Chapter 5
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Orion AQUAfast Reagent Chemistry Instructions for Orion AquaMate
106
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Orion AquaMate Spectrophotometer User Manual
Thermo Scientific
ACD095AH Phosphate (Acid Hydrolysable) Digestion Tube Test
Acid Digestion/Ascorbic Acid Method
0.02 – 1.6 mg/l P (Phosphate as Phosphorous)
1.
Open one 16 mm PO4-P Acid Reagent Digestion Tube and add 5 ml of sample.
2.
Close the vial tightly with the cap and gently invert the vial several times to mix the
contents.
3.
Heat the vial for 30 minutes in the preheated reactor at a temperature of 100 °C.
4.
CAUTION: The vial will be hot. Remove the vial from the reactor and allow it to cool to
room temperature.
5.
Open the cooled digestion vial and add 2 ml of 1.00 N Sodium Hydroxide Solution to the
vial.
6.
Close the vial tightly with the cap and gently invert the vial several times to mix the
contents. Wipe the exterior of the vial.
7.
Load and run the ACD095AH method.
8.
Place the vial into the holder in the sample chamber and close the chamber door.
9.
Press the Measure Blank function key to measure the blank.
10.
Open the sample chamber door. Remove the vial from the holder.
11.
Add the contents of one Phosphate Rgt. F10 Power Pack straight from the foil into the vial.
Use a funnel to add the reagent.
12.
Close the vial tightly with the cap and swirl the vial for 10-15 seconds to mix contents. The
reagent will not completely dissolve. Wipe the exterior of the vial.
13.
Wait for a reaction period of 2 minutes.
14.
Place the vial into the holder in the sample chamber and close the chamber door.
15.
Press the Measure Sample function key to display the result in mg/l acid hydrolysable
phosphate as phosphorus (P).
Notes:
•
Appropriate safety precautions and good lab technique should be used during the whole
procedure.
•
Ortho-phosphate ions react with the reagent to form an intense blue color.
•
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