Analytical Method: Nitrate (direct measurement in the UV spectrum) as per APHA 4500-NO3 B for Prove

Materials and reagents:
Cat.No. 173017  Spectroquant® UV/VIS Spectrophotometer Prove 300 or
Cat.No. 173018  Spectroquant® UV/VIS Spectrophotometer Prove 600
Cat.No. 100784  Rectangular cells quartz 10 mm
Cat.No. 100716  Hydrochloric acid 1 mol/l 
Cat.No. 116754  Water for analysis or distilled water
Membrane filter with 0.45 μm pore diameter


Spectrophotometric measurement in the UV range at 220 nm and 275 nm


Measuring range: 
Method No. 2503
0.0 – 7.0 mg/l NO3-N in the 10-mm quartz rectangular cell


Working instructions:
Sample preparation:
Filter turbid sample solutions over a membrane filter.
Add 1 ml of hydrochloric acid 1 mol/l to 50 ml of the filtrate and mix.


Zero adjustment:
It is recommended to perform a zero adjustment for this method each new working day.
It is recommended to use the same cell for zero adjustment and for sample measurement.
Select method 2503 "Nitrate (UV)" from method list.
In case of an expired zero adjustment the system automatically prompts a zero adjustment, otherwise press "Settings" and select “ZERO ADJUSTMENT” from selection list.
Fill a 10-mm rectangular quartz cell with distilled water (or water for analysis) and insert the cell into the cell shaft. The zero adjustment is executed automatically.
Confirm the implementation of zero adjustment with "OK".


Measurement procedure:
Select method 2503 "Nitrate (UV)" from the method list.
Perform the zero adjustment prior to the first measurement (procedure see "Zero adjustment").

Fill the pretreated sample into a 10-mm quartz rectangular cell and place the cell into the cell compartment, the measurement is performed automatically.
Confirm measurement with "OK".
The nitrate content in mg/l NO3-N appears in the display.


Press "START" to start the measurement procedure for the next sample. 


During the measurement procedure, the system automatically tests for sample-dependent interferences (matrix effects). Dissolved organic constituents in the sample, such as e.g. humic acids, may produce false results.
If the message “Condition not fulfilled” appears in the display, this indicates that a sample-dependent interference is present. Evaluation is not possible in this case. The method is not suited for the analysis of samples of this type.


Results of the direct measurement of nitrate in the UV range:
Standard solutions prepared using Cat.No. 119811 Nitrate Standard Solution Certipur®


[mg/l NO3-N]

[mg/l NO3-N]
0.7 0.7
1.4 1.5
2.1 2.2
2.8 3.0
3.5 3.7
4.2 4.4
4.9 5.1
5.6 5.8
6.3 6.4
7.0 7.0




















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