ASTM D5303 Standard Test Method for Trace Carbonyl Sulfide in Propylene by Gas Chromatography
12. Procedure
12.1 Using either the gas sampling valve or a gas tight syringe, as described in 9.3, inject the sample into the gas chromatograph.
12.2 Record the response of the FPD on the strip chart recorder as the COS elutes from the column.
12.3 Alternatively, obtain the computer or integrator output of COS retention time and peak area.
12.4 Obtain duplicate chromatograms of the sample. Fig. 2 illustrates a typical analysis using a Carbopack BHT-100 column.
13. Calculation
13.1 Depending on the method of calibration used (see Section 11), determine the concentration of COS in the sample.
13.1.1 If the system provides a linearized output, determine COS concentration according to (Eq 2), below:
COS, mg/kg = F x S
where:
F = calibration factor from (Eq 1), and
S = area (uVs) of the COS peak from the sample.
13.1.2 If a calibration curve of 1n peak area versus 1n (ng) sulfur was used (see 11.5.1), then determine the concentration of COS as shown in Appendix X1.
13.1.3 If a calibration curve of concentration versus log peak area was used (see 11.5.2), then determine the COS concentration as follows:
13.1.3.1 Calculate the log of the area of the COS peak of sample.
13.1.3.2 Take the COS concentration directly from the curve using the log value from 13.1.3.1.
NOTE 5 - If a calibration method is used that gives results in cm3/m3 (ppm by volume), such as that in Test Method D4468, then results must be converted to mg/kg. Use the following formula to do this:
COS, mg/kg = B x M1/M2
where:
B = COS, cm3/m3,
M1 = mole weight, COS = 60.1, and
M2 = mole weight, propylene = 42.1.
