title: Determination of Dacarbazine Φ-Order Photokinetics, Quantum Yields, and Potential for Actinometry.
abstract: The characterization of drugs' photodegradation kinetics is more accurately achieved by means of the recently developed Φ-order kinetics than by the zero-, first-, and/or second-order classical treatments. The photodegradation of anti-cancer dacarbazine (DBZ) in ethanol has been investigated and found to obey Φ-order kinetics when subjected to continuous and monochromatic irradiation of various wavelengths. Its photochemical efficiency was proven to be wavelength dependent in the 220-350 nm range, undergoing a 50-fold increase. Albeit this variation was well defined by a sigmoid pattern, the overall photoreactivity of DBZ was proven to depend also on the contributions of reactants and experimental attributes. The usefulness of DBZ to serve as a drug-actinometer has been investigated using the mathematical framework of Φ-order kinetics. It has been shown that DBZ in ethanol can represent a good candidate for reliable actinometry in the range 270-350 nm. A detailed and easy-to-implement procedure has been proposed for DBZ actinometry. This procedure could advantageously be implemented prior to the determination of the photodegradation quantum yields. This approach might be found useful for the development of many drug actinometers as alternatives to quinine hydrochloride.
authors.affiliation: Leicester School of Pharmacy, De Montfort University, The Gateway, Leicester, LE1 9BH, UK.
authors.forename: Mounir
authors.initials: M
authors.lastname: Maafi
authors.affiliation: Leicester School of Pharmacy, De Montfort University, The Gateway, Leicester, LE1 9BH, UK.
authors.forename: Lok-Yan
authors.initials: LY
authors.lastname: Lee
mesh_terms: D000465:Algorithms; D000970:Antineoplastic Agents / Q000737:chemistry* / Q000528:radiation effects*; D003606:Dacarbazine / Q000737:chemistry* / Q000528:radiation effects*; D000431:Ethanol / Q000737:chemistry; D007700:Kinetics; D010777:Photochemistry; D010782:Photolysis; D011803:Quinine / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D014466:Ultraviolet Rays
chemical_list: D000970:Antineoplastic Agents; D012997:Solvents; D000431:Ethanol; D003606:Dacarbazine; D011803:Quinine
keywords: UV/Vis spectroscopy; actinometry; dacarbazine; kinetics; photochemistry; photodegradation; photolysis; quantum yield; reaction mechanism; Φ-order kinetics