4. Sodium sulfate (Na 2 SO 4 ).
5. Magnesium sulfate heptahydrate (MgSO 4 ·7H 2 O).
6. Ammonium heptamolybdate tetrahydrate ((NH 4 ) 6 Mo 7 O 24 Á4H 2 O).
7. Ascorbic acid (C 6 H 8 O 6 ).
8. Potassium antimony tartrate (K(SbO)C 4 H 4 O 6 ).
9. Potassium dihydrogen phosphate (KH 2 PO 4 ).
10. Ultrapure water (e.g., Milli-Q).
11. 100–1000 ml volumetric flasks.
12. 100–1000 ml storage bottles.
13. 20 glass vials with screw caps (e.g., scintillation vials).
14. Forceps.
15. Spatulas.
16. Adjustable pipette and pipette tips.
17. Oven (450
C).
18. Vacuum filtration device with a vacuum pump.
19. Analytical balance.
20. Refrigerator.
21. Water bath.
22. Spectrophotometer or automatic analyzer.
23. 2 cm quartz glass cuvette (for manual analyses).
3 Methods
Use acid-washed glassware (soaked for 4 h in 6% HCl and rinsed
with deionized water).
3.1 Phosphate
The procedure follows that of Koroleff [4].
1. Prepare 4.5 mol/l sulfuric acid solution. Carefully add 125 ml
concentrated acid to 375 ml ultrapure water, cool, and make up
to 500 ml with ultrapure water. Store in a glass or polyethylene
bottle at room temperature.
2. Prepare molybdate solution dissolving 4.75 g ammonium heptamolybdate tetrahydrate in 45 ml ultrapure water, and make
up to 50 ml with ultrapure water. Store in a glass or polyethylene bottle at room temperature (usable as long as clear).
3. Prepare tartrate solution by dissolving 1.67 g potassium antimony tartrate in 50 ml ultrapure water. Store in a glass bottle at
room temperature (usable as long as clear).
4. Prepare reagent I (acidified ascorbic acid solution) by dissolving 7.0 g ascorbic acid in 65 ml ultrapure water, and then add
35 ml 4.5 mol/l H 2 SO 4 . Store in an amber glass bottle in a
refrigerator (usable as long as colorless).
Determining Phosphorus Concentration
89
5. Magnesium sulfate heptahydrate (MgSO 4 ·7H 2 O).
6. Ammonium heptamolybdate tetrahydrate ((NH 4 ) 6 Mo 7 O 24 Á4H 2 O).
7. Ascorbic acid (C 6 H 8 O 6 ).
8. Potassium antimony tartrate (K(SbO)C 4 H 4 O 6 ).
9. Potassium dihydrogen phosphate (KH 2 PO 4 ).
10. Ultrapure water (e.g., Milli-Q).
11. 100–1000 ml volumetric flasks.
12. 100–1000 ml storage bottles.
13. 20 glass vials with screw caps (e.g., scintillation vials).
14. Forceps.
15. Spatulas.
16. Adjustable pipette and pipette tips.
17. Oven (450
C).
18. Vacuum filtration device with a vacuum pump.
19. Analytical balance.
20. Refrigerator.
21. Water bath.
22. Spectrophotometer or automatic analyzer.
23. 2 cm quartz glass cuvette (for manual analyses).
3 Methods
Use acid-washed glassware (soaked for 4 h in 6% HCl and rinsed
with deionized water).
3.1 Phosphate
The procedure follows that of Koroleff [4].
1. Prepare 4.5 mol/l sulfuric acid solution. Carefully add 125 ml
concentrated acid to 375 ml ultrapure water, cool, and make up
to 500 ml with ultrapure water. Store in a glass or polyethylene
bottle at room temperature.
2. Prepare molybdate solution dissolving 4.75 g ammonium heptamolybdate tetrahydrate in 45 ml ultrapure water, and make
up to 50 ml with ultrapure water. Store in a glass or polyethylene bottle at room temperature (usable as long as clear).
3. Prepare tartrate solution by dissolving 1.67 g potassium antimony tartrate in 50 ml ultrapure water. Store in a glass bottle at
room temperature (usable as long as clear).
4. Prepare reagent I (acidified ascorbic acid solution) by dissolving 7.0 g ascorbic acid in 65 ml ultrapure water, and then add
35 ml 4.5 mol/l H 2 SO 4 . Store in an amber glass bottle in a
refrigerator (usable as long as colorless).
Determining Phosphorus Concentration
89