A mechanistic study on the disproportionation and oxidative degradation of phenothiazine derivatives by manganese(III) complexes in phosphate acidic media

Oxidation of Selected Phenothiazine Drugs During Sample Preparation: Effects of Varying Extraction Conditions on the Extent of Oxidation

Characterization of degradation products formed from selected phenothiazine drugs during standard solid-phase extraction (SPE) approaches is described. An analytical method for promethazine (PMZ), chlorpromazine (CPZ) and their respective N-desmethyl and sulfoxide metabolites in biological samples (bone tissue extract and blood) by ultra performance liquid chromatography-photodiode array detection, using mixed-mode SPE for basic drugs was developed. When ethyl acetate:isopropanol:ammonium hydroxide (80:17:3) was used as the elution solvent during method development, extraneous peaks were observed that were absent in the negative controls. Analysis of extracts of PMZ and CPZ individually showed extraneous peaks, including peaks with retention time and UV spectra suggesting the formation of the sulfoxide metabolites, amongst others. Analytes were then extracted individually and analyzed by ultra performance liquid chromatography-quadrupole time-of-flight mass spectrometry. The results confirmed the oxidation of PMZ to its sulfoxide and N-oxide metabolites and oxidation of CPZ to its sulfoxide metabolite. Oxidation was also observed in analysis of whole blood, and thus was not specific to bone tissue extract. To determine if extraction with minimal oxidation was possible, extractions using SPE with a different elution solvent system (dichloromethane:isopropanol:ammonium hydroxide) and filtration/pass through extraction (FPTE) with and without evaporation were evaluated. The results demonstrated that the sample preparation method highly influenced the extent of oxidation. FPTE without an evaporation step was the only method that did not measurably induce analyte oxidation.

Carbonate and carbonate anion radicals in aqueous solutions exist as CO3(H2O)62− and CO3(H2O)6˙− respectively: the crucial role of the inner hydration sphere of anions in explaining their properties

An effort to reproduce the physical properties of CO₃²⁻ and CO₃˙⁻ in water proves that one has to include an inner hydration sphere of six water molecules for both anions.

The role of carbonate as a catalyst of Fenton-like reactions in AOP processes: CO3˙− as the active intermediate

The reaction Co(H₂O)₆²⁺ + H₂O₂ proceeds via a transient that decomposes into Co^II(H₂O)(OOH)(OH)₂ + CO₃˙⁻. Plausible biological implications are pointed out.