JP3114926U - Flow controller and sample concentrator using the same - Google Patents

Abstract

The present invention provides a flow controller capable of stopping gas when the amount of gas passed through reaches a set value, and a sample concentrator using the same to simplify the structure and operation.
A flow controller provided with a gas flow rate detection unit integrates a signal from the flow rate detection unit, and closes the gas flow path when an output signal of the integration unit reaches a predetermined value. A flow path closing means is provided. Further, the sample concentrating device is configured such that the sampling gas whose flow rate is controlled by the flow controller configured as described above first flows in contact with the solid or liquid sample in the sample container and then passes through the concentrating tube. .
[Selection] Figure 1

Description

  The present invention relates to a flow controller that controls a gas flow rate and a sample concentrator using the same in various analyzes including gas chromatography.

  In the past, pressure control valves and mass flow control valves were used for gas flow control in gas chromatographs, etc., but in recent years the opening of the control valve is adjusted by feedback control based on signals from pressure sensors and flow sensors. A flow controller using an electronic control system has been proposed and widely used (for example, see Patent Document 1).

FIG. 4 shows a configuration example of such a conventional electronic flow controller.
In the figure, in a gas flow path 17 through which a gas to be controlled flows, in order from the upstream side, a control valve 16 for adjusting the gas flow, a pressure sensor 12 for detecting the pressure on the outlet side of the control valve 16, A flow path resistance 14 that causes an appropriate pressure drop in the gas and a differential pressure sensor 13 that detects a differential pressure between both ends of the flow path resistance 14 are provided.

In the configuration of FIG. 4, it is known that the flow rate F per unit time of the gas flowing through the gas flow path 17 can be calculated by the following equation.
F = K × p1 × Δp ⁿ (1)
Here, Δp is a pressure difference between both ends of the flow resistance 14, p 1 is a pressure upstream of the flow resistance 14, n is a constant of about 0.5 to 1, and K is a proportional constant determined by the flow resistance 14. is there.
The flow rate calculation unit 11 constituted by a computer calculates the value of the flow rate F by calculating the value of Δp and p1 input from the differential pressure sensor 13 and the pressure sensor 12 to obtain the value of the flow rate F. By adjusting the opening degree of the control valve 16 via the control unit 15 so as to be close to the set value, the flow rate of the gas flowing through the gas flow path 17 is controlled.
Since the pressure sensor 12, the flow path resistance 14, the differential pressure sensor 13, and the flow rate calculation unit 11 are used to obtain the value of the flow rate F as described above, these are collectively shown as indicated by a dotted line in the figure. Thus, it can be handled as the flow rate detection means 10.

JP 2004-354126 A

The flow controller as described above is mainly used for controlling the flow rate of a carrier gas in a gas chromatograph. One of other uses is a sample concentrator.
A sample concentrator extracts a small amount of a volatile component in a solid or liquid sample with a sampling gas, and then passes the sampling gas through a concentration tube filled with an adsorbent or the like to collect and concentrate the volatile component. . There is a limit (breakthrough capacity) in the total amount of sampling gas that can be passed through the concentrating tube. When this limit is exceeded, the volatile components of the sample to be collected pass through the concentrating tube. This phenomenon is called breakthrough, and care must be taken to avoid breakthrough when performing sample concentration. For this reason, conventionally, a separate timer and solenoid valve are provided, and after the sampling gas is allowed to flow for the time set in the timer, the solenoid valve is closed to stop the gas. However, this method requires a separate timer and solenoid valve, which complicates the device configuration. Also, when setting the timer, the total amount of sampling gas must be converted into time and set. It was.
The present invention has been made in view of such circumstances, and a flow controller that can stop gas when the amount of gas passed through reaches a set value, and a sample that is simpler in both structure and operation by using the flow controller. An object is to provide a concentrator.

  In order to solve the above problems, the present invention provides a flow controller equipped with a gas flow rate detecting means, an integrating means for integrating signals from the flow rate detecting means, and an output signal of the integrating means when a predetermined value is reached. A channel closing means for closing the gas channel is provided. In addition, the sample concentrator is configured such that the sampling gas whose flow rate is controlled by the flow controller configured as described above first flows in contact with the solid or liquid sample in the sample container and then passes through the concentrating tube. .

  Since the flow controller according to the present invention can automatically stop the gas after flowing a set amount of gas, the sample concentrator that uses this to control the flow rate of the sampling gas is accurate. Sample components can be extracted and concentrated with a certain amount of sampling gas, and for that purpose, it is not necessary to add a timer, a solenoid valve, etc., and the apparatus configuration is simplified.

