ASTM D5303 Standard Test Method for Trace Carbonyl Sulfide in Propylene by Gas Chromatography
6. Apparatus
6.1 Gas Chromatograph - Any gas chromatograph (GC) equipped with a flame photometric detector/electrometer system (FPD), as described in 6.2, may be used. A GC/FPD equipped with an output signal linearizer is also permitted.
6.2 Detector System, flame photometric detector, either single or dual burner design. Noise level must be no more than one recorder chart division (see 6.5). The signal for COS must be at least twice the noise level at the 0.1 mg/kg level. A discussion of this detector is presented in Practice E 840. The electrometer used with the detector must have a sensitivity of 10(−12) A full scale on a 1 mV recorder to achieve optimum detectability at lowest levels.
6.3 Column - Any column that will effect the complete separation of COS from propylene and other compounds normally present in propylene concentrates, and that is sufficiently inert to preclude the loss of COS, may be used. Columns that meet these criteria, and that were used in the cooperative study for this test method, are listed in Table 1.
6.4 Sample Inlet System - Any gas sampling valve or gas tight syringe that will permit introduction of up to 5.0 mL to the column, and that will not cause any loss of COS, is suitable.
6.5 Recorder - Any strip chart recorder with a full scale range of 1 mV, a maximum full scale balance time of 2 s, and a minimum chart speed of 0.5 cm/s, may be used.
6.6 Data Handling System - Any commercially available GC integrator or GC computer system capable of accurately integrating the area (uVs) of the COS peak is satisfactory. Data systems that will linearize the logarithmic output of the FPD are also satisfactory.
6.7 Sample Cylinders, 300 mL capacity or larger, fluorocarbon lined stainless steel, Type DOT 3E, 12409 kPa (1800 psi) working pressure.
7. Reagents and Materials
7.1 Air, zero grade.
7.2 Carbonyl sulfide (COS), lecture bottle, 97.5 % min. (Warning - Toxic! See Section 8, Hazards.)
7.3 Gas Calibration Blends, 1 to 10 mg/kg COS in either nitrogen, argon, propylene or a propylene/argon mixture. They can be obtained from any commercial supplier or prepared as shown in Appendix X1 or Test Method D4468.
7.4 Gas Sampling Syringe, 0.1, 1.0, and 5.0 mL.
7.5 Gas Sampling Valve and Sample Loops, fluorocarbon or 316 stainless steel. See Footnote B of Table 1.
7.6 Glass Vials, 125 cm.
7.7 Hydrogen, pure grade, 99.9 %.
7.8 Isooctane (2,2,4-trimethylpentane), sulfur free, minimum purity 99 mol %. (Warning - Flammable! Health Hazard.)
7.9 Nitrogen or helium, 99.999 % min.
7.10 TFE-fluorocarbon septa and aluminum seals for vials.
8. Hazards
8.1 Carbonyl sulfide is toxic and narcotic in high concentrations, and upon decomposition can liberate hydrogen sulfide. Exposure to dangerous concentrations of COS is most likely when handling the pure component for preparation of standard blends for assaying the COS calibration gas standards.
