RU2324173C1 - Method of reception of calibration mixes of volatile components and device for its realisation - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: at a method realisation the noble gas stream continuously contacts to the granulous bed of the stationary phase consisting from put on corpuscles of the solid carrying agent of a low-volatile liquid. Saturation of a stationary phase by vapours of volatile components is carried out to equilibrium concentrations on entry and exit of the flowing system at the temperature exceeding operating temperatures for gained calibration mixes of various compositions. Device consists of noble gas preparations consistently connected blocks, unit of feeding into of a sample with the evaporator, the temperature-controlled tubular flowing system filled with the granulous bed of a stationary phase and the detector. Tubular flowing system is executed, at least, from three consistently connected sections with equal geometrical sizes, first of which connected with the evaporator of unit of feeding into of sample and has a bigger percent of the solid carrying agent impregnating of a low-volatile liquid in comparison with the subsequent. Detector by means of the additional gas crane is connected with exit and entry of tubular flowing system.

EFFECT: reception of calibration mixes of volatile components.

2 cl, 1 dwg, 1 tbl

Description

The invention relates to the field of gas analysis and can be used for calibration of gas analysis equipment, in particular for calibrating gas chromatographic detectors, creating calibration gas-vapor mixtures when developing methods for analyzing environmental objects and in toxicological studies, as well as in various industries where it is necessary to create time-constant concentrations of volatiles in an inert diluent gas.

There is a method of preparing calibration mixtures for gas chromatography, in which the initial volatile substance is fed into the diluent gas stream by bubbling part of the diluent gas stream through the stationary phase, which is a low-volatile liquid in which this starting substance is dissolved [see Pankov A.G., Trubin A.M., Berezkin V.G. et al. Auth. testimonial. USSR No. 603898 // Bull. fig. No. 15 of April 25, 78].

However, the known method does not ensure the constant microconcentration of volatile substances in the flow of diluent gas, since the concentration of the starting materials continuously decreases according to the exponential law, which limits the scope of this method for metrological support of gas analytical measurements.

There is also known a method and apparatus for producing vapor-gas mixtures in which a diluent gas stream is passed through a solution of volatile substances in a low-volatile liquid with a fixed concentration of liquid. The solution container is connected to a mixer, into which a diluent gas is simultaneously supplied. As a result of contact with the liquid solution, the gas stream is saturated to equilibrium concentrations with vapors of volatile substances in accordance with the distribution constant at a constant temperature. After contacting the gas stream with a solution of volatile substances, the depleted part of the liquid solution depleted in volatiles is continuously separated from the vapor-gas stream and the initial solution [see Berezkin V.G., Budantseva M.N. Auth. testimonial. USSR No. 697922 // Bull. fig. No. 42 dated 11/15/79].

A disadvantage of the known method and device is the need to use a significant amount of a solution of volatile substances in a low-volatile solvent, as well as the insufficient accuracy of preparing vapor-gas mixtures by the dynamic method, since the amount of volatile substances recovered is affected by the accuracy of maintaining at a given level both the parameters of the diluent gas stream and the stream liquid solution of volatile substances.

The closest to the claimed invention in terms of essential features is a method for obtaining constant concentrations of volatile compounds in a gas stream, in which the gas stream is saturated to a predetermined equilibrium concentration by successively bubbling contact of the gas stream with at least three fixed portions of a solution of volatile compounds in a low-volatile solvent the concentration of which successively decreases from the first portion of the solution to the next or remains constant except for the first ortsii solution, wherein the concentration of volatile substances above [see. Berezkin V.G., Platonov I.A., Onuchak L.A., Lepsky M.V. RF patent №2213958 from 11.23.01 // Bull. fig. No. 28 of 10/10/03].

Closest to the invention in terms of essential features is a device containing a serially connected inert gas carrier preparation unit, a sample inlet unit with an evaporator, a thermostatic tubular system filled with a granular layer of a stationary phase consisting of particles of a solid adsorbent or an inert solid carrier with a layer of low-volatility fluid and detector [see Devices for chromatography. / K.I. Sakodynsky, V.V. Brazhnikov, A.N. Burov, etc. M .: "Mechanical Engineering", 1973. 368 p.].

