Formaldehyde titration determines amino acid content.

I. Purpose Preliminary understanding of formaldehyde titration to determine the
amino acid
content of the principle and operating points 2, principleamino acids in aqueous solutions are both ions, so can not be directly used alkali titration amino acids of the carboxyl. Formaldehyde can be combined with the amino acids on the -N-H3, the formation of - NH-CH2OH, -N (CH2-OH) 2 and other hydroxymethyl derivatives, so that the N-H3 on the H-plus free out, so that you can use alkali titration N-H3 to release H-plus, measure amino nitrogen, so as to calculate the amino acid content.
if the sample contains only a single known amino acid, the amino acid content can be calculated from the results of this titration.
if the sample contains a variety of amino acids (e.g.
protein
hydrolyte), the amount of amino acids cannot be calculated.
proline and formaldehyde, the resulting
compound
is unstable, resulting in low titration results, tyrosine phenolic structure, resulting in high titration results.
III, materials,
reagents
and appliances(i) reagents
1, 0.5% phenolic alcohol solution
said 0.5g phenol in 100ml 60% alcohol.
2, 0.05% brominated vanilla phenol blue solution
take 0.05 bromide herb phenol blue solution dissolved in 100 ml 20% ethanol solution.
3, 1% glycine solution
1g glycine dissolved in 100 ml distilled water.
4, standard 0.100mol/L sodium hydroxide solution
5, neutral formaldehyde solution
take formaldehyde solution 50 ml, plus 0.5% phenolic indicator about 3 ml, drop plus 0.1mol/LnaOH solution, so that the solution is slightly pink, before use neutral.
(ii) Experimental equipment
1, conical bottle 2, alkaline titration tube
3, pipe wash ball 4,
balance 5,
capacity bottle
6 Reagent bottle
7,
barrel
8, glass rod and
beech 4, operating procedure 1, take 3 100ml conical bottles, press the table to add reagents. 2, after mixing and mixing with the standard 0.100mol/L sodium hydroxide solution titration to purple (pH8.7 to 9.0)
3, the results calculated
the number of milligrams of amino nitrogen per milliliter amino acid solution is 5, Notethe use of formaldehyde tricure can be used to determine the degree of hydrolysolization of proteins. With the increase of protein hydrolyseration, the titration value also increases, and when the hydrolysing of protein is completed, the titration value does not increase..