154
800-356-1688 or 814-353-1300
HPLC COLUMNS
USLC™
USLC™ is the directed application of selectivity—the most influential factor affecting resolution—to optimize separations and
improve method performance. Restek has extensively studied reversed phase selectivity to provide practicing chromatographers with
the most effective and widest range of USLC™ stationary phase chemistries available.
Selectivity Drives Separations
By understanding and controlling selectivity through USLC™, chromatographers have the best opportunity for fast,
effective analyte resolution.
One of the most significant challenges in method development is finding the proper stationary and mobile phase chemistry for a par-
ticular separation. As sample complexity increases, achieving adequate resolution between matrix components and target analytes
becomes more difficult. Despite recent advancements in column format, such as sub-2 micron packings and pellicular particles, reso-
lution can still be difficult to obtain because, while these formats can increase chromatographic efficiency and analysis speed, they do
not significantly influence resolution. Selectivity, as shown in Equation 1, is the single most powerful factor affecting resolution, and
it is largely dependent upon stationary phase composition.
Real Diversity in Phase Chemistry
Restek columns offer the widest range of selectivities available on a single column line.
More choices mean optimized separations and more robust methods.
While numerous bonded phases are available for reversed phase chromatography,
many are similar and offer only moderate changes in retention (e.g. C8 and C18),
rather than significant differences in selectivity. Method development is less laborious
and time-consuming when using a full range of column selectivities, including
orthogonal phase chemistries like polar embedded, phenyl, and fluorophenyl
columns. Restek has led the development of unique USLC™ phases across these phase
classes in order to provide chromatographers with a more effective range of column
selectivities and innovative column chemistries for method development. The phases
shown in Figure 1 provide the widest range of reversed phase selectivity available on any column line, and can be used to guide the
least understood and most practically significant part of method development—proper column selection.
Figure 1
Restek offers the widest range of unique column chemistries to aid in fast, easy method development.
RESTEK
USLC
™
Ultra Selective Liquid Chromatography
™
Restek phase
(column class)
Aqueous C18
(alkyl)
IBD
(polar embedded)
Biphenyl
(phenyl)
PFP Propyl
(fluorophenyl)
Ligand type
Proprietary polar modified and
functionally bonded C18
Proprietary polar functional
embedded alkyl
Unique Biphenyl
Proprietary end-capped
pentafluorophenyl propyl
Characteristics
and uses
• C18 phase for balanced
retention of multiple
solute types.
• Compatible with up to 100%
aqueous mobile phases.
• Enhanced retention of
polar acids.
• Moderate retention of
both acidic and basic
solutes.
• Increased retention of
aromatic, unsaturated,
conjugated solutes, or
solutes containing an
electron withdrawing ring
substituent.
• Enhanced retention and
selectivity when used with
methanolic mobile phases.
• Increased retention of
protonated bases and
solutes containing
aromatic moieties.
Si
OO
P
Si
CH
3
CH
3
O
Si
CH
3
CH
3
O
F
F
F
F
F
Equation 1
Selectivity drives
resolution—USLC™ considers
column selectivity during method
development, resulting in fast,
effective separations.
R = 1/4
N
x (
k'
/
k'
+1) x (
α
-1/
α
)
Efficiency
Retention capacity
Selectivity
CH
3
CH
3
O
Si
P
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TelNo : 03 9762 2034 . . . in AUSTRALIA
Mar 2011
