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This standard is developed in accordance with the rules given in GB/T 1.1-2009.
This standard was proposed by China Petroleum and Chemical Industry Association.
This standard is under the jurisdiction of SAC/TC 134/SC 1 the Subcommittee on Textile Auxiliaries of National Technical Committee on Dyestuffs of the Standardization Administration of China.
Determination of chromium (VI) content in textiles dyeing and finishing auxiliaries
Warning: Persons using this standard shall be familiar with normal laboratory practice. This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user to establish appropriate safety and health practices and to ensure compliance with any national regulatory conditions.
1 Scope
This standard specifies the determination method of chromium (VI) in textile dyeing and finishing auxiliaries.
This standard is applicable to the determination of chromium (VI) in various textile dyeing and finishing auxiliaries.
2 Normative references
The following 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 8170 Rules of rounding off for numerical values & expression and judgment of limiting values
3 Theory
Dissolve the chromium (VI) in the textile dyeing and finishing auxiliaries with buffer solution, filter the extraction liquid formed via color development reaction and determine it using a liquid chromatograph equipped with a ultraviolet detector or a diode array detector, then quantify it with the external standard method.
4 Reagents and materials
Unless otherwise specified, only analytically pure reagent and Grade 3 water (defined in GB/T 6682) shall be adopted.
4.1 Phosphoric acid solution: dilute 700 mL of phosphoric acid (H3PO4, ρ=1.71 g/mL) to 1,000 mL with water.
4.2 Diphenylcarbazide solution: dissolve 10 g of 1, 5-diphenylcarbazide (C13H14N4O) in 100 mL of acetone and add 1 drop of glacial acetic acid.
Note: The solution shall be stored at 4℃ in a brown bottle, with the validity period being two weeks.
4.3 Buffer solution: dissolve 22.8 g (to the nearest of 0.01 g) of potassium phosphate, dibasic (K2HPO4·3H2O) in 1,000 mL of water, adjust the pH to 8.0±0.1 with phosphoric acid (4.1), and deoxidize it with argon or nitrogen.
4.4 Potassium dichromate (K2Cr2O7), guaranteed reagent: dried to constant at (120±2)℃.
4.5 Chromium (VI) standard stock solution, 1,000 mg/L: weigh 2.829 g (to the nearest of 0.0001 g) of potassium dichromate (K2Cr2O7) (4.4), dissolve it with water, then transfer, wash and dilute it to the scale into a 1,000-mL volumetric flask.
4.6 Chromium (VI) standard working solution, 10 mg/L: pipette 1 mL of chromium (VI) standard stock solution into a 100-mL volumetric flask, and dilute to the mark with potassium phosphate dibasic buffer solution (4.3).
4.7 Nitrogen (or argon): with a purity of ≥ 99.998% (volume fraction);
4.8 C18 column or glass or polypropylene specimen tube filled with suitable reversed phase material.
5 Apparatus
5.1 High performance liquid chromatograph: equipped with ultraviolet detector or diode array detector.
5.2 Balance: with a sensibility of 0.1 mg.
5.3 Ultrasonic cleaner: with an operating frequency of 40 kHz.
5.4 Gas-guide tube.
5.5 Flowmeter.
5.6 Conical flask with stopper: 250 mL and 150 mL.
5.7 Filtering membrane: 0.22 μm, inorganic phase.
6 Determination procedures
6.1 Preparation of specimen solution
Pipette 100 mL of the buffer solution (with the air removed) (4.3) into a 250-mL conical flask with stopper, insert the gas-guide tube (5.4) (which must not touch the liquid surface), and introduce the nitrogen into the conical flask (4.7) at the flow rate of (50±10)mL/min for 5min. Weigh 1 g (to the nearest of 0.0001 g) of sample into the conical flask, cover the ground-glass stopper, shake it well, and place it into the ultrasonic cleaner (5.3) to extract for 30 min.
Note 1: The ultrasonic cleaner is not heated and the extraction is carried out at room temperature.
The C18 column (4.8) should be washed with 5 mL of methanol first, then with 5 mL of Grade 3 water, and then rinsed with 10 mL of buffer solution (4.3). After extraction, the solution in the conical flask shall be filtered through the C18 column (4.8) into a 150-mL conical flask. Pipette 5 mL of the filtrate into a colorimetric tube, add 1 mL of phosphoric acid solution (4.1) and 1 mL of diphenylcarbazide solution (4.2), and dilute to 10 mL with buffer solution (4.3). Let it stand for (15±5) min at room temperature then filter it through a 0.22 μm filtering membrane for instrument analysis.
Note 2: If the sample concentration is too high, it is recommended to dilute it to the appropriate concentration before subjecting it to instrument analysis.
Foreword i
1 Scope
2 Normative references
3 Theory
4 Reagents and materials
5 Apparatus
6 Determination procedures
7 Quantitation limit, recovery rate and precision
8 Test report
Annex A (Informative) Liquid chromatogram of chromium (VI)
