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Analytical Method: Urea in Liquid Manure

Reagents and Accessories

Product No. 100573 ortho-Phosphoric acid 85 % for analysis
Product No. 100731 Sulfuric acid 95 - 97 % for analysis
Product No. 103943 Iron(III) chloride hexahydrate for analysis
Product No. 102918 Diacetyl monoxime for analysis
Product No. 108156 Thiosemicarbazide for analysis
Product No. 116754 Water for analysis
Product 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

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

Parameter list for programming the photometer SQ 118

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

Materials
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