The flow controller provided by the present invention has the following features. That is, the first feature is that the flow rate values obtained by the flow rate detection means are integrated, and the second feature is that the flow path is closed when the integrated value reaches a set value. This is the point.
Therefore, the basic configuration of the best mode is a flow controller having these configurations.

  FIG. 1 shows an embodiment of the present invention. In this figure, the same components as those in the conventional example shown in FIG. The flow rate detection means 10 in FIG. 1 has the same configuration as that shown in FIG. 4 although the internal configuration is omitted. The flow rate of the gas adjusted by the flow control valve 16 through the gas flow path 17 is detected by the flow rate detection means 10, and the flow rate value F, which is the output signal, is fed back to the control valve 16 via the control unit 15 and given a predetermined value. It is the same as before that the flow rate is controlled.

  The difference from the prior art is via an integrating unit 18 that integrates the flow rate value F that is an output signal of the flow rate detecting means 10 and a comparator 19 that compares the integrated flow rate value Q that is the output with a preset set value. Another feedback loop is provided. That is, the flow rate value F that is an output signal of the flow rate detection means 10 is integrated by the integration unit 18, and the integrated flow rate value Q that is the output is then compared with the set value in the comparator 19, and the integrated flow rate value Q is set to the set value. The signal s2 is output from the comparator 19 to reach the control valve 16, thereby closing the control valve 16. The signal s2 closes the control valve 16 in preference to the signal s1 for adjusting the opening of the control valve 16 from the control unit 15. With such a configuration, the present embodiment can automatically stop the gas after flowing a predetermined amount of gas, and thus is suitable for applications that require a certain amount of gas to be supplied accurately.

  In this embodiment, the components added to the conventional configuration, that is, the integrating unit 18 and the comparator 19 are actually configured as software together with the control unit 15 in one computer. There is virtually no need to add anything. In other words, the flow controller according to the present invention is provided with the new functions as described above while maintaining almost the same apparatus configuration as that of the prior art.

FIG. 2 shows another embodiment of the present invention, and shows a basic configuration of a sample concentrator using the flow controller shown in the first embodiment. FIG. 3A shows the case of a liquid sample, and FIG. 2B shows the case of a solid sample.
2A and 2B, reference numeral 1 denotes a flow controller as shown in the first embodiment, that is, a flow controller configured to stop the gas flow when the integrated flow rate reaches a set value. 4 is a concentrating tube (also called a collecting tube or a trap tube, which is unified as a concentrating tube here) filled with an adsorbent or the like that collects a substance to be measured in a sample. The temperature is kept below that. Reference numeral 3 denotes a sample container, which is hermetically sealed except for the gas inlet 3a and outlet 3b, and contains a liquid sample 5 (FIG. A) or a solid sample 6 (FIG. B). 7 is a gas supply of sampling gas (also referred to as extraction gas, purge gas, etc., but here unified to sampling gas) for extracting volatile components (measuring substance) contained in the liquid sample 5 or solid sample 6 Is the source.

The operation of the sample concentrator thus configured will be described next.
When the sample is a liquid (FIG. 2A), the sampling gas supplied from the gas supply source 7 is controlled in flow rate by the flow controller 1 and introduced into the sample container 3 from the inlet 3a. Pass through (bubbling). Due to this bubbling, gas-liquid contact occurs over a wide area, and volatile components dissolved in the liquid sample 5 are efficiently extracted. The sampling gas accompanied by the volatile component flows out from the outlet 3b and then passes through the concentration tube 4. At this time, the volatile component as the measurement target substance is collected by the adsorbent or the like in the concentration tube 4, Only the sampling gas passes through the concentration tube 4 and is discharged. Up to this point, it is the same as the conventionally-concentrated sampling method called the purge and trap method, but after that, when the supply amount of the sampling gas, that is, the integrated flow rate reaches the set value, sampling is performed by the action of the flow controller 1 described above. Gas supply is stopped. If the set value is appropriately set in advance in consideration of the breakthrough capacity of the concentration tube 4 or the like, it is possible to prevent the measurement target substance from being lost due to breakthrough.

  When the sample is solid (FIG. 2B), the operation is almost the same as above, but since the sample is solid, bubbling is not possible, so the sample container 3 is heated to promote volatilization of volatile components. The measurement target substance is extracted from the solid sample 6 as efficiently as possible. Others are the same as the case where said sample is a liquid.

  In both cases of liquid and solid, the volatile component that is the measurement target substance in the sample is extracted by a certain amount of sampling gas and collected in the concentration tube 4 in the above process. In order to perform the analysis, a process of introducing the concentrated measurement target substance into the analyzer is necessary. In the case of gas chromatography, the concentration pipe 4 is heated to desorb the measurement target substance from the adsorbent or the like. The thermal desorption method is often used, and in liquid chromatography and spectroscopic analysis, the solvent desorption method in which the measurement target substance is washed out with a solvent is often used. Omit.

