Hach-Lange DR 5000 drinking water analysis, supplementary software LZV571 - Manual (Page 9)

9
Section 2 Working procedures
2.1 Nitrate (intrinsic absorbance)
Principle
The parameter "nitrate” can be determined in a water sample by
measuring the intrinsic absorbance, that is without using reagents.
The nitrate ion is determined bichromatically at two wavelengths.
The difference between the measured absorbance values at the
two wavelengths is a measure of the nitrate concentration, which
can be evaluated relative to a standard concentration.
Range of application
Drinking water
Measuring range
1–60 mg/l nitrate (3 mm rectangular cuvette)
0.3–15.0 mg/l nitrate (10 mm rectangular cuvette)
Accessories
• Spectrophotometer (228 and 218 nm)
• 3 mm or 10 mm rectangular cuvette (QS)
• Sipper module: 3 mm or 10 mm pour-through cuvette (QS)
Reagents
• Standard 30 mg/l nitrate for 3 mm rectangular cuvette
• Standard 10 mg/l nitrate for 10 mm rectangular cuvette
Interferences
Organic components can interfere with the determination. Very high
nitrate concentrations of several 100 mg/l cause results within the
measuring range to be obtained.
Literature
E. Goldman, R. Jacobs:
Determination of Nitrates by Ultraviolet Absorbance, Amer. Water
Works Assoc. 53, 187–191, (1961)
2.1.1 Procedure Nitrate (intrinsic absorbance )
1. Select Stored Programs in the "Main Menu". Select test
number 901 (measuring range 3 mm or 10 mm).
2. Insert the zero cuvette (distilled water) in the cell compartment.
Close the cell compartment. Touch
Zero .
3. Insert the standard cuvette containing the nitrate standard
(30 mg/l – 3 mm rectangular cuvette – or 10 mg/l – 10 mm
rectangular cuvette) in the cell compartment and close the cell
compartment. Touch
Read . Display: E1 and E2 .
4. Insert the sample cuvette containing the first sample in the cell
compartment and close the cell compartment. Touch
Read .
Display: E3 . The result is then displayed.