Method
Gas chromatograph:
Kristall 2000M or Chromatec-Crystal 5000/9000
Detector:
FID
Capillary column:
HP-PLOT Al2O3/S column, 50 m × 0.53 mm × 15 µm, #19095P-S25 (Agilent)
or
Rt-Alumina BOND/Na2SO4 column, 50 m × 0.53 mm × 10 µm, Cat. No. 19756
or
Rt-DHA-100 column, 100 m × 0.25 mm × 0.5 µm, Cat. No. 10148
(according to the method recommendation, this column may also be used, although in practice this option is used less often)
Injection system:
Liquefied gas sampling valve with an injection volume from 0.05 to 1 µL
or
6-port sampling valve with a sample loop of 0.25–1 mL for gaseous sample injection
(for vaporization of liquefied samples, an LPG Flow Evaporator may be required)
Additional equipment:
Hydrogen generator
Air compressor
Gas fittings kit 4.078.000
Sampling cylinders:
PGO and PU sampling cylinders according to GOST 14921
PP-150 constant-pressure sampling cylinders (recommended)
Gas fittings kit 4.078.008 for filling piston sampling cylinders
Filters for gas sampling and sample injection (filter 5.884.057, filter 5.884.083, filter 5.884.056)
Method Description
The method provides for the quantitative determination of individual C1-C5 hydrocarbons in liquefied petroleum gases (LPG) and propane-propylene mixtures, excluding high-purity propylene.
Component concentrations are determined in the range from 0.01 vol.% to 100 vol.%.
The method does not allow reliable determination of hydrocarbons heavier than C5 or of non-hydrocarbon materials.
The LPG sample is analyzed by gas chromatography, with the sample introduced in either liquid or gaseous form using a sampling valve.
Sampling Considerations
Special attention should be paid to the sampling cylinder.
According to the method, light components such as methane and ethane are also determined. To avoid their partial transfer into the headspace of the sampling cylinder, the method recommends pressurizing the sample with helium to 1380 kPa (200 psi) above the sample vapor pressure.
However, a more practical solution is to use a piston-type sampling cylinder such as the PP-150. In this case, pressurization can be carried out not only with helium, but also with less expensive gases such as nitrogen or air.
In addition, pressurization with helium in a constant-volume cylinder does not eliminate the headspace completely; it still remains, although it then consists mainly of the added helium. With the PP-150 piston cylinder, the design makes it possible to achieve sampling without headspace.
Vaporization of Liquefied Samples
When gaseous sample injection is selected using a 6-port gas valve, it is recommended to use an LPG Flow Evaporator to convert liquefied samples into the gas phase.
The LPG Flow Evaporator is designed for smooth vaporization of liquefied gas and transfer of the sample to the sampling valves of the gas chromatograph.
The device provides:
- automatic sample introduction
- pressure stabilization
- purging with inert gas after analysis
The evaporator is a bench-top unit and is available in several versions differing in valve configuration.
On request, versions can be manufactured with Sulfinert coating (Inconelsteel®, Siltek®, Sulfinert®) on valves and other pneumatic components.