Deng potassium salt of L-p-hydroxyphenylglycine (two)

4 Test method

4.

Some test procedures specified by the test method may lead to dangerous situations

4.

Unless otherwise specified, only reagents confirmed to be analytically pure and grade 3 water specified in GB/T6682-1992 are used in the analysis

4.

Visual inspection

4.

4.

Electrode: E-201-C composite electrode

4.

Ferric chloride solution: 25g/L

4.

Take about 40mg of laboratory samples, add 2mL of water to dissolve, add 1 drop of ferric chloride solution, there should be a blue precipitate (an instantaneous turn into a brown precipitate)

4.

4.

4.

Using glacial acetic acid as the solvent, titrate with perchloric acid standard titration solution, determine the titration end point by measuring the electrode potential , and calculate the content of L-p-hydroxyphenylglycine Deng potassium salt in the sample according to the volume of the perchloric acid standard titration solution
.

4.
5.
1.
2 Reagents

4.
5.
1.
2.
1 Glacial acetic acid
.

4.
5.
1.
2.
2 Perchloric acid standard titration solution: c(HC1O ₄ )=0.
1mol/L
.

4.
5.
1.
3 Analysis steps

Weigh about 0.
3g laboratory sample, accurate to 0.
0001g
.
Place in a dry 150mL beaker, add 50mL of glacial acetic acid to dissolve, and titrate with perchloric acid standard titration solution to the end point
.
The determination of the volume of perchloric acid standard titration solution adopts the GB/T 9725-1988 6.
2.
2 secondary derivative method
.

4.
5.
1.
4 Result calculation

The mass fraction w _{1 of the} content of L-p-hydroxyphenylglycine Deng potassium salt , the value is expressed in %, calculated according to formula (1):

Where:

V—The value of the volume of the sample consumption perchloric acid standard titration solution (4.
5.
1.
2.
2), in milliliter (mL);

c—The exact value of the concentration of perchloric acid standard titration solution, the unit is moles per liter (mol/L);

m—The value of the mass of the sample, in grams (g);

M—The value of the molar mass of L-p-hydroxyphenylglycine Deng potassium salt, in grams per mole (g/mol)

Take the arithmetic mean of the two parallel determination results as the determination result, and the absolute difference between the two parallel determination results shall not exceed 0.
3%
.