Phosphorescence Measurements, Applications of

Abstract

Abstract Luminescence is a term used for both fluorescence and phosphorescence. These are emission processes following the absorption of light, and the distinction between them is based upon the process of the deactivation mechanism. Phosphorescence has been identified as the light emitted from the triplet excited state to the ground state, a spin‐forbidden transition. Fluorescence is a radiational transition between electronic states of the same multiplicity. The first analytical uses of phosphorescence were published in the 1950s, but the technique was not widely accepted due to the practical aspect of measuring the signal at cryogenic temperatures (77 K). Developments in room temperature phosphorescence (RTP) have given rise to fundamental and practical advances which have stimulated interest in phosphorimetry. Solid‐surface room temperature phosphorescence (SSRTP) has been generally observed by immobilizing the lumiphor on a solid support such as filter paper or polymeric resins. SSRTP has been shown to be a sensitive and selective approach for the analysis of trace components in biological, pharmaceutical, and environmental samples. Techniques such as SSRTP combined with flow injection analysis provide new avenues for optical sensing transduction and improvement of SSRTP techniques. Applications of SSRTP in flowing systems include the sensing of cations, anions, oxygen, glucose, ethanol, antibiotics, and moisture. A number of developments in RTP have focused on sensitized phosphorescence (SP) and on the use of ordered media (micelles and cyclodextrins (CDs)), allowing the observation of RTP in fluid solution. In SP the triplet energy of a donor (analyte) is transferred to an acceptor that phosphoresces in fluid solution and the emission of the acceptor is measured. Therefore, SP can only provide quantitative information. In ordered media, a micelle (or a CD) protects the long‐lived triplet state from the quenching processes that normally take place in solution, allowing both quantitative and qualitative measurements. SP and ordered media RTP provide the limits of detection for many lumiphors in the nmol −1 range and calibration graphs have a wide linear range. As new instrumental and basic insights emerge in SSRTP, Micelle Stabilized Room Temperature Phosphorescence (MSRTP), and solution‐sensitized RTP, these techniques will find much greater use in the trace and ultratrace analysis of dissolved, volatile, and gaseous substances in areas such as pharmaceutical analysis, environmental science, and clinical chemistry.