Analytical Method: Urea in liquid manure

Reagents and accessories:
Cat.No. 100573  ortho-Phosphoric acid 85 % for analysis
Cat.No. 100731  Sulfuric acid 95 - 97 % for analysis
Cat.No. 103943  Iron(III) chloride hexahydrate for analysis
Cat.No. 102918  Diacetyl monoxime for analysis
Cat.No. 108156  Thiosemicarbazide for analysis
Cat.No. 116754  Water for analysis
Cat.No. 114724  Empty cells 16 mm with screw caps
Activated charcoal for soil tests
Folded filter
Thermoreactor
 
Reagent 1:
Mix 100 ml of ortho-phosphoric acid 85 %, 100 ml of sulfuric acid 95 - 97 %, and 0.45 g of iron(III) chloride hexahydrate and dissolve.
 
Reagent 2:
Mix 13.4 g of diacetyl monoxime and 0.38 g of thiosemicarbazide and homogenize thoroughly in a porcelain mortar by trituration.
 
Sample preparation:
First dilute the liquid-manure sample 1:20 with water for analysis by filling 10 ml of the sample into a 200-ml volumetric flask and making up to the mark with water for analysis. Add 2 g of activated charcoal for soil tests and mix thoroughly, then filter off the undissolved matter over a folded filter.
 
Analysis:
Mix 5.0 ml of the clear filtrate with 2.0 ml of reagent 1 and 25 mg of reagent 2 and heat in a closed test tube in the thermoreactor at 120 °C (100 °C) for 10 minutes. Subsequently cool to room temperature in an ice-water bath and leave to stand for 10 minutes. Mix the sample thoroughly and measure the absorbance at 525 nm in the photometer against a reagent blank.

 

Calculation:
Urea content in mg/l = analysis result in mg/l x 20 

 

Parameter list for programming the photometer Spectroquant® NOVA 60 und NOVA 400

 

Method number ----
Method-designation urea
Wavelength 525 nm
Citation urea
Units mg/l
Resolution 0.01
Zero point (E0) 0.000
Slope (E/C) 0.465
Meas. range begin 0.50
Meas. range end 5.00
Reference cell 16 mm round


Calculation when measuring the absorbance value using the above NOVA photometers without programming the method in the memory of the instrument:

 

Measured absorbance
of samples in A
Result in mg/l
[A sample * 1 / 0.465]
1.000 2.15



Parameter list for programming the photometer SQ 118

 

01 Method urea
02 Cat.No. -------
03 Measuring range 0.50 - 5.00
04 Units mg/l
05 Reaction time 6 10 min
06 Cell 16 mm round
07 Wavelength 525 nm
08 Calibration Factor
09 Evaluation Linear
10 Factor 2.15

 

 
Calculation when measuring the absorbance value using the photometer SQ118 without programming the method in the memory of the instrument:

 

Measured absorbance
of samples in A
Result in mg/l
[A sample * 2.15]
1.000 2.15

 

Materials

     
Related Links

Categories