RU2194275C1 - Process of production of calibration mixtures of polar low- volatile organic substance in atmosphere - Google Patents

Abstract

FIELD: preparation of calibration mixtures. SUBSTANCE: characteristic feature of process consists in deposition of solid and liquid substances on surface of solid carrier in the form of multicomponent mixture with practically ideal properties or with positive deviations from Raoult's law and mass share of weighed-out substances from 20 to 40 per cent and in setting it in thermostated batcher coming in the form of chromatographic column. Temperature in column should not exceed temperature of thermal-oxidation decomposition of weighed-out substances. Gas carrier of constant temperature is passed through batcher. Masses of individual compounds in multicomponent mixture of polar low-volatile organic substances in batcher at start and in process of production of calibration mixture are established by injection of microdose of benzene, air and normal alkanes C₁-C₁₀ into batcher connected to thermal conductivity detector. EFFECT: increased precision in preparation of microconcentrations of multicomponent mixtures of polar low-volatile organic substances in air atmosphere for calibration of gas analyzing devices. 1 cl, 1 dwg, 3 tbl

Description

 The invention relates to the calibration of measuring instruments for monitoring air pollution, and in particular to methods for producing multicomponent calibration mixtures of microconcentrations of polar low-volatile organic substances in a gaseous medium, and can be used for comparative evaluation of methods for analyzing impurities in air, determining the degree of concentration in preparing an air sample for analysis and to normalize the metrological characteristics of gas analytical instruments for measuring the mass concentration of toxicants in ear working area and the air populated areas.

A known method of creating calibration mixtures of low volatiles, which provides for the supply of fluid using a variable volume tank to the evaporator and then the gas mixture in the chromatograph. [Auth. USSR certificate 622006, 1978]
The known method provides for the evaporation of a liquid with a constant volumetric flow rate by supplying it to the evaporator using mechanical devices. The limited contact surface between the liquid and the carrier gas does not provide a high degree of saturation of the air with the components and does not exclude the possibility of their thermal decomposition.

The closest to the claimed technical essence and the achieved result is a dynamic method of creating calibration mixtures in a gas medium, which consists in applying a volatile liquid component to the surface of a polymer ampoule, placing it in a dispenser, passing a gas stream with a volume flow of 2-10 dm ³ / h at preset thermostating temperature for a long time, with subsequent determination of the flow rate of the substance by periodically weighing the ampoule 24-48 hours after the diffusion stream reaches the hospital arry mode. The concentration of substances such as propionic acid, terpenes, hydrocarbons, is determined by the ratio of the mass loss of the ampoule per unit time at the operating temperature of the thermostat to the flow rate of the carrier gas with an error of 5-10% (Hermann G. - Luftreinhalt. Ind., Leipzig, 1976, s.233). The method requires the use of a high temperature thermostating to create the necessary concentrations of low-volatile substances in the air and certification of the calibration mixture by an independent method due to the insufficient consumption for accurate weighing of the substance, which does not allow to obtain calibration mixtures that contain microconcentrations of several components.

 The objective of the invention is to increase the accuracy of the preparation of microconcentrations of multicomponent mixtures of polar low-volatile organic substances in air for the calibration of gas analytical instruments.

 The problem is solved by applying samples of standard polar low-volatile organic substances (PMOV), which, when mixed, give practically ideal systems or systems with a significant positive deviation from Raoult's law, on the surface of an inert solid carrier with particle sizes of 0.2-0.5 mm and the minimum distribution coefficient in the hexane-benzene system. The particle size range of an inert solid carrier of 0.2-0.5 mm is due to the following factors: an increase in particle size of more than 0.5 mm will lead to a decrease in the specific surface of the carrier and the amount of applied dosing substance, and a decrease in particle size of less than 0.2 mm will increase hydraulic resistance of the dispensing column and the need to create a greater pressure of the carrier gas stream. The choice of a solid inert sorbent with a minimum hexane - benzene distribution was carried out to reduce the error in the analysis of the amount of PMO calibration mixture due to benzene adsorption on carrier active centers unoccupied by polar organic molecules, when the content of the multicomponent mixture is less than 5% at the end of dosing of the calibration mixture.

