SU1179218A1 - Method of gas chromatographic analysis of composition of mixtures containing vapours of weakly separated components - Google Patents

Abstract

1. METHOD OF GAS-CHROMLOGRAPHIC ANALYSIS OF THE COMPOSITION OF MIXTURES CONTAINING COUPLES OF WEAKLY SEPARATED COMPONENTS, including inserting a sample of the mixture in a carrier gas flow into a chromate graphical column and registering a sample application, a software program, a sample application, a software program, and a sample application, a software program, a software program, and a sample application, a software application, a heat source, a software program, and a sample application, a software program, and a sample application, a software program, and a sample application, a software program, and a sample application, a software program, and a sample application is detected by a software program, and a sample application is detected. and with that. that, in order to simplify the instrumentation of the process, gas is used as a carrier gas, the thermal conductivity of which is less than the thermal conductivity of one of the weakly separated components, but greater than the thermal conductivity of the other component of the weakly separable SL pair. 2. The method according to p.1.0 aphid and with the fact that a mixture of gases is used as a gas carrier. h

Description

one

The invention relates to a method for chromatographic analysis of the composition of mixtures containing pairs of weakly separable components, and can be used in instrument-making, chemical and other sectors.

The purpose of the invention is to simplify the instrumentation of the process.

The invention is illustrated by examples of analysis of a particular mixture.

FIG. 1 shows the chromatogram (inverse peak) of the argon-oxygen mixture; in fig. 2 - calibration straight areas of the inverse peak of the molar fraction of the component. .

Consider the dependence of the detector signal on time F (t) when dosing a mixture of two weakly separated components.

Let X | , x and Xj are the thermal conductivities of the first component and the carrier gas, respectively. For simplicity, we will consider the individual peaks to be Gaussian, and the thermal conductivity of the mixture as a linear function of the thermal conductivities of the components (violating these conditions only complicates the mathematical calculations, the result is not limited in any way) Then F (t) is proportional to

(s-x, e.pH) .A (y, -x, lexp (,

where A is the ratio of molar fractions

the first and second components

L is the difference in component retention times;

b - ratio of peak dispersions

components

If, then the first term in (1) is positive, and the second is negative and not the sum of the signals, but their difference is detected. As a result, the total peak (1) consists of positive and negative parts (the inverse peak. The ratio between the linear elements of these parts, as well as between their areas, is determined only by A, and d, and depends on these values one-digit. Therefore, if we determine the calibration dependence And from S, or in where there are 9,, 2 areas of the positive and negative parts from the mimary peak, then inverse 792182

It is possible to unambiguously find the molar fractions of the components of the analyzed mixture. ,

Example 1, Experiments were performed on a Tsvet-102 chromatograph. The chromatographic detector was recorded with a thermal conductivity detector (katharometer). Weakly separable mixture was

o a mixture of argon and oxygen. The thermal conductivity of argon at a temperature of 30-60 ° C is l-4, 5 10 the coefficient of thermal conductivity of oxygen at the same temperature

6.540-

-. Therefore, in quality. s.grad

non-carrier gas was selected nitrogen, the coefficient of thermal conductivity of which in the specified temperature range

with .p-5 cal

is 6.210, i.e.

 sm.sgrad

less than oxygen but more than argon

The nitrogen flow rate was set at 2530, the current of the katharometer was 100 mA. A 5 m long Column was used with an internal diameter of 3 mm and 5 A. molecular sieves. The temperature of the column thermostat was 50 C.

The inverse peak of the argon-oxygen mixture is presented in FIG. The composition of the mixture is determined using the calibration dependence of the area of the inverse peak of argon on its molar

shares in the mixture, pre-built on the calibration mixtures (FIG. 2, Right 1).

This dependence does not go beyond the origin, since a definite initial concentration of argon in the mixture is necessary for the appearance of the negative part V of the total peak. one

For the experimental verification of the method, test argon-oxygen mixtures of known concentrations were prepared. These mixtures were dosed using a gas syringe (dose volume 1 cm) and the resulting inverse peaks on the calibration curve

the corresponding molar fractions were found.

In tab. 1 presents the results of experiments.

Table 1

Concentrations found by the proposed method, the percentage of argon

This graph, the introduction of 10Z carbon dioxide in the carrier gas (nitrogen) leads to a shift of the calibration curve so that it goes almost from the origin. In .table 2 shows the results of measuring the composition of argon-oxygen mixtures by the proposed method using a mixture of carbon dioxide and gas.

As can be seen from the table. 1, the concentrations of argon, determined by the proposed method, differ from the known ones by preparation by no more than 1.5%.

Example 2. The experiment was carried out under the same conditions as in Example 1, but a mixture of argon and carbon dioxide was used as a carrier gas in a volume ratio of 1:10. .

FIG. 2 shows the calibration dependence (2) of the area of the negative part of the inverse peak on the mole fraction of argon. As seen and

As can be seen from the table. 2, the found concentrations of argon in the mixture differ from the known ones by no more than 2%.

O 0.25 0.50 0, 00 Mollna Figure 2

Claims (2)

1. METHOD FOR GAS-CHROMATOGRAPHIC ANALYSIS OF THE COMPOSITION OF MIXTURES CONTAINING PAIRS OF WEAKLY DISTRIBUTABLE COMPONENTS, which includes introducing a sample of the mixture in the carrier gas stream into the chromatographic column and registering the components at its output with a heat conduction detector, which is simpler for design as the carrier gas, a gas is used whose thermal conductivity is less than the thermal conductivity of one of the poorly separated components, but greater than the thermal conductivity of the other component of the weakly separated couple. 2. The method of pop. 1, characterized in that as a gas carrier using a mixture of gases. FIG. 1 eleven