6 sampling
Take samples according to the safety and technical requirements specified in GB/T3723, GB/T13289 and GB/T 13290
.
7 Analysis steps
7.
1 Set operating conditions
Install and condition the chromatographic column in the chromatograph according to the operating instructions of the instrument
.
Adjust the instrument to the operating conditions shown in Table 1, Table 2 or Table 3, and start the measurement after the instrument is stable
.
7.
2 Calibration
Use a gas sampling valve to inject 1mL～3mL of standard sample (4.
5) into the chromatograph under specified conditions for determination.
After the peak of carbon dioxide or acetylene is completed, switch the backflush valve to expel ethylene or propylene as soon as possible
.
Repeat the measurement twice to calculate the average peak area As of carbon monoxide , carbon dioxide or acetylene
.
7.
3 Sample measurement
Take a gas sample with the same injection volume as the standard sample, inject it into the chromatograph with a gas injection valve, repeat the measurement twice, record the peak area of carbon monoxide, carbon dioxide or acetylene, and compare it with the corresponding external standard peak area
.
Note: When liquid propylene is sampled, measures should be taken to ensure that the liquid propylene is completely vaporized.
Flash injection or water bath can also be used for vaporization
.
8 Expression of analysis results
8.
1 Calculation
8.
1.
1 The content of carbon monoxide, carbon dioxide or acetylene is calculated in milliliters per cubic meter (mL/m 3 ), calculated according to formula (1):
Where:
ΦS—the content of carbon monoxide, carbon dioxide or acetylene in the standard sample, in milliliters per cubic meter (mL/m 3 );
Ai—the peak area of carbon monoxide, carbon dioxide or acetylene in the tested sample;
As—the peak area of carbon monoxide, carbon dioxide or acetylene in the standard sample
.
8.
2 Presentation of results
8.
2.
1 The value of the analysis result shall be rounded according to GB/T8170, and the arithmetic average of the two repeated determination results shall be taken to represent the analysis result
.
8.
2.
2 The content of reporting carbon monoxide, carbon dioxide or acetylene should be accurate to 1 mL/m 3
.
9 Precision
9.
1 Repeatability
In the same laboratory, the absolute difference between the two independent test results obtained by the same operator using the same equipment, using the same test method, and independently testing the same object under test within a short period of time should not exceed Table 4 The repeatability limit (r) is based on the premise that the repeatability limit (r) does not exceed 5%
.
Table 4 Repeatability limit (r)
9.
2 Reproducibility
In any two different laboratories, different operators use different instruments and equipment to test the same object independently of each other to obtain two test results.
For samples with acetylene content of (5-20) mL/m³ , The difference should not be greater than 30% of its average value, assuming that it does not exceed 5% if it is greater than 30% of its average value
.
10 Test report
The test 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) Number of this standard;
c) Analysis 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 Carbon Monoxide, Carbon Dioxide and Acetylene in Industrial Ethylene and Propylene Gas Chromatography (2)
