Table 1.
Comparison of the attributes of different approaches to fast HPLC
| Characteristics | Small Particles | High Pressure | Non-Porous Particles | Core-Shell Particles | High Temperature | Chemometric Curve Deconvolution |
|---|---|---|---|---|---|---|
| Overall Impact on Speed | ++ | ++ | + | ++ | +++ | ++ |
| Primary Effect on Speed | Lower plate heights, shorter column lengths, and higher optimum eluent velocities | Drives fluid faster. Used in conjunction with smaller particles and narrower columns (≤ 2.1 mm i.d.) | Improved interphase mass transfer and eddy dispersion | Lower reduced plate height through improved eddy dispersion, improved interphase mass transfer. | Reduces viscosity and thus pressure; allows fluid to move faster at same pressure. Improves interphase mass transfer. Can be combined with use of smaller particles | Decreases resolution needed for analytical purposes and thus can speed up analysis considerably |
| Requirements | Needs high pressure instrument; requires dramatic decrease in extra-column broadening | Needs high pressure instrument; requires dramatic decrease in extra-column broadening when used with small particles | Generally needs high pressure to drive liquid through particles around 1 micron; ultra low dispersion equipment | Requires low extra-column dispersion; almost as important as with sub-two micron porous particles | Does not require high pressure instruments but does require specialized solvent pre-heater and column temperature controller. Generally requires narrow column (≤ 2.1 mm) to minimize thermal mismatch. No PEEK in columns when used above 100 °C | No changes in hardware. But some approaches require extreme repeatability in peak shape and retention time. |
| Equipment Cost | High | High | High | Medium | Low | N/A |
| Primary Advantages | Can improve speed significantly. Has minimal effect on selectivity and thus simplifies method transfer from bigger particles of same manufacture. | Can improve speed significantly; The use of narrower columns can lower solvent consumption. | High efficiency for separations of large molecules, especially proteins. | Can be done with conventional HPLC equipment. | Can be done with conventional HPLC equipment. | No real change in instrument. |
| Primary Disadvantages | Requires mechanically very stable particles; frictional heating. | Generally requires narrow column (≤2.1 mm i.d.) to minimize frictional heating. | Very low sample load capacity and much less retention. Very small particles are hard to pack. | Slightly decreased sample load capacity and retention. | Requires thermally stable stationary phase and stable analytes. | Mathematically complex. Must have very precise retention if deconvolution methods are used. |
| Effect on relative retention | None provided the substrate and stationary phase chemistry are the same as for larger particles (excluding pressure effects, see right). | Small but real, and analyte dependent. | Minimal | Minimal under isocratic elution, larger under gradient elution. | Considerable | N/A |
| Sample Capacity | Good | Good | Much less | Somewhat less | Good | N/A |
| Available | Quite a few and | Quite a few and | Very limited | Few but growing. | Quite a few | N/A |