Hanna Instruments HI 83214 - Manual (Page 61)

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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
Interference may be caused by:
Bismuth
Fluoride
pH: the sample should have a neutral pH
Sulfide:
to eliminate sulfide add Bromine Water drop-wise until a pale yellow color develops; remove Bromine
Water excess by adding Phenol solution drop-wise.
Temperature: the method is temperature sensitive.
It is recommended 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, Reactive HR