RESUMEN
This study is an investigation of the physicochemical interaction of Losartan potassium (LST K), an angiotensin-II receptor (type AT1) antagonist, with micelles of triton X, a nonionic surfactant. The effect of micelles on the spectral properties of LSTK was monitored on at pH 7.4 and at room temperature. The spectrum of LST K showed gradual and progressive bathochromic and hypochromic shift in presence of increasing concentrations of triton X 100. The binding constant Kb of LST K to triton X 100 micelles was calculated using the differential absorbance at λ = 225 nm& was found to be 4.13 ± 0.35 ×105 mol-1 L. By using pseudo-phase model, the partition coefficient between the bulk water and Triton X 100 micelles, Kx, was calculated from both differential absorbance Δ A225, Kx = 2.26 ±0.12 x105 mol-1 L. The binding of LST K to Triton X 100 micelles implied a shift in drug acidity constant (Δ pKa = 0.8).
RESUMEN
Two novel Sitagliptin (STG) selective electrodes were investigated with di-octyl phthalate as a plasticizer in a polymeric matrix of polyvinyl chloride (PVC). Sensor 1 was fabricated using β-cyclodextrin, while sensor 2 was constructed using calix-8-arene as ionophores. Linear responses of STG within the concentration ranges of 10−7 to 10−2, and 10−8 to 10−2 mol L−1 were obtained using sensors 1 and 2, respectively. Nernstian slopes of 58.57 and 59.88 mV/decade over the pH range of 5-6.5 were observed. The selectivity coefficients of the developed sensors indicated excellent selectivity for STG. The proposed sensors displayed useful analytical characteristics for the determination of STG in bulk powder, different pharmaceutical formulations, and biological fluids (plasma and urine).The two novel electrodes offer the advantage of determination of STG in biological fluids without pretreatment which is convenient for monitoring STG levels in clinical studies.