Diffuse Reflectance Spectroscopy

Frei, R.W.; Zeitlin, Harry

doi:10.1080/10408347108542764

Cited by 11 publications

(11 citation statements)

References 212 publications

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“…The sample was used in the form of self-supported discs (3 mm width, 25 mm diameter) obtained by compressing the powder in the sample-holder provided by the manufacturer. The application of this technique to inorganic chemistry (Simmons, 1974), materials science (Jones and Klier, 1972), analytical chemistry (Frei et al, 1975) and the surfaces of dispersed solids (Frei, 1976;Kellerman, 1979) has been discussed previously.…”

Section: Ch3mentioning

confidence: 99%

Adsorption and Desorption of N-Methyl 8-Hydroxy Quinoline Methyl Sulfate on Smectite and the Potential Use of The Clay-Organic Product as an Ultraviolet Radiation Collector

Vicente

1989

Clays and clay miner.

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Abstract--The interaction between N-methyl 8-hydroxy quinoline methyl sulfate, a drug that absorbs erymathogenic near-ultraviolet radiation, and smectite was studied by X-ray powder diffraction (XRD) and adsorption and desorption techniques. From the adsorption studies, (1) the amount of the drug adsorbed by Na-smectite increased with the pH of the solution to pH 6.5 and then decreased as the pH was further increased; (2) the maximum amount adsorbed at pH 6.5 was 102 meq/100 g of clay; and (3) the maximum amount of drug adsorbed, according to the adsorption isotherms at pH 4, was close to the cation-exchange capacity of the smectite (80 meq/100 g). The XRD studies showed that the drug molecules were adsorbed in the interlayer space of smectite and that cation exchange was the chief mechanism responsible for these interactions. The results of the adsorption-desorption cycles of the drug by smectite showed that this clay is a good support for this compound. In addition, an alternative method was developed to obtain the intercalation compound to avoid the standard method of exchange by impregnation. The method consisted of grinding a mixture of the drug with the clay. The characteristics of the complex thus formed were similar to those of the complex formed by exchange at pH 4 to 7.To gain insight into the pharmacological properties of the intercalation compound studied, its capacity for absorption of visible and near-ultraviolet light was investigated. The diffuse reflectance spectrum of the complex showed intense absorption bands, absent or weak in the spectra of the pure drug or the untreated clay, at 250, 290, and ~390 nm.Resumen--Se ha estudiado mediante difracci6n de rayos X (DRX) y t6cnicas de adsorci6n-desorci6n la interacci6n entre el metil-sulfato de N-metil 8-hidroxiquinolina, una droga que absorbe las radiaciones erimat6genas de la zona ultravioleta pr6xima, con la esmectita. A partir de los estudios de adsorci6n se ha encontrado que: (1) la cantidad de droga adsorbida por la esmectita s6dica aumenta con el pH hasta 6.5 y luego disminuye; (2) la mfixima cantidad adsorbida a pH 6.5 fue de 102 meq/100 g de arcilla; y (3) la cantidad mfixima adsorbida, seg6n los datos de la isoterma medida a pH 4, es similar a la capacidad de cambio de la esmectita (80 meq/100 g). Los estudios de DRX sefialan que las mol6culas de droga se adsorben en el espacio interlaminar de la esmectita y que el mecanismo principal de la interacci6n esmectita-droga es el cambio cati6nico. Los resultados de los estudios de ciclos de adsorci6n-desorci6n sefialan que esta arcilla es un buen soporte para este compuesto. Ademfis, se ha desarrollado un m&odo alternativo para obtener compuestos de intercalaci6n que evitan el m&odo convencional de intercambio por impregnaci6n. E1 m&odo consiste en la molienda de una mezcla de la droga y de la arcilla. Las caracteristicas del complejo asi formado son similares alas del complejo formado por intercambio a pH entre 4 y 7.Con objeto de profundizar en el conocimiento de las propiedades farmacol6gicas...

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Section: Ch3mentioning

confidence: 99%

Adsorption and Desorption of N-Methyl 8-Hydroxy Quinoline Methyl Sulfate on Smectite and the Potential Use of The Clay-Organic Product as an Ultraviolet Radiation Collector

Vicente

1989

Clays and clay miner.

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“…Spectral maxima are commonly observed at higher wavelengths in the adsorbed state than those measured for the same species in solution (8).…”

Section: Measurements On Cellulosementioning

confidence: 91%

“…5). Kubelka-Munk plots (8) show non-linear~ty at low concentrations. The failure of these results to satisfy the Kubelka-Munk theory may be attributed to too thin a layer to approximate an infinite layer thickness.…”

Section: Measurements On Cellulosementioning

confidence: 95%

“…a blank cellulose reference from 400-700 nm. The samples were backed with white cardboard during the reflectance measurements to approximate an infinite layer thickness (8).…”

Section: Measurenzent O F Spectramentioning

confidence: 99%

“…The failure of these results to satisfy the Kubelka-Munk theory may be attributed to too thin a layer to approximate an infinite layer thickness. However, a plot of reflectance versus the square root of concentration, which approximates the Kubelka-Munk functions and has been used previously in measurements on thin-layer chromatograms (8), was found to yield linear plots over the concentration range studied for all four complexed pesticides. This could thus possibly be used to extend the u s e f~~l range of analysis (6,7 1 useful analytical range for the determination of I complexed pesticides in situ on a thin-layer chromatogram by reflectance spectroscopy may be extended by plotting reflectance (or peak area) us.…”

Section: Measurements On Cellulosementioning

confidence: 99%

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The Interactions of Four Carbamate Pesticides with Electron-acceptor Reagents

MacNeil¹,

Frei²,

Hutzinger³

1973

Can. J. Chem.

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The interactions between several electron-acceptor reagents and some pesticides having donor properties were investigated in solution and on cellulose thin-layers by spectrophotometric methods. In solution, formation constants and extinction coefficients were evaluated from absorbance measurements for complexes of the pesticides carbaryl, IPC, CIPC, and swep with the electron-acceptor reagent 9-dicyanomethylene-2,4,7-trinitrofluorene using the Benesi-Hildebrand method. Values were also calculated for the carbaryl-mellitic trianhydride complex. Extinction coefficients for the complexes were less than 1000, while formation constants were 1-4 1 mol-'.Reflectance spectroscopic measurements showed similar relationships between absorption maxima and intensities of the complexes and the donor properties of the pesticides to those observed in solution. A linear relationship between reflectance and the square root of concentration was found for all four pesticide-CNTNF complexes in the range from 5-50 pg.

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