Using COSMOSIL PBr, the analysis of 9 purine nucleoside metabolites, including uric acid and allantoin, required approximately 40 minutes. Changing to COSMOSIL 1.8PBr, packed with smaller particles, allowed the analysis to be completed in approximately 10 minutes with equivalent separation.

Conditions
Column size	4.6 mm I.D. × 250 mm	Temperature	30°C
Mobile phase	Methanol / 0.1% Formic acid aq. = 10 / 90	Detection	UV 240 nm
Flow rate	PBr ; 1.0 mL/min, 1.8PBr ; 0.4 mL/min	Inj. Vol	1.0 μL
Sample	Allantoin Guanine Hypoxanthine Uric acid Xanthine Adenosine Inosine Guanosine Xanthosine

COSMOSIL PBr columns can be used in the same reversed‑phase mode as ODS columns; however, due to the high polarizability of bromine atoms, it exhibits unique retention and separation behavior. This is attributed to dispersion interactions and the recently recognized halogen bonding, which differ from conventional ODS columns. These interactions occur between highly polarizable atoms and π-electrons, as well as oxygen or nitrogen atoms possessing lone electron pairs. As a result, PBr columns can retain hydrophilic compounds that are difficult to retain on ODS columns, and enable the analysis of difficult compounds.