O. Hutzinger

An investigation of fluorigenic labelling of chlorophenols with dansyl chloride

Abstract : Chlorophenols have been evaluated semiquantitatively on thin-layer chromatographic (TLC) plates by using different spray reagents. The detection limits reported are in the submicrogram range. An approach to the development of a more sensitive and selective method, which involves the formation of dansyl derivatives separated by TLC and in situ fluorescence measurements, is outlined in the note. Although derivatization of free hydroxyl groups is a common procedure in gas chromatographic analysis, it has not been the usual practice to do so in TLC. (Modified author abstract)

Determination of hydroxybiphenyls as dansyl derivatives

Abstract The reaction conditions for the fluorigenic labelling of mono- and dihydroxybiphenyls withdansyl chloride were investigated. The hydroxybiphenyls were made to react in an acetone-water solution with a 10-fold exces of dansyl chloride, buffered with sodium carbonate at about pH 11. The reaction was carried out at 45° for 15 min. After hydrolysis of the excess of dansyl chloride and subsequent extraction with n -hexane, an aliquot of the reaction mixture was spotted on to a thin-layer plate. The separated derivatives were identified by their R F values as well as by their mass and fluorescence spectra. The yellow fluorescent derivatives can be analyzed with a relative standard deviation of 4-5%. Detection limits are in the low nanogram region and linear calibration curves between 5 and 500 ng are observed. As an application of this method, 4-hydroxybiphenyl, which was isolated from the urine of rats treated with biphenyl, was derivatized with dansyl chloride and its identity confirmed by thin-layer chromatography and fluorescence and mass spectrometry.

Indoles and auxins: II. Non-destructive detection of indoles by electron acceptors

Abstract : The color reactions of several electron acceptors with 48 indoles and related compounds have been studied. The advantages of these complexing spray reagents are that they: (1) are non-destructive (i.e. indoles can usually be regenerated); (2) give an indication of the type of ring substitution (electron-donating or -withdrawing groups); (3) react with 2,3-disubstituted indoles. 2,4,7-Trinitro-9-fluorenone is the generally most useful reagent. These complexing agents are less sensitive and less specific than other chromogenic reagents for indoles. (Author)

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.

Interaction of tetracyanoethylene with indoles on silica gel and cellulose thin-layer plates

Abstract Tetracyanoethylene and indoles readily form dark coloured π-complexes in solution. In most instances the components of such complexes formed from indoles unsubstituted in the 3-position, interact on standing with the formation of 3-tricyanovinylindole derivatives. However the use of tetracyanoethylene as a spray reagent for detecting indoles on thin-layer plates leads exclusively to the formation of these 3-tricyanovinyl substituted products. The structures of some of these compounds have been confirmed using physical and chemical methods.

The thin-layer chromatography of the hydroxyindole-3-carboxylic acids.

Abstract : Two of the main problems that are often encountered in the use of paper and thin-layer chromatographic procedures for the detection and identification of hydroxyindoles are the lack of suitable standard compounds and reliable data on their R(F) values. The chromatographic behaviour of all four isomeric hydroxyindoles (hydroxylated in the benzene ring) has only been studied in a relatively few cases including indole, skatole, tryptamine, tryptophan, acetyltryptophan and oxindole. The 4-, 5-, 6- and 7-hydroxyindole-3-carboxylic acids have recently all been synthesized by unambiguous routes in these laboratories and the article reports the results of some investigations into the TLC properties of this group of hydroxyindoles. (Author)