GB/T 20899.2-2019Methods for chemical analysis of gold ores - Part 2:Determination of silver content - Flame atomic absorption spectrometric method (English PDF)

Foreword

GB/T 20899 "Chemical Analysis Methods for Gold Ore" is divided into the following sections.

--- Part 1. Determination of the amount of gold;

--- Part 2. Determination of silver content by flame atomic absorption spectrometry;

--- Part 3. Determination of arsenic content;

--- Part 4. Determination of copper content;

--- Part 5. Determination of lead content;

--- Part 6. Determination of zinc content;

--- Part 7. Determination of iron content;

--- Part 8. Determination of sulfur content;

--- Part 9. Determination of carbon content;

--- Part 10. Determination of the amount of antimony;

--- Part 12. Determination of arsenic, mercury, cadmium, lead and bismuth by atomic fluorescence spectrometry;

--- Part 13. Determination of lead, zinc, bismuth, cadmium, chromium, arsenic, and mercury; inductively coupled plasma atomic emission spectrometry;

--- Part 14. Determination of plutonium inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry.

This part is the second part of GB/T 20899.

This section is drafted in accordance with the rules given in GB/T 1.1-2009.

This section replaces GB/T 20899.2-2007 "Methods for chemical analysis of gold ores Part 2: Determination of silver content".

Compared with GB/T 20899.2-2007, the main technical changes in this section are as follows.

--- Increased "repetitive" and "reproducible" requirements (see 8.1 and 8.2);

--- Removed the "allowable difference" requirement (see Chapter 8 of the 2007 edition);

--- Modified the pre-treatment method, using polytetrafluoroethylene beaker tetraacid solution (see 6.3, 2007 version 6.3.1).

1 Scope

This section of GB/T 20899 specifies the method for determining the amount of silver in gold ores.

This section applies to the determination of silver in gold ores. Measurement range: 2.00g/t ~ 1000.0g/t.

2 Principle

The sample was decomposed by hydrochloric acid, nitric acid, perchloric acid, and hydrofluoric acid. In a dilute hydrochloric acid medium, the wavelength was 328.1 nm in a flame atomic absorption spectrometer.

At the same time, the absorbance value of silver was measured by air-acetylene flame, and the amount of silver was calculated according to the standard curve method.

3 Reagents

Unless otherwise stated, only reagents and distilled or deionized or fairly pure water identified as analytically pure were used in the analysis.

3.1 Hydrochloric acid (rho = 1.19g/mL).

3.2 Nitric acid (rho = 1.42g/mL).

3.3 Perchloric acid (rho = 1.67g/mL).

3.4 Hydrofluoric acid (rho = 1.15g/mL).

3.5 Hydrochloric acid solution (3 17).

3.6 Silver standard storage solution: Weigh 0.5000g of pure silver (wAg>=99.99%), put it in a 100mL beaker, and add 20mL nitric acid (3.2), heat to completely dissolve, remove nitrogen oxides by boiling, remove and cool, move into 1000mL brown volumetric flask with water without chloride ion In 30 mL of nitric acid (3.2), dilute to the mark with chloride-free water and mix. 1 mL of this solution contained 0.5000 mg of silver.

3.7 Silver standard solution: Pipette 50.00mL of the silver standard storage solution (3.6), and put it in a 500mL brown volumetric flask, and add 10mL nitric acid (3.2) Dilute to the mark with chloride-free water and mix well. 1 mL of this solution contained 50 µg of silver.

4 Instruments

Atomic absorption spectrometer with silver hollow cathode lamp.

Under the optimal working conditions of the instrument, any flame atomic absorption spectrometer that can meet the following indicators can be used.

--- Sensitivity: In a solution consistent with the matrix of the measurement solution, the characteristic concentration of silver should not be greater than 0.034 µg/mL.

--- Precision: Use the highest concentration standard solution to measure 11 absorbances, and the standard deviation should not exceed 1.0% of the average absorbance;

Use the lowest concentration standard solution (not "zero" standard solution) to measure 11 absorbances, and the standard deviation should not exceed the highest concentration The standard solution has an average absorbance of 0.5%.

--- Standard curve linear: Divides the standard curve into five segments according to the concentration. The difference between the absorbance difference between the highest segment and the absorbance difference between the lowest segment. The ratio should not be less than 0.8.