SU1670595A2 - Device for taking vapor phase samples and feeding samples to gas chromatograph - Google Patents

Abstract

The invention relates to gas chromatography and can be used in the determination of volatile impurities in natural and waste waters, biological objects, polymeric materials, food products, etc. The purpose of the invention is to accelerate the time to reach equilibrium without reducing the measurement error in the analysis on the stream. The device includes sample and standard solution tanks, a metering valve with a metering volume, and a switching valve for supplying additional carrier gas to the vessel. The tanks for establishing vapor-phase equilibrium are placed in a single massive thermostatted housing with flow-through liquid phase; they have fittings for supplying and discharging the analyzed liquid and standard solution. The device is equipped with pumps, the hydraulic path of which is tightly closed when the analyzed liquid is supplied, which eliminates the flow of gas and liquid from the technological and analytical systems. 2 Il.

Description

The invention relates to the field of analytical instrumentation, namely, devices for analyzing vapor phase samples that are in thermodynamic equilibrium with the liquid under study, and can be used to determine volatile impurities of natural and waste waters, biological and polymeric materials, food products and other objects by the method gas chromatography.

The purpose of the invention is to accelerate the time to reach equilibrium without reducing the measurement error when analyzing the flow.

FIG. 1 is a schematic diagram of the device; in fig. 2 - cyclogram of cranes and pumps.

The device contains a three-cell metering valve 1 and a three-cell switching valve 2, indicated in FIG. 1 in one of two positions (bottom). The containers for product 3 and for standard solution 4 are placed in a single massive case 5. The dosing volume 6 is connected to the crane dispenser 1. The source 7 of the main carrier gas is connected to the dosing valve 1, and the chromatographic column 8 is installed at its outlet detector E. Source 10 additional carrier gas flow soeo

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An 11 reset is provided to reset the analyzed mixture through the dosing volume 6. Both taps 1 and 2 and tanks 3 and 4 in housing 5 are placed in thermostat 12, column 8 and detector 9 can be in separate thermostat 13. Outside of thermostat

12 installed pumps 14 and 15. designed to supply liquids, respectively, product and standard solution. The product is supplied through a stream from the process pipe 16, in which a throttling valve 19 is installed in the area between the nozzles 17 and 17 and the liquid discharge 18. The product from the process pipe 16 enters the product container 3 via a discharge line including pipes 20, 21, a pump 14 and the inlet fitting 22 installed in the bottom of the housing 5. From the tank 3, the product is taken out through the fitting 23 located in the middle part of the tank, then through the discharge line including pipelines 24, 25 and the pump 14. Standard solution using Asosa 15 are removed from vessel 26 through conduits 27 and discharge line 28, through the inlet 29 and outlet 30 fittings pumped through the tank 4 and discharged through line consisting of pipes 31 and 32.

The device operates in accordance with the sequence diagram shown in FIG. 2. In the initial position, the taps 1 and 2 (Fig. 1) (indicated in Fig. 2, respectively, Kp1 and Kp2) are in the lower position, and the pumps 14 and 15 (indicated in Fig. 2, respectively, Hi and On) are turned off. After the introduction of a steam test standard, carried out when switching taps 1 and 2 at times ti, t2, ta (Fig. 2), at the moment

13 turn on the pump H2 and for the period of time III wash the tank 4 (Fig. 1) with a standard solution. Section IV of the sequence diagram (Fig. 2) is consistent with the analysis of the standard, which is highlighted at time t5. By the moment of time re, the first half of the analysis cycle is completed and the next steam sample of the product is dispensed after switching on valves KP 1 and Kp 2 at times t, t, t. In gap VII, pump Hi is operated and the fluid in tank 3 (Fig. 1) is exchanged with the product. In section VIII of the cyclogram, the peak of the product is released at tio. The time of operation of the pumps is selected according to the cyclogram in such a way as to ensure sufficient time (almost the entire analysis cycle) for establishing vapor-phase equilibrium in the tanks. The duration of the period of operation of the pumps and their performance is determined by the required frequency of washing of tanks and communications.

Example 1. The operation of the device is tested on the example of the analysis of a-ethanol

solutions. The unit is assembled on the basis of a Tsvet-100 chromatograph. The tanks 3 and 4 are made in a steel massive case 5. Case 5 is placed in a column thermostat together with a crane assembly and a chromatographic column. The delivery of liquids is carried out using a peristaltic pump. The pump allows you to install two pairs of flexible silicone hoses (3 mm in diameter) for supplying and discharging liquids into the product container and standard solution. To eliminate the possibility of liquid entering the gas path of the analytical circuit and eliminating the filling of containers with liquid, the supply of liquid to the tank was carried out during the period when the tanks were under excess pressure of additional carrier gas (Fig. 3) and flexible hoses were used on the lines The discharge of pumps is somewhat larger than the hoses on the discharge line, in order to ensure that there is obviously more fluid withdrawn from the tanks than the inlet. The operation of the cranes and the pump is controlled from the calculating integrator.

0 Fluids through the product and standard lines are supplied from individual vessels. When fluid is supplied to one of the containers while the pump is running, the hoses to the other tank are clamped with a Koch clamp. Conditions

5 chromatographic separation: column 60x0.3 cm, filled with Polysorb-1, temperature in the thermostat 60 ° C, flame ionization detector, flow rates of the main carrier gas (gels) 30 cm3 / min, water 30 cm / min, air 300 cm / min, the pressure of the main carrier gas at the inlet to the column is 0.01 MPa, the pressure of the additional carrier gas (on the overhead) is 0.08 MPa. Total capacity of tanks 3 and 4

5 (Fig. 1) 7 cm3, the ratio of the gas volume and the liquid-filled 1: 1. The size of the dosed volume is about 0.2 cm3. The volume of gas per flush dose is 5 cm3. The analysis cycle time is 10 minutes. The integrator allows you to build a calibration curve in the coordinates Snp / Scr from Cpr / Cst, where Snp, Set are the peak areas of the product and the standard, Cpr, Seth are the concentrations of the solutions of the product and the standard.

5 Experiments show that the direct supply of liquid through the steel capillary into the thermostat leads to a noticeable change in temperature in the thermostat cabinet. This requires preheating of liquids, eliminating the influence of temperature fluctuations, ensures that the tanks for vapor-phase analysis are executed in one massive steel case. The identity of the conditions for the supply of the liquid product and the standard solution reduces the measurement error from 3-5% to 1%.

Thus, the use of flow vessels placed in a single thermostatically controlled block when conducting analysis on a flow (when different temperature perturbations are possible) allows one to quickly achieve the same equilibrium in the tanks without reducing the measurement error.

Claims (1)

Claims An apparatus for taking and introducing samples of the vapor phase into a gas chromatograph according to ed. No. 1520435. characterized in that, in order to accelerate the time to reach equilibrium without reducing the measurement error in the flow analysis, the sample containers and the standard solution are made flow through the fluid and placed in a single massive body, and the liquid inlets and outlets from the tanks are connected with the lines of injection and discharge of two pumps, which ensure the tight shut-off of the liquid flows and the pumping of the sample and standard solution through the indicated containers. sixteen 12 26 St figure 1 ft tits t "t5 tgtitafy tfo tff Fig. g