Determination of trace dimer in industrial butadiene by gas chromatography (3)

7 measurement steps

7.

After starting the chromatograph, make necessary adjustments to achieve the typical operating conditions listed in Table 1 or other suitable conditions that can obtain the same separation

7.

According to the approximate value of the expected dimer content in the sample to be tested, weigh an appropriate amount of 4-vinylcyclohexene, accurate to 0.

The content of 4-vinylcyclohexene (dimer) in the standard sample is calculated according to formula (1)):

(1) In the formula: C _s —— content of dimer in the standard sample, mg/kg;

m _s ——the amount of dimer, g;

m——the total amount of standard samples, g

7.

7.

Before or after each sample analysis, a standard sample is required for calibration

7.

Connect the sample cylinder to the liquid phase injection valve in the same way as in 7.

7.

Calculate the dimer content in the sample according to formula (2):

In the formula: X _i —— content of dimer in the sample, mg/kg;

A _i —the peak area of ​​the dimer in the sample;

A _s —the peak area of ​​a polymer in the standard sample;

P _i —the density of the sample at 20°C, g/mL

ps—The density of the standard sample at 20°C, g/mL, which can be assumed to be equal to the density of the solvent used to prepare the standard sample.

Cs—The content of dimer in the standard sample, mg/kg

8 Presentation of results

For any sample, the arithmetic mean of two or more repeated measurement results shall be used to express the analysis result, and shall be rounded to 1mg/kg according to GB/T8170

9 Precision

9.
1 Repeatability

In the same laboratory, the same operator uses the same instrument to perform two repeated measurements on the same sample.
When the dimer content is within the range of not more than 1000 mg/kg, under the 95% confidence level, the result is The difference between the results should not be more than 50mg/kg
.

10 Test report

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 standard;

c) Measurement results;

d) Details and descriptions of any abnormal phenomena observed in the test;

e) the name of the analyst and analysis date
.