Determination of 22 metal elements in solid waste by inductively coupled plasma emission spectrometry (2)

(5) Sample pretreatment

1.

The solid waste leachate is in accordance with "Solid waste leaching toxicity leaching method: sulfuric acid and nitric acid method" (HJ/T299), "solid waste leaching toxicity leaching method acetic acid buffer solution method" (HJ/T300), "solid waste leaching toxicity leaching method horizontal oscillation method" (HJ557) to prepare

(1) Microwave digestion method

Take 25.

Note 1: There are many types of solid waste, and the organic matter contained is quite different.

Note 2: The temperature of the electric heating plate should not be too high to prevent deformation of the polyvinyl crucible

Note 3: When the sample is digested, it is necessary to prevent evaporation to avoid the loss of the element to be tested

Note 4: The total volume of the sample and added acid should not exceed 1/3 of the volume of the digestion tank

Table 5-25 Reference heating program for microwave digestion of solid waste leachate

(2) Electric heating plate digestion method

Measure 25.

2.

(1) Microwave digestion method

For solid or dry semi-solid samples, weigh 0.

Table 5-26 Reference heating program for microwave digestion of solid waste

Note 1: After the final digestion, there are still particles precipitated, it needs to be centrifuged or filtered with a 0.

Note 2: For samples with high organic content, 5mL of concentrated nitric acid should be added in advance to soak overnight
.

(2) Electric heating plate digestion method
.

For solid or dry semi-solid samples, weigh 0.
1～0.
5g (m3, accurate to 0.
0001g) of sieved samples; for liquid or semi-solid samples that do not need to be dried, directly weigh 0.
5g (m3, accurate to 0.
0001g) sample (oily solid waste should be taken less appropriately), placed in a polytetrafluoroethylene crucible, in a fume hood, add 1mL of experimental water to the crucible to moisten the sample, add 5mL of concentrated hydrochloric acid and place it on the electric hot plate for 180～ Heat at 200°C to near dryness, remove and cool slightly
.
Add 5mL of concentrated nitric acid, 5mL of hydrofluoric acid , and 3mL of perchloric acid.
After capping, heat it on a hot plate at 180°C until the remaining liquid is 2mL, continue heating, and shake well
.
When it is heated to emit thick white smoke, cover it to decompose the black organic carbide
.
After the black organic matter on the wall disappears, open the lid, drive off the white smoke and steam until the contents are viscous
.
Depending on the digestion situation, add 3mL concentrated nitric acid, 3mL hydrofluoric acid , 1mL perchloric acid , and repeat the above digestion process
.
Remove the crucible and let it cool slightly, add 2 mL of nitric acid solution, and warm to dissolve the soluble residue
.
After cooling, transfer to a 25mL volumetric flask, rinse the crucible with an appropriate amount of nitric acid solution, transfer all the eluent to the volumetric flask, dilute to the mark with nitric acid solution, mix well, and wait for measurement
.
For samples with high organic content, add mL of concentrated nitric acid in advance to soak overnight
.

3.
Preparation of blank sample

(1) Blank solid waste
.

Without adding the sample, the preparation of the solid waste blank sample is carried out according to the same operation steps as the preparation of the solid waste sample
.

(2) The solid waste leachate is blank
.

Use experimental water to prepare the extractant, prepare the solid waste leachate blank according to the same steps as the solid waste leachate sample preparation, and perform digestion according to the same steps as the solid waste leachate sample preparation
.