Determination of Trace Benzene in Industrial Styrene—Gas Chromatography (3)

6 sampling

Take samples according to GB/T6680 and GB/T3723

7 Measurement procedure

7.

According to the operating instructions of the instrument, install the chromatographic column in the chromatograph according to 5.

7.

Prepare the n-heptane solution containing n-octane and n-nonane , inject the sample with the valve circuit in the pre-separated state in Figure 1 (position a), record from the injection to the complete peak of n-octane, and the n-nonane has not The time of outflow .

7.

Prepare a styrene solution with a benzene content of about 100mg/kg, and inject the sample with the solenoid switch valve in the pre-separation state in Figure 2 (position a).

7.

7.

7.

Note 1: During the storage of the ethylene standard sample, the phenomenon of white polymerization will occur, and the calibration mixture needs to be replaced in time.

7.

Take 1.

Note: When measuring the sample, the temperature of the sample should be consistent with the temperature of the calibration mixture

8 Expression of analysis results

8.

The content of benzene in styrene is calculated in w, and the value is expressed in milligrams per kilogram (mg/kg), calculated according to formula (1):

Where:

w _s ——the value of benzene content in the standard sample, in milligrams per kilogram (mg/kg);

A _s ——the value of the peak area of ​​benzene in the standard sample;

A——The value of the peak area of ​​benzene in the sample
.

8.
2 Presentation of results

8.
2.
1 The analysis result is expressed as the arithmetic mean of the two repeated measurement results, and the rounding of the value shall be carried out in accordance with GB/T8170.

8.
2.
2 The reported content should be accurate to 0.
1mg/kg
.

9 Repeatability

In the same laboratory, the same operator uses the same equipment, according to the same test method, and the same test object is tested independently in a short time.
The absolute difference between the two independent test results does not exceed the following repeatability Limit (r), on the premise that the repeatability limit (r) does not exceed 5%:

0.
2mg/kg≤w<1mg/kg is 30% of its average value

1mg/kg≤w<100mg/kg is 20% of its average value

10 report

The report should include the following:

a) all information relating to the sample, for example, sample name, batch number, sampling sites, sampling date, sampling time
.

b) Number of this part
.

c) Analyze the results
.

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

e) the name of the analyst and analysis date
.

Related Links: Determination of Trace Benzene in Industrial Styrene-Gas Chromatography (2)