Analysis of Polywax 655 using an Agilent J&W VF-5ht UltiMetal Column

Importance of Topic

The analysis of high-boiling polyolefin standards such as Polywax 655 is critical for generating accurate boiling point versus retention time calibrations in simulated distillation (SimDist) methods. These calibrations underpin quality control in petroleum refining, fuels analysis, and polymer research. Reliable separation and detection of long-chain n-alkanes enhance method robustness in industrial and research laboratories.

Objectives and Overview of the Study

This study aims to evaluate the performance of an Agilent J&W VF-5ht UltiMetal GC column in the analysis of Polywax 655. Key goals include assessing column inertness, temperature stability, separation efficiency, and sensitivity when coupled with chemical ionization mass spectrometry using a triple quadrupole detector.

Methodology

• Sample preparation: 0.1 percent (w/v) Polywax 655 in carbon disulfide (CS2).
• Injection: On-column injection with temperature ramp from 100°C to 400°C at 15°C/min; injection volume 1.0 µL.
• Chromatography: 30 m × 0.25 mm, 0.1 µm Agilent J&W VF-5ht UltiMetal column; temperature program from 50°C (1 min) to 450°C (20 min) at 10°C/min; helium carrier gas at 3 mL/min.

Instrumentation

• Gas chromatograph: Agilent UltiMetal GC column technology for enhanced mechanical strength and inertness.
• Detector: Triple quadrupole mass spectrometer operating in chemical ionization mode with methane at 5 Torr; transfer line and ion source at 300°C; manifold at 40°C; monitored m/z range 45–900.

Main Results and Discussion

The UltiMetal column demonstrated excellent separation of n-alkanes up to C40 with sharp peak shapes and minimal bleed at high temperatures. Chemical ionization mass spectrometry provided improved sensitivity for hydrocarbon ions compared to electron ionization, although detection of very heavy alkanes approached instrumental limits. High maximum operating temperature allowed rapid bake-out of residual sample.

Benefits and Practical Applications

• Robust calibration for simulated distillation and boiling point determination in fuels and petrochemical quality control.
• High-temperature stability enabling extended analyses of heavy hydrocarbons without column degradation.
• Improved inertness reducing adsorption of polar contaminants and ensuring reproducible retention times.

Future Trends and Potential Applications

Advances in metal GC column technologies will likely expand high-temperature applications, including polymer characterization and grease analysis. Coupling with high-resolution mass spectrometry and automated sample preparation can further enhance sensitivity and throughput in industrial laboratories.

Conclusion

The Agilent J&W VF-5ht UltiMetal column coupled with chemical ionization mass spectrometry offers a reliable approach for analyzing long-chain n-alkanes in Polywax 655, delivering robust separations, high-temperature endurance, and enhanced detection sensitivity. This method supports precise simulated distillation calibrations and extends analytical capabilities for heavy hydrocarbon matrices.

Reference

John Oostdijk; Analysis of Polywax 655 using an Agilent J&W VF-5ht UltiMetal Column; Agilent Technologies Application Note SI-01317; September 17, 2012.