Method
Gas Chromatograph
Kristall 2000M or Chromatec-Kristall 5000/9000
Detector
Thermal Conductivity Detector (TCD) or Flame Ionization Detector (FID)
Possible Packed Columns
Column M, SS 316, 3 m × 3 mm, 15% mineral oil on alumina, 0.16–0.25 mm
Column M, SS 316, 3 m × 3 mm, 15% dibutyl phthalate (DBP) on Spherokhrom-2, 0.16–0.25 mm
Column M, SS 316, 2 m × 2 mm, Porapak N, 80/100 mesh
Possible Precolumns
Column M, SS 316, 0.5 m × 3 mm, 30% OV-101 on Chromosorb P-AW, 60/80 mesh
Sample Inlet
Packed-column vaporizing injector
Backflush system based on a rotary or automatic valve
Additional Equipment
Hydrogen generator when using an FID
Air compressor when using an FID
Gas fittings kit, Part No. 4.078.000
Sampling Devices
PGO samplers compliant with GOST 14921
Method Description
This method determines C₁–C₆ hydrocarbons with a mass fraction greater than 0.01% in crude oil prepared in accordance with GOST 9965. The method is based on separating the C₁–C₆ hydrocarbons present in crude oil by gas–liquid chromatography, followed by their detection using a Thermal Conductivity Detector.
Although the GOST standard specifies the use of a TCD, a Flame Ionization Detector may also be used for this application.
Special attention must be paid to the sampling procedure and the sampling devices. Only PGO-type steel samplers are recommended. The crude-oil sample should be collected directly with a syringe through a dedicated sampling fitting. Other sampling procedures may produce inaccurate results.
GOST 13379 specifies packed columns containing alumina modified with mineral oil for separating C₁–C₅ hydrocarbons and a column containing dibutyl phthalate on Spherokhrom for C₂–C₆ hydrocarbons.
Modern packed columns containing Hayesep N or Porapak N can cover the entire C₁–C₆ range. The range can be extended to C₁–C₉ by using a capillary column with a 100% polydimethylsiloxane stationary phase—such as BP-1, DB-1, ZB-1, or CP-Sil 5 CB—together with an FID. However, this configuration is not covered by GOST 13379-82. The use of an FID and a capillary column is specified in ASTM D7900.
Components heavier than hexane are backflushed to protect the analytical columns. The backflush system can be configured in two ways:
Using a rotary valve
Using an automatic valve
The automatic-valve configuration is preferred.
To minimize column contamination by heavy sample components, a packed inlet liner is used and its packing is replaced regularly. The vaporizer liner is filled with a strip of filter paper rolled into a tube. Specially prepared calcined glass-fiber cloth may also be used.