To do this, weighed portions are introduced into the flask containing such an amount of solid inert carrier that corresponds to the volume of the dispenser, made in the form of a thermostated chromatographic column with a size of 100-300 mm and an internal diameter of 3-4 mm, and mixed using an electric vibrator. The prepared multicomponent stationary phase is quantitatively transferred to the dispenser using the vacuum of a water-jet pump. The dispenser is thermostated at a temperature (up to 100 ^o C), which allows to obtain a multicomponent stationary phase in the liquid state and the required concentration range of PMW in the air, the dosed substances are evaporated in a gas stream from the surface of the solid carrier with the stationary phase applied. The carrier gas passes through the dispenser, is saturated with the vapors of the multicomponent mixture and is fed into the mixer for dilution, where a cleaned and stabilized air stream is supplied at a known speed. The mass of the individual components of the stationary phase in the dispenser at the beginning of purging and in the process of obtaining the calibration mixture is controlled by determining the retained volume of benzene relative to air and C ₁ -C ₁₀ alkanes of normal structure, the number of which corresponds to the number of components to be dosed. The large surface on which the stationary phase in the chromatographic column is distributed, the increased volatility of the components in the prepared stationary phase, and a small helium consumption (5-60 cm ³ / min) ensure high saturation of the gaseous medium with dosed components, which leads to the formation of an equilibrium PMOV concentration and constant mass flow components from the dispenser.

 The drawing shows a flowchart of a method for producing calibration mixtures of PMOV in air.

The carrier gas is sent at a constant and adjustable speed using a rotameter 1 to the dispenser 2, made in the form of a chromatographic column, which is placed in the thermostat 3. The dispenser is filled with a solid inert carrier, on the surface of which a multicomponent dosing mixture is distributed. In the thermostat maintain a temperature of up to 100 ^o C, not exceeding the temperature of the thermo-oxidative degradation of the dosed substances. The carrier gas after the dispenser enters the distributor, with which you can direct the gas flow to measure the volumetric velocity with a soap-and-water meter 5, or to determine the retention time of benzene and other alkanes in the detector 4, or in the mixer 6, where the carrier gas is mixed in a certain ratio with air cleared of organic impurities.

 To determine the mass of the dosed components, a mixture of benzene, air, and other alkanes was injected in approximately equal proportions into the dosing device using a microsyringe or dosing valve 7 in an amount of 2-5 μl, which ensured a state close to infinite dilution of the hydrocarbon in the components of the stationary phase and did not change its composition. A further decrease in the sample size of benzene, air, and other alkanes had practically no effect on the amount of benzene retained.

 A thermal conductivity detector was used as a detector, and helium or other gases inert to the dosed compounds were used as a carrier gas to determine the mass of components in the dispenser.

The pressure at the inlet to the column was 800-900 mm Hg, and at the outlet of the column it was equal to atmospheric pressure. The carrier gas velocity was measured by a soap-film volumetric flow meter and was 5-60 cm ³ / min.

 The retention time of benzene and other alkanes was measured by the chromatogram from the moment the peak of air (alkane) exited until the benzene peak exited.

где F - объемная скорость газа-носителя;
τ - время удерживания бензола относительно воздуха или других алканов;
Р - давление на выходе из колонки;
P₀ - давление на входе в колонку;
РН₂О - давление пара воды при температуре пенного измерителя скорости газа-носителя;
T_f - температура пенного измерителя скорости газа-носителя, К.The retention volumes of benzene relative to air and other alkanes in the analyzed stationary phase of the compound were calculated by the equation

where F is the space velocity of the carrier gas;
τ is the retention time of benzene relative to air or other alkanes;
P is the pressure at the outlet of the column;
P ₀ - pressure at the inlet to the column;
RN ₂ O - water vapor pressure at the temperature of the foam meter for the velocity of the carrier gas;
T _f is the temperature of the foam meter for the velocity of the carrier gas, K.

