Determination of the color of 50% aqueous solution of caprolactam for industrial use—spectrophotometry (1)

1 Scope

This part of GB/T 13255 specifies the spectrophotometric method to determine the color of 50% aqueous caprolactam solution for industrial use

2 Normative references

The clauses in the following documents are quoted in this part of GB/T13255 and become clauses of this part.

GB/T 6682-1992 Analytical laboratory water specifications and test methods (ncq ISO 3696: 1987)

GB/T 8170 Numerical Rounding Rules and the Expression and Judgment of Limit Values

3 Principles of the method

Use a spectrophotometer to measure the absorbance of a 50% caprolactam aqueous solution at a wavelength of 390nm, and multiply the absorbance by the constant 150 to convert it into the Hazen unit—the chromaticity of the platinum-diamond color number

4 Reagents

Unless otherwise specified, only Grade 3 water that meets the requirements in GB/T6682-1992 is used in the analysis

5 Instruments

Spectrophotometer: accuracy ±0.

6 Analysis steps

6.

Weigh 50.

6.

Inject water into the absorption cell instead of the sample solution, and measure the difference between the absorbance of the two absorption cells at a wavelength of 390 mm, which is the correction value of the absorbance of the absorption cell

7 Result calculation

Chromaticity x (Hazen unit-platinum-diamond color number) is calculated according to formula (1):

x=150×(A ₁ -A ₀ ).

Where:

A ₁ ——The absorbance of the sample solution;

A ₀ —— the corrected value of absorbance of the absorption cell;

150-Absorbance converted to Hazen unit-the constant of platinum-cobalt color number

The difference between the two parallel determination results is not more than 0.

8 reports

The report should include the following:

a) All information about the sample, such as sample name, batch number, sampling location, sampling date, sampling time, etc.

b) Code of this part;

c) Analysis results and presentation methods;

d) Details and descriptions of any abnormal phenomena observed in the measurement:

e) The name of the analyst and the date of analysis, etc.

f) Any description of operation or test conditions not included in this section

Related links: Typical chromatograms and relative retention values ​​for the determination of acetate content and alcohol content (2)