However, in the known method and device, there is a significant consumption of initial solutions of volatile substances to obtain a gas stream with constant concentrations of volatile substances for a given time.

The objective of the invention is a more complete use of volatile substances to obtain several calibration mixtures with different concentrations.

This problem is solved due to the fact that in the method for producing calibration mixtures of volatile components, in which the inert gas stream is continuously contacted in a flow system containing at least three portions from the stationary phase with a fixed amount of volatile components, the inert gas being in contact with the granular a layer of a stationary phase consisting of a low volatile liquid deposited on the particles of a solid carrier, and saturation of the stationary phase with pairs of volatile components is carried out to equilibrium concentrations at the input and the outlet of the flow system at a temperature exceeding the operating temperature at which constant concentrations of volatile components in an inert gas stream are obtained for calibration mixtures of various compositions.

This problem is also solved due to the fact that in the device for producing calibration mixtures of volatile components containing inert gas preparation unit connected in series, a sample inlet unit with an evaporator, a thermostatically controlled tubular flow system filled with a granular layer of a stationary phase, consisting of a low-volatile supported particle on a solid carrier fluid, and the detector, and the tubular flow system is made of at least three series-connected sections with the same geometric dimensions and, the first of which is connected to the evaporator unit has a sample input and a greater percentage of impregnation of the solid support low volatile fluid compared with later, and the detector with an additional gas valve is connected both to the output and to the input via pnevmosoprotivlnenie tubular running system.

When solving this problem, a technical result is created consisting in a more complete extraction of volatile components from the stationary phase due to a significant increase in the contact surface area of the inert gas with the granular layer of the stationary phase. In addition, by setting the various operating temperatures of the tubular flow system to be lower than the saturation temperature of the sorbent with volatile components, several calibration mixtures with different but constant in time concentrations of volatile components are obtained, and the use of a larger percentage of impregnation of a solid support with a low-volatile liquid in the first section increases the time interval maintaining constant concentrations of volatile components in the inert gas stream by feeding the second and third sections of the tubular prot ary system of volatile components from the first section having the larger diameter.

This allows us to conclude that the claimed invention is interconnected by a single inventive concept.

An example of a specific implementation of the method and device for its implementation

The drawing schematically shows a device for producing calibration mixtures of volatile components. The device comprises: a line 1 for supplying an inert gas, an inert gas preparation unit 2, a sample inlet unit 3 with an evaporator 4, a thermostat 5 for maintaining a constant temperature in the tubular flow system, consisting of a first section 6 connected in series with a larger percentage of impregnation of a solid carrier of low-volatility liquid than the second 7 and third section 8, switching the gas valve 9 into two positions, with which the detector 10 is connected to the output of the third section 8 of the tubular flow system (position (a) is on) or to ode first tubular section 6 through the flow system pnevmosoprotivlenie 11 (position (b) is included). The output of the detector 10 is connected to line 12 for the flow of calibration mixtures.

The proposed device operates as follows.

Pre-saturate the sorbent in the tubular flow system with volatile components to equilibrium concentrations or to "slip" at a temperature T _us exceeding the operating temperature of the device. For this, the mixture of volatile components is repeatedly dosed in certain portions to the sample inlet 3 with the evaporator 4. Then, the concentration of volatile components at the outlet of the tubular flow system (gas valve 9 is in position (a)) and at the entrance to the tubular flow system (gas the tap is in position (b)). Saturation is carried out until the concentration of volatile components at the outlet and inlet of the tubular flow system is equalized. Pneumatic resistance 11 sets the same gas flow in the detector 10 in both positions of the gas valve 9. After saturation of the sorbent with volatile components in the thermostat 5 set the first operating temperature of the device T ₁ <T _us . Withstand sections 6, 7 and 8 of the tubular flow system at a temperature T ₁ is not less than 15-20 minutes and the system was purged with pure inert gas to reach a constant concentration of the volatile components at the output of the third section 8 of the tubular flow indications detector system 10. When the temperature T ₁ is obtained the first calibration mixture with concentrations of volatile components With ₁ .

