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

Materials and reagents:
Cat.No. 100707  Spectroquant® UV/VIS Spectrophotometer Pharo 300
Cat.No. 100784  Rectangular cells quartz 10 mm
Cat.No. 100716  Hydrochloric acid 1 mol/l 
Cat.No. 116754  Water for analysis (optional)
Membrane filter with 0.45 μm pore diameter

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

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

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.

Zeroing the photometer:
When this method is used, the photometer must be zeroed each new working day. To do this call up the stored method 2503 and fill the 10-mm quartz rectangular cell with distilled water or water for analysis.
Subsequently press the BLANK ZERO key of the photometer and select “Zero photometer”. Insert the cell into the compartment to start the zeroing procedure.

Measurement procedure:
Select method 2503.
Fill the pretreated sample into a 10-mm quartz rectangular cell and insert the cell into the cell compartment to start the automatic measurement procedure.
The nitrate content in mg/l NO3-N appears in the display.

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

















Related Links