GB/T 17139-1997Soil quality. Determination of nickel. Flame atomic absorption spectrophotometry (English PDF)

1.3 Interference

1.3.1 When using the 232.0 nm line as the absorption line, there are three nickel lines

with very close wavelength distances, which shall be overcome, by selecting a narrower spectral passband.

1.3.2 The 232.0 nm line is in the ultraviolet region. The light scattering and molecular absorption, which are caused by salt particles and molecular compounds, are relatively serious, which will affect the measurement. Use background correction to overcome this type of interference. If the concentration permits, the method of diluting the test solution can also be used, to reduce background interference.

6.1 Preparation of test solution

Accurately weigh 0.2 ~ 0.5 g (accurate to 0.0002 g) of the specimen, in a 50 ml polytetrafluoroethylene crucible. Add 10 ml of hydrochloric acid (3.1), after wetting it with water. Place it on the electric heating plate in the fume hood, to heat it at low temperature, to decompose the sample initially. When it evaporates to about 3 ml left, take it off and cool slightly. Then add 5 ml of nitric acid (3.2), 5 ml of hydrofluoric acid (3.5), 3 ml of perchloric acid (3.6). After adding the cover, heat it on the electric heating plate at medium temperature for about 1 hour. Then open the cover. Continue heating to remove silicon. In order to achieve a good effect of silicon removal, shake the crucible frequently. When heated to the generation of thick perchloric acid white smoke, cover it to decompose the black organic carbon. After the black organic matter on the crucible wall disappears, open the lid. Drive off the white smoke. Steam until the contents are viscous. Depending on the digestion situation, add another 3 ml of nitric acid (3.2), 3 ml of hydrofluoric acid (3.5), 1 ml of perchloric acid (3.6). Repeat the above digestion process. When the white smoke is exhausted again and the contents are viscous, take it out and cool it slightly. Use water to rinse the inner wall and the crucible lid. Add 1 ml of nitric acid solution (3.3) to warm to dissolve the residue. Then transfer the whole amount into a 50 ml volumetric flask. After cooling, make the volume reach to the mark. Shake well. Prepare for measurement.

Since there are many types of soils and the organic matter contained in it varies greatly, it shall be carefully observed during digestion. The consumption of various acids can be increased or decreased, according to the digestion situation. The soil digestate shall be white or light yellow (for soils with high iron content), with no obvious sediment.

Note. The temperature of the heating plate should not be too high; otherwise, the PTFE crucible will be deformed.

6.2 Determination