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RestekCorporation • (800)356-1688 • (814)353-1300 •
When analyzing steroids by LC/mass spectrometry (MS),
the extra retention offered by the Ultra C18 column may
prove advantageous. LC/MS sensitivity can be enhanced
by increasing the organic content of the mobile phase. The
added retention of the Ultra C18 phase allows the use of
mobile phases with higher organic content to speed elution
of the analytes and increase LC/MS sensitivity. Keep in mind
that increasing the organic solvent content of the mobile
phase may alter the elution order of the components.
Polar Interaction
Hydrophobic interaction is only one mechanism for resolv-
ing related compounds. Phases that can introduce a polar
mechanism of retention can sometimes provide selectivity
not offered by C18 phases. The Ultra Cyano and Allure
™
Basix phases have shown excellent utility in the analysis
of steroids and provide an alternative selectivity to the
C18 phase.
When measuring impurities by analytical chromatography
or separating impurities by preparative chromatography, it
often is better to have the impurity elute before the major
analyte peak. If the major analyte peak tails badly or must
be injected at high concentration, an impurity residing in
the tail of the primary analyte peak may reduce fractional
purity and analytical reproducibility. The Ultra Cyano and
Ultra C18 phases demonstrate the outstanding peak shape
and selectivity toward beclomethasone and des-
chlorobeclomethasone (Figure 2). The elution order of
Figure2
The elution order change exhibited by the Ultra Cyano column can aid in the separation of
beclomethasone from its des-chlorinated impurity.
LC_0119
LC_0070
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9 min.
Peak List:
1. des-chlorobeclomethasone
2. beclomethasone
Column:
Ultra Cyano
Catalog #:
9106565
Dimensions:
150 x 4.6mm
Particle Size:
5µm
Pore Size:
100Å
Conditions:
Mobile Phase: water:acetonitrile
(70:30, v/v)
Flow:
1.0mL/min.
Temp.:
ambient
Det.:
UV @ 238nm
Sample:
Inj.:
10µL
Conc.:
100µg/mL
(Beclomethasone)
Solvent:
water:acetonitrile
(9:1, v/v)
Column:
Ultra C18
Catalog #:
9174565
Dimensions:
150 x 4.6mm
Particle Size:
5µm
Pore Size:
100Å
Conditions:
Mobile Phase: water:acetonitrile
(50:50, v/v)
Flow:
1.0mL/min.
Temp.:
25°C
Det.:
UV @ 238nm
Sample:
Inj.:
10µL
Conc.:
100µg/mL
(Beclomethasone)
Solvent:
water:acetonitrile
(9:1, v/v)
