%0 Journal Article
%T A Recent Review on Chemiluminescence Reaction, Principle and Application on Pharmaceutical Analysis
%A Tadesse Haile Fereja
%A Ariaya Hymete
%A Thirumurugan Gunasekaran
%J ISRN Spectroscopy
%D 2013
%R 10.1155/2013/230858
%X This paper provides a general review on principle of chemiluminescent reactions and their recent applications in drug analysis. The structural requirements for chemiluminescent reactions and the different factors that affect the efficiency of analysis are included in the review. Chemiluminescence application in immunoassay is the new version for this review. Practical considerations are not included in the review since the main interest is to state, through the aforementioned applications, that chemiluminescence has been, is, and will be a versatile tool for pharmaceutical analysis in future years. 1. Introduction Luminescence is the most conveniently defined as the radiation emitted by a molecule, or an atom, when these species return to the ground state from the exited state. According to the source of excitation, luminescence phenomenon could be classified as photoluminescence (fluorescence and phosphorescence) when the excitation source is energy from absorbed light, chemiluminescence-energy from chemical reactions and bioluminescence energy from biologically catalysed reactions. An exited molecule has the same geometry and is in the same environment as it was in ground state. In this situation it either emits a photon from the same vibrational level to which it was exited initially or it undergoes in vibrational level prior to emission of radiation [1, 2]. For an isolated molecule in the gas phase, the only way to lose vibrational energy is to emit an infrared photon, which is less probable than undergoing an electronic transition to return to the ground state. Therefore, one tends to see photon emission from higher vibrational levels of exited states in gas phase spectra at low pressure. In a solution, however, thermal relaxation of a vibrationally exited molecule is quite rapid through transfer of excess vibrational energy from the solute molecule to the solvent. In fact, this process is so efficient that all the excess vibrational energy of the exited state is lost, and this process occurs in to £¿sec. This means that before an exited molecule in a solution can emit a photon, it will undergo vibrational relaxation, and therefore photon emission will always occur from the lowest vibrational level of an excited state [3, 4]. Once a molecule arrives at the lowest vibrational level of an exited singlet state, it can do a number of things, one of which is to return to the ground state by photon emission. This process is called fluorescence. The lifetime pf an exited singlet state is approximately to £¿sec and therefore the decay time of fluorescence is
%U http://www.hindawi.com/journals/isrn.spectroscopy/2013/230858/