Lawrence Fishbein

Relationship of structure to sensitivity in electron capture analysis : III. Chloronitrobenzenes, anilines and related derivatives

Abstract In an extension of an earlier study describing the delineation of molecular sensitivity values for pesticides obtained via electron capture gas chromatographic analysis using a multiple linear regression program, relative sensitivity data were obtained for classical substituted benzenes for the purpose of estimating the quantitative contribution of individual aryl substituents (viz. Cl, No2 and NH2 groups) to the overall molecular electron capture sensitivity values, and in order to evaluate the efficacy of a multiple linear regression model for this purpose. Values were obtained for individulal substituents located at different positions of attachment to the ring. Indications are that the NH2 substituent in aniline derivatives substantially diminisches sensitivity. The possibility that the moiety contributions for wide ranges of compound sensitivities may be curvilinear is suggested.

Thin-layer chromatography of isomeric halo and nitro derivatives of aniline and benzene

Abstract The chromatogenic behavior of a variety of isomeri chalo and nitro derivatives of aniline and benzene respectively was elaborated on Silica Gel DF-5 utilizing three solvent systems. The chromogenic behavior of the isomeric bromo-, chlori, fluoro-, dichloro-, dibromo-, trichloro- and nitro-anilines towards three pi-electron detectors is also described.

Gas chromatography and structural correlation of substituted aziridines

A diverse selection of alkyl and substituted aryl N-carbamoylaziridines were prepared via reaction of ethylenimine and various isocyanates. The gas chromatographic behavior of these derivatives was reported on five liquid phases and the data obtained reported relative to N-phenyl-carbamoylaziridine and as Kovats indices. Degradation to the isocyanate and the aniline derivatives was observed for aryl aziridines on XE-60. The N-alkyl-aziridines were found to chromatograph without thermal rupture. To correlate structural features with the analytical results, structural and positional moiety values were obtained from the log differences of the N-aryl-carbamoylaziridines with N-phenyl-carbamoylaziridine in a manner similar to which the sigma-rho product is obtained in the Hammett equation from equilibrium or rate constants in organic reactions. Separations of o, m and p substituted N-chlorophenyl derivatives were successful. n nThe influence of functionality in the para position of N-aryl derivatives revealed an elution order of F < CH3 < Cl < Br, CH3O < CN.

Structural correlations to solute elution and molecular sensitivity data in the electron capture analysis of isomeric chlorophenyl m-fluorosulfonylbenzoates

Abstract This study describes the chromatographic behavior and relative electron capturing ability of a number of m-fluorosulfonylbenzoate aryl esters. The discussion attempts to relate various portions of the ester molecules to the analytical results which were obtained. This was done by logarithmic differences for chromatographic interpretations, and by multiple linear regression analysis of the electron capture sensitivity data.

Chromatography of methylenedioxyphenyl compounds. I. Simple and pesticidal derivatives.

Abstract Chromatographic analysis has played an important role in the elaboration of metabolism, degradation and mode of action of a variety of methylenedioxyphenyl derivatives. Thin-layer and gas chromatography have been singularly effective in the separation and identification of isomeric mixtures as well as elaborating the influence of substituents on the basic methylenedioxy moiety to chromatographic behavior. A variety of chromatographic techniques undoubtedly will be in the forefront of attempts to further elaborate the possible dichotomy of action of the methylene-dioxyphenyl synergists 60,122 .

Chromatography of carbamates.

Abstract We have attempted to stress the major areas of chromatographic techniques for carbamate analyses and also to illustrate the influence of carbamate moiety substituents on chromatographic behavior. The remarkable versatility of chromatographic techniques, as demonstrated by their many applications to complex analyses, is apparent from the foregoing review. It has also been shown how powerful a tool chromatography is for research as well as for routine analytical work. Thin-layer chromatography, introduced by S thal in 1956 216 , has largely replaced paper chromatography in many applications. In the past three years it has been increasingly applied to pharmaceutical and pesticidal analysis because of its simplicity of operation, rapidity and the high degree of resolution achieved. Under specified conditions, TLC lends itself to quantitation interpretation and is being used for analytical control and toxicological investigation. Although gas chromatography was introduced only in 1952, it has seen extensive utility in many areas. However, it has not, until recent years, been widely used for either pesticidal or pharmaceutical analysis. This has been due not entirely to the expense of the equipment or the degree of operational sophistication required. A major difficulty has been the thermal instability of many of the carbamates and the necessary high operating temperatures required for compound volatilization. Derivatives of carbamates, such as trimethylsilyl 135 and acetyl 217 (successfully utilized in pesticidal gas chromatographic analysis because of the thermally stable nature of the respective compounds formed) suggest a similar feasibility for pharmaceutical carbamate analysis. The desirability of a satisfactory selective detection system for nitrogen (alluded to in the work of C oulson 134 should greatly enhance the utility of gas chromatography to pharmaceutical and pesticidal carbamate analysis.

Crystal form of precipitated calcium carbonate as influenced by adsorbed magnesium ions.

WE are at present investigating in our laboratory the effects of “weathering” (ultra-violet, thermal, humidity) on 3,4-methylenedioxy benzene derivatives such as piperonal, piperonyl butoxide and piperonyl sulphoxide, which are widely used as pesticides, for example, as allethrin1,2 and carbamate2 synergists, flea3 and mosquito repellents4–6, and fungicides7–9. At present, information is scarce about their stability under conditions of exposure.

Chromatography of methylenedioxyphenyl compounds: II. Alkaloidal derivatives

Abstract There is no apparent paucity of paper and thin-layer chromatographic techniques that have been used both for isolation, proof of homogeneity and as analytical adjuncts to spectrometry (N.M.R., mass, I.R. and U.V.) for the identification of a broad spectrum of alkaloidal methylenedioxyphenyl alkaloids. Gas chromatography, however, has not been as extensively employed either for structural elaboration studies or for routine forensic and toxicological analysis. In many cases dealing with gas-liquid chromatography of alkaloids, it has been found necessary to form a derivative and/or a treated support to obtain a satisfactory elution 106,116,117 . The recent work of S treet 244,245 in which it was found that the surface properties of diatomaceous earth and of oxidized stainless steel can be modified to produce GLC columns which show very little absorption and which can be used for analysis of submicrogram amounts of alkaloids holds great promise, particularly for the analysis of alkaloids in biological media.

Chromatography of ureas thioureas and related mammalian metabolites

Abstract The literature is abundant with examples of the remarkable versatility of chromatography for the detection and separation of a wide variety of ureas and thioureas. Thin-layer chromatography with its inherent simplicity of operation, rapidity, high degree of sensitivity and resolution (and utility for “pre-cleanup” prior to gas chromatographic analysis) is rapidly replacing paper chromatography. Gas chromatography is becoming more useful as a method for analyzing residues of compounds of pharmaceutical and agricultural interest in plants, soils and animal tissues and fluids. Its ability for the simultaneous determination of several components, such as isomers, homologs and metabolites during a single operation has been amply demonstrated. The utility of gas chromatography will increase with the possibility of decreasing the thermal instability of ureas by the preparation of suitable derivatives such as trimethylsilyl 121 , or possibly acetyl derivatives 193 (successfully utilized for pesticidal carbamates). The desirability of a satisfactory selective system for nitrogen as suggested by C oulson 194 as well as the use of pyrolytic techniques 195,196 (utilized in combination with gas chromatography for the analysis of barbiturates) appears to offer enhanced prospects for the greater utility of gas chromatography to urea and thiourea analysis.