title: Acid-base behavior of quinolones in aqueous acetonitrile mixtures.
abstract: Quinolones are a family of antibacterial agents that are used extensively in both human and veterinary clinics. Their antibacterial activity is pH-dependent, and therefore an examination of protonation equilibria in quinolone solutions is essential. pK-Values of nine quinolone antibacterials in acetonitrile-water mixtures containing 0, 10, 30, 40, 50 and 70%(w/w) acetonitrile were determined according to the rules and procedures endorsed by IUPAC. In order to obtain quinolone pK-values in any acetonitrile-water mixture up to 70%(w/w) acetonitrile, relationships between pK-values and different bulk properties (such as dielectric constant) and some microscopic parameters (such as solvatochromic parameters alpha, beta and pi*) were established. These relationships and the application of the preferential solvation theory of electrolytes in acetonitrile-water mixtures permit the interpretation of acid-base behaviour of these important antimicrobials in the widely used acetonitrile-water media.
authors.forename: V
authors.initials: V
authors.lastname: Sanz-Nebot
authors.forename: I
authors.initials: I
authors.lastname: Valls
authors.forename: D
authors.initials: D
authors.lastname: Barbero
authors.forename: J
authors.initials: J
authors.lastname: Barbosa
mesh_terms: D000097:Acetonitriles / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D011199:Potentiometry; D015363:Quinolones / Q000737:chemistry*; D012996:Solutions
chemical_list: D000097:Acetonitriles; D007202:Indicators and Reagents; D015363:Quinolones; D012996:Solutions