где Δτ и Δt_ск - среднеарифметические ошибки определения времени удерживания углеводорода и времени прохождения мыльной пленки между метками пенного измерителя при определении скорости газа-носителя;
ΔT_f - ошибка определения температуры пенного измерителя скорости потока газа-носителя;
Δp и Δp_o - ошибки определения давления на входе и выходе из колонки соответственно.

where Δτ and Δt _ck are the arithmetic errors of determining the retention time of the hydrocarbon and the transit time of the soap film between the marks of the foam meter when determining the velocity of the carrier gas;
ΔT _f is the error in determining the temperature of the foam meter for the flow rate of the carrier gas;
Δp and Δp _o - errors in determining the pressure at the inlet and outlet of the column, respectively.

The column temperature is maintained with an accuracy of ± 0.1 ^o C, while ΔP $\genfrac{}{}{0ex}{}{\text{0}}{\text{i}}$ ≈ ± 0.2 mm Hg As a result, the error in determining the retention volumes in the stationary phase is 2–4% (Table 1).

 The calibration of multicomponent calibration mixtures of PMOV was carried out on LHM-8 MD chromatographs available for sanitary and hygienic laboratory studies, equipped with thermal conductivity detectors. A dispenser in the form of a chromatographic column with a solid carrier and a mixture of polar low-volatile organic compounds deposited on the surface of the particles of a solid carrier layer of a stationary liquid phase, placed in the thermostat of the chromatograph and set the desired batch temperature.

Then helium is supplied with a predetermined speed of 5 to 60 cm ³ / min into the gas lines of the chromatograph, and the required amount of the test mixture of benzene, air and other alkanes is injected using a metering valve or a syringe depending on the sensitivity of the katharometer (thermal conductivity detector).

где l - расстояние между пиком воздуха (вводом пробы) или алкана и максимумом концентрации бензола, мм;
F_o - объемный расход газа-носителя, см³/с;
ν - скорость движения диаграммной ленты, мм/с;
j - поправка на сжимаемость газа-носителя.On the obtained chromatogram, the retention time of benzene with respect to hexane, other alkanes and air on the applied PMOV mixture is determined by measuring the distance between the peak of air or hexane and the maximum concentration of benzene. The retention volumes of benzene are calculated with respect to hexane (alkanes) and air according to the formula

where l is the distance between the peak of air (sample inlet) or alkane and the maximum concentration of benzene, mm;
F _o - volumetric flow rate of the carrier gas, cm ³ / s;
ν is the speed of movement of the chart tape, mm / s;
j is the correction for the compressibility of the carrier gas.

An analysis of the quantitative composition of polar low-volatile organic compounds in the dispenser at the beginning of the preparation of calibration mixtures is carried out according to the calibration dependence of the logarithm of the benzene retention volume on the mass concentration of the components or a mixture of benzene, air and such a number of C ₁ -C ₁₀ alkanes, which corresponds to the number of dosed substances, is introduced. The volumes of benzene retention relative to air and alkanes are determined, after which the initial masses of the dosed substances are calculated.

The quantitative composition of polar low-volatile organic compounds in the dispenser during the preparation of calibration mixtures and the change in the mass of the components are determined by introducing a mixture of benzene, air and the same amount of C ₁ -C ₁₀ alkanes. Why measure the retention volumes of benzene relative to air and alkanes and calculate the final mass of the dosed substances.

 The method is simple to implement, does not require certification of multicomponent calibration concentrations by an independent analytical method and allows to obtain calibration mixtures that contain microconcentrations of several components.

