Analysis of Thiophene in Benzene using Nexis GC-2030

Importance of the Topic

In petroleum refining and fuel quality control, even trace levels of sulfur compounds such as thiophene can lead to catalyst poisoning and harmful emissions of sulfur oxides. Reliable, high-sensitivity analysis is therefore critical for regulatory compliance and process optimization.

Study Objectives and Overview

This application report demonstrates the determination of thiophene in benzene at trace concentrations (0.1–10 ppm) using the Nexis GC-2030 gas chromatograph equipped with a flame photometric detector (FPD-2030). The goal is to evaluate detection limits, linearity, and repeatability under standardized conditions in accordance with ASTM D7011.

Instrumentation and Methodology

Key analytical setup and procedures:

• Gas chromatograph: Nexis GC-2030 with AOC-20i autosampler
• Software: LabSolutions LC/GC
• Injection: WBI direct injection unit, 1 µL at 200 °C
• Column: SH-Stabiliwax capillary (0.53 mm I.D. × 30 m, 2.0 µm film)
• Oven program: Isothermal at 75 °C for 7 min
• Carrier and purge gas: Helium (99.999 %), constant flow at 10 mL/min (He), purge at 3 mL/min
• Detector: FPD-2030 (S mode) at 230 °C with H₂ (40 mL/min) and air (60 mL/min)

Results and Discussion

• Detection limit: Thiophene at 0.1 ppm in benzene yielded a signal-to-noise ratio of 16.
• Linearity: Excellent correlation over 0.1–10 ppm with R² of 0.9998 when plotting ln(concentration) vs. ln(area), reflecting the square-law response of FPD for sulfur.
• Repeatability: Six consecutive injections of 1 ppm thiophene gave an average peak area of 97 948 µV·s with an RSD of 0.91 %.

Practical Benefits and Applications

• High sensitivity allows reliable detection of trace sulfur species, essential for fuel specification testing.
• Robust linear response facilitates accurate quantification across regulatory ranges.
• Low variability supports consistent quality control in refinery and petrochemical environments.

Future Trends and Applications

• Integration with automated sample handling and data processing for higher throughput.
• Coupling GC-FPD with mass spectrometry for enhanced compound identification.
• Application of chemometric and machine-learning approaches to improve calibration robustness and predictive maintenance of the system.

Conclusion

The Nexis GC-2030 with FPD-2030 provides a sensitive, stable, and reproducible method for trace analysis of thiophene in benzene. Its performance meets stringent industry standards, making it a valuable tool for fuel quality assurance.