Method
Gas chromatograph:
Chromatec-Crystal 5000/9000
Detector:
FID
Capillary columns used:
CP-Lowox column, 10 m × 0.53 mm × 10 µm
MXT-1 column, 30 m × 0.53 mm × 1 µm
T-piece for semi-backflush – 1 pc.
Injection devices:
Capillary evaporator
DAZh-2M injector
4-port automatic valve for liquefied gases with a 2 µL sample volume
6-port thermostated automatic valve with a 1 mL loop
Additional equipment:
Hydrogen generator
Air compressor
Gas fittings kit 4.078.000
Catalytic purification filter for air and carrier gas
Carrier gas preparation unit
Universal filter for purification of the carrier gas from oxygen, moisture, CO, CO2, and hydrocarbons
Reference standards for the target oxygenates (these may be pure substances for preparation of liquid standards or ready-made certified reference mixtures)
Method Description
This method describes the procedure for the determination of trace amounts of oxygenates in C2, C3, C4, and C5 hydrocarbon matrices, as well as in straight-run gasoline (naphtha) with a final boiling point not higher than 200°C.
The determination range for oxygenates is 0.5 to 100 mg/kg (ppm).
The LowOx oxygenates column imposes very strict requirements on the purity of the carrier gas. The presence of moisture or oxygen in the gas creates serious analytical problems.
For this analysis, additional purification of the helium used as carrier gas is mandatory. Filters capable of removing trace amounts of oxygen and water are applied.
We recommend sequential installation of filter 20.0-02 together with combined imported filters, with and without indication.
Even with these precautions, the columns still require periodic restoration of their performance characteristics.
For calibration, prepared liquid mixtures of the target oxygenates are generally used.
The following solvents may be used:
isooctane, cyclohexane, methylcyclohexane, straight-run gasoline fraction (naphtha), or isooctane-benzene 3:1.
The solvent must not contain the target oxygenates.