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HPLC COLUMNS
USLC™
Evaluating and Extending Selectivity
Restek leads the industry in USLC™ phase diversity because optimal differences in selectivity are built in during the research and
development of our bonded phases.
The diversity in selectivity provided by USLC™ columns can be demonstrated empirically using the hydrophobic-subtraction (HS)
model [1]. This model is a novel procedure for characterizing selectivity that uses test probes to define the solute and stationary phase
interactions in reversed phase separations. Restek is leading the commercial application of this model by implementing it in the
research and development of USLC™ bonded phases. To evaluate phase selectivity using the hydrophobic-subtraction model, the
retention characteristics of the solute probes are compared across different phases on the same silica base. In this approach, the range
of selectivity is indicated by the degree of scatter along the regression line; high correlations indicate similarity and low correlations
represent changes in selectivity across phases (Figure 2). The difference in selectivity across columns can then be quantified based on
the correlation by calculating the selectivity (S) statistic for the comparison [2].
Figure 2
Restek has extended the selectivity range for reversed phase separations as illustrated by the
hydrophobic-subtraction model and corresponding selectivity (S) value.
USLC™ Columns: Selectivity Choices Optimize Separations
Restek USLC™ columns offer the widest range of selectivities available and are an integral part of successful method development
(Figure 3). Ideal for column switching systems, these columns provide the orthogonal separations needed to create optimal resolu-
tion and robust methods. Combining USLC™ phases with a suitable column format gives practicing chromatographers the most
powerful tool available for successful method development.
HS Model Test Probe Retention Across USLC Phases
r
2
= 0.7138
0
2
4
6
8
10
12
0
2
4
6
8
10
12
14
k' C18 phase on Ultra II
k' Orthogonal phase on Ultra II
Ultra II PFPP
Ultra II Biphenyl
Ultra II IBD
Ultra II Aqueous C18
High degree of scatter indicates
greater differences in selectivity.
Selectivity (S) = 100 x 1-r
2
S = 53.5
We’re here to help!
To discuss the right selectivity for your separation or to find a comparable
column,
contact us at support@restek.com or 800-356-1688.
References (Not available from Restek.)
[1] L.R. Snyder, J.W. Dolan, P.W. Carr, J. Chromatogr. A 1060 (2004) 77.
[2] U.D. Neue, J.E. O’Gara, A. Mendez, J. Chromatogr. A 1127 (2006) 161.
Figure 3:
Restek offers the widest range of selective phases available on any column line.
Column Line
Common
Reversed Phase
Column Type
Restek Ultra II
1.9, 2.2, 3, 5 and
10μm
Waters
Acquity CSH
1.7, 3.5 and 5 μm
Waters
Acquity HSS
1.8, 3.5 and 5 μm
Waters
Acquity BEH
1.7, 2.5, 3.5, 5 and
10 μm
Phenomenex
Kinetex
1.7 and 2.6 μm
Agilent
Zorbax RRHD
1.8, 3.5 and 5 μm
Agilent
Poroshell 120
2.7 μm
Alkyl
(C18 and C8)
•
•
•
•
•
•
•
Phenyl
•
•
•
Polar Embedded
Alkyl
•
Fluorophenyl
•
•
•
Website : www.chromtech.net.au E-mail : info@chromtech.net.au TelNo : 03 9762 2034 . . . in AUSTRALIA
Mar 2011