RU2348454C1 - Gas chromatography sorbent - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: sorbent consists of solid carrier and 4-(3-hydroxypropyloxy-4)-formylazobenzene as stationary phase.

EFFECT: high selectivity for isomers with low and high boiling point.

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Description

Introduction

The invention relates to the chemical industry, and in particular to the production of a sorbent consisting of a solid carrier and a crystalline stationary phase, which can be used for analytical separation of chemicals in gas chromatography.

State of the art

One of the main instrumental methods of quantitative analysis, widely used in the chemical, biochemical and food industries for environmental monitoring and in other industries, is the method of gas chromatography. The progress of gas chromatography recently depends not so much on the development of electronic components of the chromatograph as on the properties of chromatographic columns and, in particular, on the performance and, especially, the selectivity of the sorbents contained in them. The sorbent for gas chromatography is a solid carrier on which a monolayer of the stationary phase is applied. Liquid crystals are most widely used as stationary phases due to their unique selective properties, which are manifested in the separation of boiling structural isomers of various chemicals due to the ordered arrangement of molecules in the temperature range of the existence of the mesophase [Vigdergauz MS, Vigalok RV, Dmitrieva R.V. . Chromatography in a gas-liquid crystal system // Uspekhi Khimii, 1981, vol. 50, pp. 943-972].

Known sorbent consisting of a solid carrier and 4-methoxy-4'-ethoxyazoxybenzene as a liquid crystal stationary phase [Egorova K.V., Belyaev N.F., Wigderhaus M.S. P, p'-methoxyethoxyazoxybenzene as the preferred liquid crystal stationary phase of the chromatographic fragment of the universal chemical analysis system // Izv. universities. Chemistry and chemical technology, 1985, t.28, No. 6, p.3]. This sorbent shows sufficient selectivity with respect to low boiling chemicals, in particular p- and m-xylenes, but cannot be used to separate chemicals with higher boiling points, in particular p- and m-methylanisoles, 3,4- and 3,5-lutidines, etc.

Therefore, to separate high-boiling isomers, it is necessary to replace the sorbent in the chromatographic column, which entails the time and labor required to calcine the solid support, applying another stationary phase to it, filling the chromatographic column with the prepared sorbent, conditioning the column with another sorbent in a helium stream, changing operating modes chromatograph.

The sorbent closest to the invention is also known [XVI International Conference on Chemical Thermodynamics in Russia; X International Conference on the Problems of Solvation and Complexation in Solutions. Suzdal, July 1-6, 2007 T.II, 4S-500. Kuvshinova S.A., Burmistrov V.A., Blokhina S.V., Sharapova A.V., Fokin D.S., Koifman O.I. The influence of the associative state of polar mesogens on their mesomorphism and structural selectivity]. It consists of a solid support and 4-butyloxy-4'-formylazobenzene as the liquid crystal stationary phase. This compound is a derivative of 4-hydroxy-4'-formylazobenzene.

However, this sorbent exhibits low selectivity with respect to isomers both low boiling and high boiling.

SUMMARY OF THE INVENTION

An inventive task is to search for a sorbent for gas chromatography, consisting of a solid support and a derivative of 4-hydroxy-4'-formylazobenzene as a stationary phase, which would have higher selectivity for isomers of both low-boiling and high-boiling substances.

The problem is solved by a sorbent for gas chromatography, consisting of a solid support and a derivative of 4-hydroxy-4'-formylazobenzene as a stationary phase, which contains 4- (3-hydroxypropyloxy) -4 'as a derivative of 4-hydroxy-4'-formylazobenzene -formylazobenzene.

The claimed sorbent has a higher selectivity with respect to the isomers of substances of both low-boiling and high-boiling, therefore, when separating high-boiling isomers of substances, the sorbent does not need to be replaced in the chromatographic column, which saves time and labor for calcining a solid support, and provides a different stationary phase filling the chromatographic column with the prepared sorbent, conditioning the column with another sorbent in a helium stream, changing the chromatograph operating modes.

