Separation of Permanent Gases by Surface-Bubble-Modulated Liquid Chromatography with Direct Injection of Gas Samples

Area of Science:

• Analytical Chemistry
• Chromatography

Background:

• Surface-bubble-modulated liquid chromatography (SBMLC) utilizes a hybrid stationary phase with a fixed gas phase.
• Previous attempts to separate nonpolar gases using SBMLC faced low resolution due to poor column efficiency.
• High analyte diffusivity in the stationary gas phase was identified as a key factor limiting efficiency.

Purpose of the Study:

• To investigate methods for enhancing the separation efficiency of SBMLC for nonpolar gaseous compounds.
• To address the limitations of low column efficiency in existing SBMLC methods.
• To demonstrate an improved SBMLC technique for the separation of permanent gases.

Main Methods:

• Investigated the impact of gas phase diffusivity on SBMLC column efficiency.
• Developed a mix-packing strategy by combining porous particles with fixed gas phase and non-porous particles without gas phase.
• Utilized nonporous octadecyl-bonded silica (ODS), pure silica, and large-pore ODS as complementary packing materials.

Main Results:

• Preventing direct contact between gas phases in porous particles significantly enhanced column efficiency.
• The mix-packing approach enabled direct injection of gas samples into the SBMLC column.
• Achieved efficient separation of argon and oxygen, a challenging separation for conventional gas chromatography.
• Demonstrated unique selectivity for nonpolar gases, free from water and carbon dioxide interference.

Conclusions:

• Mix-packing SBMLC columns with particles containing and lacking a fixed gas phase is an effective strategy to improve separation efficiency.
• This advanced SBMLC method provides a viable alternative for separating nonpolar gases, including challenging mixtures like Ar/O2.
• SBMLC offers distinct advantages for nonpolar gas analysis due to its unique selectivity and resistance to common gaseous interferences.