James D. MacNeil

The ultraviolet absorption spectra of some chlorinated biphenyls

The UV spectra of 29 chlorobiphenyls have been examined. With increasing chloro substitution in which there are less than two chlorine groupsortho to the Ph-Ph bond the λmax values for the κ band (attributed to conjugation between the two phenyl rings) are shifted to longer wavelengths and for the more highly substituted chlorobiphenyls there is also a bathochromic shift of the main band (due to the benzenoid skeleton). Introduction of two or more chlorine atoms ortho to the Ph-Ph bond results in a hipsochromic shift of κ band and diminished ɛ value due to steric inhibition of resonance between the two phenyl rings. The sterically hindered chlorobiphenyls and the more highly chlorinated Aroclors also exhibit a series of low-intensity finestructured absorption maxima between 268–302 nm. The UV spectra of chlorobiphenyls are particularly diagnostic with respect to the degree of substitution at the 2, 2′, 6 and 6′ positions and can be used in the structural analysis of separated chlorobiphenyls. The data may also aid in correlating the photochemical reactivities.

Indoles and auxins : XIII. Identification and analysis of naturally occurring indoles via electron donor-acceptor complexes

Abstract The formation of electron donor-acceptor complexes of some representative indoles with a number of electron acceptors has been investigated with particular emphasis on qualitative and quantitative aspects of analysis involving thin-layer chromatography (TLC). This non-destructive method shows a detection limit for indoles, after chromatography, from 0.5 to 1 μg, depending on the structure of the indole and the electron acceptor employed. An in situ method was developed for quantitation of indoles on the sprayed chromatograms and a linear relationship between concentration of the indole and detector response of a TLC scanner for reflectance at the charge transfer band maxima was observed in the range of 0.5–10 μg. With the same electron acceptor, charge transfer band maxima from complexes on a layer of silica gel shift to longer wavelength when substituents on the indoles are changed from electron withdrawing ( e.g. −CN) to electron donating ( e.g. −OH). Separate mass spectra for indoles and complexing reagents can be obtained directly from the complex, as previously observed, at different temperatures. Some of the newer electron acceptors having low vapor pressures allow application of this method at much higher temperatures, i.e. less volatile indoles can be identified in this manner.

Characterization of indoles by thin-layer chromatography and in situ fluorometry.

Abstract The characterization of microgram quantities of a number of naturally occurring and synthetic indoles through a combination of thin-layer chromatography and in situ fluorescence spectroscopy is reported. Instrumental detection limits of 0.03–0.05 μg of the indoles are possible using the native fluorescence of the indoles in the ultraviolet range, with excitation maxima in the range 285–310 nm and emission maxima in the range 345–360 nm. Spraying with a dilute acid solution (0.1 N H 2 SO 4 in methanol) produces an additional pair of maxima, with excitation at about 350 nm and emission at about 450 nm. The presence of a polar compound such as sulfuric acid or dimethyl sulfoxide in the spray produces an enhancement of the indole fluorescence. The procedure should find application in the determination of indoles in biological samples.

Electron Donor-Acceptor Complexing Reagents for the Detection of Pesticides on TLC

Abstract The formation of π-complexes to detect and identify a representative group of carbamate, anilide and urea pesticides was investigated. Results obtained with several electron-acceptor reagents used by previous workers are compared with those obtained with a group of nitro-substituted fluorene derivatives. The pesticides studied were chosen for their potential ability to act as electron donors. Detection limits after thin-layer chromatography ranged from 0.5 to 5.0 micrograms, depending upon the strength of the complex formed. Various chromatographic systems were studied and applications of in situ reflectance spectroscopy and mass spectrometry were investigated. The method combines a reasonable sensitivity with good selectivity and the pesticide may be recovered from the complex for further study. This non-destructive method of analysis should be of particular use in the separation and identification of these pesticides and their metabolites.

Quantitative analysis of 3-indoleacetic acid and serotonin by in situ fluorescence on thin-layer chromatograms

SummaryThe characterization and quantitation of indoles by thin-layer chromatography followed by fluorometric scanning of the chromatographed species on the thin-layer provides a rapid and sensitive method of analysis at theμg level and lower. Considerable increases in fluorescence intensity may be achieved if the plate is sprayed with a polar compound such as dimethylsulfoxide prior to measurement. The method may be used to quantitatively determine directly 50 ng samples of serotonin and indoleacetic acid and should be equally sensitive for other indolic compounds. The analysis of biological extracts for low levels of indoles should be a particular application for the method.ZusammenfassungDie Charakterisierung und Bestimmung von Indolen durch Dünnschicht-chromatographie und nachfolgende Fluoreszenzmessung der chromatographierten Substanzen auf der Dünnschichte erfordert eine rasche und empfindliche Analysenmethode für die Größenordnung von Mikrogramm und darunter. Eine erhebliche Verstärkung der Fluoreszenz läßt sich durch Sprühen mit einer polaren Verbindung wie z. B. Dimethylsulfoxid erreichen. Diese Bestimmungsmethode eignet sich für die direkte Bestimmung von 50 ng Serotonin und Indolessigsäure und dürfte auch für andere Indolderivate gleich empfindlich sein. Insbesondere Extrakte biologischen Materials dürften sich zur Analyse anbieten.

Electron Donor-Acceptor Reagents in the Analysis of Pesticides. VII. A Simple Model System Hydrolysis of Some Carbamate Pesticides,

Abstract The decomposition of the carbamate insecticides carbaryl and Mobam and the herbicides IPC and CIPC in water at various pHs was investigated. Analyses were performed in situ on silica-gel thin-layer chromatograms by reflectance spectroscopy after the developed chromatograms had been sprayed with the reagent CNTNF (9-dicyanomethylene-2,4,7-, trinitrofluorene) to form visible pi-complexes of the pesticides. Carbaryl and Mobam decomposed rapidly at basic pHs but were stable in acid. IPC and CIPC were stable in water at pHs tested.

Electron Donor-Acceptor Complexing Reagents in the Analysis of Pesticides: III. Quantitative in situ Analysis by Reflectance Spectroscopy on Thin-layer Chromatograms

Abstract The quantitative in situ determination of pi-complexed pesticides by reflectance spectroscopy is discussed and quantitative results and stability studies obtained on cellulose and silica-gel thin-layer plates are presented. Detection limits are in the microgram region, with the linear working range for the Mobam-CNTNF complex chosen as an example being 1–10 meg on cellulose and 3–10 meg on silica gel. The complexed pesticide may be recovered following quantitative determination for mass spectral confirmation. The method shows particular utility in studying the degradation of pesticides.

An Investigation of the Trace Element Status of Bison in Wood Buffalo National Park and of Ranch-Raised Bison in Saskatchewan, Canada

Abstract Trace metal levels were compared in ranched bison receiving a dietary supplement and in wild bison in Wood Buffalo National Park. Data collected in this study were also assessed with regard to information previously published on healthy wild bison resident in the Mackenzie Bison Sanctuary. Ninety percent of ranched animals contained lead, with mean levels of 0.06 and 0.10 ppm in liver and kidney, respectively, while lead was present in only 20% of samples from wild bison. Similarly, arsenic was more prevalent in ranched animals, though at levels below 0.05 ppm. Cadmium levels were significantly higher in the wild bison and traces of mercury were also more prevalent in the wild herd. Levels of copper, manganese, selenium and zinc, which are considered essential nutrients, showed variations between the ranched and wild bison, but were within the range considered acceptable for cattle, with the exception of selenium. This was found to be lower in the wild herd. Further research is required to define...