154
800-356-1688or 814-353-1300
HPLCCOLUMNS
USLC™
USLC™ is the directed application of selectivity—the most influential factor affecting resolution—to optimize separations and
improvemethodperformance.Restekhas extensively studied reversedphase selectivity toprovide practicing chromatographerswith
themost effective andwidest range of USLC™ stationaryphase chemistries available.
SelectivityDrivesSeparations
Byunderstandingandcontrollingselectivity throughUSLC™, chromatographershave thebestopportunity for fast,
effectiveanalyte resolution.
Oneof themost significant challenges inmethoddevelopment is finding theproper stationaryandmobilephase chemistry for apar-
ticular separation. As sample complexity increases, achieving adequate resolution betweenmatrix components and target analytes
becomesmoredifficult.Despite recent advancements in column format, such as sub-2micronpackings andpellicular particles, reso-
lution can still bedifficult toobtainbecause,while these formats can increase chromatographic efficiency and analysis speed, theydo
not significantly influence resolution. Selectivity, as shown inEquation 1, is the singlemost powerful factor affecting resolution, and
it is largelydependent upon stationaryphase composition.
RealDiversity inPhaseChemistry
Restekcolumnsoffer thewidest rangeofselectivitiesavailableonasinglecolumn line.
Morechoicesmeanoptimizedseparationsandmore robustmethods.
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 significantdifferences in selectivity.Methoddevelopment 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.Restekhas led thedevelopmentof uniqueUSLC™phasesacross thesephase
classes in order to provide chromatographers with amore effective range of column
selectivities and innovative column chemistries formethoddevelopment.Thephases
shown in Figure 1 provide thewidest range of reversed phase selectivity available on any column line, and can be used to guide the
least understood andmost practically significant part ofmethoddevelopment—proper column selection.
Figure1
Restekoffers thewidest rangeof uniquecolumnchemistries toaid in fast, easymethoddevelopment.
RESTEK
USLC
™
UltraSelectiveLiquidChromatography
™
Restekphase
(column class)
AqueousC18
(alkyl)
IBD
(polar embedded)
Biphenyl
(phenyl)
PFPPropyl
(fluorophenyl)
Ligand type
Proprietarypolarmodifiedand
functionallybondedC18
Proprietarypolar functional
embeddedalkyl
UniqueBiphenyl
Proprietaryend-capped
pentafluorophenyl propyl
Characteristics
anduses
• C18phase for balanced
retentionofmultiple
solute types.
• Compatiblewithup to100%
aqueousmobilephases.
• Enhanced retentionof
polar acids.
• Moderate retentionof
bothacidic andbasic
solutes.
• Increased retentionof
aromatic, unsaturated,
conjugated solutes, or
solutes containingan
electronwithdrawing ring
substituent.
• Enhanced retentionand
selectivitywhenusedwith
methanolicmobilephases.
• Increased retentionof
protonatedbases and
solutes containing
aromaticmoieties.
Si
OO
P
Si
CH
3
CH
3
O
Si
CH
3
CH
3
O
F
F
F
F
F
Equation1
Selectivitydrives
resolution—USLC™considers
column selectivityduringmethod
development, resulting in fast,
effective separations.
R=1/4
N
x (
k'
/
k'
+1) x (
α
-1/
α
)
Efficiency
Retentioncapacity
Selectivity
CH
3
CH
3
O
Si
P
Website :
E-mail :
TelNo : 03 9762 2034 . . . inAUSTRALIA
Mar 2011
