JP3080458U - Sampling system - Google Patents

Abstract

(57) [Summary] [PROBLEMS] In a flow injection analyzer,
Provided is a sampling system and a sampling method capable of repeating sampling and injection of a sample fluid repeatedly and stably for a long time with good reproducibility. SOLUTION: In forming a sampling system by combining solenoid valves, the number of solenoid valves to which a voltage is applied at the time of sampling and the number of solenoid valves to which a voltage is applied at the time of injection are made substantially the same, and a normally An open solenoid valve is provided, closed at the end of sampling, and injected with a time delay.

Description

[Detailed description of the invention]

[0001]

[Technical field to which the invention belongs]

 The present invention relates to a sampling unit of a flow injection analyzer.

[0002]

[Prior art]

 For example, when performing gas analysis using a gas chromatograph, which is one of the flow injection analyzers, the sample gas flows into a constant volume chamber using a six-way valve as shown in Fig. 1, and the constant volume chamber is completely filled with the sample gas. After the replacement, the method of switching the flow path as shown in FIG. 2 so that the gas sample in the fixed volume chamber is injected into the column on the carrier gas is generally performed. At the time of sampling, the sampling gas enters through the sample gas inlet (1), passes through the constant volume chamber (2), and exits through the sample gas outlet (3). At the time of injection, the sample gas contained in the fixed volume chamber (2) is pushed out by the carrier gas entered from the carrier gas inlet (21) and sent to the column (22). In auto gas chromatography, this movement will be repeated automatically.

FIG. 3 schematically shows a conventional six-way valve, in which a first disk (31) having six holes, a second disk having six arc-shaped grooves and six holes are formed. (32) face each other and rub against each other. The first disk 31 and the second disk 32 are fitted and rotated by a convex portion and a concave portion formed at the central portion thereof and rotate.

[0004] By making the groove 33 straddle 3a and 3b in Fig. 3, the state of Fig. 1 can be created. The state shown in FIG. 2 can be changed by extending the groove 33 between 3b and 3c. When performing continuous analysis using a flow injection analyzer, this operation is repeated.

Since the first disk and the second disk are rubbed so as not to leak, abrasion occurs due to repeated operation and shavings are clogged in the flow path, and for a long period (20,000 to 30,000 times), It has the disadvantage that it cannot be used stably.

As an alternative method, a method using a combination of three-way solenoid valves is known. The three-way valve consists of a common port, a normally closed port and a normally open port. When a voltage is applied to the solenoid valve coil, the common port is connected to the normally closed port. When no voltage is applied, the common port is connected to the normally open port. A three-way solenoid valve may be arranged at each of the six branch points of the six-way valve, and the flow path may be switched by sampling and injection.

[0007] By piping as shown in Fig. 4, a sampling system can be made. When no voltage is applied to the six solenoid valves, liquid or gas flows from the common port to the normally open port, the sample fluid flows into the fixed capacity pipe, and sampling is performed. A carrier flows through the column. Next, when a voltage is applied to the six solenoid valves, the fluid flows from the common port to the normally closed port, and the sample fluid sampled in the fixed volume pipe is sent to the carry flow.

[0008]

[Problems to be solved by the invention]

 When six solenoid valves and a fixed-capacity pipe (for example, an inner diameter of 1 mm and a length of 1 m) are housed in one case by this method and connected to a gas chromatograph for repeated analysis, the variation in the analysis repetition becomes CV value. It was found that there was a drawback that it increased to 3.5%.

[0009]

[Means for Solving the Problems]

 As a result of intensive studies on why the phenomenon of large variations during repeated analysis occurs, the present inventors have found that one of the causes is caused by the heat generated by the solenoid valve, and have led to the present invention. That is, during sampling, the temperature inside the case rises due to the simultaneous application of voltage to the six solenoid valves, and at the time of injection, the solenoid valves turn off all at once. Try to return. For this reason, the temperature fluctuation in the fixed capacity piping section adjacent to the solenoid valve was large, resulting in an analysis result lacking reproducibility.

The present invention relates to forming a sampling part of a flow injection analyzer for sampling a liquid or gas and injecting the sampled gas or liquid into a carrier flow of the gas or liquid by combining an electromagnetic valve. The sampling system is characterized in that the number of solenoid valves that apply a voltage during sampling and the number of solenoid valves that apply a voltage during injection are substantially the same.

In addition, as a result of intensive studies on the timing of switching the flow path after the end of the sampling, the flow of the sampling fluid is temporarily stopped at the end of the sampling, and the flow path is switched after a time delay, so that the measurement can be performed. We have found that reproducibility can be improved.

