GB/T 4325.6-2013Methods for chemical analysis of molybdenum - Part 6: Determination of arsenic content - Atomic fluorescence spectrometry (English PDF)

Foreword

GB/T 4325 "Methods for chemical analysis of molybdenum" consists of the following 26 parts:

- Part 1: Determination of lead content - Graphite furnace atomic absorption spectrometry;

- Part 2: Determination of cadmium content - Flame atomic absorption spectrometry;

- Part 3: Determination of bismuth content - Atomic fluorescence spectrometry;

- Part 4: Determination of tin content - Atomic fluorescence spectrometry;

- Part 5: Determination of antimony content - Atomic fluorescence spectrometry;

- Part 6: Determination of arsenic content - Atomic fluorescence spectrometry;

- Part 7: Determination of iron content - 1,10-phenanthroline spectrophotometry and inductively coupled plasma atomic emission spectrometry;

- Part 8: Determination of cobalt content - 5-Cl-PADAB spectrophotometry and flame atomic absorption spectrometry;

- Part 9: Determination of nickel content - Dimethylglyoxime spectrophotometry and flame atomic absorption spectrometry;

- Part 10: Determination of copper content - Flame atomic absorption spectrometry;

- Part 11: Determination of aluminum content - Chrome azurol S spectrophotometry and inductively coupled plasma atomic emission spectrometry;

- Part 12: Determination of silicon content - Inductively coupled plasma atomic emission spectrometry;

- Part 13: Determination of calcium content - Flame atomic absorption spectrometry;

- Part 14: Determination of magnesium content - Flame atomic absorption spectrometry;

1 Scope

This Part of GB/T 4325 specifies the method to determine arsenic content in molybdenum.

This Part is applicable to the determination of arsenic content in molybdenum powder, molybdenum bar, molybdenum trioxide, ammonium molybdate. The determination range is 0.0002%~0.0050%.

2 Method summary

The test material is decomposed with hydrogen peroxide. In thiourea-ascorbic acid-hydrochloric acid medium, use hydride generation-atomic fluorescence spectrometry to determine arsenic content. Within a certain range, the fluorescence intensity is proportional to the content of the measured element. Adding molybdenum matrix can eliminate interference.

3 Reagents

Unless otherwise specified, the reagents used in this Part are guaranteed reagents; water used is grade two or above.

3.1 Sodium borohydride.

3.2 Sodium hydroxide.

3.3 Molybdenum matrix (wAs<=0.00002%).

3.4 Arsenic trioxide (wAs2O3>=99.99%).

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

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

3.7 Sulfuric acid (rho=1.84g/mL).

3.8 Hydrogen peroxide.

3.9 Sulfuric acid (1+1).

3.10 Sulfuric acid (1+4).

3.11 Sodium hydroxide solution (200g/L).

3.12 Thiourea-ascorbic acid solution: Weigh 10g of thiourea and 10g of ascorbic acid respectively to dissolve in 200mL of water. Mix well. Prepare when it is required.

3.13 Arsenic standard stock solution: Weigh 0.1320g of arsenic trioxide (3.4). Add 20mL of water, 0.2g of sodium hydroxide (3.2). Heat to dissolve. Use sulfuric acid (3.10) to neutralize to slightly acidic. Transfer into a 1000mL volumetric flask. Use water to dilute to the scale. 1mL of this solution contains 100µg of arsenic.

3.15 Sodium borohydride solution: Weigh 1.5g of sodium borohydride (3.1). Add into 100mL of water that 1g of sodium hydroxide (3.2) is pre-dissolved. Shake well after dissolving completely. Prepare when it is required.

3.16 Hydrochloric acid (1+9).

3.17 Argon: the volume fraction is not less than 99.99%.

4 Instruments

Atomic fluorescence spectrometer, with arsenic special hollow cathode lamp.

Under the best working conditions of the instrument, anyone who can reach the following indicators can be used.

- Detection limit: not more than 1 x 10^-9g/mL;

- Precision: use 0.02µg/mL arsenic standard solution to measure fluorescence intensity 10 times; its standard deviation does not exceed 5.0% of the fluorescence intensity;

- Linear of working curve: divide the working curve into five equal segments according to the concentration; the ratio of the difference in fluorescence intensity between the highest segment and the lowest segment shall be […]