);
—the accuracy of sample weighing and the deviation of water bath temperature during extraction have been modified (see 6.2 of this standard and 4.4.3 of 2005 Edition);
—the plotting of calibration graph has been modified, and the provision that formaldehyde standard solution may be prepared directly with commercially available standard materials has been added (see 6.5.1 of this standard and 4.4.6 of 2005 Edition);
—the content of plotting calibration graph with derivatized DNPH-formaldehyde has been added (see 6.5.2 of this standard);
—the calculation equation for formaldehyde content has been modified (see 6.6 of this standard and 4.4.7 of 2005 Edition);
—relevant provisions for test results calculated on the basis of dry substance, detection limit of methods and method for dispute settlement have been added (see Clause 7 of this standard);
—the requirements for "description and packaging method of test samples", "analytical method used" and "test personnel and date" in "8 Test report" have been deleted (see Clause 7 of 2005 Edition);
—the preparation of formaldehyde stock solution, determination of formaldehyde concentration and related reagents and apparatus have been transferred to Annex C, the titration times of blank solution in formaldehyde stock solution has been added, and the molecular mass of formaldehyde has been modified to 30.02 g/mol (see Annex C of this standard and Clause 3 of 2005 Edition).
This standard is a redraft based on modified adoption of ISO 17226-1:2018 Leather—Chemical determination of formaldehyde content—Part 1: Method using high performance liquid chromatography.
This standard is changed largely from ISO 17226-1:2018 in terms of structure. See Annex A for cross references to the clauses/subclauses between this standard and ISO 17226-1:2018.
Technical differences have been made in this standard with respect to cross reference, and have been listed together with the justification in Annex B.
The following editorial changes have been made in this standard:
—the standard name has been changed to "Leather and fur—Determination of formaldehyde content—Part 1: High performance liquid chromatography method";
—Notes to the measured formaldehyde have been added in "3 Principle";
—the example of diluting filtrate in "8.2.3 Reaction with DNPH” of ISO 17226-1:2018 has been deleted;
—Annex A of ISO 17226-1:2018 has been deleted.
This standard was proposed by the China National Light Industry Council.
This standard is under the jurisdiction of National Technical Committee on Leather of Standardization Administration of China (SAC/TC 252).
The previous edition of this standard is as follows:
—GB/T 19941-2005.
Leather and fur—Determination of formaldehyde content—Part 1: Method using high performance liquid chromatography
1 Scope
This part of GB/T 19941 specifies a method for the determination of free and hydrolyzed formaldehyde content in leather and fur using high performance liquid chromatography (HPLC).
This standard is applicable to the determination of formaldehyde contents 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 19941.2 Leather and fur—Determination of formaldehyde content—Part 2: Spectrophotometric method (GB/T 19941.2-2019, ISO 17226-2:2018, 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 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 2717-2018, ISO 4684:2005, MOD)
3 Principle
The sample is extracted with an extraction solution under specified conditions. Formaldehyde reacts with the mixture of extraction solution and 2,4-dinitrophenylhydrazine (DNPH) to generate formaldehyde hydrazone. Carry out quantitative determination at specified wavelength by means of a reversed-phase HPLC method.
Note1: The formaldehyde content is taken to be the quantity of free-formaldehyde and formaldehyde extracted through hydrolysis contained in water extract from the leather and fur under standard conditions.
Note 2: This method is selective and not sensitive to coloured extracts.
4 Reagents and materials
Use only reagents of recognized analytical grade, unless otherwise stated. All solutions are aqueous solutions.
4.1 Water, Grade 3 according to GB/T 6682, for test purpose.
4.2 Extraction solution, consisting of 0.1 %, 1 g sodium dodecylsulfonate or sodium dodecylsulfate (extraction solution) dissolved in 1,000 mL distilled water.
4.3 DNPH solution, consisting of 0.3 g DNPH (2,4-dinitrophenylhydrazine) dissolved in 100 mL concentrated phosphoric acid (85 % mass fraction).
4.4 Acetonitrile HPLC grade.
5 Apparatus
5.1 Volumetric flasks, of capacities 10 mL, 500 mL and 1,000 mL.
5.2 Erlenmeyer flasks, of capacities 100 mL and 250 mL.
5.3 Strainer with glass fibre filter, GFS (or glass filter strainer G3, diameter 70 mm to 100 mm).
5.4 Thermostatic water bath oscillator, at a frequency of (50±10) times/min.
5.5 Thermometer, with 0.1°C graduations over the range 0°C to 100°C.
5.6 HPLC system with UV detection, (355±5) nm.
5.7 Membrane filter, polyamide, 0.45 μm.
5.8 Analytical balance, weighing to an accuracy of 0.1 mg.
6 Test procedures
6.1 Sampling and preparation of samples
6.1.1 Sampling
Leather sampling shall be in accordance with QB/T 2706.
Fur sampling shall be in accordance with QB/T 1267.
If sampling in accordance with QB/T 2706 or QB/T 1267 is not possible (e.g. leathers from finished products like shoes, garments), provide details about sampling together with the test report.
6.1.2 Preparation of samples
Leather samples shall be prepared in accordance with QB/T 2716.
Fur samples shall be prepared in accordance with QB/T 1272. During the preparation, fur samples shall be kept intact as far as possible and avoid any damage.
6.2 Extraction
Weigh approximately (2±0.1) g of samples to the nearest 0.01 g into a 100 mL glass Erlenmeyer flask. Add 50 mL of extraction solution (4.2) (previously preheated at 40°C) and fit the Erlenmeyer flask with a glass stopper. Shake the contents of the flask in the water bath for (60±2) min at (40±1)°C. Immediately filter the warm extract solution by vacuum (use not less than 50 mbar) through a glass fibre filter into another flask. Cool the filtrate, in a closed flask, down to room temperature (18°C to 26°C).
Note: Do not modify the sample/solution ratio. The extraction and analysis shall be performed within the same working day.
6.3 Reaction with DNPH
Pipette 4.0 mL of acetonitrile (4.4), a 5.0 mL of filtrate (6.2) and 0.5 mL of DNPH solution (4.3) into a 10 mL volumetric flask. Fill the volumetric flask with distilled water up to the mark and shake it briefly by hand to mix the components. Allow it to stand for at least 60 min, but not more than a maximum of 180 min. After filtering through a membrane filter (5.7), analyze the sample using HPLC.
Note: For a high content of formaldehyde (>100 mg/kg), the weighing amount of samples or the pipetting amount of the filtrate may be reduced. For pipetted filtrate less than 5 mL, make it up to 5 mL with distilled water (by diluting).
Foreword i
1 Scope
2 Normative references
3 Principle
4 Reagents and materials
5 Apparatus
6 Test procedures
7 Expression of results
8 Test report
Annex A (Informative) Structural changes of this standard with respect to ISO 17226-1:
Annex B (Informative) Technical differences between this standard and ISO 17226-1:2018, and justification
Annex C (Normative) Determination of formaldehyde content in stock solution
