GB/T 28019-2011 English PDF
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GB/T 28019-2011: Adornment - Determination of Chromium (VI). 1, 5-Diphenylcarbohydrazide spectrophotometric method
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GB NATIONAL STANDARD OF THE PEOPLE’S REPUBLIC OF CHINA ICS 39.060 Y 88 Adornment - Determination of Chromium (VI) - 1,5- Diphenylcarbohydrazide Spectrophotometric Method Issued on. OCTOBER 31, 2011 Implemented on. FEBRUARY 1, 2012 Issued by. General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword... 3 1 Scope... 4 2 Method and Principle... 4 3 Reagents and Materials... 4 4 Apparatus... 5 5 Analysis Steps... 6 6 Representation of the Result... 7 7 Test Report... 8Foreword
This Standard was drafted in accordance with the rules given in GB/T 1.1-2009. This Standard was proposed by the China National Light Industry Council. This Standard shall be under the jurisdiction of the National Technical Committee of Jewelry Standardization (SAC/TC 256). Drafting organizations of this Standard. National Jewelry Quality Supervision and Inspection Center. Main drafters of this Standard. Li Suqing, Li Yukun, Li Wujun. Adornment - Determination of Chromium (VI) - 1,5- Diphenylcarbohydrazide Spectrophotometric Method1 Scope
This standard specifies the 1,5-Diphenylcarbohydrazide spectrophotometric method for Chromium (VI). This Standard applies to the determination of Chromium (VI) in adornment.2 Method and Principle
Use alkaline leaching solution to leach the water-soluble and water-insoluble hexavalent chromium compounds from the sample. In acidic solution, the hexavalent chromium from the leachate reacts with the diphenylcarbazide and the reaction forms the purple-red complex. At the wavelength of 540 nm, perform spectrophotometric determination.3 Reagents and Materials
Unless otherwise stated, in analysis, it can only use the reagents, which are confirmed as the analytic reagents and distilled water, or deionized water, or the water with the equal purity. 3.1 Nitric acid - guarantee reagent. 3.2 Sulfuric acid - guarantee reagent. 3.3 Sodium hydroxide. 3.9 Acetone. 3.10 Sulfuric acid solution (1+9). 3.11 Nitric acid solution - c (HNO3) = 5mol/L. Weigh and take 31mL of nitric acid (3.1); add it into 69mL of water. Nitric acid with brown smoke shall not be used for preparation. 3.15 Standard solution of hexavalent chromium - c [Cr (VI)] = 5.0mg/L. Pipette 5.0mL of standard stock solution of hexavalent chromium (3.14) in a 100 mL volumetric flask; dilute it to the mark with water; shake it evenly. Prepare it when it is used. 3.16 Diphenylcarbazide (DPC) solution. Weigh and take 0.5g of diphenylcarbazide (3.8); dissolve it in 100 mL of acetone (3.9); store it in a brown bottle. When solution's color fades, it should be reconstituted.4 Apparatus
Common laboratory apparatus and the following items. 4.1 Spectrophotometer - wavelength 420nm~700nm. 4.2 Oscillating water bath kettle.5 Analysis Steps
5.1 Sample Preparation 5.1.1 Metal Material Process the sample into the crumb or strip whose diameter are no more than 1 mm and whose length are no more than 5 mm. 5.3 Color Rendering Add 2.0mL of diphenylcarbazide (DPC) solution (3.16) into the filtrate (5.2); mix it evenly; add sulfuric acid solution (3.10); make filtrate’s pH reach 2±0.5; then transfer the whole filtrate into a 100mL volumetric flask; use water to dilute it until the mark; shake it evenly; place it for 0.5h. 5.4 Calibration Solution Respectively pipette 0.0mL, 2.0mL, 4.0mL, 6.0mL, 8.0mL and 10.0mL of standard solution of hexavalent chromium (3.15) into the 100mL volumetric flask; add 50mL of water; add 2.0mL of diphenylcarbazide (DPC) solution (3.16); mix it evenly; add 2 drops of sulfuric acid solution (3.10); make filtrate’s pH reach 2±0.5; use water to dilute it until the mark; shake it evenly; place it for 0.5h. 5.5 Determination Adopt 1 cm absorption pool; at the place whose absorption wavelength is 540 nm, use ultraviolet-visible spectrophotometer (4.1) to measure the absorbance value of the calibration solution; draw the calibration curve by corresponding the absorbance value with the concentration value.6 Representation of the Result
In the sample, the content of hexavalent chromium shall be counted in mass fraction - w. The numerical value shall be expressed in milligrams per kilogram (mg/kg) and shall be calculated according to formula (1).7 Test Report
Test report shall at least include the following information. ......Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
