Nickel- Determination by AAS
COEI-2-NICKEL Determination of nickel by atomic absorption spectrometry
- Principle
The nickel is directly determined by atomic absorption spectrometry without flame (electro-thermal atomisation).
- Apparatus
2.1. Instrumental parameters: (given as an example)
Atomic absorption spectrophotometer equipped with an atomiser with a graphite tube.
- wave length: 232.0 nm
- hollow-cathode lamp (nickel)
- width of the slit: 0.2 nm
- intensity of the lamp: 4 mA
- correction of continuum by the Zeeman effect
- Introduction in hot conditions of the samples in the graphite oven with an automatic distributor
- rinsing water contains 2 drops of Triton per litre.
- measurement of signal: peak height.
- Time of measurement: 1 second.
- pyrolytic graphite tube:
- pyrolytic graphite oven containing a platform of L’Vov tantalised.
- tantalisation of a platform: see above.
- inert gases: argon and argon + hydrogen mixture (95%: 5%).
Parameters for oven:
|
Parameters for oven for determining nickel |
|||||
|
step |
temperature |
time |
gas flow rate |
type of gas |
reading of signal |
|
n° |
(°C) |
(s) |
(l/min) |
||
|
1 |
85 |
5.0 |
3.0 |
argon |
no |
|
2 |
95 |
40.0 |
3.0 |
argon |
no |
|
3 |
120 |
10.0 |
3.0 |
argon |
no |
|
4 |
800 |
5.0 |
3.0 |
argon |
no |
|
5 |
800 |
1.0 |
3.0 |
argon |
no |
|
6 |
800 |
2.0 |
0 |
argon |
no |
|
7 |
2 400 |
1.1 |
0 |
argon + hydrogen |
yes |
|
8 |
2 400 |
2.0 |
0 |
argon + hydrogen |
yes |
|
9 |
2 400 |
2.0 |
3.0 |
argon |
no |
|
10 |
75 |
11.0 |
3.0 |
argon |
no |
2.2. Adjustment of automatic sampler (given as an example)
|
- Parameters of automatic sampler |
|||
|
volume injected in µl |
|||
|
solution of Ni |
blank |
matrix modifier |
|
|
at 50 μg/l |
|||
|
blank |
17 |
3 |
|
|
calibration 1 |
5 |
12 |
3 |
|
calibration 2 |
10 |
7 |
3 |
|
calibration 3 |
15 |
2 |
3 |
|
sample |
5 |
12 |
3 |
- Reagents
3.1. Pure demineralised water for analysis
3.2. Pure nitric acid for analysis at 65%
3.3. Anhydrous palladium chloride (59% in Pd)
3.4. Pure hexahydrated magnesium nitrate for analysis
3.5. Ammonium dihydrogenophosphate
3.6. Matrix modifier: mixture of palladium chloride and magnesium nitrate (dissolve 0.25 g of PdCl2 and 0.1 g of Mg(NO3)2.6H2O (3.4) in 50 ml of demineralised water) ammonium dihydrogenophosphate at 6% (dissolve 3 g de NH4H2PO4 in 50 ml of demineralised water), (3.1).
3.7. L-ascorbic acid
3.8. Analytical blank solution: L-ascorbic acid solution at 1% (m/v).
3.9. Nickel reference solution at 1 g/l (1000 µg/ml) off the shelf or prepared as follows: dissolve 4.9533 of Ni(NO3)2.6H2O in a solution of HNO3 0.5 M, adjust at 1 l with HNO3 0.5 M.
- Procedure
Nickel solution at 10 mg/l: place 1 ml of the reference solution (3.8) in a 100 ml graduated flask, add 5 ml of nitric acid (3.2); complete to volume with demineralised water.
Nickel solution at 50 μg/l: place 1 ml of the nickel solution at 10 mg/l in a 200 ml graduated flask, 10 ml of nitric acid (3.2) and complete with demineralised water.
Set of calibration solution: 0, 50, 100 and 150 μg/l of nickel.
The automatic distributor cycle enables to perform this calibration on the platform from a nickel solution at 50 μg/l.
- Preparation of samples
5.1. Case of liquid or solution samples
No preparation or sample dilution is necessary; the samples are placed directly in the cups of the automatic injector.
5.2. Case of solid samples
The solid samples are mineralised by dry process.
- Determinations
The calibration graph (absorbance depending on the concentration of nickel) gives the concentration of nickel in the samples.