Determination of Carbonyl Compounds in Organic Chemical Products (2)

4.

4.

Pipette 2.

Note: If the content of carbonyl compounds in the 2.

4.

Operate in accordance with 4.

4.

The mass fraction w ₁ of the carbonyl compound is calculated in terms of carbonyl (CO), and the value is expressed in %.

Where:

m ₁ —The value of the mass of the carbon-based compound obtained from the standard online check corresponding to the absorbance of the sample, in micrograms (ug);

m ₀ —The value of the mass of the carbonyl compound found on the internal standard curve corresponding to the blank absorbance, in micrograms (ug);

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

4.

4.

The carbonyl compound in the sample reacts with hydroxylamine hydrochloride .

Reaction formula: RCHO+H ₂ NOH·HCl=RCH=NOH+HCI+H ₂ O

RCOR'+H ₂ NOH·HCI=RR'C=NOH+HCI+H ₂ O

4.

4.

4.

Weigh 4g of hydroxylamine hydrochloride, dissolve it in a 250mL iodine flask containing 20mL of water, dilute with 95% ethanol to 200mL, reflux in a boiling water bath for 30 minutes, cool to room temperature, add 5.

4.
3.
2.
3 Sodium hydroxide standard titration solution: c(NaOH)=0.
1mol/L;

4.
3.
2.
4 Sodium hydroxide solution: c(NaOII)=0.
01mol/L;

4.
3.
2.
5 Hydrochloric acid solution: c(HCl)=0.
01mol/L:

4.
3.
2.
6 Bromophenol blue indicator solution: 2g/L

Weigh 0.
2g of bromophenol blue indicator, add 1.
5mL of 0.
1mol/L sodium hydroxide standard titration solution to dissolve, and dilute to 100mL with 95% ethanol
.

4.
3.
3 Instruments

Micro burette: 10mL
.

4.
3.
4 Analysis steps

Measure 50 mL of hydroxylamine hydrochloride solution and place it in a 250 mL iodine measuring flask as a standard color for titration
.

Pipette 50.
0mL laboratory sample into a 250mL iodine measuring bottle towel, add 1.
25mL bromophenol blue indicator solution: dropwise add sodium hydroxide solution or hydrochloric acid solution until the sample solution is consistent with the standard color, this is the sample solution
.

Add 25.
0 mL of hydroxylamine hydrochloride solution to the sample solution, gently move the stopper of the iodine flask, cover it, put it in a boiling water bath for 10 minutes, cool to room temperature, and titrate with sodium hydroxide standard titration solution to the standard color For the end
.
When the color change of the end point is not obvious, the end point can be determined according to the potentiometric titration method of GB/T9725-2007
.

4.
3.
5 Result calculation

The mass fraction w2 of the carbonyl compound is calculated as carbonyl (CO), and the value is expressed as %, calculated according to formula (2):

Where:

V—The value of the volume of the standard titration solution (4.
2.
3.
2) of sodium hydroxide consumed by the sample, in milliliters (mL);

The value of the density of the sample at p-20℃, the unit is grams per liter (g/L);

M—the value of the molar mass of the carbonyl group, in grams per mole (g/mol) [M=28.
01];

c—The value of the concentration of the standard titration solution of sodium oxide, in moles per liter (mol/L)
.

5 Presentation of results

Take the arithmetic mean of the two parallel determination results as the determination result
.

If the carbonyl compound is expressed in other forms, multiply the results of formulas (1) and (2) by E/28.
01, where E is the relative molecular weight of the carbonyl compound in this form
.

Related Links: Determination of Carbonyl Compounds in Organic Chemical Products (1)