FIG. 3 shows another embodiment of the present invention.
A concentrated sample introduction method called PTV (Programmed Temperature Vaporization) has been conventionally known in gas chromatography. In this example, the sample concentrator shown in Example 2 is combined with PTV.

In the figure, the flow controller 2 used for the flow control of the carrier gas in the gas chromatograph 20 is a conventional flow controller, and has a configuration as shown in FIG. 4, for example.
Reference numeral 21 denotes a sample vaporizing chamber for PTV whose program temperature can be controlled, in which the concentration tube 4 is supported by a seal ring 25. The concentration tube 4 in this case is generally configured by filling a glass tube called a liner inserted into the sample vaporizing chamber 21 with an adsorbent or the like, but is functionally equivalent to the concentration tube 4 shown in FIG. .
22 is a column for separating the measurement target substance sent from the sample vaporizing chamber 21 into each component, 23 is a detector for detecting each separated component and outputting it as an electrical signal, and 24 is for discharging the gas in the sample vaporizing chamber 21 It is a split valve. In addition, in FIG. 3, the same functional elements as those in FIG. 2 are denoted by the same reference numerals as those in FIG.
The seal ring 25 divides the internal space of the sample vaporizing chamber 21 into upper and lower portions, and the divided upper and lower spaces are communicated only through the concentrating tube 4. Accordingly, both the carrier gas and the sampling gas introduced into the upper space flow through the concentrating tube 4 to the lower space, and further to the column 22 and the split valve 24 connected thereto.

The present embodiment configured as described above operates as follows.
The carrier gas in the gas chromatograph 20 is flow-controlled by the conventional flow controller 2 and supplied to the sample vaporizing chamber 21, passes through the concentration tube 4 provided therein, and further passes through the column 22 to the detector 23. It is flowing.
In the sample concentration process, the sampling gas (here, the same type of gas as the carrier gas) is controlled in flow rate by the flow controller 1 having an integrating function and passes through the liquid sample 5 in the sample container 3, The volatile component dissolved in the liquid sample 5 is extracted and transported to the concentration tube 4 in the sample vaporization chamber 21, where the substance to be measured is collected and concentrated as in the second embodiment. The same applies when the sample is solid. The sampling gas that has passed through the concentrating tube 4 is discharged through an open split valve 24.
When the integrated flow rate of the sampling gas reaches a set value, the supply is stopped, and then the split valve 24 is closed by a timer device or the like (not shown), and then the sample vaporizing chamber 21 is rapidly heated and concentrated inside. When the tube 4 is heated, the concentrated substance to be measured is desorbed from the concentration tube 4 and introduced into the column 22, and thereafter normal gas chromatography analysis is performed.

  The present invention is not limited to the above-described embodiments, and there are various other modifications. For example, the flow path closing means is not limited to the one that uses the control valve 16 shown in FIG. 1 and may be configured to be closed by providing another electromagnetic valve or the like. In addition, a hot-wire flow meter or the like may be used as the flow rate detection means 10.

  The present invention can be used for various analyzes including gas chromatography.

It is a figure which shows one Example of this invention. It is a figure which shows the other Example of this invention. It is a figure which shows the other Example of this invention. It is a figure which shows the conventional structural example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Flow controller 2 Flow controller 3 Sample container 3a Inlet 3b Outlet 4 Concentration tube 5 Liquid sample 6 Solid sample 7 Gas supply source 10 Flow rate detection means 11 Flow rate calculating part 12 Pressure sensor 13 Differential pressure sensor 14 Channel resistance 15 Control part 16 Control Valve 17 Gas flow path 18 Accumulator 19 Comparator 20 Gas chromatograph 21 Sample vaporization chamber 22 Column 23 Detector 24 Split valve 25 Seal ring

Claims (3)

  A control valve for controlling the gas flow rate by changing the opening of the valve, a flow rate detecting means for detecting the flow rate of the gas controlled by the control valve, and a feedback signal from the flow rate detecting means to feed back the control valve. A flow controller comprising a control means for controlling the opening; an integrating means for integrating the signals from the flow rate detecting means; and a gas flow when the output signal of the integrating means reaches a predetermined value. A flow controller comprising a flow path closing means for closing a path.   The sampling gas whose flow rate is controlled by the flow controller first flows in contact with the solid or liquid sample in the sample container to extract volatile components in the sample, and then collects and concentrates the volatile components. A sample concentrator configured to pass through a concentrator tube, wherein the flow controller according to claim 1 is used as the flow controller.   The sample concentrating device according to claim 2, wherein the concentrating tube is provided in a sample vaporizing chamber capable of controlling a program temperature of the gas chromatograph.

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