The application of ultraviolet reflectance spectroscopy to thin-layer chromatography

Simultaneous Analysis of Two-Component Systems by Diffuse Reflectance Spectroscopy

“…Within the concentration ranges studied, the Kubelka-Munk relationship was valid for all four dyes, and the T values for the slopes of the KubelkaMunk curves required for eqs. [4] and [5] were readily obtained. Sample mixtures were prepared and, to test the reliability of the method, were analyzed as unknowns by students of the junior and senior level.…”

“…Analytical applications of diffuse reflectance spectroscopy to chromatographic separation procedures (1)(2)(3)(4) have stimulated development, by the same techniques, of a method for simultaneous analysis of multicomponent systems. Such a method is analogous to procedures for absorptiometric analysis of multicomponent mixtures in solution and would find application for systems in which incomplete chromatographic separation would ordinarily prevent quantitative evaluation by reflectance spectroscopy.…”

Diffuse Reflectance Spectroscopy

“…This ranges from a few grams for the above-mentioned commercial sample holders to 0.5 and 1 g, depending on the material, for the cell described by Barnes et al 92 A new line of reflectance cells had to be designed when spots scraped off from chromatoplates had to be accommodated for reflectance measurements. Three types of cells were designed by Frodyma and co-workers in conjunction with these problems: (a) a glass window cell, 33 (b) a quartz window cell, 93 and (c) a windowless cell. 94 Cell a is depicted in Figure 14.…”

“…Reflectance techniques are very suitable to study such parameters, as can be seen from an investigation of color stabilities of ninhydrin complexes of amino acids. 2 ' 6 Simple heating of the plates will occasionally result in the formation of a colored product 93 and if a fluorescent compound is available, observation under UV light enables location of the spot. 245 For many UV-active compounds detection of the spots as dark areas is possible on a fluorescent background.…”

“…93 This system had the advantage of forming brown spots upon heating the plates, hence facilitating the location of the spot areas before a spectral investigation. After separation the plates were dried for 2 hr at 90°C, during which period the aspirin converted quantitatively to salicylic acid.…”