Unison UK-Phenyl Excels in Isomer Separation and Exhibits Excellent Selectivity

The Application Notebook

The Application Notebook, The Application Notebook-06-01-2013, Volume 0, Issue 0

Imtakt USA

Standard C18 HPLC columns struggle to offer the unique selectivity needed for separation of structural isomers or aromatic compounds. Through pi-pi electron interactions between the compound and the stationary phase, Imtakt's Unison UK-Phenyl column overcomes this challenge. This column successfully resolved isomers 2-FMP, 3-FMP, and 4-FMP, all of m/z value 154. In addition, isomers N-methyl-2-FMP, N-methyl-3-FMP, and N-methyl-4-FMP, all of m/z value 168, were successfully resolved. The Unison UK-Phenyl column also effectively separates the structurally similar and highly aromatic benzodiazepine drugs Triazolam and Etizolam.


All data was generated with a semi-micro HPLC system equipped with MS detection. 4-Fluoroamphetamine, 3-fluoroamphetamine, 2-fluoroamphetamine, 4-fluoromethamphetamine, 3-fluoromethamphetamine, and 2-fluoromethamphetamine were separated on a Unison UK-Phenyl column of dimensions 150 × 3 mm (see Figure 1). Isocratic elution was utilized with a mobile phase of methanol/acetonitrile/10 mM ammonium formate (pH 3.5) = 9 /1 /90. Flow rate was 0.4 mL/min and column temperature was 40 °C.

Figure 1: LC–MS: Fluoroamphetamine and fluoromethamphetamine isomer separation.

Triazolam, etizolam, 8OH-etizolam, 1OH-triazolam, 4OH-triazolam, and 1OH-etizolam were separated on a Unison UK-Phenyl column of dimensions 150 × 2 mm (see Figure 2). Gradient elution was utilized with mobile phase of A: 0.1% HCOOH in water and B: 0.1% HCOOH in methanol. Flow rate was 0.25 mL/min and column temperature was 40 °C.

Figure 2: LC–MS: Anxiolytics and metabolites.

Results and Discussion

The Unison UK-Phenyl column exhibits pi-pi electron interaction characteristics, enabling it to separate structural isomers of identical mass. The column also shows selectivity that allows it to differentiate between aromatic anxiolytic drugs of similar structure. The Unison UK-Phenyl column, offering a stationary phase which is more selective for aromatic compounds, is an important addition to a forensic or pharmaceutical scientist's HPLC column library. This column can diversify separation ability and offer significant advantages in separation science.

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