Evaluation of Gas Chromatography Columns with Radially Elongated Pillars as Second-Dimension Columns in Comprehensive Two-Dimensional Gas Chromatography

The present study investigated the use of a dedicated gas chromatography (GC) column (L = 70 cm, 75 mu m deep, and 6.195 mm wide) with radially elongated pillars (REPs) as the second column in a comprehensive two-dimensional gas chromatography (GC x mu GC) system. Three stationary phases [apolar polydimethylsiloxane (PDMS), medium polar room temperature ionic liquid (RTIL) based on monocationic phosphonium, and polar polyethylene glycol (PEG-1000)] have been coated using the static method at constant pressure or using an original vacuum pressure program (VPP) from 400 to 4 mbar. The best efficiency reached up to N = 62,000 theoretical plates for a film thickness of 47 nm at 100 degrees C for an iso-octane peak (k = 0.16) at an optimal flow rate of 4.8 mL/min. The use of the VPP improved the efficiency by approximately 15%. Efficiencies up to 28,000 and 47,000 were obtained for PEG-1000 and RTIL, respectively. A temperature-programmed separation of a mixture of 11 volatile compounds on a PDMS-coated chip was obtained in less than 36 s. The PDMS-, PEG-1000-, and RTIL-coated chips were tested as the second column using a microfluidic reverse fill/flush flow modulator in a GC x mu GC system. The REP columns were highly compatible with the operating conditions in terms of flow rate and with more than 30,000 plates for the iso-octane peak. Moreover, a commercial solvent called white spirit containing alkanes and aromatic compounds was injected in three sets of columns in normal and reverse modes, demonstrating the great potential of the chip as a second-dimension separation column.