GB/T 19941.1-2025 Leather and fur — Determination of formaldehyde content — Part 1: High-performance liquid chromatography method
1 Scope
This document specifies a method for the determination of free and hydrolyzed formaldehyde content in leather and fur using high-performance liquid chromatography.
This document is applicable to the determination of formaldehyde contents in various leathers, furs and their products.
Note: The method specified in this document is selective and less affected by colored extracts, making it particularly suitable for the precise quantification of formaldehyde content.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions 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 39364 Leather - Chemical, physical, mechanical and fastness tests - Sampling location (GB/T 39364-2020, ISO 2418:2017, MOD)
QB/T 1267 Fur - Chemical, physical and mechanical and fastness tests - Sampling location
QB/T 1272 Fur - Preparation of chemical test samples
QB/T 1273 Fur - Chemical tests - Determination of volatile matter
QB/T 2716 Leather - Preparation of chemical test samples
QB/T 2717 Leather - Chemical test - Determination of volatile
3 Terms and definitions
No terms and definitions are listed in this document.
4 Principle
The sample of leather or fur is eluted at specified conditions. The eluate is mixed with 2,4-dinitrophenylhydrazine (DNPH), whereby aldehydes and ketones react to give the respective hydrazones. These are separated by means of a reversed-phase HPLC with ultraviolet (UV) detector or diode array detector (DAD).
Note: The formaldehyde content is taken to be the quantity of free formaldehyde and formaldehyde extracted through hydrolysis contained in a water extract from the leather under standard conditions of use.
5 Reagents and materials
5.1 Use only reagents of recognized analytical grade, unless otherwise stated. The test water shall meet the requirements of Grade 3 water specified in GB/T 6682. All solutions are aqueous solutions.
5.2 Formaldehyde solution, approximately 37% (mass fraction).
Note: Certified solutions of formaldehyde or formaldehyde-2,4-DNPH are commercially available. When these solutions are used, the procedure in 8.1 is not required.
5.3 Iodine solution, 0.05 mol/l, i.e. 12.68g iodine per litre.
5.4 Sodium hydroxide (NaOH) solution, 2.0 mol/L.
5.5 Sulfuric acid (H₂SO₄) solution, 2.0 mol/L.
5.6 Sodium thiosulfate (Na₂S₂O₃) solution, 0.1 mol/L.
5.7 Starch solution, 1% (mass fraction), i.e. 1g in 100mL distilled water.
5.8 Acetonitrile, chromatographically grade.
5.9 Extract solution, 0.1% (mass fraction), i.e. 1g sodium dodecylsulfonate or sodium dodecylsulfate in 1 000mL water.
5.10 2,4-dinitrophenylhydrazine (DNPH) solution, consisting of 0.3g DNPH (2,4-dinitrophenylhydrazine) dissolved in 100mL acetonitrile (5.8).
6 Apparatus
6.1 Volumetric flasks, of capacities 10mL, 500mL and 1 000mL.
6.2 Conical flasks with stopper or screw cap, of capacities 100mL and 250mL.
6.3 Strainer with glass fibre filter, GF8 (or glass filter strainer G3, diameter 70mm to 100mm).
6.4 Water bath, thermostatically controlled to (40 ± 2)°C, fitted with a flask shaker, frequency (50 ± 10)r/min.
6.5 Water bath or oven, thermostatically controlled to (50 ± 2)°C.
6.6 HPLC system with UV or DAD detection.
6.7 Membrane filter, for example polyamide, 0.45µm.
Contents
Foreword II
Introduction V
1 Scope
2 Normative references
3 Terms and definitions
4 Principle
5 Reagents and materials
6 Apparatus
7 Sampling and preparation of samples
8 Test procedure
9 Calculation and expression of results
10 Feasibility of the method
11 Test report
Annex A (Informative) Comparison of clause/subclause numbers between this document and ISO 17226-1:2021
Annex B (Informative) Technical differences between this document and ISO 17226-1:2021 and their justifications
Annex C (Informative) HPLC conditions
Annex D (Informative) Precision: reliability of the HPLC method