 The presented set of claimed features provides a solution to the problem of the invention: applying a mixture of PMOV, which is a liquid-phase system whose properties are almost ideal or deviate from Raoult's law in a positive way, allows you to obtain the required range of microconcentrations of a multicomponent mixture at low temperatures, which prevents decomposition of the components during dosing, and therefore, increases the reliability of the quantitative analysis of individual polar low-volatile organic compounds. Dilution of the gas-vapor mixture with air in the range of 0.1-10.0 maximum permissible concentrations in the mixer allows you to get a calibration air mixture with the required concentration of components. Measurement of benzene retention volumes relative to air and such a number of alkanes that corresponds to the number of dosed components allows determining the quantitative composition of individual polar low-volatile organic compounds at the beginning and end of dosing without weighing, which makes it possible to measure the mass of each component during the operation of a parodynamic installation to create multicomponent calibration mixtures of MPOV in the air.

 The proposed method is illustrated by the following examples.

 Example 1

 Obtaining a calibration (almost perfect) mixture of dimethylacetamide (DMAA) and N-methylcalrolactam (MK) in air.

 A portion of DMAA weighing 609.3 mg and a portion of MK weighing 614.4 mg are applied to 5,000 g of solid support with a minimum distribution coefficient for the hexane-benzene system of the type of silanized chromosorb with a particle size of 0.25-0.36 mm by mixing using an electric vibrator. The prepared stationary phase is quantitatively transferred to a dispenser made in the form of a thermostated chromatographic column with a size of 100-300 cm and an internal diameter of 3-4 mm using a vacuum water-jet pump, after which both ends of the dispenser are closed with a small amount of glass wool purified from organic impurities. When transferring an inert solid carrier with a liquid multicomponent mixture applied, there always remains a certain amount of a finely dispersed fraction of the prepared sorbent (not more than 0.5 mg), which must be taken into account in comparative tests of the method for producing multicomponent calibration mixtures of MPOV in air and a single-component calibration mixture.

 The amount of solid sorbent coated with a multicomponent liquid phase is controlled both by the required concentration of polar low-volatile organic matter in the air and by the set operating time of the installation to obtain calibration mixtures, and is substantially independent of other factors, therefore, quantitative carrier transfer is necessary only if analysis carried out by the weight method for one component.

The dispenser is placed in a thermostat of an LKhM-8 MD chromatograph (equipped with a thermal conductivity detector) in which a constant temperature of 30 ± 0.1 ^° C is maintained. A stabilized inert carrier gas stream is fed into the dispenser, using helium at a speed of 10 cm ³ / min The carrier gas passes through the dispenser, is saturated with vapors of an almost perfect mixture of DMAA and MK components, and goes to the mixer for dilution, where a cleaned and stabilized air stream is supplied at a speed of 10 dm ³ / min.

 At the beginning of the dispenser operation, the initial masses of the DMAA and MK components are checked, for which a carrier gas stream is supplied from the dispenser to the detector for thermal conductivity, and 1-5 μl of a mixture of air, hexane and benzene are introduced in approximately the same ratio.

 On the obtained chromatogram, the retention time of benzene with respect to hexane and air is determined for the applied mixture of dosed components by measuring the distance between the peak of air or hexane and the maximum concentration of benzene. The retention volumes of benzene are calculated with respect to hexane and air according to the formula 3.

The benzene retention volume relative to air V ⁰ _{g (b / c)} was 1142.0 ml, and the benzene retention volume relative to hexane V ⁰ _{g (b / g) was} 1033.5 ml. Since the mixture of DMAA and MK is practically ideal, the retention volume of benzene relative to air is additive and the mass fraction of DMAA at the beginning of dosing is 49.8%.

 The flow of carrier gas from the dispenser to the mixer is switched and a calibration mixture of DMAA and MK in air is obtained during the entire working time of the parodynamic installation. After a predetermined (6-8 h) dosing time, the change in the mass of the individual components in the dispenser is determined. To do this, switch the flow of helium from the dispenser to the detector for thermal conductivity, introduce a mixture of air, hexane and benzene, measure the retention time of benzene relative to air and hexane from the chromatogram and calculate the final retention volumes of benzene according to the above formula 3.

