Solid-surface luminescence analysis

R. J. Hurtubise. Solid Surface Luminescence Analysis. Marcel Dekker, New York, 1981. Practical aspects of analysis for organics adsorbed onto solids. 

Applications and Interactions in Solid-Surface Luminescence Analysis... 

Solid-surface room-temperature phosphorescence (RTF) is a relatively new technique which has been used for organic trace analysis in several fields. However, the fundamental interactions needed for RTF are only partly understood. To clarify some of the interactions required for strong RTF, organic compounds adsorbed on several surfaces are being studied. Fluorescence quantum yield values, phosphorescence quantum yield values, and phosphorescence lifetime values were obtained for model compounds adsorbed on sodiiun acetate-sodium chloride mixtures and on a-cyclodextrin-sodium chloride mixtures. With the data obtained, the triplet formation efficiency and some of the rate constants related to the luminescence processes were calculated. This information clarified several of the interactions responsible for RTF from organic compounds adsorbed on sodium acetate-sodium chloride and a-cyclodextrin-sodium chloride mixtures. Work with silica gel chromatoplates has involved studying the effects of moisture, gases, and various solvents on the fluorescence and phosphorescence intensities. The net result of the study has been to improve the experimental conditions for enhanced sensitivity and selectivity in solid-surface luminescence analysis. 

Solid-surface luminescence analysis involves the measurement of fluorescence and phosphorescence of organic compounds adsorbed on solid materials. Several solid matrices such as filter paper, silica with a polyacrylate binder, sodium acetate, and cyclodextrins have been used in trace organic analysis. Recent monographs have considered the details of solid-surface luminescence analysis (1,2). Solid-surface room-temperature fluorescence (RTF) has been used for several years in organic trace analysis. However, solid-surface room-temperature phosphorescence (RTF) is a relatively new technique, and the experimental conditions for RTF are more critical than for RTF. 

Since publication of these two studies (15,16), several researchers have used solid-surface luminescence analysis in trace organic analysis (1,2). 

Recent Uses of Solid-Surface Luminescence Analysis in Environmental Analysis. Vo-Dinh and coworkers have shown very effectively how solid-surface luminescence techniques can be used for environmentally important samples (17-22). RTF has been used for the screening of ambient air particulate samples (17,18). In addition, RTF has been employed in conjunction with a ranking index to characterize polynuclear aromatic pollutants in environmental samples (19). A unique application of RTF reported recently is a personal dosimeter badge based on molecular diffusion and direct detection by RTF of polynuclear aromatic pollutants (20). The dosimeter is a pen-size device that does not require sample extraction prior to analysis. 

Several solid surfaces, such as filter paper, sodium acetate, and silica gel chromatoplates with a polyacrylate binder, have been used in solid-surface luminescence work (1,2). Experimentally it is relatively easy to prepare samples for analysis. With filter paper, for example, a small volume of sample solution is spotted onto the surface, the filter paper is dried, and then the measurement is made. In many cases, an inert gas is passed over the surface during the measurement step to enhance the RTF signal. For powdered samples, the sample preparation procedure is somewhat more involved. Commercial instruments can be readily used to measure the luminescence signals, and a variety of research instruments have been developed to obtain the solid-surface luminescence data (1,2). 

Interactions in Solid-Surface Luminescence Temperature Variation. Solid-surface luminescence analysis, especially solid-surface RTF, is being used more extensively in organic trace analysis than in the past because of its simplicity, selectivity, and sensitivity (,1,2). However, the interactions needed for strong luminescence signals are not well understood. In order to understand some of the interactions in solid-surface luminescence we recently developed a method for the determination of room-temperature fluorescence and phosphorescence quantum yields for compounds adsorbed on solid surfaces (27). In addition, we have been investigating the RTF and RTF properties of the anion of p-aminobenzoic acid adsorbed on sodium acetate as a model system. Sodium acetate and the anion of p-aminobenzoic acid have essentially no luminescence impurities. Also, the overall system is somewhat easier to study than compounds adsorbed on other surfaces, such as filter paper, because sodium acetate is more simple chemically. 

Solid-surface luminescence analysis is a useful approach for organic trace analysis because of its simplicity, sensitivity, and selectivity. It will continue to be used in environmental analysis and other areas not only for the reasons mentioned above but also because it is readily adaptable to field work. By developing a fundamental understanding of the interactions responsible for strong RTF and RTF signals, the advantages and disadvantages of the luminescence approach will be more specifically defined in the future. 

Hurtubise RJ (1981) Solid Surface Luminescence Analysis. Theory, Instrumentation, Applications. New York Dekker. 

Luminescence - fluorescence, phosphorescence, and even chemiluminescence - may be emitted from the surface of powdered solid supports with small-sized particles or from membranes coming from compounds immobilized by physical or chemical procedures when exposed to by external radiation. The selectivity, sensitivity, speed, flexibility, and simplicity of solid-phase luminescence spectrometry (SPLS) make it a good analytical tool, especially in trace analysis. Because of its ease in handling, the use of SPLS has increased in different fields of interest and many different formats have emerged. 

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