65
• Remove the blank vial.
• Place the sample vial into the holder and push it completely down.
• Press Read. The instrument will perform the reading. The instrument displays concentration in
mg/L of phosphorus (P).
The method detects free (orthophosphate), condensed inorganic forms (meta-, pyro- and other
polyphosphates) and organic forms of phosphates present in the sample.
• Press s or t to convert the result in mg/L of phosphate (PO
4
3
-
) or mg/L of P
2
O
5
.
Note: For accurate measurements
1) wash glassware only with phosphate-free detergents
2) clean all glassware with 1 : 1 hydrochloric acid solution and rinse with deionized water.
INTERFERENCES
Arsenate
pH: the sample should have a neutral pH
Temperature: the method is temperature sensitive.
It is recommended to add the Molybdovanadate Reagent and to run measurements at T = 20 to 25 °C:
T < 20 °C causes a negative error
T > 25 °C causes a positive error
Turbidity and suspended matter in large amounts may cause interference because the strongly acidic
reaction conditions may dissolve suspended matter or cause desorption of phosphates from particles. Before
measurement, turbidity or suspended matter should be removed by treatment with active carbon and by
prior filtration.
Phosphorus, Total HR
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