Thermodynamic Study on the Interaction of Ampicillin and Amoxicillin with Ca²⁺in Aqueous Solution at Different Ionic Strengths and Temperatures

Abstract

A potentiometric and UV spectrophotometric study on Ca 2+ −ampicillin and −amoxicillin systems in NaCl aqueous solution is reported. The potentiometric investigation was carried out at different ionic strengths, I = (0.15 to 1) mol kg −1 , and temperatures, T = (288.15 to 310.15) K. The most reliable speciation models include two species, namely, CaLH and CaL for the Ca 2+ −ampicillin system and CaLH 2 and CaLH for the Ca 2+ − amoxicillin system. The spectrophotometric results obtained for both of the systems are fully consistent with potentiometric ones, confirming the formation as well as the stability of the complex species. The dependence of formation constants of the species on ionic strength over the range I = (0.15 to 1) mol kg −1 in NaCl and on temperature over the range T = (288.15 to 310.15) K is also reported. pL 0.5 empirical parameter (i.e., the concentration of ligand required to bind 50% of the metal cation present in the trace) was employed to evaluate the ability of both of the ligands to sequester Ca 2+ under different conditions of pH, ionic strength, and temperature. For example, pL 0.5 = 1.82 and 2.88, for ampicillin and amoxicillin, respectively, were obtained under physiological conditions.

Interaction of Ampicillin and Amoxicillin with Mn2+: A Speciation Study in Aqueous Solution

“…It emerges that under physiological conditions the binding capacity of Amox is more than one logarithmic unit compared to Amp. These results are comparable with those obtained with another divalent cation, Ca 2+ , under the same conditions, pL 0.5 = 1.82, 2.88 for Amp and Amox, respectively [22]. Another comparison can be made with Zn 2+ , in this case in the same conditions the sequestering ability is comparable for Amox, while for Amp it is significantly different.…”

“…More in detail, for the system containing Amp, formation constant values for MgLH and MgL species are 2.54, 2.86, respectively (at I = 0.15 mol L −1 and t = 25 °C) [21], for the same species containing Mn 2+ are 2.47, 2.37, respectively, as reported here under the same conditions. For the system containing Amox, formation constant values for MLH and ML species with Ca 2+ are 2.69, 2.59, respectively (at I = 0.15 mol L −1 and t = 25 °C) [22], for the same species with Mn 2+ are 2.78, 3.20, respectively, as reported here under the same conditions.…”

“…Only formation constant values for Cu 2+ , Ni 2+ , Zn 2+ , Cd 2+ , Co 2+ are found. As far as we know, no thermodynamic data are reported on the complex species formed by Amox with any metal cation, apart from the results already published on Ca 2+ , Mg 2+ , Cu 2+ , Zn 2+ cations [19][20][21][22]. Therefore, it is possible to compare simply the results here reported on Mn 2+ with those obtained with other divalent cations.…”

“…For this reason, the assessment of the interactions of these antibiotics with metal cations which play biological roles in the human body is crucial [18]. Complexing abilities of the most important amino-penicillins, i.e., ampicillin and amoxicillin, with some metal cations, namely Zn 2+ , Cu 2+ , Ca 2+ and Mg 2+ , were already studied [19][20][21][22].…”

Oxazolidinone Antibiotics: Chemical, Biological and Analytical Aspects

“…The interactions among oxazolidinone antibiotics and metal ions are a completely unexplored topic. Metal complexation is known to affect the action of many drugs [ 70 , 71 ] and it plays a vital role in a vast number of biological processes contributing to the health or toxicity of the organism. As is known, the antibiotic interaction in vivo with several metal cations influences their bioavailability.…”