Mesoporous polybutadiene-modified zirconia for high-temperature packed capillary liquid chromatography: column preparation and temperature programming stability

Abstract

In the present study, three different methods for packing of 3 μm PBD–ZrO 2 particles in 0.5 mm i.d. glass-lined stainless steel columns have been examined. The two first methods were based on a traditional downstream high-pressure technique using tetrachloromethane (Method I) or aqueous Triton X-100 (Method II) as slurry solvents, while Method III was an upstream high-pressure flocculating method with stirring, using isopropanol both as the slurry and packing solvent. Method I was found to be superior in terms of efficiency, producing 0.5 mm i.d.×10 cm columns with almost 90,000 plates m −1 for toluene (R.S.D.=8.7%, n=3), using a slurry concentration of 600 mg ml −1, ACN–water (50:50 (v/v)) as the packing solvent and a packing pressure of 650 bars. For Method I, the slurry concentration, column i.d., column length and initial packing pressure were found to have a significant effect on column efficiency. Finally, the long-term temperature stability of the prepared columns was investigated. In isothermal mode, using ACN–20 mM phosphate buffer, pH 7 (50:50 (v/v)) as the mobile phase, the columns were found to be stable for at least 3,000 void volumes at 100 °C. At this temperature, the solute efficiencies changed about 5–18% and the retention factors changed about 6–8%. In temperature programming mode (not exceeding 100 °C), on the other hand, a rapid decrease in both column efficiency and retention factors was observed. However, when the columns were packed as initially described, ramped up and down from 50 to 100 °C for 48 h and refilled, fairly stable columns with acceptable efficiencies were obtained. Although not fully regaining their initial efficiency after refilling, the solute efficiencies changed about 19–28% (32–37%) and the retention factors changed about 4–5% (13–17%) after running 3,000 (25,000) void volumes or 500 (3,900) temperature programs.