Impurity profiling of trandolapril under stress testing: Structure elucidation of by-products and development of degradation pathway

The chlorination of dissolved amino acids can generate disinfection by-products (DBPs). To prevent the formation of DBPs, we examined the UV-induced degradation of tryptophan (Trp). In order to further understand the impact of UV disinfection on Trp, the effects of initial concentrations of Trp, pH, temperature, concentrations of NO3−, HCO3− and Cl− on Trp removal were investigated, and a degradation mechanism was also proposed. The results demonstrated that degradation fitted a pseudo first-order reaction kinetic model. The degradation of Trp was mainly caused by direct UV degradation. The apparent rate constant kobs decreased with the increase in initial Trp concentration and increased with increases in pH and temperature. The thermal degradation activation energy was 19.65 kJ/mol. Anions in water also had a significant influence on the degradation of Trp. HCO3− and NO3− contributed to the kobs of Trp, but Cl− inhibited the degradation rate. By electron paramagnetic resonance (EPR) spectroscopy, ·OH was proven to be formed during the degradation of Trp by UV. Based on the intermediate products of C11H15NO3, C10H15N and C9H13N detected by LC-MS-MS, the degradation pathway of Trp was speculated.

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Electrochemical Degradation of Metoprolol Using Graphite-PVC Composite as Anode: Elucidation and Characterization of New by-products Using LC-TOF/MS

Journal of the Mexican Chemical Society ◽

10.29356/jmcs.v64i3.1139 ◽

2020 ◽

Vol 64 (3) ◽

Author(s):

Fouad Fadhil Al-Qaim ◽

Zainab Haider Mussa ◽

Ali Yuzir ◽

Kamyar Shameli

Keyword(s):

Degradation Pathway ◽

Strong Electrolyte ◽

Electrochemical Degradation ◽

Kinetic Rate Constant ◽

Flight Mass Spectrometry ◽

Nacl Concentration ◽

Insuficiencia Cardiaca ◽

Consumption Energy ◽

Wastewater Samples ◽

By Products

Abstract. Metoprolol (MTP) is one of pharmaceuticals used for treatment of heart failure and hypertension. It was frequently detected in wastewater samples either influent or effluent. The application of graphite-PVC composite as anode was investigated for the degradation of metoprolol in the presence of strong electrolyte such as sodium chloride (NaCl). The degradation rate was strongly influenced by initial concentrations of metoprolol, NaCl concentration and applied voltage. An initial concentration of 2 mg/L was eliminated more than 95% after 30 min under optimum conditions; 5000 mg/L NaCl and 5 V. The consumption energy of the electrochemical reaction was 0.665 Wh/mg for metoprolol after 30 min. The kinetic rate constant of metoprolol could be ranged between 0.0016 and 0.0801 min-1. The electrochemical degradation efficiency of metoprolol and its by-products has been achieved. The degradation of metoprolol produced four transformated products as investigated and elucidated using liquid chromatography-time of flight/mass spectrometry. The proposed degradation pathway of metoprolol was schemed on the base of the identified intermediates. Resumen. El metoprolol (MTP) es uno de los fármacos utilizados para el tratamiento de la insuficiencia cardíaca y la hipertensión. Se detecta frecuentemente en muestras de aguas residuales, ya sea de afluentes o efluentes. Se investigó la aplicación del compuesto de grafito-PVC como ánodo para la degradación del metoprolol en presencia de un electrolito fuerte como el cloruro de sodio (NaCl). La velocidad de degradación depende de las concentraciones iniciales de metoprolol, la concentración de NaCl y el voltaje aplicado. Una concentración inicial de 2 mg/L de MTP fue eliminada con más del 95% después de 30 minutos en condiciones óptimas; 5000 mg/L de NaCl y 5 V. La energía de consumo de la reacción electroquímica fue de 0,665 Wh/mg para el metoprolol después de 30 min. La constante cinética de degradación metoprolol oscila entre 0.0016 y 0.0801 min-1. Se logró la eficiente degradación electroquímica del metoprolol y sus subproductos, ya que se detectaron cuatro subproductos electrogenerados según los resultados de cromatografía líquida - tiempo de vuelo/espectrometría de masas. La vía de degradación propuesta del metoprolol se esquematizó sobre la base de los productos intermedios identificados.

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