Atomic Absorption Flame Spectroscopy
AA Standards
- 10 mL total solution stored in 15 mL centrifuge tubes
- Used CuSO4 stock solution (13.30 ppm Cu2+ as CuSO4)
- Diluted with 16.7 MΩ DI
- 100 - 1000 μL pipetters were sticking, so precision of solutions likely to be low
- Prepared 10:0, 5:5, 2:8, & 1:9 dilutions
Cu exchange of NaMT
- 10 min exchange, 1:5 salt to clay
- 0.100 g CuSO4 in 20 mL DI
- Added 0.500 g NaMT
- Stirred 10 min ± 5 sec and filtered through 41 Whatman paper into dried filter flask
- filtrate stored in 20 mL vial & clay air-dried overnight
- 30 min exchange, 1:5 salt to clay
- 0.100 g CuSO4 in 20 mL DI
- Added 0.500 g NaMT
- Stirred 30 min ± 1 min and filtered through 41 Whatman paper into dried filter flask
- filtrate stored in 20 mL vial & clay air-dried overnight
- 60 min exchange, 2:2 salt to clay
- 0.200 g CuSO4 in 20 mL DI
- Added 0.200 g NaMT
- Stirred 60 min ± 2 min and filtered through 41 Whatman paper into dried filter flask
- filtrate stored in 20 mL vial & clay air-dried overnight
AA Clay Exchange Solutions
- 10 mL total solution stored in 15 mL centrifuge tubes
- Used clay exchange filtrate solutions
- Diluted with 16.7 MΩ DI
- 100 - 1000 μL pipetters were sticking, so precision of solutions likely to be low
- Mixed 50 μL filtrate and 9.950 mL DI
- 2:5 salt to clay (10 min, 30 min, 2 hr, & 24 hr) and 1:1 (1 hr)
AA Flame Spectroscopy
- Cu lamp, 0.2 cm slit
- AA Wizard, single measurement per sample
|
Sample
|
[Cu2+] (ppm, measured)
|
[Cu2+] (ppm, solution)
|
[Cu2+] (ppm, adsorbed)
|
|
Stnd 0
|
-0.0101 (abs)
|
0.0000
|
|
Stnd 1
|
-0.0028 (abs)
|
1.3300
|
|
Stnd 2
|
+0.0019 (abs)
|
2.6600
|
|
Stnd 3
|
+0.0080 (abs)
|
6.6400
|
|
Stnd 4
|
+0.0290 (abs)
|
13.3000
|
|
Water
|
-0.2536
|
|
1-5_24h
|
1.9010
|
380
|
1906
|
|
1-5_2h
|
2.4853
|
497
|
1789
|
|
1-5_30m
|
3.7270
|
745
|
1541
|
|
1-5_10m
|
4.0556
|
811
|
1475
|
|
1-5_ctrl
|
11.4324
|
2286
|
0
|
|
2-2_1h
|
25.6748
|
5135
|
-563
|
NOTE 1: Based on AA absorbance of Ctrl soln, 0.18 g CuSO4 added
NOTE 2: Theoretical maximum [Cu2+] exchanged in interlayer of 0.5 g NaMT = 763 ppm. Surface adsorption taking place!
NOTE 3: Higher concentration solution outside calibration. Absorbance may not be linear here, as noted by neg. exchange.
|