Trace Moisture Analysis System

Importance of the Topic

Moisture content in liquefied petroleum gas (LPG) critically influences pipeline integrity, catalyst performance and overall product quality. Accurate determination of trace water levels prevents freezing in infrastructure and poisoning of downstream processes. Traditional Karl Fischer titration (KFT) struggles with low‐level measurements and is prone to side reactions and interferences.

Objectives and Overview of the Study

This work presents a novel gas chromatographic method using Shimadzu’s Barrier Discharge Ionization Detector (BID) and MilliporeSigma’s Watercol ionic liquid column to quantify moisture in LPG down to parts per million concentrations. A new ASTM standard (WK59649) has been submitted to formalize this approach based on its superior sensitivity versus conventional thermal conductivity detectors.

Methodology

Moisture is separated from hydrocarbon and sulfur compounds on a Watercol GC column. The eluted water is detected by BID, which offers high ionization efficiency and low background noise. External calibration with moisture standards enables quantification. Key performance metrics are signal‐to‐noise ratios of 350 at 25 ppm, detection limit of 0.22 ppm (S/N=3.3) and quantification limit of 0.66 ppm (S/N=10). Analysis time is under 15 minutes per run.

Used Instrumentation

• Shimadzu Nexis GC-2030
• BID-2030 Detector
• Liquid/Gas Sampling Valve
• MilliporeSigma Watercol GC Column
• Helium Carrier Gas (>99.9999%) with Purifier
• LabSolutions LC/GC Software

Main Results and Discussion

The method demonstrated excellent repeatability with relative standard deviation below 2 % for five replicate measurements at 25 ppm water. Chromatographic separation effectively resolved moisture from sulfur components such as ethyl mercaptan. Retention time for water was ~14.3 minutes. These figures underline the robustness and reliability of the GC/BID approach compared to KFT and TCD methods.

Benefits and Practical Application

• Trace‐level sensitivity down to 0.22 ppm
• Rapid analysis (<15 min) suitable for routine QC
• Minimal interference from organic and sulfur compounds
• High repeatability and linear dynamic range
• External standard calibration simplifies quantification

Future Trends and Possibilities for Use

Upon ASTM approval, this GC/BID method may become a new industry benchmark for moisture analysis in LPG and other gas streams. Potential extensions include on‐line process monitoring, automated sampling integration and adaptation to other challenging matrices requiring trace water determination.

Conclusion

The combination of Shimadzu’s BID technology with a Watercol ionic liquid column offers a powerful and sensitive solution for trace moisture analysis in LPG. It overcomes limitations of traditional KFT and TCD methods and is poised for standardization in ASTM WK59649.

Reference

• ASTM WK59649: New Standard Test Method for the Determination of Water in LPG using GC/BID