Anaerobic Hydrolytic Degradation of Cefpodoxime Proxetil in the Presence of UV Irradiation and in Darkness: Kinetics and pH Effect

Abstract

Abstract. In this study, the anaerobic hydrolytic degradation of cefpodoxime proxetil (CP) in the presence of UV-light irradiation and in darkness has been studied at Britton-Robinson (B-R) buffer solutions (pH 2.5-11) by cyclic and square-wave voltammetry techniques. By means of these electrochemical techniques, the hydrolytic degradation of CP was successfully followed. The pH effect on this degradation was also investigated. In darkness, the decrease in the peak current of CP was not practically observed at the acidic and physiological pHs (2.5, 5.0 and 7.4). But, in the basic medium (pH 9.0 and 11.0), a decrease in the peak current was detected. On the other hand, UV irradiation caused a decrease in the peak current of CP and a positive shift in its cathodic peak potential. Under the UV irradiation, the maximum stability of CP was observed in B-R buffer of pH 5. It has been determined that UV irradiation has a great effect on hydrolytic degradation of CP at basic medium. On the other hand, at pHs  7.4, a new peak has been also obtained at more positive potential than that of the first reduction peak of CP. The current of this peak increases by increasing UV irradiation time. This peak could be assigned to the reduction of a new electroactive product which was formed from the hydrolytic degradation of CP under UV irradiation. The hydrolytic degradation reaction of CP followed pseudo-first order kinetics.(doi: 10.5562/cca2071)

Utilizing the Synergetic Benefit of Synthesized NiO Nano Flakes and Natural Activated Charcoal (an Alternative of Graphene) as a Novel Platform for Voltammetric Determination of Chronic Hepatitis C Virus Inhibitor Ledipasvir

“…Based on the proportional of the i p with the surface concentration of Ledipasvir at equilibrium, the above equation can be rearrangement to 81,82 :…”

A First Efficient Voltammetric Approach for Detection of Octreotide, an Octapeptide Analogue of Somatostatin Natural Hormone, in Sandostatin Intramuscular Injection and Human Plasma Based on Modification Free Electrochemical Sensor

“…Langmuir isotherm takes assumptions that adsorption occurs at specific homogeneous sites within the adsorbent, the adsorbent surface consists of a certain number of active sites at each of which only one molecule may be adsorbed, no lateral interaction between the adsorbed molecules, and at maximum adsorption only a monolayer is formed and that eventually surface saturation occurs. 61,62 The Langmuir adsorption isotherm describes the relationship between the equilibrium coverage ( ) of an adsorbate (adsorption density) and the bulk (equilibrium) solution concentration, C, Eq. 15: 61,62…”

“…61,62 The Langmuir adsorption isotherm describes the relationship between the equilibrium coverage ( ) of an adsorbate (adsorption density) and the bulk (equilibrium) solution concentration, C, Eq. 15: 61,62…”

“…Where: θ is the degree of surface coverage (the fraction of occupied surface), max is the maximum adsorption capacity (maximum surface concentration) corresponding to complete monolayer coverage and K L (monolayer binding constant) is the Langmuir constant related to energy of the adsorption. 61,62 Equation 15 can be rearranged to the following linear form: [16] Taking into account that the stripping peak current (i p ) at equilbrium is proportional to surface concentration of OCT, Eq. 16 can be written as: 61,62 C/i p = 1/i pmax K L + C/i pmax [17] i pmax is the maximum peak current when the electrode is fully covered at a fixed accumulation time.…”

“…61,62 Equation 15 can be rearranged to the following linear form: [16] Taking into account that the stripping peak current (i p ) at equilbrium is proportional to surface concentration of OCT, Eq. 16 can be written as: 61,62 C/i p = 1/i pmax K L + C/i pmax [17] i pmax is the maximum peak current when the electrode is fully covered at a fixed accumulation time. The Freundlich model is also one of the more widely used models for describing adsorption equilibrium.…”