Information confirming the reproducibility of the invention

The following substances are used to prepare the sorbent:

1. Solid media brand Chromaton N-AW (0,40-0,63 Chemapol, Czech Republic).

2. The liquid-crystalline stationary phase of 4- (3-hydroxypropyloxy) -4'-formylazobenzene [S. A. Kuvshinova, A. V. Zavyalov, V. V. Aleksandriysky, V. A. Burmistrov, O. I. Koifman. Mesogenic 4- (ω-hydroxyalkyloxy) -4'-formylazobenzenes. Journal of Organic Chemistry, 2004, v.40, issue 8, p.1161-1164]

4- (3-hydroxypropyloxy) -4'-formylazobenzene is prepared by boiling 4-hydroxy-4'-formylazobenzene and 3-chloropropanol-1 in dimethylformamide in the presence of potash for 3.5 hours. The product is purified by recrystallization from ethanol until the phase transition temperatures are constant.

3. Chloroform GOST 20015-88.

The preparation of the sorbent and the test of its selectivity by gas-liquid chromatography is illustrated by the following example.

Example. 4- (3-hydroxypropyloxy) -4'-formylazobenzene in an amount of 0.36 g is dissolved in 30 ml of chloroform of the grade ChP. The resulting solution was added to 3.6 g of a solid carrier of the Chromaton N-AW brand (0.40-0.63 Chemapol, Czech Republic) and heated in a water bath with stirring until the solvent completely evaporated. To remove traces of chloroform, drying is carried out for 12 hours in vacuum at 70 ° C and a residual pressure of 2 mm Hg. Next, the sorbent, which is a solid carrier with a stationary phase deposited on it, is placed in a stainless steel column (1000 × 3 mm) and conditioned for 6 hours in a helium stream at 100 ° C. The amount of stationary phase is 10% by weight of the carrier. The constant composition of the stationary phase in the column is controlled by weighing the column before each series of experiments.

The retention time of the sorbates is measured on a Chrom-5 gas chromatograph (Czech Republic) with a flame ionization detector at a sensitivity that ensures the detection of an ionization current of 3.2 · 10 ^-10 A. The measurements are carried out in isothermal mode in the temperature range 120-200 ° C. Thermostating accuracy 0.1 ° C. The temperature of the evaporator and detector is set at 20 ° C above the temperature of the column. As the carrier gas, helium is used with a basic substance content of 99.99%. Helium flow rate is maintained within the range of 30-35 ml / min, measuring it with a foam flowmeter. Flow measurements are performed at each temperature of the experiment after the determination of the retention time of the sorbate. The outlet pressure equal to atmospheric is determined by the BR-52 barometer with a division price of 0.5 mm Hg. In order for the experimental conditions to correspond to the limiting dilution, and the sorbate concentration to the linear portion of the dissolution isotherm, small volumes of not more than 0.1 μl of sorbates are introduced into the column. A 1 μl syringe was used (Hamilton, Switzerland). The "dead" retention time is determined by methane. The retention time is recorded by the IT-2 integrator with an error of not more than 0.01 s. This allows us to measure the retention times of compounds in five parallel experiments with a deviation from the average statistical value of not more than 0.5%.

Herrington selectivity coefficients (α) are defined as the quotient of dividing the retention time of the p-isomers by the retention time of the m-isomers, taking into account the “dead” retention time. The average selectivity of five measurements is calculated.

The preparation and testing of the sorbent, consisting of a solid carrier and a liquid crystal stationary phase based on the compound of the prototype 4-butyloxy-4'-formylazobenzene, was carried out similarly to the preparation and testing of the claimed sorbent.

The table shows the selectivity coefficients of sorbents containing 4- (3-hydroxypropyloxy) - and 4'-butyloxy-4'-formylazobenzenes as a stationary phase.

These tables clearly confirm that the claimed sorbent exhibits higher selectivity with respect to isomers of both low-boiling, in particular p- and m-xylene, and high-boiling, in particular p- and m-methylanisole and 3,4- and 3, 5-lutidine, which makes it possible to use it in gas chromatography in the processes of quantitative analysis of mixtures of organic compounds.

Table
Sorbent selectivity coefficients N p / p Liquid crystal stationary phase α for xylenes α for methylanisoles α for lutidines one. 4- (3-hydroxypropyloxy) -4'-formylazobenzene 1.17 1.30 1,60 2. prototype 4-butyloxy-4'-formylazobenzene 1.008 1,02 1.27

Claims (1)

Sorbent for gas chromatography, consisting of a solid support and a derivative of 4-hydroxy-4'-formylazobenzene as a stationary phase, characterized in that it contains 4- (3-hydroxypropyloxy-4 'as a derivative of 4-hydroxy-4'-formylazobenzene -formylazobenzene.