Automated determination of fluorine, chlorine, and sulfur in LPG by Combustion-IC

Combustion-IC is accepted as the best approach for determining individual halides like fluorine, chlorine, bromine, and sulphur compounds in LPG samples. It combines a combustion system with the analytical separation capability of an ion chromatograph in a fully automated matrix independent configuration. TE Instruments’ offers the Xprep C-IC sample prep system with GLS autosampler to enable fast, safe, and reliable Combustion-IC analyses of LPG samples. This unique configuration redefines automated combustion IC analysis through its innovative design and functionalities.

The Xprep C-IC stands for true automation. Once the sample cylinder is connected to the GLS autosampler, the complete sequence is undertaken automatically. First, the GLS autosampler flash-evaporates a sample loop with liquid LPG and transfers the gas cloud towards the direct injection module of the combustion unit. The combustion unit oxidises the sample by pyrohydrolitic combustion in an oxygen-rich environment at high temperatures. After combustion, absorber solution is added to the output gas stream to guarantee complete absorption of analytes in the 65 position Fraction Collection unit. Finally, the absorbent containing the captured analytes is transferred from the Fraction Collection unit towards any renowned IC for accurate determination of the fluorine, chlorine, and sulphur content.

Safety is a critical aspect related to LPG sampling due to the flammable nature of these matrices. Related sampling systems must handle a wide range of sample matrices contained in cylinders at varying pressure levels. The easy to use GLS autosampler stands out from other sampling systems with its safety features. The automatic safety lock prevents cylinders from being disconnected if pressure is detected.  The gas leakage sensor automatically aborts activity when a small hydrocarbon spill is detected. Real-time software notifications warn the operator about potential hazards and auto-shutoff sample inlet ports prevent uncontrolled release of LPG from the autosampler. 

The Xprep C-IC and GLS autosampler ensure that sample preparation runs smoothly, allowing the IC to perform excellently. TE Instruments has generated data to demonstrate the capabilities of this configuration. Table 1 shows great results with excellent standard deviations, far below the repeatability limits (r) of related test methods such as the ASTM D7994 and UOP 1001. A strong asset of the direct injection module is that multiple sample injections and subsequent combustions can be captured easily in the same collection vial. As a result, the absorbance liquid injected onto the IC column contains a high concentration of analytes, providing accurate results even at trace level.