Separation of Drugs in Mixed-Mode HPLC

Obelisc R column can be successfully used for analysis of hydrophobic and hydrophilic basic and acidic drugs and corresponding counter-ions. This approach can be used for analysis of various cold and cough composition, pain killers, and other prescription and over-the-counter medications. Within pH 3-5, both cation- and anion mechanism are present on the column, along with hydrophobic interaction. Selectivity of this mixed-mode separation is controlled by the amount of acetonitrile, buffer concentration and buffer pH. Method is robust and reproducible, and can be used as a common HPLC method for analysis of drug molecules and compositions.


Column Obelisc R, 4.6×150 mm, 5 µm, 100A
Mobile Phase MeCN
Buffer AmFm
Flow Rate 1.0 ml/min
Detection UV, 270 nm




Class of Compounds
Drug, Analgetic, Acid, Hydrophilic, Ionizable,
Analyzing Compounds Maleate, Chlorpheniramine, Dextromethorphan

Application Column

Obelisc R

SIELC has developed the Obelisc™ columns, which are mixed-mode and utilize Liquid Separation Cell technology (LiSC™). These cost-effective columns are the first of their kind to be commercially available and can replace multiple HPLC columns, including 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. By controlling just three orthogonal method parameters - buffer concentration, buffer pH, and organic modifier concentration - users can adjust the column properties with pinpoint precision to separate complex mixtures.

Select options
Application Analytes:
Acetaminophen (Paracetamol)

Application Detection:
UV Detection
SIELC Technologies usually develops more than one method for each compound. Therefore, this particular method may not be the best available method from our portfolio for your specific application. Before you decide to implement this method in your research, please send us an email to so we can ensure you get optimal results for your compound/s of interest.