The method of chromatographic separation of vapor mixtures

 

(57) Abstract:

Use: in analytical chemistry. The inventive method of chromatographic separation of the vapor mixture includes introducing it with the flow of eluent in a chromatographic column filled with electrically conductive sorbent, and creating a potential difference between electrodes placed in the column. The potential difference creates between the electrodes placed at the ends of the column and in contact with the sorbent made of metal. As metal can be used Zirconia or scandium. 1 C.p. f-crystals.

The invention relates to a chromatographic separation of a mixture of solutes, in particular to increase separation efficiency due to design features of the column.

There is a method to control the selectivity of the chromatographic column by means of an electric field [1] the Method includes introducing a sample share mixes with the flow of eluent in a glass capillary chromatographic column with sorbent in the form deposited on the inner wall of the column stationary phase. The inside of the capillary is inserted electrode in the form of wire, the outside wall of the column applied with a conductive layer, avialalbe, leading to polarization as molecules of the sorbate and sorbent molecules.

How difficult to organize practically, such a design of the column does not allow a significant influence on the retention time of components of the vapor mixture at chronographically separation and, accordingly, to effectively change the selectivity of the separation.

The closest technical solution [2] which implements the chromatographic separation of vapor mixtures using chromatographic column, comprising a housing filled with electrically conductive sorbent, and an auxiliary electrode connected to the source voltage (polarization). This auxiliary electrode is located on the body surface of the column facing the sorbent, and is separated therefrom by a diaphragm made of a material having ionic conductivity, in particular of the ion-exchange resin. As electrically conductive sorbent used activated charcoal SCM with a grain size 50-63 mm.

In the known technical solution of the auxiliary electrode in the chromatographic column is coaxial electrically conductive sorbent. The potential difference created by IU the EBM movement eluent with a partial mixture of sorbents, what is the reason of low efficiency effects of electric field on the separation selectivity of the chromatographic column and accordingly by the amount of degrees of separation of the components.

The difference of this method is that the potential difference creates between the electrodes placed at the ends of the column and in contact with the sorbent made of metal. When this gradient polarizing voltage is directed in the direction of eluent through a chromatographic column or opposite to this direction when changing the polarity of the potential difference. This arrangement of electrodes in a chromatographic column leads to the possibility of effective influence of electric field on the selectivity and accordingly the degree of separation of components.

Another difference of this method is that as electrically conductive sorbent use powdered or granular (e.g., spherical particles) metals exhibiting sorption activity. Such metals may be scandium, zirconium. The modification of the surface structure of these sorbents, form (from scaly or plate or spherical) and size h is e factors provide an opportunity to adjust the density of gas chromatographic columns, what leads to change and specific resistance of the used sorbent in the column. Selected as sorbents metals are sorption and catalytic properties, i.e. have a high surface activity. The metals scandium and zirconium have a low resistivity 5,7610-7MSM and r 4,4110-7OSM respectively, that is, have a high conductivity, characteristic for metals. However, it is the volume or crystalline resistivity of metals. The value of the specific resistance of the layer of powders of these metals in the chromatographic column with regard to grain resistance of the powder particles may vary over a wide range. However due to the small crystal of resistance set by the application of an external electric potential of the surface charge on the particles of the sorbent is proportional to the magnitude of this potential. The coefficient of proportionality depends on the intergranular resistance, that is, shape, specific surface, porosity of the sorbent particles. This dependence of the surface charge of the sorbent particles, which determines its sorption parameters, the magnitude (and sign) the potential difference supplied with nonintel mixture in analytical chromatography and production of high-purity substances of natural and industrial objects in the case of preparative separation.

Example 1. Model vapor mixture of equal volume amounts of chlorinated saturated hydrocarbons: CCl4carbon tetrachloride, l3chloroform and C2H4Cl2dichloromethane syringe with a volume of 1 Ál injected into the gas chromatography column. As sorbent use of metallic zirconium. The particle shape is spherical sorbent. The diameter of the spheres of 0.2-0.4 mm Sorbent is calcined in air at 450oC for one hour and then treated with in hydrochloric acid. Material glass column, internal diameter 3 mm, length 3 meters. At the inlet and outlet ends of the column onto a platinum electrode. The resistance of the sorbent in the column 3,7102Om. The temperature of the column 10oC. the Volumetric rate of the carrier gas helium, 30 ml/min Detector flame ionization. The potential difference applied to the ends of the column, 7,8 kV. These conditions ensure complete separation of the mixture components in the model. The relative retention time of carbon tetrachloride, chloroform and dichloroethane equal to 1:1,7:2,5 respectively. However due to the small interaction with the surface of the sorbent components come in the form of narrow symmetrical peak, which is reflected in the values of the degrees of separation of the components is ode and of chloroform, chloroform and dichloroethane, equal to 2.3 and 1.9, respectively.

Example 2. The separation of components of the same model mixture is performed on a chromatographic column filled with powdered scandium. The sorbent particles with a size of 0.25-0.4 mm have a plate shape. Sorbent previously subjected to washing and dried in vacuum. Filling a glass column with a length of 1.2 m and an inner diameter of 3 mm is carried out in an inert atmosphere. Conditions for the separation of mixtures of similar conditions as in example 1. The relative retention time of carbon tetrachloride, chloroform and dichloroethane, respectively equal to 1:2,3:3,1. The degree of separation of carbon tetrachloride and chloroform, chloroform and dichloroethane equal to 2.7 and 2.1, respectively.

Example 3. Preparative chromatographic separation of a mixture of dimethoxymethane and dichloromethane.

Dimethoxymethane CH3-O-CH2-O-CH3and dichloromethane CL2-CH2-Cl2have similar boiling point equal to 42 and 41oS, respectively. These compounds are extremely difficult to separate extraction methods of distillation and rectification. For the preparative chromatographic razdelnoe continuous chromatographic PTS is selenia these components, but because of their high dissolving ability in the process of separating polluting compounds factions stationary liquid phase.

Separation of the mixture is conducted on a compact annular chromatographic column, which is a modification of the column Barqueta (see UK patent N 1418503, class B 01D, from 24.12.75). In the input devices and output shared components mounted electrodes. As the sorbent used scandium powder with a particle size of 0.4 to 1 mm and a specific surface area of 2.3 m2/year the Total volume of the sorbent in the column reaches a value of 1.4 DM3. Mass feed rate of the mixture with the high volume of sorbent is 250 ml/hour. The electrodes serves voltage of 3.7 kV to the electrode, mounted at the entrance, serves a negative potential). The resistivity of the sorbent in the column is equal to 1.1 Omsm. The total separation efficiency 315 theory.plates/m, the value of WATT of 5.92 see

Thus, this method allows to increase the degree of separation trudnoreshaemyh components of the vapor mixture in 7-10 times in comparison with the prototype.

Literature

1. Ezrez Century A. Garusov A. B. Vigdergauz M. C. Regulation selectivity of chromatography the torki's certificate of the USSR N 1099275, G 01 N 30/60, 1984.

1. The method of chromatographic separation of vapor mixtures, including the introduction of flow element in a chromatographic column filled with electrically conductive sorbent, and creating a potential difference between electrodes placed in the column, characterized in that the potential difference creates between the electrodes placed at the ends of the column and in contact with the sorbent made from metal.

2. The method according to p. 1, characterized in that the quality of metals used zirconium, scandium.

 

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