Obelisc™ HPLC columns are the latest, innovative columns from SIELC Technologies, the inventors of Primesep. With multiple patents pending, Obelisc columns are the first commercially available columns with Liquid Separation Cell technology ( LiSC ™). Obelisc R, with reversed-phase characteristics, and Obelisc N, with normal-phase characteristics, separate polar and non-polar compounds using multiple separation mechanisms.

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Obelisc R and Obelisc N explained

This cost effective duo replaces multiple HPLC columns such as reversed-phase (RP), AQ-type reversed-phase, polar-embedded group RP columns, normal-phase, cation-exchange, anion- exchange, ion-exclusion, and HILIC (Hydrophilic Interaction Liquid Chromatography) columns.
Method development is simplified by using only two Obelisc columns and a few simple mass spec or low UV (<220 nm) compatible mobile phases.
Obelisc R and Obelisc N differ in the type and proximity of their charged groups and the hydrophobicity of their long chains. Obelisc R has cationic groups close to the silica surface separated from anionic groups by a hydrophobic chain. Obelisc N has anions close to the surface separated from cationic groups by a hydrophilic chain.

Obelisc R interactions Obelisc N interactions

Obelisc R and Obelisc N Columns – A Powerful Duo for HPLC

  • Two columns able to retain and separate all types of small molecules and their mixtures
  • Fast method development with only two columns
  • Simple mobile phase selection
  • Multiple separation modes (RP, NP, HILIC, IE)
  • Mass spec, ELSD, preparative and low UV (<220 nm) compatible, low concentration buffers
  • Adjustable selectivity in all modes based on organic content, pH, and buffer strength

Applying Obelisc liquid separation cells to chromatographic separations provides very different results from all other chromatographic columns. Charge and chain conformation are tunable properties that allow dramatic changes in separation selectivity. Method development now returns to an experimental science rather than trial-and-error screening of columns.
Figure 1 shows the separation of a mixture with similar mobile phases on Obelisc R and N. Peak order is reversed just by changing acetonitrile content in the mobile phase. The hydrophobic propyl paraben retains much longer on Obelisc R due to the column’s reversed-phase characteristics. The polar compounds, dopamine and DOPA retain much longer in normal-phase mode on Obelisc N.

Obelisc R and Obelisc N - Propyl paraben, Dopamine, DOPA - chromatograms

Loading capacity of Obelisc R column

Obelisc columns have high density of positive and negative ions on a stationary-phase surface. This property is favorable for using Obelisc column for preparative chromatography. The Obelisc columns offer significantly higher loading capacity (more than 10 times) with charged compounds compared to traditional RP columns. Neutral molecule can be preparatively separated on Obelisc similar to other RP columns.

Having two opposite charges allows to retain polar compounds on Obelisc columns without using ion-pairing reagents.
Obelisc technology allows to use much higher organic concentration than traditional RP columns while separating polar compounds.

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Loading of dopamine study with Obelisc R