Reagents - enough for 40 samples
0.5M NaHCO 3
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 NaHCO 3 , 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.
NaHCO 3 P
- 25 ml 0.5M NaHCO 3
Vortex briefly to break up soil plug.
Shake for 18 hours, centrifuge, and store supernatant at 4°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°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°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°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% H 2 O 2 (Careful, it may overflow.) Reheat for 30 minutes.
Repeat H 2 O 2 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(ml) |
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.
NaHC0 3 (5 to 20 ppm)
In a 15 ml disposable centrifuge tube
- 3 ml 100 ppm solution
- 12 ml 0.5M NaHCO 3 (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