Determination of non-protein nitrogen.

the nitrogen content of
proteins
was fairly constant (about 14% to 18%), with an average content of about 16%. Therefore, protein nitrogen multiplied by 6.25% is the protein content.
can also be measured directly using the following methods if the experiment requires it.
the process of measurement is to take 0.2-0.5g air-dried plant material, put 100ml
beast
, add 50ml water, boil 5min, keep warm at 40-50C 30min. Slowly add 10 ml of 6% copper sulfate, shake well, set aside l h (or overnight).
filtration
, the residue is digested, distilled and measured with ammonia in the collection fluid according to the Kye nitrogen fixation method, and nitrogen content is calculated. Non-protein nitrogen includes water-soluble nitrides, such as
amino acids
, acidic nitrogen and
organic
containing nitrogen base.
its total amount can be calculated by subtracting protein nitrogen from the total nitrogen, or it can be determined by pressing the method, that is, to take 0.2-0.5g plant samples, put 2 ml of water into the research, grinding into a uniform slurry state. Add 3 ml of copper sulfate solution, shake well, transfer the slurry to
centrifugal tube
, while rinsing the residue with 8 ml of water.
the centrifuge tube into boiling water and stir 3min with a glass stick. Remove and add 3ml 0.2mol/L of NaOH, stir well, leave 10min, centrifuge. Put the solution in a 100 ml Keshi bottle, rinse the precipitation 2 times with hot water, each time with 10 ml, each rinse to the flushed water to add 3% copper sulfate solution.
then add 2 ml of thick sulphuric acid, O.3m110% sodium vanadiate (10gNa2MoO4.2H2O dissolved in 100m1 water, 0.5ml 2mol/LNaOH) to the leachate of the Keshi bottle.
heat
to boil and bring to the boil for 15min, cool and add 100ml ammonia-free water), 4 drops of 3% hydrogen peroxide. Place on the furnace and evaporate until foam appears, then lower the temperature to prevent the foam from spilling onto the bottleneck. Continue to heat with a low heat until white steam appears in sulphuric acid.
the bottle with spherical glass plugs to enhance firepower and digest until the solution is transparent. After cooling, add 10 ml of water to the residue in the bottle. In a 50 ml
bottle
, rinse the residue with water and add water to 50ml and mix well. Take 25 ml of solution and let the person titrate in the beech. Add 1 drop of 0.1% methyl orange solution, cool down, titrate with 2mol/LNaOH solution until the indicator is yellow, not too much. Then add 10 ml of pH 6.7 containing potassium bromate and 5 ml of 0.12mol/L chloramine solution (15g chloramine dissolved in water, diluted to 1L with water, mixed well, filtered with cotton) , in a dark bottle), i.e. cover the beech with a glass cover, mix the solution in a circular motion and set aside 25min, followed by 2 ml of potassium iodate solution, 10m18% asphalt solution.
iodine released by titration with a solution of 0.02mol/L sodium sulfate in the presence of starch indicators. 1 ml 0.02mol sodium dithionate is equivalent to 0.09338 mg nitrogen. In addition, according to this method without sample control, the operating procedure is exactly the same as above.
the non-protein nitrogen content in the sample is calculated according to the formula below.
X (non-protein nitrogen content) s.4667×50×K× (6z-6) 1/(25×7 n) s.9338×K× (a-b)/72
:
50 is a test liquid product (ml);

25 is the volume (ml) of the test fluid taken for test fluid determination by chlorine method;
a is the volume of 0.02mol sodium dithionate used for titration control (ml);
b is the volume of 0.02mol/L sodium sulfate used for titration test fluid (ml);
K is the titration of sodium sulfate for analysis of heavy samples.
.