How to inject liquefied gases for a safe and accurate GC analysis?

The analysis of impurities and contaminants in liquefied gases can be challenging. High-boiling and unstable components are prone to adsorption and discrimination effects during conventional sample introduction, which may compromise analytical performance. An alternative is the Da Vinci LS Liquefied Gas Injector (LGI). 

This sample introduction system enables direct injection of liquefied gases into a gas chromatograph while maintaining the sample in its liquid phase. By eliminating the need to evaporate large sample volumes, the LGI improves safety, provides high repeatability, and enables fast gas chromatographic analysis. The technique is standardised in ASTM D7756 and EN 16423 for the determination of oily residue in LPG.

Direct Injection of Liquefied Gases - ASTM D7756 & EN 16423

The Liquefied Gas Injector is designed to introduce liquefied gas samples directly into a gas chromatograph under controlled pressure conditions. The system combines the LGI, a Pressure Station, and a dedicated controller integrated with an Agilent GC platform.

The Pressure Station safely manages sample introduction by pressurising the sample cylinder and maintaining a constant outlet pressure and flow. Using a standard GC injector needle and an on-column injection technique, the liquefied sample is transferred directly onto the GC column. Following sample introduction, the chromatographic separation is based on boiling point differences of the impurities and contaminants present in the sample. Results are reported in mg/kg, and a complete analysis can be achieved within thirty minutes.

Broad Application Range

The Liquefied Gas Injector supports a wide range of gas chromatographic applications, including:

• Oily Residue Analysis in LPG
  The Liquefied Gas Injector is standardised in ASTM D7756 and EN 16423 to determine oily residues and contaminants in liquefied petroleum gas (LPG). The method quantifies residues in the C10 to C40 range and reports results within 10 – 600 mg/kg. The range can be extended to C60.
• Elemental Sulphur in Liquefied Gases
  Direct injection by the LGI onto a GC equipped with a Sulphur Chemiluminescence detector ensures efficient transfer and accurate quantification of elemental sulphur in LPG samples.
• Composition and Impurities in Butadiene, Crude C4 and Raffinate
  A dual-channel GC configuration including the LGI enables the simultaneous determination of composition and impurities according to ASTM and industry-specific methods within 30 minutes.
• Oxygenate Traces in Liquid Hydrocarbon Matrices 
  A GC configuration including the LGI complies with ASTM D7423 and ASTM D7754 to analyse oxygenate traces in liquid hydrocarbon matrices within 25 minutes from 100 mg/kg down to 50 µg/kg. 
• Gas Condensate Analysis
  Single-run determination of N₂, CO₂, H₂S and hydrocarbons in both stabilised and stabilised gas condensates using a dual-channel configuration with LGI.

Learn More

The Liquefied Gas Injector eliminates the need for manual evaporation or liquid sampling valves, reducing safety risks while improving repeatability and analytical accuracy for liquefied gas applications. The direct injection principle has been standardised in ASTM D7756 and EN 16423 for the determination of oily residue in LPG.

Contact Da Vinci Laboratory Solutions for more information on the Liquefied Gas Injector.