2024-09-18
Determination of Heavy Metals in soil by Atomic Absorption Spectrophotometer
1. Experiment Method
Keywords: Atomic absorption spectrophotometer, autosampler, graphite furnace, flame, soil, heavy metals.
1.1 Instrument Configuration
Table 1 Configuration Lists of AAS
|
No |
Module |
Qty |
|
1 |
Atomic Absorption Spectrophotometer AA2310 |
1 |
|
2 |
Graphite Furnace Power GF2310 |
1 |
|
3 |
Autosampler AS2310 |
1 |
|
4 |
Cooling Circulator |
1 |
|
5 |
High Purity Argon |
1 |
|
6 |
Graphite Tube |
1 |
|
7 |
Oilless Air Compressor |
1 |
|
8 |
High Purity Acetylene |
1 |
1.2 Reagents and Experiment Material
Nitric acid solution (1+99): Measure 10mL of nitric acid and slowly add to 990mL of water and mix well.
Pb Standard Solution:1000mg/L
Cd Standard Solution: 1000mg/L
Ni Standard Solution: 1000mg/L
1% diammonium hydrogen phosphate: take 1g of diammonium hydrogen phosphate in a 100mL volumetric flask, and fix the volume with ultrapure water;
Nitric Acid: GR
Hydrochloric Acid: GR
Hydrofluoric Acid: GR
perchloric acid: GR
One in ten thousand analytical balances
Electrothermal blast thermostatic drying oven
Digital display electric hot plate
Teflon crucible
1.3 Sample Pretreatment
Sample digestion: Weigh 0.2g of sample in a PTFE crucible, add one to two drops of water to moisten, add 10ml hydrochloric acid, 9ml nitric acid, 4ml hydrofluoric acid, and 2ml perchloric acid in turn, shake well, cover and heat on a hot plate at 150℃ for 6 hours, open the lid and continue to be heated in addition to silicon. In order to achieve a good effect of flying silica, it is necessary to shake the crucible frequently and drive the acid steaming until the content is viscous. Remove and cool slightly, add 0.5ml of nitric acid to dissolve the soluble residue, rinse the crucible lid and inner wall with water, transfer the whole amount to a 50ml volumetric flask, and fix the volume with ultrapure water, shake well. Store in PTFE reagent bottles for testing. Replace the sample with water and prepare a full program blank solution following the steps above. To be measured.
2. Conclusion and Discussion
2.1 Spectral Conditions for Lead
|
Heating Method |
Graphite Furnace |
||
|
Test Method |
Peak Height |
||
|
Injection Volume |
20μL Sample + 5μL Diammonium Hydrogenphosphate |
||
|
Bandwidth |
0.4nm |
Wavelength |
283.3nm |
|
Ignite |
AA-BG |
Lamp Current |
5mA |
|
Concentration Table of Standard Curves (μg/L) |
|||||
|
Standard Curve |
1 |
2 |
3 |
4 |
5 |
|
Leak Standard Solution |
5.00 |
10.0 |
20.0 |
30.0 |
40.0 |
Standard Curve Testing
Linearity of Standard Curve
2.3 Spectral Conditions for Cadmium
|
Heating Method |
Graphite Furnace |
||
|
Testing Method |
Peak Height |
||
|
Injection Volume |
15μL sample + 5μL 1% diammonium hydrogenphosphate |
||
|
Bandwidth |
0.4nm |
Wavelength |
228.8nm |
|
Ignite |
AA-BG |
Lamp Current |
4mA |
|
Concentration Table of Standard Curves (μg/L) |
||||
|
Standard Curve |
1 |
2 |
3 |
4 |
|
Cd Standard Solution |
0.5 |
1.5 |
2.0 |
2.5 |
Standard Curve Testing
Linearity of Standard Curve
2.4 Spectral Conditions for Nickel
|
Heating Method |
Flame |
||
|
Burner Height |
10mm |
||
|
Acetylene Flow Rate |
2.0L/min |
||
|
Bandwidth |
0.2nm |
Wavelength |
232.0nm |
|
Ignite |
AA |
Lamp Current |
4mA |
|
Concentration Table of Standard Curve (μg/mL) |
|||||
|
Standard Curve |
1 |
2 |
3 |
4 |
5 |
|
Ni Standard Curve |
0.5 |
1.0 |
1.5 |
2.0 |
2.5 |
Standard Curve Testing
Linearity of Standard Curve
3. Calculation of Results
|
Sample |
No |
Sample Volume (g) |
Testing concentration |
Content(mg/kg) |
Theoretical Concentration (mg/kg) |
Standard Deviation |
|
Pb |
1# |
0.2005 |
16.2420μg/L |
21 |
21±2 |
Qualified |
|
1#- parallel |
0.2009 |
17.6490μg/L |
||||
|
Cd |
1# |
0.2005 |
0.4897μg/L |
0.12 |
0.14±0.02 |
Qualified |
|
1#- parallel |
0.2009 |
0.4991μg/L |
||||
|
Ni |
1# |
0.2005 |
0.1180μg/L |
29 |
30±2 |
Qualified |
|
1#- parallel |
0.2009 |
0.1159μg/L |
4. Note
Perchloric acid and nitric acid used in the experiment have strong oxidizing and corrosive properties, hydrochloric acid and hydrofluoric acid have strong volatility and corrosiveness, so reagent preparation and sample digestion should be carried out in a fume hood; protective equipment should be worn as required to avoid inhalation into the respiratory tract or contact with the skin and clothing during operation.
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