Introducing the Hamilton PRP-C18 High-Efficiency Separations at Any pH

Derek Jensen and Mark Carrier, Hamilton Company

The Hamilton PRP-C18 is a new column designed to provide high-efficiency reversed phase separations over an extended column life in nearly any mobile phase or pH. The rigid stationary phase has excellent mechanical and thermal stability (> 100 °C), does not experience shrinkage or swelling and is completely inert to most conditions commonly encountered in reversed phase chromatography. In this study the pH stability of the PRP-C18 is evaluated. Even after prolonged exposure to concentrated (1 molar) NaOH and H₂SO₄ there was no measurable deterioration in performance.

Octadecyl silane (ODS) is the prevailing stationary phase in reversed-phase HPLC. Despite a well-celebrated, widespread use in chromatography, traditional ODS columns are not without limitations. Acidic conditions promote hydrolytic stripping of octadecyl functionalization, while alkaline conditions (pH > 7) attack the silica bed, both of which are principle sources for anomalous peak shape and shifting retention times that progressively worsen over the life of the column.

The PRP-C18 reversed phase column has similar mechanical stability (up to 5000 psi) and separation efficiency to that of traditional ODS, but without many of the chemical restrictions. The PRP-C18 stationary phase does not experience stripping or dissolution under the most extreme conditions. This allows for an expanded mobile phase repertoire for use in methods development or aggressive regeneration procedures.

Figure 1: Separation of standard mix after 200 column volumes 1 M NaOH, 1 M H2SO4.

Experimental Conditions

Column: PRP-C18, 4.1 × 50 mm, 5 μm

Instrumentation: Agilent 1100 quaternary pump with UV detector

Standards: acetone, phenol, benzyl alcohol, benzene, toluene, ethylbenzene, propylbenzene, napthalene, pentylbenzene, hexylbenzene

Mobile phase A: 0.2% Phosphoric acid

Mobile phase B: A + 95% CAN

Gradient: 5 to 100% B in 20 min

Flow rate: 2 mL/min

Temperature: Ambient

Injection volume: 2 μL

Detection: UV at 205 nm

Conclusion

Mobile phase pH is a useful tool in methods development, particularly for separation of neutral forms of amines or other organic bases under alkaline conditions. Although a few more recent C18 columns boast stability in alkaline pH, column life is still considerably shorter than if used under more favorable conditions. On the other hand, the PRP-C18 has genuine pH and chemical stability. The stationary phase is devoid of free silanols, does not strip, bleed, or dissolve at any pH, and therefore can be expected to perform reliably and reproducibly throughout the extended life of the column, regardless of mobile phase conditions.

Hamilton Company

4970 Energy Way, Reno, NV 89502

tel. (800) 648-5950, fax (775) 858-3026

Website: www.hamiltoncompany.com