Reversed-Phase HPLC Column at Extreme High Temperature (150°C or Higher)

Ken Tseng¹ , Gerd Vanhoenacker² , Takashi Kotsuka³ , and Pat Sandra² ,¹ Shodex, Showa Denko American, Inc., ² Research Institute for Chromatography, and ³ Showa Denko K.K.

In general, polymer-based columns have a broad pH range (pH 2 to 13), and some have high temperature tolerance (up to 150°C or higher). Considerably large selectivity changes can be obtained by varying analysis temperature and mobile phase pH. Having control on these two parameters over wide ranges can be especially useful in method development.

Figure 1

At high temperature,

• Decreased mobile phase viscosity enhances diffusion rate between the mobile phase and the polymer-based stationary phase

• Shodex polymer-based ET-RP1 column - minimal plate height (h_min) decreased significantly

• Silica-based columns - the h_min is more or less constant

• Consequently, efficiency of the polymer-based column at high temperature and high flow rate is similar to the efficiency obtained with traditional columns

A new polymer-based reversed-phase HPLC column, Shodex ET-RP1, was developed jointly between Research Institute for Chromatography (RIC) and Shodex. It provides,

• 5 times faster analysis time

• Better efficiency

• Improved control in selectivity

• Less organic solvent consumption

• Decreased risk in sample degradation

• Long column life

Figure 2

Experimental Conditions

System: Agilent 1100

Column oven: SandraSelerity Technologies, Polaratherm

9000 Series

Mobile phase: A = ammonium acetate pH 8 in water

B = acetonitrile

Temperature: 40 to 150°C

Flow rate: 0.5 to 2.4 mL/min

Figure 3

Results and Conclusions

High temperature is especially beneficial for polymer-based column performance. This is mainly due to the decreased mobile phase viscosity, thus, enhanced diffusion rate between mobile phase and polymer-based stationary phase. The relatively low efficiency of polymer-based columns that generally is a major drawback can be overcome by applying high temperature, resulting in sharp peaks. The decreased solvent viscosity means flow rate can be increased significantly while maintaining a conventional HPLC pressure. Less organic solvents are needed at high temperature means less impact on the environment (and your budget). The results are even better if the flow rate is increased to greatly shorten analysis time, up to five times faster.

Figure 4

Furthermore, polymer-based columns have the advantage over silica-based in that they can be applied in a much wider pH range (pH 2 to 13) and at higher temperatures (up to 150 °C or higher). This expands the application range for these types of stationary phases. pH and temperature can be used more extensively in method development. The potential catalytic activity originating from the stationary phase material is substantially smaller in polymer-based columns compared to silica- and zirconium-based columns. Consequently the risk for sample degradation at high temperature conditions is reduced. In these experiments, the Shodex ET-RP1 column has shown good durability.

Table I

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