After the first use of the calibration mixture, for example, to construct calibration curve of the test gas analyzer 5 is set in a thermostat second operating temperature T _2> T _1. A second calibration mixture is obtained with concentrations of volatile components C ₂ > C ₁ . The operating temperature is increased in the range from T ₁ to T _us , depending on the receipt of the required number of calibration mixtures with different concentrations of volatile components.

The material balance equations for a flowing tubular system, conditionally consisting of three sections 6, 7 and 8, through which an inert gas stream is passed, have the form [see Forina M. // Annali di Chimica, 1975. V. 65. P.49]:

and

и

- количество летучего вещества, поступившего из секции 6 в секцию 7 и из секции 7 в секцию 8 с объемом инертного газа-разбавителя dV_G соответственно;Where

and

- the amount of volatile matter received from section 6 to section 7 and from section 7 to section 8 with an inert diluent gas volume dV _G, respectively;

и

- количество летучего вещества, извлекаемого из секций 7 и секции 8 объемом инертного газа-разбавителя dV_G соответственно;

and

- the amount of volatile matter extracted from sections 7 and section 8 with an inert diluent gas volume dV _G, respectively;

dn _{L (7)} -dn _{G (7)} and dn _{L (8)} -dn _{G (8)} - change in the amount of volatile matter in the liquid and gas phases in sections 7 and 8, respectively;

dV _G = F · dτ is the volume of diluent gas; F is the inert gas space velocity; dτ is the transmission time of the diluent gas volume dV _G.

Wherein

- константа распределения летучего вещества между жидкой и газовой фазами (константа фазового распределения жидкость-пар при T=const).Where

- constant distribution of volatile matter between the liquid and gas phases (constant phase distribution of liquid-vapor at T = const).

An experimental evaluation of the implementation of the proposed and known methods for producing calibration mixtures of volatile components in an inert gas stream was carried out using five calibration mixtures with different but constant in time concentrations of toluene and octane:

Mixture 1: T = 25 ° C,

Mixture 2: T = 50 ° C,

Mixture 3: T = 60 ° C,

Mixture 4: T = 70 ° C,

Mixture 5: T = 80 ° C,

In this case, the inert nitrogen gas flow rate (osch) was equal to F = 10 cm ³ / min.

A comparison of the known and proposed methods was carried out at the same times τ to maintain a constant concentration of volatile components in an inert gas stream.

для различных градуировочных смесей при соответствующей температуре Т.In the known method, the nitrogen stream was saturated to the specified equilibrium concentrations for each of the five calibration mixtures at the corresponding temperatures of 25, 50, 60, 70 and 80 ° C by successive bubbling contact of nitrogen with three fixed portions of a liquid solution of volatile substances in squalane. The amount of solution in each bubbler is 20 cm ³ , or taking into account the density of squalane, the total mass in three bubblers is W _p = 48.5 g. Moreover, the concentration of each volatile substance in the first bubbler was 0.15 mg / cm ³ , and in the second and third bubblers 0.12 mg / cm ^3, and the steam-gas stream from the first bubbler fueled solutions second and third bubblers for their equilibrium concentration in the nitrogen stream at the outlet of the bubbler in a third range

for various calibration mixtures at the corresponding temperature T.