The final volume of benzene retention relative to air V ^to _{g (b / c)} was 1110.6 ml, and the volume of benzene retention relative to hexane V ^to _{g (b / g)} was 1005.3 ml.

To determine the mass of the components that form the ideal system and transferred to the air due to diffusion, we solve the system of the following equations:
V ^to _{g (b / g)} - V ⁰ _{g (b / g)} = V _{gDM AA (b / g)} • x + V _{gMK (b / g)} • y; (4)
V ^to _{g (b / c)} - V ⁰ _{g (b / c)} = V _{gDM AA (b / c)} • x + V _{gMK (b / c)} • y, (5)
where x is the change in the mass of DMAA as a result of diffusion, mg;
y - change in the mass of MK in the dispenser, mg;
V _{gDMA A (b / g)} is the specific volume of benzene retention relative to hexane in DMAA, ml;
V _{gMK (b / g)} is the specific volume of benzene retention relative to hexane in MK, ml;
V _{gDMA A (b / c)} is the specific volume of benzene retention relative to air in DMAA, ml;
V _{gMK (b / c)} is the specific volume of benzene retention relative to air in MK, ml.

 The values of the specific retention volumes of benzene in the dosed components are given in table 1.

где Δm - изменение массы индивидуального компонента в дозаторе, мг;
Q_v - суммарная объемная скорость газовоздушной смеси, м³/мин;
τ - время дозирования градуировочной многокомпонентной смеси, мин.Substituting the obtained experimental data, we have a system of two equations:
0.67 • x + 1.018 • y = 28.2;
0.748 • x + 1.117 • y = 31.4
Solving the system, we obtain a change in the mass of DMAA as a result of diffusion of m _{DMAA of} 36.0 mg, and a change in the mass of MK in the dispenser m _MK is 4.0 mg. Then the concentration of the components of the calibration mixture in the air is calculated by the formula

where Δm is the change in mass of the individual component in the dispenser, mg;
Q _v - the total space velocity of the gas-air mixture, m ³ / min;
τ is the dosing time of the calibration multicomponent mixture, min

The concentration in the air of DMAA was 10.0 mg / m ³ and the concentration of MK was 1.11 mg / m ³ .

 Example 2

 Obtaining a binary calibration mixture with a positive deviation from the Raoult law of malonic acid dimethyl ether (DMM) and diethylene glycol (DEG) in air.

A DMM sample weighing 750.0 mg and a DEG sample weighing 750.0 mg are weighed in a container into which 5,000 g of solid support are then added with a minimum distribution coefficient to the hexane-benzene system of the type of silanized chromosorb with a particle size of 0.25-0.36 mm and mixed with an electric vibrator. The prepared stationary phase is quantitatively transferred to a dispenser made in the form of a thermostated chromatographic column with a size of 100-300 cm and an internal diameter of 3-4 mm using a vacuum water-jet pump, after which both ends of the dispenser are closed with a small amount of glass wool purified from organic impurities. The dispenser is placed in a thermostat of an LKhM-8 MD chromatograph (equipped with a thermal conductivity detector) in which a constant temperature of 30 ± 0.1 ^° C is maintained. A stabilized inert carrier gas stream is fed into the dispenser, using helium at a speed of 10 cm ³ / min The carrier gas passes through the dispenser, is saturated with vapors of a mixture of DMM and DEG components, which is a system with a positive deviation from Raoult law and is diluted into the mixer, where a cleaned and stabilized air stream is supplied at a speed of 10 dm ³ / min.

 The initial masses of the DMM and DEG components in the dispenser at the beginning of helium purging are determined by the calibration dependence of the logarithm of the benzene retention volume relative to air, for which a carrier gas stream from the dispenser is fed into the detector for thermal conductivity and 1-5 μl of a mixture of air, hexane and benzene are introduced into approximately same ratio.

