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What GC setup do I need for LPG composition testing?

 

LPG composition testing requires a 200 Series GC configured with a Flame Ionisation Detector (FID). Because LPG consists of hydrocarbons in the C3 to C5 range with no permanent gases to measure, a single FID is sufficient.

Sample introduction

LPG is stored and transported as a pressurised liquid. This means sample introduction is different from natural gas analysis. The sample is either injected as a liquid or introduced as a controlled vapour from the pressurised container. The 200 Series GC is configured with the appropriate sampling hardware for pressurised liquid handling.

Getting sample introduction right matters. Inconsistent sampling from a pressurised LPG source is one of the most common causes of poor repeatability in LPG analysis. The instrument configuration addresses this.

What the analysis measures

A single run separates and quantifies the individual hydrocarbon components present in the LPG sample. Typical measured compounds include propane, propylene, iso-butane, n-butane, butylenes, iso-pentane, n-pentane, and any heavier residues.

The relative proportions of these components determine the product grade and whether it meets the relevant specification for its intended use.

Calculated properties

The measured composition is used to calculate vapour pressure and density. These are important for storage, transport, and end-use behaviour. Calculations are performed automatically by the Clarity data station software.

Standards compliance

The 200 Series GC LPG configuration produces results in compliance with ASTM D2163 (standard test method for analysis of LPG by GC), ASTM D2598 (calculation of physical properties from composition), and ASTM D2421 (practice for interconversion of analysis of C5 and lighter hydrocarbons).

Where this is used

LPG composition testing is standard practice at import terminals, storage and blending facilities, distribution depots, bottling plants, and quality control laboratories supporting LPG supply chains.

What about LPG that also contains permanent gases?

If your LPG samples occasionally contain measurable levels of nitrogen, CO₂, or other non-hydrocarbon gases, a dual-detector configuration (TCD and FID) may be more appropriate. This is the same configuration used for natural gas analysis. Get in touch to discuss which setup fits your sample types.

Want to discuss LPG analysis for your facility? Get in touch with the team.