Analysis of Methyl-t-Butyl Ether (MTBE) and related impurities per ASTM test method D5441 using Zebron™ ZB-DHA-PONA Gas Chromatography Column

Importance of the Topic

Analysis of methyl-tert-butyl ether (MTBE) purity is crucial for spark-ignition fuel performance and regulatory compliance. Trace contaminants introduced during production, storage or transport can impair octane rating and engine operation. Employing a robust chromatographic method ensures reliable detection of C1–C12 olefins, alcohols and ether isomers at low concentrations.

Objectives and Study Overview

This work applies ASTM D5441 to quantify MTBE impurities using the Zebron™ ZB-DHA-PONA gas chromatography column. A comparative evaluation against three competitive columns (Restek® Rtx®-DHA-50, Supelco® Petrocol®-DH 50.2 and Agilent® HP®-PONA) was conducted under identical GC-FID conditions. The primary goal was to assess peak shape, separation efficiency and resolution of mandated critical pairs: trans-2-pentene/tert-butanol and tert-butanol/cis-2-pentene.

Methodology and Instrumentation

Samples containing 1% (w/w) of each impurity in MTBE were injected by pulse split (50:1) at 200 °C. Helium served as carrier gas (0.9 mL/min constant flow) and FID detection was set at 250 °C. The following stationary phases and dimensions were compared:

• Zebron ZB-DHA-PONA: 100 % dimethylpolysiloxane, 50 m × 0.20 mm × 0.50 µm
• Restek Rtx-DHA-50: 100 % dimethylpolysiloxane, 50 m × 0.20 mm × 0.50 µm
• Supelco Petrocol-DH 50.2: 100 % dimethylpolysiloxane, 50 m × 0.20 mm × 0.50 µm
• Agilent HP-PONA: 100 % dimethylpolysiloxane, 50 m × 0.20 mm × 0.50 µm

Oven programming ramped from 40 °C (hold 13 min) to 180 °C at 10 °C/min (hold 3 min). A deactivated fused-silica liner (Zebron PLUS Z-Liner™) minimized active sites.

Results and Discussion

The Zebron column delivered excellent peak symmetry for polar and nonpolar impurities owing to its specially deactivated surface. It exceeded the ASTM D5441 resolution requirement (≥ 1.3) for both critical pairs, with values of 1.6 (trans-2-pentene/tert-butanol) and 1.5 (tert-butanol/cis-2-pentene). Competitive columns showed lower resolution (0.8–1.7), with two failing to meet the 1.3 threshold for the tert-butanol/cis-2-pentene pair. The tight 0.20 mm inner diameter and optimized film thickness enhanced mass transfer and boiling-point separation.

Benefits and Practical Applications

• Reliable compliance with ASTM D5441 for fuel quality control
• Improved reproducibility and peak shape for routine QA/QC
• Efficient separation of low- and high-boiling ethers and olefins
• Reduced analysis time with high-efficiency dimensions

Future Trends and Potential Applications

Advances in stationary-phase engineering may further reduce bleed and expand polar-compound compatibility. Integration with mass spectrometry and automated sample handling will enable real-time monitoring of ether additives in refinery streams. Emerging ultra-high-efficiency microbore columns and two-dimensional GC approaches could push detection limits even lower.

Conclusion

The Zebron ZB-DHA-PONA column offers superior resolution, peak shape and robustness for ASTM D5441 analysis of MTBE and related impurities. Its performance exceeds that of tested competitive columns, making it a preferred choice for accurate fuel additive quality control.