 On the obtained chromatogram, the retention time of benzene with respect to hexane and air on the applied mixture of dosed components is determined by measuring the distance between the peak of air or hexane and the maximum concentration of benzene. The retention volumes of benzene are calculated with respect to hexane and air according to the formula 3.

The benzene retention volume relative to air V ⁰ _{g (b / c)} was 478.6 ml, and the benzene retention volume relative to hexane V ⁰ _{g (b / g) was} 446.6 ml. Since the mixture of DMM and DEG represents a system with a significant deviation from Raoult's law, the benzene retention volume relative to air is not additive and the mass fraction of DMM according to the calibration curve at the beginning of dosing is 49.8%.

 The flow of carrier gas from the dispenser to the mixer is switched and a calibration mixture of DMM and DEG in air is obtained during the entire working time of the parodynamic installation. After a predetermined dosing time (24 h), the change in the mass of the individual components in the dispenser is determined. To do this, switch the flow of helium from the dispenser to the detector for thermal conductivity, introduce a mixture of air, hexane and benzene, measure the retention time of benzene relative to air and hexane from the chromatogram and calculate the final retention volumes of benzene according to the above formula 3.

The final retention volume of benzene relative to air V ^to _{g (b / g)} was 436.5 ml, and the volume of benzene retention relative to hexane V ^to _{g (b / g)} was 406.3 ml. From the calibration dependence of the logarithm of the benzene retention volume relative to air on the mass fraction of components, we determine the change in benzene retention volumes relative to air and hexane.

To determine the mass of the components that make up the system with a positive deviation from Raoult law, which transferred to the air due to diffusion, we solve the system of the following equations:
V ^to _{g (b / g)} -V ⁰ _{g (b / g)} = V _{g DDMM (b / g)} • x + V _{g DEG (b / g)} • y;
V ^to _{g (b / c)} -V ⁰ _{g (b / c)} = V _{g DDMM (b / c)} • x + V _{g DEG (b / c)} • y,
where x is the change in mass of DMM as a result of diffusion, mg;
y - change in the mass of DEG in the dispenser, mg,
V _{gDMM (b / g)} is the specific volume of benzene retention relative to hexane in DMM, ml;
V _{g DEG (b / g)} is the specific volume of benzene retention relative to hexane in DEG, ml;
V _{gDMM (b / c)} is the specific volume of benzene retention relative to air in DMM, ml;
V _{g DEG (b / c)} - specific volume of benzene retention relative to air in DEG, ml.

 The values of the specific retention volumes of benzene relative to air and hexane in the dosed components are given in table. 2.

Substituting the obtained experimental data, we have a system of two equations:
0.5956 • x + 0.2396 • y = 48.0;
0.6325 • x + 0.25 • y = 50.93
Solving the system, we obtain a change in the mass of DMM as a result of diffusion of m _DMM - 80.4 mg, and a change in the mass of DEG in the meter m _DEG - 4 mg. Then the concentration of the components of the calibration mixture in the air was calculated by the formula 6. The concentration of DMM in the air was 5.57 mg / m ³ and the concentration of DEG was 0.00236 mg / m ³ .

 Example 3

 Obtaining a triple calibration mixture with a positive deviation from Raoult law of diethyl sulfoxide (DESO), thiophan sulfoxide (TCO) and N-methylcaprolactam (MK) in air.

