Polystyrene sulfonate], a [[cation exchange resin, is typically supplied with Na+ as the counterion.

Counterion binding in polyelectrolyte theory
Counterion-Induced Attraction between Rigid Polyelectrolytes
Counterion-induced condesation of deoxyribonucleic acid. a light-scattering study.
A powerful chiral counterion strategy for asymmetric transition metal catalysis
ChemInform Abstract: Counterion Specificity as the Determinant of Surfactant Aggregation
Glutamic acid-113 serves as the retinylidene Schiff base counterion in bovine rhodopsin.
C2‐Symmetric Cationic Copper(II) Complexes as Chiral Lewis Acids: Counterion Effects in the Enantioselective Diels–Alder Reaction
Direct measurement of the intermolecular forces between counterion-condensed DNA double helices. Evidence for long range attractive ...
ChemInform Abstract: C2‐Symmetric Cationic Copper(II) Complexes as Chiral Lewis Acids: Counterion Effects in the Enantioselective D...
Molecular Dynamics Simulation of Sodium Dodecyl Sulfate Micelle in Water:? Micellar Structural Characteristics and Counterion Distr...