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By Sharon Lupo, Ty Kahler, and Paul Connolly
• Switch from FPP to SPP for faster, more efficient analyses on existing instrumentation.
• Substitute Raptor™ 5 µm SPP columns for current FPP columns on traditional LC systems.
• Upgrade to Raptor™ 2.7 µm SPP for larger analyte lists on systems that can sustain higher pressures.
The fully porous particles (FPP) used in traditional LC columns are just
that—fully porous—so mobile phase permeates the entire silica par-
ticle as it travels through the column. As an alternative, newer super-
ficially porous particles (commonly referred to as SPP or “core-shell”
particles), like those used in Restek’s Raptor™ LC columns, feature a
solid, impermeable core enveloped by a thin, porous layer of silica.
As a result, SPP columns offer a greatly decreased diffusion path and
reduced peak dispersion.
By comparing the performance of Raptor™ SPP LC columns to tradi-
tional FPP LC columns, it is easy to understand why you should switch
to superficially porous particles. When you do switch, choose the
Raptor™ SPP LC particle that is best for your intended experimental
conditions and instrument capability.
Why Switch from FPP to SPP LC Columns?
By switching your 3 or 5 µm FPP column to a Raptor™ 5 µm SPP LC
column of similar dimension, you gain greater efficiency, reduced
system pressure, and dramatically faster analyses (Figures 1 and 2),
as well as more sensitivity—all without changing instrumentation.
Certain assays may require some degree of method development to
achieve optimal results, but whether you are developing new assays
or looking to improve existing methodologies, Raptor™ 5 µm LC
columns are compatible with most assays and offer an excellent way
to increase performance over 3 or 5 µm FPP columns without extra
cost or labor.
How to Choose between Raptor™ 2.7 vs. 5 µm
SPP LC Columns
In addition to 5 µm, Restek’s Raptor™ SPP LC columns are also avail-
able in 2.7 µm diameter particles, giving you flexibility to select the
most appropriate particle size for your specific assay.
Figure 1: Switch from a 3 µm FPP column to a Raptor™ 5 µm
SPP to cut backpressure in half.
The Effects of LC Particle Choice
on Column Performance:
Fully Porous Particles (FPP) vs. Superficially Porous Particles (SPP)
Raptor™ 5 µm diameter particle columns display low backpressure as
well as good efficiency and sensitivity. These columns can be substi-
tuted into existing methods to increase analysis speed on traditional
LC systems, especially those with pressure limitations (i.e., maximum
operating pressure of 400 bar) and a larger amount of system vol-
ume. Raptor™ 5 µm SPP is an ideal LC particle choice for fast assays
containing fewer analytes.
Raptor™ 2.7 µm diameter particle columns exhibit greater efficiency
and sensitivity than the 5 µm, but the operating pressures are
somewhat higher. Since extra-column peak broadening is most
pronounced with short, small-diameter columns packed with small
particles, 2.7 µm columns are best suited for instrumentation with
reduced system volume that does not exceed pressures of 600 bar.
Raptor™ 2.7 µm SPP is the right LC particle choice for larger analyte
lists that require additional peak capacity.
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0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2
Pressure (bar)
Flow Rate (mL/min)
Fully porous 3 µm Raptor™ 5 µm SPP Fully porous 5 µm
Selectivity Accelerated
Column Dimensions: 150 mm x 4.6 mm ID; Temp.: 30 °C; Mobile Phase: water: acetonitrile (45:55)