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Advantage™ FluroPhase™ Premium HPLC Columns
Fluorinated packings show increased retention and extra selectivity for compounds that have flourine and chlorine substituents. They exhibit shape selectivity for closely related compounds, especially positional isomers on aromatic rings and other rigid systems.Our Flourinated packings show excellent results on non-halogenated compounds such as Lipids, Surfactants, Taxanes, Catechins and many other polar compounds with carboxyl or nitro groups.
Halogenated analytes are generally retained longer on the FluroPhase RP phase when compared to C4 and C8 non-fluorinated alkyl phases. This makes FluroPhase RP useful for separating mixtures containing both non-halogenated and halogenated analytes because of the increased retention for the halogenated components. It has also been shown that polyflourinated solutes are better retained on FluroPhase RP.
The Advantage™ FluroPhase PFP is a fluorinated phenyl ring. The types of applications include separation of natural products, halogenated compounds, aromatics, conjugated compounds and trace impurities in complex matrices.
Figures 1 and 2 show how improved resolution can be obtained using Advantage™ FluroPhase RP and Advantage™ PFP when compared to analysis of the same compounds using a typical reverse phase column.
Enhanced Selectivity for Closely Related Compounds and Structural IsomersAdvantage™ FluroPhase PFP is an excellent solution for the difficult analysis of structural isomers, especially those associated with rigid ring systems.
Positional isomers on a ring structure are often difficult if not impossible to separate on an alkyl stationary phase. As the substituents move around a ring structure, as in the isomers of difluorophenol (Figure 3), the hydrophocity of the molecule remains nearly constant. Because the primary interaction between an analyte and an alkyl stationary phase is primarily hydrophobic the selectivity is based only on differences in the hydrophobicity. Often when a separation can not be achieved on an alkyl phase, a phenyl phase may be used for pi-pi interactions.
As Figure 4 illustrates, although the phenyl phase offers different selectivity than a C18 phase for the isomers of nitronaphthalene, neither phase offers complete resolution of all 4 compounds under the conditions tested. The rigid nature of the fluorine substituted FluroPhase PFP coupled with pi-pi and dipole-dipole interactions may help explain the improved selectivity observed for this phase.
Employing different organic modifiers in the mobile phase can control the pi-pi interactions or aromatic selectivity. Methanol will maximize these interactions, while acetonitrile will minimize these interactions. This can be a powerful tool for improving selectivity between closely eluting conjugated and non-conjugated compounds as the retention of a specific compound can be selectively changed.
The Advantage™ FluroPhase columns are also highly shape selective for hon-halogenated compounds as illustrated in the separation of dinitronaphthalene isomers in Figure 4. The rigid nature of the fluorine substituted bonded phase may explain why the perfluorinated phases offer enhanced shape selectivity for isomers.
The superior structural recognition offered by Advantage™ FluroPhase makes it ideal for the difficult separation of epimers found in natural products, API impurity identification and purification, steroids, and antibiotics. API impurity identification is often complicated by the fact that impurities are often present in trace levels making quantitation of poorly resolved peaks difficult as the minor peaks are often “lost” under the major components.
Increased Retention for Polar Compounds
Retention of polar compounds is often difficult to achieve on ODS phases where the primary solute-phase interaction is hydrophobic. However the strong interaction between the polar groups of the analyte and the dipole properties of the fluorine-carbon bond offers increased retention for polar compounds.
The separation of aminophenols in Figure 5 clearly illustrates the increased retention behavior of polar compounds on FluroPhase RP. The log P value is the octanol/water partition coefficient. The lower the log P value, the more polar the compound and less it will be retained on C18 or other hydrophobic surfaces. At less than 0.1, the log P values of ortho and meta isomers of phenylene diamine would suggest very little retention on a hydrophobic alkyl phase, however, due to the polar fluorine-carbon bond these compounds are well retained and separated on the Advantage™ FluroPhase RP column.
The polar nature of Advantage™ FluroPhase columns makes them ideal for use in HILIC mode, where retention increases with increasing organic concentration. This is another useful tool for alternative retention and selectivity, especially for LC-MS applications, where sensitivity can be increased with higher organic concentrations.
Increased Retention and Selectivity for Halogenated Compounds
Advantage™ FluroPhase RP and PFP exhibit improved selectivity and retention patterns for halogenated compounds when compared to their non-flourinated counterparts such as C8 and Phenyl. As illustrated in Figures 6 & 7 halogenated compounds are more retained than their non-halogenated analogs.
In addition fluorinated phases are highly selective for halogenated compounds. This effect is most appreciable for fluorinated compounds due to specific fluorine-fluorine interactions.
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