GB/T 22807-2019 Leather and fur - Chemical tests - Determination of chromium (VI) content: Colorimetric method
1 Scope
This standard specifies a colorimetric method for the determination of chromium (VI) content in leather and fur.
The method described is applicable to quantify the chromium (VI) 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 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)
GB/T 2706 Leather - Chemical, physical and mechanical and fastness tests - Sampling location (QB/T 2706-2005, ISO 2418:2002, MOD)
GB/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
Extractable chromium (VI) is leached from the specimen in phosphate buffer and coextracted coloured substances which influence the detection are removed by solid phase extraction if necessary. After filtration, chromium (VI) in the filtrate is reacted with 1,5-diphenylcarbazide under acidic conditions to generate a red/violet complex. Measure the absorbance of the complex at a specified wavelength, and calculate the content of chromium (VI).
4 Reagents and materials
Unless otherwise specified, analytical reagents shall be adopted.
4.1 Water, which shall meet the requirements for Grade 3 water specified in GB.T 6682.
4.2 Phosphate buffer (0.1 mol/L): Dissolve 22.8 g dipotassium hydrogenphosphate (K2HPO4?3H2O, with the relative molecular mass of 228) in 1,000 mL distilled water, adjusted to pH 8.0 ± 0.1 with phosphoric acid (4.4). Degas this solution with either argon or nitrogen (4.8) or ultrasonic bath.
Note: Phosphate buffer is recommended to be freshly prepared. However, the solution may be kept for up to one week at 0℃ to 4℃ but shall be warmed to room temperature and degassed prior to use.
4.3 1,5-Diphenylcarbazide (DPC) solution: Dissolve 1.0 g 1,5-diphenylcarbazide in 100 mL acetone, and acidified with one drop of glacial acetic acid.
Note: The solution shall be kept in a brown glass bottle and stored under protection from light at 0℃ to 4℃, with the shelf life up to 14 days. The solution can no longer be used if it has obvious discoloration (especially pink).
4.4 Phosphoric acid (H3PO4) solution: Dilute 700 mL phosphoric acid (with a mass fraction of 85% and a density of 1.71 g/mL) to 1,000 mL with distilled water.
4.5 Potassium dichromate (K2Cr2O7) reference substance: dried for (16 ± 2) h at (102 ± 2)℃ before use.
4.6 Chromium(VI) standard stock solution ......
GB/T 22807-2019 The following standards are cited：
