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Table II:
Use these time settings to achieve a defined, linear gradient slope that is ideal for
mobile phase scouting.
Figure 1:
Choosing the ideal column/mobile phase combination for a method is simple if you run a scouting gradient using a four–
mobile phase system and the USLC® four column set. The 16 chromatograms from your scouting run will fall into one of four categories.
Void
Time
Retention
factor (k) is 2
Recommended
for LC-MS!
Column Dimensions
Time Settings
Column Inner
Diameter (mm)
Column Length
(mm)
Particle Diameter
(µm)
Flow Rate
(mL/min)
Gradient Time
(t
G
)
Post Gradient
Equilibration Time (min)
2.1
30
1.9
0.6
2
1
3
0.3
4
2
5
0.2
6
2
50
1.9
0.6
4
1
3
0.3
7
3
5
0.2
10
4
100
1.9
0.6
7
3
3
0.3
13
5
5
0.2
20
8
3.0
50
1.9
1.1
4
1
3
0.7
6
2
5
0.4
10
4
100
1.9
1.1
7
3
3
0.7
13
5
5
0.4
21
8
150
1.9
1.1
11
6
3
0.7
19
11
5
0.4
31
17
4.6
50
3
1.5
6
3
5
1.0
10
4
100
3
1.5
13
5
5
1.0
19
8
150
3
1.5
19
8
5
1.0
29
11
250
3
1.5
32
13
5
1.0
49
19
All the Right Tools—
All in One Box
Introducing the
USLC® Method
Development Toolbox
www.restek.com/toolboxRESTEK
USLC
®
Ultra Selective Liquid Chromatography
™
Choose Columns Fast.
Develop Methods Faster.
• USLC® method development toolbox
contains all four USLC® stationary phases
in one convenient package.
• Available for UHPLC (1.9 μm) and
HPLC (3 or 5 μm) in 50, 100, or
150 mm lengths.
• Included selection guide makes it
even easier to pick the right column
the first time.
Summary
It is said that the first step is the hardest, but it can be the easiest when you start your method
development by simplifying your mobile phase and focusing on selectivity and retention to
choose a column/mobile phase combination based on your desired elution profile. With this
dependable approach, scouting gradients and USLC® columns are a method developer’s most
effective tool. To learn more about LC column selectivity or the USLC® column set, visit
www.restek.com/uslcDO NOT USE
this column/mobile phase
combination for reversed phase LC.
Δt/t
G
is less than 0.25, but
retention is too limited.
Choose this column/mobile phase
combination for
isocratic analyses
.
Δt/t
G
is less than 0.25, and
retention is acceptable.
Choose this column/mobile phase combination for
long gradient analyses
or if
unknown peaks are an issue
.
Δt/t
G
is greater than 0.25, retention
acceptable, and selectivity is higher.
Choose this column/mobile phase combination
for
fast, shallow gradient analyses
.
Δt/t
G
is greater than 0.25, retention
acceptable, and selectivity is lower.
1.
2.
3.
4.