Introducing Titan UHPLC Columns


The following was generated with the assistance of an outside source using Sigma-Aldrich® products. Technical content was generated and provided by:
Richard A. Henry, Technical Advisor

Introduction

The first decade of the new millennium has seen several important advancements in HPLC technology.

  • Porous, spherical silica particles below 2 µm have become commercially available for the first time, and column efficiency has been doubled at the expense of a very significant increase in column pressure requirement.
  • Separation speed has more than doubled because the minimum in the plate height or van Deemter equation has almost disappeared, and efficiency of smaller particle columns can be maintained at higher flow velocities and higher pressures.
  • Instruments with a much higher pressure rating and lower internal volume were developed to efficiently use the new sub-2 µm particles and columns; the term ultra HPLC or UHPLC has been used to describe HPLC experiments with smaller particles and higher pressures.
  • Spherical silica particles with a 2.7 µm solid-core design appeared commercially to provide serious competition to sub-2 µm porous particles because the core-type design delivered similar, higher efficiency at much lower pressure.

Desmet1 and others have provided evidence that superior HPLC and UHPLC column performance for solid-core and other columns correlates well with a tighter particle distribution and lower A-term (also called eddy diffusion or multipath term) in the van Deemter equation.

Figure 1. Comparison of Particle Size Distribution for Different Sub-2 µm Porous Particles

Figure 1. Comparison of Particle Size Distribution for Different Sub-2 µm Porous Particles

 

The Ecoporous™ process has been developed by Supelco to commercialize the first sub-2 µm porous silica for UHPLC, called Titan™, which features a very narrow PSD of ca. 6% rsd (Figure 1).  Our new 1.9 µm porous particles do not require further sizing so particle waste is not generated by the new process.

Figure 2 shows an SEM photo for the new Titan silica. Performance tests on Titan columns with 1.9 µm monodisperse, porous silica show that more than 300,000 N/m can be generated for small molecules with a lower pressure drop than C18 columns with 1.7 or 1.8 µm C18 silica.

Figure 2. Titan 1.9 µm SEM Photo

Figure 2. Titan 1.9 µm SEM Photo

Titan UHPLC Performance

The very high performance of narrow PSD Titan 1.9 µm C18 columns in two popular geometries is shown in Figure 3. The van Deemter performance for a Titan column is compared in Figure 4 to smaller porous particles that have broader size distributions. Lower values for reduced plate height (h), which is plate height (H) divided by particle diameter, is very significant for Titan columns because it means that higher column efficiency is observed with larger particles which create lower pressure drop. Figure 4 demonstrates this efficiency advantage for Titan over commercial 1.8 and 1.7 µm porous particles. Figure 5 shows the pressure drop for Titan and two other commercial columns. It confirms that Titan 1.9 µm column pressure is lower than 1.7 µm or 1.8 µm particle columns and is actually closer to a 2.5 µm particle column. Figure 6 shows a separation of barbiturates on a Titan C18 10 cm x 2.1 mm column. The narrow PSD of Titan columns is expected to produce very rugged columns that hold up well in use over a range of UHPLC operating conditions.

Figure 3. Titan C18 Performance at Different Column IDs

Figure 3. Titan C18 Performance at Different Column IDs
Conditions: columns: Titan C18, 1.9 µm; mobile phase: 50% acetonitrile; temp: 35 °C; det: 254 nm

 

Figure 4. Performance (h) with Pharmaceutical Molecule

Figure 4. Performance (h) with Pharmaceutical Molecule
Columns: 5 cm x 3.0 mm I.D., 60% acetonitrile (single column tests).

 

Figure 5. Independent Evaluation of Titan Pressure Drop

Figure 5. Independent Evaluation of Titan Pressure Drop

 

Figure 6. Titan C18: Barbiturates

Figure 6. Titan C18: Barbiturates
Conditions: column: Titan C18, 10 cm x 2.1 mm I.D., 1.9 µm (Product No. 577124-U); mobile phase: 30:70, acetonitrile:0.1% ammonium acetate, pH 7.1; temp: 35 °C; det: 230 nm; flow rate: 0.4 mL/min; test mix: barbiturate test mix

Conclusions

Results indicate that higher performance to pressure ratio for Titan columns with very narrow PSD porous silica promises to become another important development in this era of rapid advancements in HPLC technology.

Materials

     

 References

  1. D. Cabooter, A. Fanigliulo, G. Bellazzi, B. Allieri, A. Rottigni, G. Desmet, J. of Chromatography A, 1217 (2010) 7074–7081.

 

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