Phase separation and conductivity studies on the interaction of promethazine hydrochloride drug with cationic and nonionic surfactants: influences of electrolytes and temperature

Abstract

• Phase separation of TX-100 + promethazine hydrochloride (PMH) was studied in presence of salts. • Assembly of TTAB + PMH drug has been investigated at different temperatures. • CP of TX-100 + PMH mixture in salts media, follow the order: K 3 PO 4 < K 2 SO 4 < KCl. • Thermodynamic parameters (phase separation/aggregation processes) are computed. • Phase separation/aggregation of system was found nonspontaneous/spontaneous. Here, the phase separation of the mixture of triton X-100 (TX-100) and promethazine hydrochloride (PMH), as well as the assembly of the mixture of tetradecyltrimethylammonium bromide (TTAB) and PMH drug, have been investigated. The cloud points (CP) of TX-100 in the manifestation of PMH/PMH + salts (KCl, K 2 SO 4 , and K 3 PO 4 ) were determined, while the CP values were found to vary with the contents of PMH and salts. The CP of TX-100 + PMH mixture, at a particular PMH concentration in salts media, follow the order: K 3 PO 4 < K 2 SO 4 < KCl. The micellar parameters were determined from the conductivity versus [TTAB] plots. The conductivities and micellar parameters of the TTAB + PMH mixture in salts media were found to vary through the fluctuation of temperature. The thermodynamic variables (free energy (Δ G 0 ), enthalpy (Δ H 0 ), and entropy (Δ S 0 ) changes) for the phase separation and aggregation phenomena of the mixture of surfactant + drug mixture have been computed in the current studies. The phase separation of TX-100 + PMH mixtures was nonspontaneous (+Δ G 0 c values) and assembly of the TTAB + PMH mixture was spontaneous (–Δ G 0 m values). The other thermodynamic variables, in addition to enthalpy–entropy compensation parameters, have also been evaluated and illustrated with proper explanation.