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5 Apparatus and equipment
5.
5.
5.
5.
5.
5.
5.
5.
6 sampling
Take samples according to GB/T3723, GB/T6678, GB/T6680
Analysis steps
7.
Use a pipette to pipette 0.
Take 1.
Then draw 2mL of oxidant solution (4.
Use the concentration of acetaldehyde as the abscissa and the corresponding absorbance (the absorbance of each acetaldehyde standard solution minus the absorbance of the control solution) as the ordinate to draw a standard curve
Note: If the sample to be tested contains the polymerization inhibitor MEHQ, before adding the MBTH solution, add 1 mL of MEHQ solution (4.
7.
Draw 1mL sample into a 50mL volumetric flask, add 25mL MBTH solution (4.
1) and let stand for 45min
.
At the same time, take another volumetric flask as a reagent blank
.
The following steps are the same as described in (7.
1)
.
According to the measured absorbance (here, the absorbance of the sample solution is subtracted from the absorbance of the reagent empty), the total aldehyde content (in terms of acetaldehyde) is checked on the standard curve
.
Note: ① If the total aldehyde content in the sample is greater than 0.
0050%, the sampling amount is halved
.
② If the sample contains the polymerization inhibitor MEHQ, 1mL MEHQ solution (4.
3) should also be added to the reagent blank before adding the MBTH solution
.
8 Presentation of results
Take the arithmetic mean of the two repeated measurement results as the analysis result.
The difference between the two measurement results should meet the precision specified in Chapter 9
.
The measurement result should be accurate to 0.
00001%
.
9 Precision
9.
1 Repeatability
In the same laboratory, the same operator uses the same instrument, under the same operating conditions, using normal and correct operating methods to perform two repeated measurements on the same sample, and the difference between the measured values should not be greater than 10 of the average value.
% (95% confidence level)
.
10 report
The report should include the following:
a.
All information about the sample, such as the name of the sample, batch number, sampling point, sampling date, time, etc.
;
b.
Code of this standard;
c.
Analysis results;
d.
Details and descriptions of any abnormal phenomena observed during the measurement;
e.
the name of the analyst and analysis date
.
Related Links: Determination of Total Aldehyde Content in Industrial Acrylonitrile Spectrophotometry (1)