Correct specific retention volume determination in inverse gas chromatography

Area of Science:

• Physical Chemistry
• Materials Science
• Surface Science

Background:

• Inverse Gas Chromatography (IGC) is crucial for solid material characterization.
• Key physico-chemical properties like heat of sorption are derived from specific retention volume.
• Existing methods for calculating specific retention volume have thermodynamic inconsistencies.

Purpose of the Study:

• To compare heats of sorption calculated using two different specific retention volume equations.
• To evaluate the impact of temperature normalization on thermodynamic parameters.
• To assess the accuracy of IGC analysis for microcrystalline cellulose and natural graphite.

Main Methods:

• Utilized Inverse Gas Chromatography (IGC) to analyze microcrystalline cellulose and natural graphite.
• Employed two distinct equations for calculating specific retention volume.
• Compared thermodynamic data derived from retention volumes normalized to 0°C versus measurement temperature.

Main Results:

• Specific retention volume is highly dependent on column temperature.
• Normalizing retention volume to 0°C consistently overestimates heats of sorption by up to 10%.
• The standard temperature normalization method inaccurately represents temperature's influence on retention and derived thermodynamics.

Conclusions:

• The thermodynamic approach using retention volume at measurement temperature is more accurate.
• Incorrect normalization of retention volume can lead to significant overestimation of sorption heats.
• Accurate thermodynamic characterization using IGC necessitates using retention volumes at the actual measurement temperature.