Abstract: Interactions of ciprofloxacin hydrochloride (CPFH) with sodium dodecyl sulfate (SDS) were investigated by conductivity measurement in H₂O/electrolyte solutions (NaCl, Na₂SO₄ & Na₃PO₄) over 298.15-318.15 K temperature range (with 5 K interval) considering the human body temperature. In all cases, two critical micelle concentrations (c^*) were observed which are increased in the presence of drug and decreased in the presence of salts enunciating the presence of interaction amongst the studied components. For (CPFH+SDS) system in the presence of salt, the c^* values at 303.15 K and I=0.50 mmol·kg^-1 followed the order:C_NaCl > C_Na2SO4 > C_Na3PO4. The G_1,m⁰ and ΔG_2,m⁰ values are found to be negative for all systems that show that the micellization process is thermodynamically spontaneous. For (CPFH+SDS) system in water, the ΔH_m⁰ & ΔS_m⁰values reveal that the micellization processes is both entropy dominated in almost all cases. In the occurrence of electrolytes, ΔH_m⁰ and ΔS_m⁰ values indicate that micellization processes are both entropy & enthalpy restricted at upper temperature but it becomes totally entropy dependent at higher temperature. The higher positive ΔS_m⁰ values indicate the enhanced hydrophobic interaction in presence of salts. The enthalpy-entropy compensation was determined from the linear relationship between ΔH_m⁰ and ΔS_m⁰ values in every state. Different transfer energies as well as compensation temperature and intrinsic enthalpy were also evaluated and the behaviors were comparable to other biological system.

Key words: Ciprofloxacin hydrochloride, Sodium dodecyl sulfate, Critical micelle concentration, Thermodynamic indices, Hydrophobic effect

摘要： Interactions of ciprofloxacin hydrochloride (CPFH) with sodium dodecyl sulfate (SDS) were investigated by conductivity measurement in H₂O/electrolyte solutions (NaCl, Na₂SO₄ & Na₃PO₄) over 298.15-318.15 K temperature range (with 5 K interval) considering the human body temperature. In all cases, two critical micelle concentrations (c^*) were observed which are increased in the presence of drug and decreased in the presence of salts enunciating the presence of interaction amongst the studied components. For (CPFH+SDS) system in the presence of salt, the c^* values at 303.15 K and I=0.50 mmol·kg^-1 followed the order:C_NaCl > C_Na2SO4 > C_Na3PO4. The G_1,m⁰ and ΔG_2,m⁰ values are found to be negative for all systems that show that the micellization process is thermodynamically spontaneous. For (CPFH+SDS) system in water, the ΔH_m⁰ & ΔS_m⁰values reveal that the micellization processes is both entropy dominated in almost all cases. In the occurrence of electrolytes, ΔH_m⁰ and ΔS_m⁰ values indicate that micellization processes are both entropy & enthalpy restricted at upper temperature but it becomes totally entropy dependent at higher temperature. The higher positive ΔS_m⁰ values indicate the enhanced hydrophobic interaction in presence of salts. The enthalpy-entropy compensation was determined from the linear relationship between ΔH_m⁰ and ΔS_m⁰ values in every state. Different transfer energies as well as compensation temperature and intrinsic enthalpy were also evaluated and the behaviors were comparable to other biological system.

关键词: Ciprofloxacin hydrochloride, Sodium dodecyl sulfate, Critical micelle concentration, Thermodynamic indices, Hydrophobic effect