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Chapter 5 | Orion AQUAfast Reagent Chemistry Instructions for Orion AquaMate
AC2096 Phosphate (Ortho) High Range Tablet Test
Vanado-Molybdate Method
1 – 80 mg/l PO4
1. Load and run the AC2096 method.
2. Fill a clean AQUAfast 24mm round vial, Cat. No. AC2V24, with 10 ml of sample. Close the
vial tightly with the cap. Wipe the exterior of the vial.
3. Place the vial into the holder in the sample chamber and close the chamber door.
4. Press the Measure Blank function key to measure the blank.
5. Open the sample chamber door and remove the vial from the holder.
6. Add one Phosphate HR P1 Tablet straight from the foil into the vial. Crush the tablet with a
clean stir rod.
7. Add one Phosphate HR P2 Tablet straight from the foil into the vial. Crush the tablet with a
clean stir rod.
8. Close the vial tightly with the cap and swirl or invert several times until the tablets are
dissolved. Wipe the exterior of the vial.
9. Wait for a reaction period of 10 minutes.
10. Place the vial into the holder in the sample chamber and close the chamber door.
11. Press the Measure Sample function key to display the result in mg/l ortho-phosphate.
Notes:
Thermo Scientific
•
For samples under 5 mg/l PO4, it is recommended to analyze the sample using the AC2095
phosphate (ortho) low range tablet test method.
•
Only ortho-phosphate ions react.
•
Phosphate in organic and condensed inorganic forms (meta-, pyro- and polyphosphates)
must be converted to ortho-phosphate ions before analysis. Pretreatment of the sample
with acid and heat provides the conditions for hydrolysis of the condensed inorganic forms.
Organically combined phosphates are converted to ortho-phosphate ions by heating with
acid and persulfate. The amount of organically combined phosphates can be calculated:
mg/l phosphate (organic) = mg/l phosphate (total) - mg/l phosphate (acid hydrolysable)
•
The ortho-phosphate ions react with the vanadate-molybdate reagent under acid conditions
to form a yellow colored product.
•
Phosphate, ortho = Phosphorus, reactive
Orion AquaMate Spectrophotometer User Manual | 101