Hydrocarbons, aliphatic thin layer chromatography

Plasticizers include the esters of a few aliphatic and aromatic mono and dicarboxylic acids, aliphatic and aromatic phosphorus acid esters, ethers, alcohols, ketones, amines, amides, and non-polar and chlorinated hydrocarbons. These additives are used in various mixtures. For their separation and qualitative detection, thin-layer chromatography (TLC) is preferred. Usually Kieselgur plates, 0.25 mm thick, activated at 110°C for 30 min, in the saturated vapor are used. Methylene chloride and mixtures of diisopropyl ether/petether at temperatures between 40 to 60°C have been successfully used as the mobile phase. Refer to Table 1. 

Suryaraman, M.G. and Cave, W.T., Detection of some aliphatic saturated long chain hydrocarbon derivatives by thin-layer chromatography, Anal. Chim. Acta, 30, 96, 1964 Chem. Abs., 60, 7463e, 1964. 

The method applied consists in a prior, basic hydrolysis (saponification) of the oil sample, followed by thin layer chromatography (TLC) fractionation of the classes of compounds, namely hydrocarbons, tocopherols, long-chain aliphatic alcohols, triterpenic alcohols, methyl sterols, sterols and triterpenic dialcohols. This procedure loses all information about the combination of polycyclic triter-penes with fatty acids. 

It was of interest to examine how the vegetation which grows in polluted wetlands contributes to their additional purification. For that purpose plant samples, after preliminary preparation, were extracted in an Soxlet s apparatus using a mixture of methanol/chloroform. After that the extracts were let through a column filled with aluminum oxide and by Thin Layer Chromatography were separated to three fractions sterols, terpenic and aliphatic alcohols and hydrocarbons. The hydrocarbon fractions were analyzed by Gas Chromatography and Mass Spectrometry. 

Liu XH, Bi XH, Mai BX, Sheng GY, Fu JM (2005) Separation of PAHs in aerosol by thin layer chromatography for compound-specific stable carbon isope analysis. Talanta 66 487 94 Mandalakis M, Tsapakis M, Tsoga A, Stephanou EG (2002) Gas-particle concentrations and distribution of aliphatic hydrocarbons, PAHs, PCBs and PCDD/Es in the atmosphere of Athens (Greece). Atmos Environ 36 4023 035... 

In extraction techniques (LLC, SPE, etc.), normal-phase liquid chromatography (NPLC), and thin-layer chromatography, aliphatic hydrocarbons (e.g., -hexane, -heptane) are usually used. The elution strength of these solvents is often modified by addition of more polar solvents. The fundamental problem with the eluents in NPLC is dissolved water and trace amounts of olefins. These contaminations can induce a change in the wavelength cut-off values (UV detection, spectrophotometry), baseline perturbation, and poor reproducibility of retention data. Halogenated solvents such as dichloromethane can react with some organic solvents (e.g., acetonitrile) to form crystalline products. 

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