Definition

1. Reagents that dissociate positively charged active groups when dissolved in water, functioning via electrostatic adsorption, complexation and flocculation. They fall into two categories: industrial cationic surfactants/polymer reagents and analytical reagents for detecting metal cations.
2. Main Classifications

   Small-molecule quaternary ammonium salts (positively charged at all pH values)

   CTAB, CPC, Tetrabutylammonium bromide; applied in DNA extraction, sterilization and ion-pair chromatography.

   Cationic polymers

   CPAM, PDADMAC, Polybrene; used for water flocculation, sludge dewatering, cell transfection and paper retention aid.

   Amines (charged only under acidic conditions)

   Mineral flotation, metal corrosion inhibition.

   Analytical identification reagents (negatively charged, for metal cation detection)

   Dimethylglyoxime, Nessler’s reagent, KSCN, for testing Ni²⁺, NH₄⁺ and Fe³⁺ respectively.
3. Basic Properties

   Quaternary ammonium salts are stable across acid and alkaline environments, while ordinary amines only work in acidic media.

   They possess surface activity with wetting, emulsifying and foaming capabilities.

   Mixing with anionic reagents is prohibited, as precipitation will occur and cause deactivation.

   Most irritate skin and mucous membranes; high concentrations are toxic to aquatic organisms.
4. Common Applications

   Biological experiments: nucleic acid extraction, cell transfection

   Water treatment: flocculation & decolorization, sludge dewatering

   Papermaking & textile: starch modification, softening & color fixing

   Daily chemicals: bacteriostasis & disinfection, hair conditioning

   Chemical chromatography: ion-pair separation of anionic substances

   Mineral processing: reverse ore flotation
5. Operation & Storage Guidelines

   Store sealed away from light; prevent polymer products from freezing; wear gloves and goggles during handling; neutralize waste liquid before discharge.