Detection of some aliphatic saturated long-chain hydrocarbon derivatives by thin-layer chromatography

The aliphatic saturated long-chain alcohols, aldehydes, and diols were identified to a sensitivity of 50 μg from the parent hydrocarbons (C₁₀, C₁₂, C₁₄ and C₁₆) by thin-layer chromatography using “Silica Gel G”-coated pyrex chromatoplates for the fixed phase and ethyl acetate-n-hexane mixtures as the mobile phase. Identification of the developed spots was made by a modified charring technique employing ground glass pyrex plates coated with pyrosulfuric acid. Identification of the 1,n-dicarboxylic acid from the n-mono- or the 1,n-hydroxycarboxylic acid derived from the same parent hydrocarbon was effected in a mobile phase of 7:3:3 v/v ethanol- ammonia (conc.)-tetrahydrofuran. The indicator spray employed was an ethanolic solution of bromothymol blue. The spray was followed by exposure to ammonia vapor for intensification of the yellow acid spots.R_F value trends for the n-mono- and 1,n-bifunctional derivatives of the C₁₀ C₁₂, C₁₄ and C₁₆ aliphatic saturated hydrocarbons based on the—OH, —COOH and —CHO groups as the possible substituents are outlined.     

Overpressured thin-layer chromatography

The properties, apparatus and applications of overpressured thin-layer chromatography (OPTLC) have been reviewed. In the Introduction planar chromatography has been briefly characterized, with particular attention to TLC. The general properties of OPTLC and methods of development of chromatograms in this technique have been then given. The construction of chambers and equipment for OPTLC has been described, paying attention to two-dimensional columns. The properties of chambers for OPTLC have been characterized considering the flow of eluent, sorbent-eluent interactions and the efficiency of various systems. OPTLC, TLC and HPTLC have been compared and also a comparison between OPTLC with a constant (linear) eluent flow-rate and with a decreasing eluent flow-rate has been made. Analytical applications of OPTLC have been described and examples of separations of mixtures have been given.     

Nitrogen oxide generation during reduction of nitrofuran antibacterial drugs

Proof of the nitrogen oxide generation during the chemical reduction of a series of nitrofuran derivatives is obtained by polarographic detection of the nitroprusside anion. A hypothesis is made about the mechanism of the peroxynitrite anion formation, which is responsible for the biological activity of nitrofurans during the course of their reduction.Russian Federation State Scientific Center NIOPIK, Moscow 103787, Russia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 902–906, July, 1999.     

Cone thin-layer chromatography

A new variant of chromatography, cone chromatography, is suggested. In this variant, a thin-layer chromatography (TLC) plate on a flexible support (for example, foil) is cone-shaped. This variant is compared with the classic linear and circular variants using chromatographic characteristics (retardation factor R _f and efficiency H, μm) and the time of chromatographing with ethanol as a mobile phase. Cone chromatography is intermediate in the series linear-cone-circular TLC variants.     

Automated multiple development thin-layer chromatography for separation of opiate alkaloids and derivatives

There are three types of opiate alkaloids. First, the poppy alkaloids: morphine, codeine, thebaine, noscapine and papaverine; then, the semi-synthetic and synthetic derivatives used in therapy as antitussives and analgesics, such as pholcodine, ethylmorphine and dextromethorphan; at last narcotic compounds, diacetylmorphine (heroin) and opiates employed as substitutes in treatment of addiction: buprenorphine and methadone. For classical thin-layer chromatography (TLC) of opium alkaloids, it is necessary to use complex eluents with strong alkaline substances to obtain a clean separation between morphinan and isoquinoline compounds. This study purposes the planar chromatographic analysis of these substances by the automated multiple development (AMD) compared with results obtained by classical TLC method. The aim of this work was to achieve the best separation of these opiate alkaloids and derivatives by this modern technique of planar chromatography. The AMD system provided a clean separation for each of three opiates groups studied and the best results have been obtained with universal gradient: methanol 100, methanol-dichloromethane 50/50, dichloromethane 100, dichloromethane 100, hexane 100 for opium alkaloids and with gradient A: 5% of 28% ammonia in methanol 100, acetone 100, acetone 100, ethyl acetate-dichloromethane 50/50, dichloromethane 100 for antitussives and substitutes. Two reagents were used for the detection of alkaloids by spraying: Dragendorff and iodoplatinate reagents. The detection limits with these two reagents were 1 microg for ethylmorphine, thebaine, papaverine, codeine, and 2 microg for morphine and noscapine and other alkaloids.