Soil P Hedley Fractionation
Reagents - enough for 40 samples
0.5M NaHCO3
1liter volumetric flask
- 42 g Sodium Bicarbonate
- Bring to volume with DI water.
- Adjust to pH 8.5.
0.1 M NaOH
1 liter volumetric flask
- 4 g Sodium Hydroxide
- Bring to volume with DI water.
1.0 M HCl
1liter volumetric flask
- 83.3 ml Hydrochloric Acid (12 M)
- Bring to volume with DI water.
0.5 M HCl
1liter volumetric flask
- 41.7 ml Hydrochloric Acid (12 M)
- Bring to volume with DI water.
Sequential Extraction Procedure
In a 50 ml centrifuge tube
- 10 g Field fresh, sieved soil
Resin P
- 1 Bicarb charged resin strip (2 x 6 cm; Charging: shake strips 10 min in 100 ml 0.5 M NaHCO3, rinse 3 times with DI water, shake dry.)
- 25 ml DI water
Shake for 4 hours, centrifuge, and discard supernatant.
In a 250 ml flask
Extract resin with 25 ml of 0.5 M HCl for 1 hour on a shaker.
NaHCO3 P
- 25 ml 0.5M NaHCO3
Vortex briefly to break up soil plug.
Shake for 18 hours, centrifuge, and store supernatant at 4掳C.
NaOH P
- 25 ml 0.1M NaOH
Vortex briefly to break up soil plug.
Shake for 18 hours, centrifuge, and store supernatant at 4掳C.
Sonicate NaOH P
- 25 ml 0.1M NaOH
Vortex briefly to break up soil plug and Sonicate for 2 minutes.
Shake for 18 hours, centrifuge, and store supernatant at 4掳C.
HCl P
- 25 ml 1.0M HCl
Vortex briefly to break up soil plug.
Shake for 18 hours, centrifuge, and store supernatant at 4掳C
P Residue
In a 60 ml heat treated test tube
- Add soil from HCl P fraction with a minimal amount of DI water.
- 5 ml Sulfuric acid
Heat slowly to evaporate water (block digester) & allow cooling to hand-warm.
- 0.5 ml 30% H2O2 (Careful, it may overflow.) Reheat for 30 minutes.
Repeat H2O2 additions until liquid is clear (usually 10 times).
Cool, make to volume (i.e., 25 ml) and analyze on the ICP.
Standards
|
Dilution |
Working Standard |
Matrix (ml) |
|
0% |
0.0 |
5.0 |
|
1% |
0.1 |
9.9 |
|
10% |
1.0 |
9.0 |
|
25% |
2.5 |
7.5 |
|
50% |
3.0 |
3.0 |
|
100% |
6.0 |
0.0 |
In a 50 ml volumetric flask
- 5 ml of a 1000 ppm certified stand P solution
- Bring to volume with DI water to make a 100 ppm standard.
Mix standards with the extracting solution (matrix).
Resin (5 to 10 ppm)
In a 15 ml disposable centrifuge tube
- 1.5 ml 100 ppm solution
- 13.5 ml 0.5 M HCl (matrix)
Will make a 10 ppm working solution
Follow dilution table.
NaHC03 (5 to 20 ppm)
In a 15 ml disposable centrifuge tube
- 3 ml 100 ppm solution
- 12 ml 0.5M NaHCO3 (matrix)
Will make a 20 ppm working solution
Follow dilution table.
NaOH (50 ppm)
In a 15 ml disposable centrifuge tube
- 7.5 ml 100 ppm solution
- 7.5 ml 0.1M NaOH (matrix)
Will make a 50 ppm working solution
Follow dilution table.
HCl P (10 to 20 ppm)
In a 15 ml disposable centrifuge tube
- 3 ml 100 ppm solution
- 12 ml 1.0M HCl (matrix)
Will make a 50 ppm working solution
Follow dilution table.
P Residue (50 to 100 ppm)
Follow dilution table with DI water.
Revised: 06/30/09 Revised: 10/10/11