Industrial Ethylene Oxide (4)

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Using gas chromatography, under selected working conditions, the sample is vaporized and separated by a chromatographic column, detected by a thermal conductivity detector, and quantified by an external standard method

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The recommended chromatographic columns and typical operating conditions in this standard are shown in Table 2, and the typical chromatogram is shown in Figure 2

Table 2 Chromatographic column and typical operating conditions

Figure 2 Typical chromatogram for determination of carbon dioxide content

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5 Analysis steps

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1 Setting operating parameters

According to the instrument manual, adjust the instrument to the operating conditions shown in Table 2, and start the measurement after the instrument is stable
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2 Standard sample analysis

Through the gas sampling valve of the standard volume of sample into the chromatograph, chromatographic analysis, measurement of the carbon dioxide peak area of the standard sample measured in duplicate difference between the peak areas should not 5% carbon dioxide in its arithmetic mean, whichever The arithmetic mean is used to calculate the carbon dioxide content in the sample
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3 Sample analysis

Replace the gas sampling bag repeatedly with high-purity ammonia, and empty the gas in the sampling bag
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Use a medical syringe that has been frozen at a low temperature to suck 1mL-2mL of liquid laboratory samples into the metal sampling bag towel, so that the samples are completely vaporized at room temperature
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Purge the gas sampling valve or glass syringe of the chromatograph with the vaporized sample, inject a gaseous sample of the same volume as the standard sample into the chromatograph for analysis, and record the peak area of carbon dioxide
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After that, the temperature of the chromatograph oven can be increased to 180°C, so that the ethylene oxide component can flow out of the chromatographic column as soon as possible, and the temperature of the chromatograph oven can be reduced to the operating conditions for normal measurement.
After the instrument is stable, the next time will be started.
Analysis
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6 Result calculation

The mass fraction of carbon dioxide content w ₄ , the value is expressed in %, calculated according to formula (4):

Where:

A— The peak area of carbon dioxide in the sample ;

As— the peak area of carbon dioxide in the standard sample ;

cs—The volume fraction of the concentration of carbon dioxide in the standard sample, and the value is expressed in %
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Take the arithmetic mean of the two parallel determination results as the determination result, and the absolute difference between the two parallel determination results shall not exceed 30% of the arithmetic mean of the two determination values
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When the measured value of carbon dioxide is less than 0.
0005%, report as less than 0.
0005%
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9 Determination of chromaticity

Add laboratory samples to the mark in a 50mmL colorimetric tube cooled to 0°C to 4°C
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Use absorbent paper to dry the condensed water on the outer wall of the colorimetric tube, and quickly determine it in accordance with the provisions of GB/T3143
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