Application Notes: Reflectometry – Ammonium in Natural Fertilizer (Faeces, Dung)

Reflectometric determination by using the indophenol blue method

Reagents:

Cat. No. 116892 Reflectoquant® Ammonium Test
Cat. No. 117246 Reflectometer RQflex® 20

This application note pertains to RQflex® 20 and all discontinued instruments (RQflex® 10, RQflex® plus)

Sample preparation:
At first homogenize sample in a blender by mixing 100 g sample with 100 ml distilled water. Weigh 2 g of this homogenized sample into a 1 l volumetric flask, make up to 1 l by adding distilled water and shake thoroughly.

Allow the insoluble particles to be deposited and use the supernatant solution for analysis.

RQflex® 20 Reflectoquant®
RQflex® 20 Reflectoquant®

Analysis:

Rinse the test vessel several times with the sample solution and fill to the 5-ml mark. Add 10 drops of reagent NH4-1and swirl. Add 1 level blue microspoon of reagent NH4-2 and swirl again. Press the reflectometer START button and simultaneously place the test strip in the sample (20 - 30 °C) for
8 min, ensuring that both reaction zones are immersed. Allow excess liquid to run off via the long edge of the strip on to an absorbent paper towel.

Measure the strip in the reflectometer. The value [mg/l] will be stored automatically. (Please refer to the RQflex® operating instructions and the package insert of the Reflectoquant® Ammonium Test.)

Calculation:

Ammonium content [mg/kg] = Measured value [mg/l] x 2 x 1000 [ml]
weight of homogenized sample in [g]
Ammonium content [kg/t] = Ammonium content [mg/kg] : 1000
Ammonium-N content [kg/t] =
Ammonium content [kg/t] x 0.777.


Results - comparison with official LUFA method (Kjeldahl distillation):

Ammonium content in [kg NH4-N/t fresh matter]

 

Sample Reflectoquant® [kg/t] LUFA [kg/t]
1 4.0 3.6
2 6.7 7.8
3 3.9 4.1
4 2.9 3.5
5 4.8 3.6
6 6.8 6.3
7 3.0 2.8
8 4.3 4.3
9 3.8 3.7
10 2.6 3.4
11 6.7 8.3
12 3.7 4.6
13 3.0 3.6
14 4.7 4.0
15 6.8 6.4
16 2.9 3.1
17 4.4 4.3

 Materials

     
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