Method
Gas chromatograph:
Chromatec-Crystal 5000/9000
Detector:
FPD, or FPD with PID sensor; any other sulfur-selective detector is also acceptable – 2 pcs.
Sulfinert-treated lines in contact with the sample
Capillary columns used:
BP-5 column, 60 m × 0.53 mm × 5.0 µm
GS-GasPro column, 30 m × 0.32 mm, Cat. No. 113-4332
Injection system:
Thermostated 6-port or 10-port valves (automatic or manual, Valco or Chromatec valves)
Capillary evaporator – 2 pcs.
Liquefied gas sampling valve (optional) – 2 pcs.
Liquefied gas evaporator – 1 pc.
3-way valve – 2 pcs.
T-piece for connecting capillary columns – 2 pcs.
Heated transfer line with an inner tube made of a material inert to sulfur-containing compounds – 1 pc.
Additional equipment:
Hydrogen generator
Air compressor
Gas fittings kit 4.078.000
Catalytic air purification filter for removal of organic impurities
Electronic gas flow indicator 5.183.004
Certified gas mixtures of the target sulfur-containing compounds
Method Description
Method FR.1.31.2020.37947, developed by VNIIUS, applies to liquefied petroleum gases (LPG). It allows the determination of individual sulfur-containing compounds in the range from 0.0001 to 0.05% as elemental sulfur. The data obtained are used to calculate mercaptan sulfur and total sulfur values according to FR.1.29.2021.40985.
The method recommends the use of an FPD detector, although other sensitive sulfur-selective detectors are also permitted. According to the measurement procedure, the following compounds are determined: hydrogen sulfide, carbonyl sulfide, mercaptans, sulfides, disulfides, thiophenes, and thiophanes.
An important aspect of the method is the choice of the LPG sample introduction principle. The method provides two options for the user:
- Injection of a liquid LPG sample
- Injection of a vaporized LPG sample
When selecting the approach, it should be taken into account that liquid LPG sample injection also requires calibration using LPG certified reference materials. This is feasible, but significantly more expensive. A full set of LPG reference materials including all sulfur-containing components at four calibration levels may exceed the cost of the chromatograph itself.
The option using gaseous reference materials is much more economical, and the use of the Chromatec LPG flow evaporator together with automatic valves not only does not complicate the chemist’s work, but actually simplifies it.
Our recommendation is to use the vaporization option with gaseous sample injection.
The method takes into account the signal quenching effect of the FPD detector caused by hydrocarbons and recommends monitoring the separation between sulfur-containing compounds and hydrocarbons.
For this control, it is convenient to use an FPD with a PID sensor. The FPD with PID sensor is an FPD detector equipped with a collector electrode similar to the one used in an FID detector. This collector electrode makes it possible to analyze organic compounds via the PID/FID-type channel simultaneously with the analysis of sulfur-containing compounds via the FPD channel.
Methods
FR.1.31.2020.37947
Determination of the mass fraction of individual sulfur-containing compounds by gas chromatography.
(Developer: OAO “VNIIUS”)
FR.1.29.2021.40985
Determination of mercaptan sulfur and total sulfur mass fraction based on component composition data by gas chromatography.
(Developer: OAO “VNIIUS”)