A DESO weighing 495.7 mg is weighed, a TESO weighing 499.0 mg and a MK weighing 512.7 mg are weighed in a container into which 5,000 g of solid support is then added with a minimum distribution coefficient to the hexane-benzene system of the type of silanized chromosorb with particle size 0.25-0.36 mm and mixed with an electric vibrator. The prepared stationary phase is quantitatively transferred to a dispenser made in the form of a thermostated chromatographic column with a size of 100-300 cm and an internal diameter of 3-4 mm using a vacuum water-jet pump, after which both ends of the dispenser are closed with a small amount of glass wool purified from organic impurities. The dispenser is placed in a thermostat of an LKhM-8 MD chromatograph (equipped with a thermal conductivity detector) in which a constant temperature of 30 ± 0.1 ^° C is maintained. A stabilized inert carrier gas stream is fed into the dispenser, using helium at a speed of 10 cm ³ / min The carrier gas passes through the dispenser, is saturated with vapors of a ternary mixture of components DESO, TCO and MK, which is a system with a positive deviation from Raoult law, and is diluted into the mixer, where a cleaned and stabilized air stream is supplied at a speed of 10 dm ³ / min.

 The initial masses of the DESO, TCO, and MK components in the batcher at the beginning of helium purging are determined by the calibration dependence of the logarithm of the benzene retention volume relative to air, hexane, and heptane in a ternary diagram, for which a carrier gas stream is supplied from the batcher to the detector by thermal conductivity and 1-5 μl of a mixture of air, hexane, heptane and benzene in approximately the same ratio.

 On the obtained chromatogram, the retention time of benzene with respect to hexane and air on the applied mixture of dosed components is determined by measuring the distance between the peak of air, hexane, heptane and the maximum concentration of benzene. The retention volumes of benzene are calculated with respect to hexane, heptane and air according to the above formula 3.

The initial volume of benzene retention relative to air V ⁰ _{g (b / c)} was 1502.0 ml, the initial volume of benzene retention relative to hexane V ⁰ _{g (b / g) was} 1401.1 ml, the initial volume of retention relative to heptane 1252.8 ml Since the mixture of DESO, TCO and MK represents a system with a significant deviation from Raoult law, the volume of benzene retention relative to air is not additive and the mass fraction of DESO according to the calibration dependence at the beginning of dosing is 32.9%, TCO 33.1% and MK 34.0% .

 The carrier gas flow is switched from the dispenser to the mixer and a calibration mixture of DESO, TCO, and MK is obtained in air during the entire working time of the dynamic setup. After a predetermined dosing time (24 h), the change in the mass of the individual components in the dispenser is determined. To do this, switch the flow of helium from the dispenser to the detector for thermal conductivity, introduce a mixture of air, hexane, heptane and benzene, measure the retention time of benzene relative to air, hexane and heptane from the chromatogram and calculate the final retention volumes of benzene relative to air and alkanes according to the above formula 3.

The final retention volume of benzene relative to air V ^to _{g (b / c)} was 1465.0 ml, the retention volume of benzene relative to hexane V ^to _{g (b / g)} was 1370.3 ml, the final retention volume of benzene relative to heptane 1231.3 ml From the calibration curve of the logarithm of the benzene retention volume relative to air from the mass fraction of components, we determine the change in benzene retention volumes relative to air, hexane and heptane.

To determine the mass of the components that make up the system with a positive deviation from Raoult law, which have passed into the air due to diffusion, we solve the system of the following equations:
V ^to _{g (b / g)} -V ⁰ _{g (b / g)} = V _{g DEE СО (b / g)} • х + V _{gТСО (b / g)} • у + V _{gMK (b / g)} • z;
V ^to _{g (b / gt)} -V ⁰ _{g (b / gt)} = V _{g DEE CO (b / gt)} • x + V _{gT CO (b / gt)} • y + V _{gMK (b / gt)} • z;
V ^to _{g (b / c)} -V ⁰ _{g (b / c)} = V _{g Д ЭСО (b / c)} • х + V _{gТСО (b / c)} • у + V _{gMK (b / c)} • z,
where x is the change in DESO mass as a result of diffusion, mg;
y is the change in the mass of TCO in the dispenser, mg;
z — change in the mass of MK as a result of diffusion, mg;
V _{g Д ЭСО (b / g)} - specific volume of benzene retention relative to hexane in DESO, ml;
V _{g TCO (b / g)} is the specific volume of benzene retention relative to hexane in TCO, ml;
V _{gMK (b / g)} is the specific volume of benzene retention relative to hexane in MK, ml;
V _{gDE DE (b / gt)} - specific volume of benzene retention relative to heptane in DESO, ml;
V _{gT СО (b / gt)} - specific volume of benzene retention relative to heptane in TCO, ml;
V _{gMK (b / gt)} is the specific volume of benzene retention relative to heptane in MK, ml;
V _{g DE CO (b / c)} is the specific volume of benzene retention relative to air in DESO, ml;
V _{gТСО (b / c)} is the specific volume of benzene retention relative to air in ТСО, ml;
V _{gMKG (b / c)} is the specific volume of benzene retention relative to air in MK, ml.

