Method
Gas chromatograph:
Kristall 2000M or Chromatec-Crystal 5000/9000
Sulfinert-treated lines in contact with the sample
Detector:
FPD – 2 pcs. (flame photometric detector)
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
Column with 1st or 5th phase, length 30–60 m, diameter 0.32 mm, film thickness 4–5 µm
Injection system:
6-port or 10-port thermostated valves (automatic or manual, Valco or Chromatec valves)
Capillary evaporator – 2 pcs.
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
GOST R 57975.2 allows the analysis of sulfur-containing compounds in associated petroleum gas as well as in natural gas, including:
hydrogen sulfide, C1-C4 mercaptans, carbonyl sulfide, carbon disulfide, alkyl sulfides, alkyl disulfides, tetrahydrothiophene, thiophene and its derivatives, and benzothiophene.
Compared with GOST R 53367 and GOST 34723, this standard covers a broader list of components and wider concentration ranges.
Measurement Range According to GOST R 57975.2-2017
| Component | Mass Fraction Range, % (Mass Concentration, mg/m³) |
|---|---|
| Hydrogen sulfide | From 0.0002 to 0.1 inclusive (from 0.2 to 100 inclusive) |
| Carbonyl sulfide | From 0.0002 to 0.05 inclusive (from 0.2 to 50 inclusive) |
| Methyl mercaptan | From 0.001 to 0.05 inclusive (from 1 to 50 inclusive) |
| Ethyl mercaptan | From 0.001 to 0.05 inclusive (from 1 to 50 inclusive) |
| Dimethyl sulfide | From 0.001 to 0.05 inclusive (from 1 to 50 inclusive) |
| Carbon disulfide | From 0.001 to 0.05 inclusive (from 1 to 50 inclusive) |
| Isopropyl mercaptan | From 0.001 to 0.05 inclusive (from 1 to 50 inclusive) |
| n-Propyl mercaptan | From 0.001 to 0.05 inclusive (from 1 to 50 inclusive) |
| 2-Methyl-2-propyl mercaptan (tert-butyl mercaptan) | From 0.001 to 0.05 inclusive (from 1 to 50 inclusive) |
| 2-Methyl-1-propyl mercaptan (isobutyl mercaptan) | From 0.001 to 0.05 inclusive (from 1 to 50 inclusive) |
| 1-Methyl-1-propyl mercaptan (sec-butyl mercaptan) | From 0.001 to 0.05 inclusive (from 1 to 50 inclusive) |
| Methyl ethyl sulfide | From 0.001 to 0.05 inclusive (from 1 to 50 inclusive) |
| n-Butyl mercaptan | From 0.001 to 0.05 inclusive (from 1 to 50 inclusive) |
| Diethyl sulfide | From 0.001 to 0.05 inclusive (from 1 to 50 inclusive) |
| Dimethyl disulfide | From 0.001 to 0.05 inclusive (from 1 to 50 inclusive) |
| 2-Methylthiophene | From 0.001 to 0.05 inclusive (from 1 to 50 inclusive) |
| 3-Methylthiophene | From 0.001 to 0.05 inclusive (from 1 to 50 inclusive) |
| Thiophene | From 0.001 to 0.05 inclusive (from 1 to 50 inclusive) |
| Tetrahydrothiophene (thiophane) | From 0.001 to 0.05 inclusive (from 1 to 50 inclusive) |
| Methyl ethyl disulfide | From 0.001 to 0.05 inclusive (from 1 to 50 inclusive) |
| 2-Ethylthiophene | From 0.001 to 0.05 inclusive (from 1 to 50 inclusive) |
| 2,5-Dimethylthiophene | From 0.001 to 0.05 inclusive (from 1 to 50 inclusive) |
| Methyl isopropyl disulfide | From 0.001 to 0.05 inclusive (from 1 to 50 inclusive) |
| Diethyl disulfide | From 0.001 to 0.05 inclusive (from 1 to 50 inclusive) |
| Methyl n-propyl disulfide | From 0.001 to 0.05 inclusive (from 1 to 50 inclusive) |
| Benzothiophene | From 0.001 to 0.05 inclusive (from 1 to 50 inclusive) |
Detector Features and Analytical Notes
The flame photometric detector (FPD) offers high sensitivity, good selectivity, and low cost. However, it also has certain limitations.
One important point is that the FPD has a signal quenching effect, which means that the resolution between sulfur-containing compounds and hydrocarbons must be at least 1.
To evaluate the degree of separation between sulfur-containing compounds and hydrocarbons in the gas, the gas should be analyzed under conditions where the selectivity of the FPD is reduced (by changing the hydrogen-to-air ratio) so that hydrocarbon peaks become visible on the chromatogram.
In addition, the detector is non-linear, therefore calibration is performed by constructing a calibration graph using the function:
lg(y) = K1 × lg(x) + K0
where:
y = amount of substance
x = detector response (peak area)
Under GOST R 57975.2, not only valves but also evaporators are commonly used to allow sample injection by syringe.
Syringe injection through evaporators is required for calibration of certain sulfur-containing compounds using liquid solutions, and also for analysis of unknown samples where valve injection is less convenient.