Phase separation of triton X-100 with tetracaine hydrochloride drug: understanding of the effects of potassium electrolytes on the physico-chemical variables and interaction forces

Present study discloses the investigation of the cloudy formation nature of the mixture of local anesthetic drug tetracaine hydrochloride (TCH) and non-ionic surfactant triton X-100 (TX-100). This investigation was performed in the presence of the potassium electrolytes media (KCl, KBr, K₂SO₄, and K₂HPO₄) with the help of cloud point procedure. In the course of the study, it was observed that the cloud point (CP) values varied with the nature and concentrations of K-electrolytes. In the  concentration effect of K-electrolytes, the CP values of the TX-100 + TCH mixture followed the trend: \({\text{CP}}_{\text{aq}.\text{ KCl}}\) > \({\text{CP}}_{\text{aq}.\text{ KBr}}\) > \({\text{CP}}_{\text{aq}. {\text{K}}_{2}{\text{SO}}_{4}}\)> \({\text{CP}}_{\text{aq}. {\text{K}}_{2}{\text{HPO}}_{4}}\) at a specific TCH and TX-100 concentration. The positive values of Gibbs free energy change (\({\Delta \text{G}}_{c}^{o}\)) were recorded during the phase transformation in the mixture, implying the nonspontaneous process of phase transformation. The magnitudes of \(+{\Delta \text{G}}_{c}^{o}\) values were reduced with the rise of the concentration of K-electrolytes. The values of enthalpy change (\({\Delta \text{H}}_{c}^{o}\)) and entropy change (\({\Delta \text{S}}_{c}^{o}\)) for phase transition of the TX-100 + TCH mixture were exhibited to be negative in the effect of the concentration of K-electrolytes. On the basis of the \({\Delta \text{H}}_{c}^{o}\) and \({\Delta \text{S}}_{c}^{o}\) values, it has been suggested that the electrostatic interactions (e.g. hydrogen bonding, dipole-dipole), hydrophobic and pi-pi interactions are predominantly working among employed constituents. The information obtained from the current investigation is probably going to be highly beneficial for drug delivery systems as well as pharmaceutical formulations.

Graphical Abstract