In the proposed method, the saturation of the nitrogen stream with volatile components to the specified equilibrium concentrations at the appropriate temperature was carried out by contacting nitrogen with a granular layer of sorbent. The sorbent was made on the basis of a solid inert carrier of diatomite brick with a grain size of 0.2-0.25 mm, modified with 0.5 wt.% Resin PN-15. Squalane in an amount of 30 wt.% (First portion) and 40 wt.% (Second portion) were applied to two portions of the solid support from the chloroform solution. After removing the solvent, the prepared sorbent of the second portion was filled into the first section 6 of the tubular flow system, and the sorbent of the first portion was filled into the second 7 and third 8 sections of the tubular flow system. Sections 6, 7 and 8 had an internal diameter of 15 mm and a length of 80 mm. The first section 6 with a high percentage of impregnation with squalane (40 wt.%) Played the role of the first bubbler and provided the necessary recharge with volatile components of the second and third sections of the tubular flow system. After filling with the sorbent, the tubular flow system was conditioned at 150 ° C in thermostat 5 for five hours with a nitrogen flow rate of 10 cm ³ / min in the system. After conditioning, a vaporizer 4, made in the form of a bubbler, was placed with a 20 cm mixture of volatile components of toluene and octane with the same concentrations and the sorbent was saturated with a nitrogen sparge rate of 15 cm ³ / min in a flow system at a temperature of 100 ° C exceeding the working temperatures for obtaining calibration mixtures. Saturation was carried out until the concentration of volatile components at the outlet of the third section 8 and at the entrance to the first section 6 of the flow system became the same. The concentration was monitored by the signal of the concentration detector 10, periodically switching the gas valve 9 from position (a) to position (b). The mass of the sorbent in the flow system to a saturation of 37.94 g, the weight of squalane W _p = 8.75 g. After saturation of the sorbent with vapors of toluene and octane, an experiment was carried out to obtain five calibration mixtures with different, but time-constant, concentrations of volatile components, setting the corresponding temperature in thermostat 5.

Calibration mixtures in line 12 were obtained using nitrogen (os) at a space velocity of F = 10 cm ³ / min. The results of the experiment are presented in the table "Comparative data of the experimental verification of the known and proposed methods."

Comparative data of experimental verification of the known and proposed methods Calibration number
mixtures and temperature, ° С

, мкг/см³

μg / cm ³ τ, hour The consumed solution W _p , g toluene octane toluene octane Known method The proposed method 1. T = 25 0,068 0,034 9.0 18.0 2. T = 50 0.147 0,077 7.5 13.5 3. T = 60 0.256 0.181 7.0 11.5 48.5 8.75 4. T = 70 0.430 0.234 5,0 10.0 5. T = 80 0.580 0.356 4,5 8.3

As can be seen from the data in the table, the proposed method provides a more efficient use of the solution of volatile substances to obtain calibration mixtures with different content of volatile components in the nitrogen stream at a given time τ.

Using the proposed method for producing calibration mixtures of volatile components and a device for its implementation allows you to:

1. Significantly reduce the consumption of a solution of volatile substances in a low-volatile solvent to obtain the same amount of volatile components in an inert gas stream with constant concentrations by increasing the efficiency of sorption and desorption processes when an inert gas contacts a granular sorbent layer having a significant surface area.

2. Significantly simplify the operation of saturation of the sorbent with volatile components, since the need for the manufacture of solutions by volume or weight methods is eliminated.

3. Repeatedly use a tubular flow system with a sorbent to obtain new vapor-gas mixtures by repeated equilibrium saturation of the sorbent with vapors of volatile components.

4. To organize the metrological support of gas analytical and chromatographic measurements during critical analytical and physico-chemical studies.

Claims (2)

1. A method of obtaining calibration mixtures of volatile components, in which the inert gas stream is continuously contacted in a flow system containing at least three portions of the stationary phase with a fixed amount of volatile components, characterized in that the inert gas is in contact with the granular layer of the stationary phase, consisting from a low volatile liquid deposited on the solid carrier particles, and the stationary phase is saturated with vapor of volatile components to equilibrium concentrations at the inlet and outlet of the flow system at temperatures exceeding operating temperatures corresponding to constant concentrations of volatile components in an inert gas stream for calibration mixtures of various compositions. 2. A device for producing calibration mixtures, containing a serially connected inert gas preparation unit, a sample inlet unit with an evaporator, a thermostatically controlled tubular flow system filled with a granular layer of a stationary phase, consisting of a low-volatile liquid deposited on a solid carrier particles, and a detector, characterized in that the flow system is made of at least three series-connected sections with the same geometric dimensions, the first of which is connected to the evaporator In order to enter the sample, it has a higher percentage of impregnation of the solid support with a low-volatile liquid compared to the subsequent ones, and the detector is connected to the outlet and through pneumatic resistance to the inlet of the tubular flow system using an additional gas valve.