Study of properties of the liquid-crystal sorbents for gas chromatography

Аuthors

Novikov V. F.^1*, Kartashova A. A.^1*, Usmanov N. T.^1*, Taneeva A. V.^2**

1. Kazan State Power-Engineering University, KSPEU, 51, Krasnoselskaja str., Kazan, Republic of Tatarstan, 420059, Russia
2. Kazan State University of Architecture and Engineering, KSUAE, 1, Zelenaya str., Kazan, 420043, Russia

*e-mail: sun-2007@list.ru
**e-mail: taneeva@mail.ru

Abstract

Nowadays in gas chromatography more than 2000 different sorbents are used. Trey are prepared on organic base and inorganic compounds. In gas chromatography liquid-crystal sorbents are used for the Trey are prepared on organic base and inorganic compounds. In gas chromatography separation of positional isomers. It is known that the selectivity of separation of the positional isomers is largely dependent on the structural characteristics of the liquid crystal molecules and the presence in sorbent of the different functional groups with different physic and chemical nature. In article studied a number of liquid crystal 4- alkoxycarbonyloxy-4’- natroazoksibenzols. The values of logarithmic and linear retention indices of standard sorbates are shown.
For the investigated series of compounds even-odd effect is observed. While for odd substituents are characterized by higher values of retention indices that than even. Methyl radical behaves abnormally, which contributes to a sharp decrease in the values of retention indices for all standard sorbates. Assuming that a methyl group, possessing electron-donating properties, contributes to a significant change in the electron density at the nearest oxygen atom in molecule azoxybenzenes and escapes his lone electron pair. As a result of the intermolecular interaction energy of polar sorbates weakened, resulting in a decrease in the values of their retention indices.
Three areas of changing of retention sorbates under the action of temperature are founded. They are areas of the isotropic liquid, the liquid crystal and solid crystalline states. There is a separation of para- and meta-xylenes which selectivity of separation varies depending on the temperature conditions of the process of chromatographic separation.

Keywords:

gas chromatography, sorption property, logarithmic retention index, liquid-crystal sorbent, temperature

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