 The values of the specific retention volumes of benzene relative to air, hexane and heptane in the dosed components are given in table. 2.

Substituting the obtained experimental data, we have a system of three equations
0.9365 • x + 0.8491 • y-1.117 • z = 23.7;
0.8755 • x + 0.8l79 • y + 1.018 • z = 21.7;
0.7787 • x + 0.7758 • y + 0.8697 • z = 15.4
Solving the system, we got a change in the mass of DESO as a result of diffusion of 2.8 mg, a change in the mass of TCO in the dispenser of 3.7 mg, and the measurement of MK 16.0. Then the concentration of the components of the calibration mixture in the air was calculated by the formula 6.

The concentration of DESO in the air was 0.195 mg / m ³ , the concentration of TCO 0.257 mg / m ³ , and the concentration of MK 1.11 mg / m ³ .

 The chromatographic characteristics of the components and systems are given in table. 2.

 Comparative characteristics of the method for producing multicomponent calibration mixtures of polar low-volatile organic substances in air and determining the concentrations of individual substances in a multicomponent or one-component calibration mixture according to the prototype by an independent analytical method are given in table. 3.

 As can be seen from the table. 3, the proposed method allows with high accuracy to obtain stable concentrations of multicomponent calibration mixtures in air, while applying components of systems with a positive deviation from Raoult law allows to obtain higher concentrations of dosed substances than the content of the same substances in one-component systems of the prototype. The mass flow rate of the dosed substances remains constant throughout the entire operating time.

 Using the proposed method allows you to create multicomponent calibration mixtures of polar low-volatile organic substances in the air to obtain calibration dependencies in the analysis of microconcentrations of liquid and solid toxicants in the environment with gas analyzers continuous tracking.

Claims (1)

A method of obtaining calibration mixtures of polar low-volatile organic substances in air by applying liquid components to the surface of a solid carrier, placing it in a batcher, passing the gas carrier through the batcher at a constant temperature, diluting it with air in the mixer to the required concentration, followed by analysis of the vapor-air mixture, characterized in that solid and liquid substances are applied to the surface of a solid carrier in the form of a liquid multicomponent mixture with practically ideal silt properties with positive deviations from Raoul’s law and a mass fraction of dosed substances from 20 to 40%, the carrier is quantitatively transferred to a thermostated dispenser made in the form of a chromatographic column, the temperature of which does not exceed the temperature of the thermooxidative decomposition of the dosed substances, allows to obtain a multicomponent stationary phase in the liquid state and the necessary concentration range of polar low-volatile organic substances in the air, an inert gas carrier stream with volume nd speed 5-60 cm ³ / min, weight of the individual compounds determined a multicomponent mixture of polar low-volatile organic compounds in the dispenser at the beginning and during the preparation of calibration mixture of polar low-volatile organic substances in air introduction microdose benzene, air and normal-alkanes C ₁ -C ₁₀ into a dispenser connected to a detector for thermal conductivity, and dilute in a mixer the flow of a calibration mixture of polar low-volatile organic substances with air purified from organic impurities.

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