SU769430A1 - Chromatograph with programmed consumption of carrier gas - Google Patents

Description

(54) CHROL1ATOGRAPH WITH PROGRAMMING

GAS-COSITEL COSTS

one

The invention relates to the field of analytical instrumentation and can be used, for example, in the chromatographic analysis of substances when it is necessary to vary the flow rate of the carrier gas according to the program.

A number of mechanical systems are known (the pro gramming of the flow of gas-user-in-Kolko, Nke: valves, pressure regulators with a mechanical drive; or a set of resistances and valves for switching them: 1.

The reproducibility of programs (especially continuous ones) is not high enough, and the difficulties of maintaining a given program caused the emergence of pneumatic program control systems.

; In these systems, a pressure regulator after se is used at the outlet to the column. Depending on the law of change in the command chamber of this pressure regulator, at the output of its executive chamber a corresponding program is formed.

Known chromatograph, which is devoid of this disadvantage. It consists of a main gas line, in which a carrier gas manifold is installed in series, a flow controller, a sample port, a column, a detector, and a bypass gas line connected to the main gas flow regulator. flit.

Yes, and in front of the detector. On this line, a pneumatic actuator is installed, the flow chamber of which is connected to the output of the flow regulator, and the chamber with the program's control is deaf. The air nozzle nozzle is connected to the outlet of the column and the detector 2.

This chromatograph, imprinted on the prototype, has several disadvantages. Most

10 significant of them is the low reliability of the air repeater, the complexity of the setter block — the programs — the result is poor reproducibility of the programMMbi.

15

The purpose of the present invention is to increase the on-boardness of the chromatograph and the analysis of its performance.

The goal is achieved by the fact that a second bypass gas line is connected to the chromatograph, connected to the main. . In addition, a capacity is connected to the line after the flow controller through a choke. Both tanks are equipped with a device for controlling their volume 30 and are connected to each other through a valve.

In a preferred embodiment of the invention, it is provided that a carrier gas flow sensor is installed in the main gas line not by the device for injecting the sample.

FIG. 1 is a schematic diagram of the proposed chromatograph, in FIG. 2 shows a gas diagram of a variant of the proposed chromatograph; FIG. Figure 3 shows the flow curves of the carrier gas obtained on this device; in fig. 4 shows the chromatogram of a mixture of n-paraffins at the rate of gas carrier / about 25.0 ml / min; in fig. 5 shows the chromatogram of mixtures of w-paraffins at a carrier gas speed of F 74.2 ml / min; in fig. Figure 6 shows the chromatogram of a mixture of clarafins obtained in the mode of programming the flow rate of the carrier gas from FQ, 10 F ,,.

The proposed chromatograph in the main gas line has a source / carrier gas, a regulator of flow rate of carrier gas 2, a flow meter 3 of carrier gas (thermal sensor), a device for sample inlet 4, a chromatographic column 5 and a detector 6. After the flow regulator 2 gas carrier main line has three branches. On one of them, a throttle 7 and a tank 8 are installed, equipped with a device 9 for smoothly changing its volume. The other two branches are bypass lines, one of which is fitted with a valve 10 and a choke. A valve 12, a tank 13, fitted with an il4 device for smoothly changing its volume, is installed on the second bypass line, choke 15, "valve 16.

The proposed chromatograph works as follows, in the image. First, the flow rate regulator 01M is set to the flow rate of the gas that corresponds to the final value of the selected program. At this point, valves 10 and 16 are closed and valve 12 is open. Ph After this, valve 12 is closed, and by opening the clan 10 with a throttle //, bypassing a part of the gas flow through the bypass line to detector 6, set up in the column the initial speed of programming FO. in this case, pressure PQ is established in front of column 5 and in vessel 8. Since, then and. After these operations, a sample is introduced and, at the required moment, the valve 16 is opened and the valve 10 is closed. The carrier gas will begin to flow in the tank 8, and the pressure drop across the throttle 7 will fall as the gas pressure in the tank 5 changes from PO to Ph the gas flow through the "olivka 5" will rise from FO to F /, according to a certain program, which is fixed by the flow sensor 3. The intensity of the rise of the carrier gas consumption through

Column 5 depends on the parameters of the throttles: 7 and the volume of the tank 5. Therefore, a change in the intensity of the rise of the carrier gas flow through the column 5 can be achieved by varying these parameters. Therefore, the container 8 is provided with a device 9 for smoothly changing its volume. The gas accumulated (up to Pk) before the start of the analysis in the buffer tank 14, the volume of which is equal to

the volume of the tank 8 is discharged through choke 1.5, which is identical to the chokes. 7, in a reversible program of maintaining the constant flow rate (Fi,) of carrier gas through the detector 6.

The container 8 is connected to the container 13 through 1 valve 1-2 (Fig. 2). The sequence of olerations is similar to that described above. However, in this case it is easier to establish the identity of the chokes 7 and 15, which is necessary

IRI using uncalibrated chokes.

On 1fig. The curves of change in the flow rate of the carrier gas, obtained with a volume of buffer capacity of 40 and 80 ml, are given.

: FIG. 4, 5, 6 chromatograms of a mixture of normal paraffins obtained in isodynamic mode and in mode of carrier gas flow rate are shown. It can be seen from them that the low velocities of the carrier gas (Fig. 4) ensure a good separation of all components, but the analysis time and dispersion of the last peaks are quite significant. The use of high velocities of the carrier gas (Fig. 4) makes it possible to reduce the analysis time and the erosion of the last peaks, but this significantly worsens the separation of the first peaks of the chromatogram.

The programming mode of the gas-carrier flow rate is a compromise solution (Fig. 5) and allows one to obtain a clear separation of all the components of the mixture with a minimum analysis time.

Thus, these results indicate the reliability of the proposed gas chromatograph and high reproducibility of the analysis of mixtures on it.

Fore iM u l a and 3 o b e te e n

Claims (3)

1. Chromatograph with carrier gas flow programming, containing a main gas line, on which a carrier gas source, a flow controller, a sample port, a column, a detector and a bypass gas line connected to the main one after the flow regulator and in front of the detector, differing in order to increase reliability and reproducibility analysis, it is equipped with a second bypass gas line connected to the main - similar to the bypass, and a valve and a choke are introduced into the bypass line, and an additional valve, tank, throttle and second valve, In addition, a second tank with a controlled choke at the entrance to it is connected to the main line after the flow controller. 2. Chromatograph according to claim. 1, which is also distinguished by the fact that the containers are connected to each other through a valve. 3. The chromatograph according to claim 1, 2, distinguishes-U and with the fact that it is equipped with a carrier gas flow sensor installed in the main gas line before sampling. Sources of information taken into account in the examination: 1 Advances in Chromatography, vol. 8, 1969, p. 271-i272. 2. USSR author's certificate number 496492, cl. G 01 N 31/08, 1970, prototype. // - L ff Q / j I & Phage. 3 Hc 3 V 76 5 fi 3 i r T FIG 4 J H-CC F l .. I I // - L -C. // HC; o HC, , J J i 3 2 I Fi & .5 H-CK HC L HC, -CB HC ,, o 6 i, 3 2 Qf- t UHfig. S