Glacial acetic acid for industrial use (6)

4.

Measure according to GB/T6283-2008

Use a syringe to weigh about 3.

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

4.

Measure according to GB/T6324.

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

4.

4.

Measure according to the regulations of GB/T3049-2006

4.

Pipette 100 mL of the sample into a porcelain or glass evaporating dish, evaporate to dryness on a boiling water bath, and dissolve the residue with 1 mL of hydrochloric acid solution (1+1)

4.

The mass fraction of iron w ₅ , the value is expressed in %, calculated according to formula (5):

Where:

m—The value of the iron mass obtained from the standard curve, in micrograms (pg);

V—the value of the volume of the sample, the unit is milliliters (mL);

p—The value of the density of the sample at 20°C, in grams per cubic centimeter (g/cm ³ )

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

4.
10.
2 Atomic Absorption Spectrometry

4.
10.
2.
1 Method summary

After the sample is evaporated, it is prepared into a solution of appropriate concentration, sprayed in an air-acetylene flame, with an iron hollow cathode lamp as the light source, and the absorbance of the sample is measured at a wavelength of 248.
3nm
.
According to the iron working curve determined under the same conditions, calculate the iron content in the sample
.

4.
10.
2.
2 Reagents

4.
10.
2.
2.
1 Water: Grade 2 water specified in GB/T6682-2008;

4.
10.
2.
2.
2 Hydrochloric acid solution: 1+1, take premium grade pure hydrochloric acid for preparation;

4.
10.
2.
2.
3 Iron (Fe) standard solution, 0.
01mg/mL: Pipette iron (Fe) standard solution (0.
1mg/mL), and dilute it with water 10 times
.
Prepared during use;

4.
10.
2.
2.
4 Acetylene : the volume fraction is not less than 99.
5%
.

4.
10.
2.
3 Instruments

Atomic Absorption Spectrometer (with iron hollow cathode lamp)

a) Characteristic concentration: In the solution consistent with the matrix of the test sample solution, the characteristic concentration of iron should not be greater than 0.
044ug/mL
.

b) Instrument precision: Under the given test conditions, the standard samples with absorbance in the range of 0.
1 to 0.
3 are measured repeatedly for 7 times, and the relative standard deviation of the results is not more than 1.
5%
.

4.
10.
2.
4 Analysis steps

4.
10.
2.
4.
1 Preparation of test specimens

Pipette 100mL sample in a 150mL round-bottomed porcelain or glass evaporating dish, evaporate to dryness on a boiling water bath, dissolve the residue with 2mL hydrochloric acid solution, transfer it into a 25mL volumetric flask, and dilute to the mark
.

4.
10.
2.
4.
2 Drawing of working curve

a) Preparation of calibration solution

Pipette 0mL, 2.
0mL, 4.
0mL, 6.
0mL, 8.
0mL, 10.
0mL iron standard solution, respectively, and place them in 6 25mL volumetric flasks, add 2mL hydrochloric acid solution, and dilute to the mark
.

b) Determination of the absorbance of the calibration solution

Under the given instrument test conditions, after the instrument is stabilized and adjusted to zero with water, measure the absorbance of the calibration solution respectively
.

c) Drawing of working curve

Take the absorbance of each standard solution minus the absorbance of the reagent blank solution as the ordinate: the concentration of the corresponding iron calibration solution is the abscissa to draw a working curve
.

If a data processing system is used, the working curve can be carried out when the sample is measured
.

4.
10.
2.
4.
3 Determination of samples

Measure the absorbance of the sample according to the method of measuring the absorbance of the standard solution
.
Check the concentration value from the working line (or directly read the concentration value)
.

4.
10.
2.
5 Result calculation

The mass fraction of iron w ₆ : the value is expressed in %, calculated according to formula (6):

Where:

c—The concentration obtained from the working curve, in micrograms per milliliter (pg/mL);

V ₁ —The value of the sample solution volume during the measurement, in milliliter (mL);

V—the value of the volume of the sample, the unit is milliliters (mL);

p—The value of the density of the sample at 20°C, in grams per cubic centimeter (g/cm)
.

Take the arithmetic mean of the results of the parallel measurement of the network as the measurement result, and the difference between the results of the two parallel determinations shall not exceed 0.
00001%
.