title: Potential of multisyringe chromatography for the on-line monitoring of the photocatalytic degradation of antituberculosis drugs in aqueous solution.
abstract: In this study, a multisyringe chromatography system (MSC) using a C18 monolithic column was proposed for the on-line monitoring of the photocatalytic degradation of isoniazid (INH, 10 mg L(-1)) and pyrazinamide (PYRA, 5mgL(-1)) mixtures in aqueous solution using a small sample volume (200 μL) with an on-line filtration device in a fully automated approach. During the photocatalytic oxidation using TiO2 or ZnO semiconductor materials, total organic carbon (TOC) and the formed intermediates were analyzed off-line using ion chromatography, ion exclusion HPLC, and ESI-MS/MS. The results showed that TiO2 exhibits a better photocatalytic activity than ZnO under UV irradiation (365 nm) for the degradation of INH and PYRA mixtures, generating 97% and 92% degradation, respectively. The optimal oxidation conditions were identified as pH 7 and 1.0 g L(-1) of TiO2 as catalyst. The mineralization of the initial organic compounds was confirmed by the regular decrease in TOC, which indicated 63% mineralization, and the quantitative release of nitrate and nitrite ions, which represent 33% of the nitrogen in these compounds. The major intermediates of INH degradation included isonicotinamide, isonicotinic acid, and pyridine, while the ESI-MS/MS analysis of PYRA aqueous solution after photocatalytic treatment showed the formation of pyrazin-2-ylmethanol, pyrazin-2-ol, and pyrazine. Three low-molecular weight compounds, acetamide, acetic acid and formic acid, were detected during INH and PYRA decomposition. PYRA was more resistant to photocatalytic degradation due to the presence of the pyrazine ring, which provides greater stability against OH attack.
authors.affiliation: Universidad Autónoma de Nuevo León, UANL, Facultad de Ciencias Químicas, Cd. Universitaria, San Nicolás de los Garza, Nuevo León C.P. 66451, Mexico.
authors.forename: E
authors.initials: E
authors.lastname: Guevara-Almaraz
authors.affiliation: Universidad Autónoma de Nuevo León, UANL, Facultad de Ciencias Químicas, Cd. Universitaria, San Nicolás de los Garza, Nuevo León C.P. 66451, Mexico.
authors.forename: L
authors.initials: L
authors.lastname: Hinojosa-Reyes
authors.affiliation: Laboratorio de Química Forense, Criminalística y Servicios Periciales, Procuraduría General de Justicia del Estado de Nuevo León, Av. Gonzalitos 452, Col. Residencial Galerías, Monterrey, Nuevo León C.P. 66451, Mexico.
authors.forename: A
authors.initials: A
authors.lastname: Caballero-Quintero
authors.affiliation: Universidad Autónoma de Nuevo León, UANL, Facultad de Ciencias Químicas, Cd. Universitaria, San Nicolás de los Garza, Nuevo León C.P. 66451, Mexico.
authors.forename: E
authors.initials: E
authors.lastname: Ruiz-Ruiz
authors.affiliation: Universidad Autónoma de Nuevo León, UANL, Facultad de Ciencias Químicas, Cd. Universitaria, San Nicolás de los Garza, Nuevo León C.P. 66451, Mexico.
authors.forename: A
authors.initials: A
authors.lastname: Hernández-Ramírez
authors.affiliation: Universidad Autónoma de Nuevo León, UANL, Facultad de Ciencias Químicas, Cd. Universitaria, San Nicolás de los Garza, Nuevo León C.P. 66451, Mexico. Electronic address: jorge.guzmanmr@uanl.edu.mx.
authors.forename: J L
authors.initials: JL
authors.lastname: Guzmán-Mar
mesh_terms: D000995:Antitubercular Agents / Q000032:analysis / Q000302:isolation & purification* / Q000528:radiation effects; D002384:Catalysis; D002851:Chromatography, High Pressure Liquid; D004784:Environmental Monitoring / Q000295:instrumentation / Q000379:methods*; D004867:Equipment Design; D007538:Isoniazid / Q000032:analysis / Q000302:isolation & purification* / Q000528:radiation effects; D010084:Oxidation-Reduction; D055668:Photochemical Processes; D011718:Pyrazinamide / Q000032:analysis / Q000302:isolation & purification* / Q000528:radiation effects; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry; D014025:Titanium / Q000737:chemistry; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000302:isolation & purification* / Q000528:radiation effects; D018508:Water Purification / Q000295:instrumentation / Q000379:methods*; D015034:Zinc Oxide / Q000737:chemistry
chemical_list: D000995:Antitubercular Agents; D014874:Water Pollutants, Chemical; C009495:titanium dioxide; D011718:Pyrazinamide; D014025:Titanium; D015034:Zinc Oxide; D007538:Isoniazid
keywords: Antituberculosis drugs; Heterogeneous photocatalysis; Multisyringe chromatography; On-line monitoring system; TiO(2)