The water soluble polymer is preferably a sulfonated polymer (e.g., a sulfonated polyurethane, a sulfonated polystyrene, or a mixture thereof).

The conductive graphite particles are coated with a charged polymer such as sulfonated polystyrene.

The metal ion is preferably a silver ion and the hydrophilic polymer preferably comprises a sulfonated polyurethane or sulfonated polystyrene.

The organic solvent soluble polymer can be at least partially sulfonated polystyrene.

Rather than using modified serum, the control reagent contains water, glucose, and the viscosity agent polystyrene sulphonate.

In one embodiment, a cation exchange resin such as sulfonated divinyl benzene-cross-linked polystyrene is employed, and the η-pyrones obtained can be further purified by crystallization from water and/or other means.

Amine modified acidic resin catalysts are prepared from acidic resins such as sulfonated polystyrene by neutralization of a portion of the acidic functional groups present with an amine such as pyridine.