SU1723517A1 - Device for pneumatic metering out of samples of equilibrium vapor to gas chromatograph - Google Patents

Abstract

The device contains a sample vessel connected through a flow switch to the entrance to the chromatographic column, a carrier gas supply line to the chromatographic column and a carrier gas supply line to the sample vessel, gauges to monitor the pressure of the carrier gas at the column inlet and in the vessel c. breakdown. The switch contains a hollow needle inserted into a vessel with a stopper and has a horizontal channel connecting alternately the carrier gas supply line with the sample vessel, or the sample vessel with the carrier gas line to the chromatographic column. 5 yl., 1 tab.

Description

The invention relates to gas chromo (Mathographs and can be applied for the analysis of the vapor phase in gas-liquid, gas-solid systems.

A device for metering samples into a chromatograph is known, which contains two vessels — an upper and a lower one, two valves, a piston and a needle.

The drawbacks of the device are the unavoidable memory of the apparatus due to the sorption of the sample components on the walls of the vessels, valves and piston, which leads to quantitative analysis error and contamination of the subsequent sample, and the practical impossibility of dosing samples containing components with low elasticity of saturated vapors, since concentration in the space under the piston during vacuum will be minimal.

The closest in technical essence to the present invention is a device for pneumatic dosing of samples of an equilibrium vapor phase 6 gas chromatograph containing a chromatographic column, a channel for supplying a stabilized flow of carrier gas to the column, a six-turn valve switch connected through the channels to the column and vessel. for the sample, as well as a channel for the supply of an abilized carrier gas stream to the column, a six-way tap switch connected through the channels to the column and to the sample vessel, as well as There is an additional channel for supplying additional carrier gas to the column.

The disadvantages of this device are the introduction of the main and residual quantities of the sample into the chromatographic column with two consecutive pulses, which inevitably leads to an error when conducting quantitative analysis, especially when analyzing micro-concentrations; the presence of a separate channel for the supply of a stabilized carrier gas flow into the column leads to the flow of a part of the sample into it when dosing the vapor-gas mixture under high pressure, which leads to erosion of the chromatographic bands, i.e. reduced chromatographic separation efficiency.

The purpose of the invention is to improve the accuracy of analysis and separation efficiency.

This goal is achieved by the fact that in a device for pneumatic dosing of samples of an equilibrium vapor phase into a gas chromatograph containing a sample vessel connected through a flow switch / equipped with a hollow needle, to the entrance to the chromatographic column and the supply line. and in the chromatographic column, manometers installed at the entrance to the column and in the sample vessel, the switch is made in the form of a hollow cylinder, inside of which is placed a rod having T-shaped through channels, a floor needle it is fixed in its vertical channel, and the horizontal channel is connected to the carrier gas supply lines to the sample vessel and to the chromatographic column.

The proposed device minimizes the size of the gas lines, i.e. reduce the surface in contact with the sample vapor and, consequently, minimize the sorption losses, which leads to an increase in the accuracy of the analysis; introduce pairs of sample components directly into the carrier gas line; entering the chromatographic column, which allows one to exclude the transfer of a part of the sample to other channels and, consequently, increase the efficiency of chromatographic separation.

FIG. 1 and 2 is a schematic diagram of the proposed device; in fig. 3. 4 and 5 - chromatograms for determination of acetone in water.

A device for pneumatic dosing of equilibrium vapor phase samples into a gas chromatograph; contains a chromatographic column 1, a sample vessel 2 with a probe, a thermostat 3, a rod with a hollow needle 4, pressure gauges 5 for controlling pressure at the column inlet and overpressure in the sample vessel, pressure stabilizers to set and maintain pressure at the column inlet and excess pressure in the sample vessel, pneumatic actuator 7, seal 8, switch housing 9.

The device works as follows.

In the upper position (Fig. 1) the needles of the switch are stabilized pressure

carrier gas through the upper horizontal and vertical channels of the needle enters the vessel with the sample (line B). At the same time, the second stabilized flow of carrier gas (line A) flows through the middle

switch housing chamber in chromatographic column.

When the needle is switched to the lower position (Fig. 2), the horizontal channel is in the chamber of the switch housing

(line A) and through it a stabilized flow of carrier gas enters the column. Simultaneously, the excess pressure of gas with sample vapors through the vertical channel of the needle -...

column and dosing occurs sample. After some time has passed (comparing the pressure of the vessel 2 with the line A, approximately 5 seconds), the moving needle returns to its original position.

For an experimental test of the device, solutions of acetone in water of 10–10 wt% were tested on a Tsvet-500 gas chromatograph with a flame ionization detector (FID), carrier gas-nitrogen, column temperature 80 ° C, temperature of the sample vessel 60 ° C. .

Experimental data is reduced-. us in the table. .....

As can be seen from the above chromatograms (Figs. 3.4 and 5), the separation efficiency is very high, since there is absolutely no erosion of the peaks.

Thus, experimental studies of a device for pneumatic dosing of samples of an equilibrium vapor phase into a gas chromatograph showed that, compared with the device of the prototype, it provides a higher accuracy of analysis due to the fact that it has dimensions

gas lines, and therefore sorption. Losses are minimal.

Claims (1)

In addition, the introduction of the sample component vapors directly into the carrier gas line entering the chromatographic column eliminates the flow of part of the sample into other channels, which increases the separation efficiency. Apparatus of the Invention A device for pneumatic dosing of samples of an equilibrium vapor phase into a gas chromatograph containing a sample vessel connected through a gas flow switch equipped with a hollow needle to an entrance to the chromatographic column supply lines of the carrier gas into the sample vessel and into the chromatographic column; manometers installed at the column entrance and into the sample vessel, characterized in that, in order to improve the analysis accuracy and separation efficiency, the switch is made in the form of a hollow cylinder, inside which a rod is placed having through-channels T-shaped, the floor of the needle is fixed in its vertical channel, and the horizontal channel is made with the possibility of alternately connecting with the carrier gas supply line to the sample vessel and carrying the gas-carrying line the chromatographic column. Phie.1 I SI one / l chucha X Phage.2 Phie. t