At the time of sampling, a gas or a liquid is fed into a fixed-capacity pipe by the pressure of a pump or a cylinder. If the injection is performed by switching the valve in this state, the pressure for the fluid to flow in the fixed capacity pipe is applied, and if the pressure of the pump or cylinder fluctuates, the fluctuation directly changes the sampling amount. .

[0013] Therefore, a method was developed in which a two-way valve was provided in front of the sampling section, closed when sampling was completed, and injection was performed after the pressure in the fixed-capacity pipe returned to atmospheric pressure.

[0014]

[Embodiment of the invention]

 In order to assemble the sampling section using a three-way valve, if the common port of the three-way valve is assigned to the common flow path at each switching point, either the normally open port or the normally closed port may sample either. Become. Considering the arrangement of the ports of the three-way valve to be used, the arrangement of the carrier flow and the sampling system, the position where the sample fluid is supplied, the position of the fixed volume piping, etc. Allocate so that the number of solenoid valves is almost the same.

By doing so, the number of applied voltages to the solenoid valve in the sampling system during the operation of the flow injection analyzer is always the same, the temperature fluctuation of the constant-volume sampling section is reduced, and the constant-volume sampling is performed. The accuracy will be higher.

If two two-way valves are used instead of one three-way valve, a sampling system can be similarly assembled. Also in this case, by making the number of solenoid valves applied at the time of sampling and the number of solenoid valves applied at the time of injection substantially the same, the constant-volume sampling accuracy is improved.

[0017] A two-way valve is connected in front of the sampling system, closed when sampling is completed, and switched to injection several seconds later. By doing so, the pressure of the fluid in the constant volume sampling section returns to the atmospheric pressure, and sampling with good reproducibility can be performed. If this operation is not performed, the pressure in the constant-volume sampling section is slightly higher than the atmospheric pressure, and the volume of the fluid when it is returned to the atmospheric pressure increases, thereby causing an error.

The two-way valve located immediately before the sampling system is closed only a few seconds after the end of sampling and is open most of the time. Therefore, if a normally open solenoid valve is used as the two-way valve, the voltage application time is shortened, energy is saved, and the life of the solenoid valve is advantageous.

It is preferable that the solenoid valve used for the purpose of the present invention has a small dead volume. If a solenoid valve with a large dead volume is used, the variation in constant capacity measurement will increase. Solenoid valves having a small dead volume are sold by several manufacturers. For example, MTV-2-M6NA and MTV-3-M6NA types manufactured by Takasago Electric Industrial Co., Ltd. may be used.

According to the present invention, the number of solenoid valves to which voltage is applied at the time of sampling is almost the same as the number of solenoid valves to which voltage is applied at the time of injection, and the temperature change of the fixed capacity sampling unit is small, so that the reproducibility is small. Good sampling can be performed. In addition, a two-way valve is provided just before the sampling part, and by closing this two-way valve just before the end of sampling, the pressure in the constant-volume sampling part returns to normal pressure, and a constant volume of fluid is always returned to the carrier flow. Be able to send.

[0021]

【Example】

 FIG. 5 shows a sampling system constructed with a three-way valve based on the present invention. C indicates a common port, NO indicates a normally open port, and NC indicates a normally closed port. At the time of sampling, voltage was applied to the solenoid valves 51, 52 and 53, and the sample fluid entered through the common port of the solenoid valve 54 and passed through the solenoid valves 51, 55 and 56 to exit the system. The carrier fluid was supplied to the column 57 through the solenoid valves 52 and 53.

At the end of sampling, the electromagnetic valve 58 placed in front of the sampling system was closed, and after a few seconds, switching to injection was performed. This solenoid valve was opened a few seconds after the end of the injection.

At the time of injection, the carrier fluid enters the electromagnetic valve 51 from the electromagnetic valve 52, flushes the fluid sampled in the fixed volume section 59, and is sent to the column 57 via the electromagnetic valves 55 and 53. Three solenoid valves were applied at the time of sampling and three solenoid valves were applied at the time of injection. Temperature fluctuation inside the sampling system was extremely small during operation of the flow injection analyzer. As a result of repeated analysis experiments using this sampling system, it was possible to obtain sufficient accuracy as an analyzer with a CV value of 0.86%.

[0024]

[Effect of the invention]

 This invention has the above-described configuration and has the following excellent effects. According to the invention described in the claim, a constant-volume sampling system having a long life and good reproducibility can be configured.

[Brief description of the drawings]

FIG. 1 shows sampling by a six-way valve.

FIG. 2 is a diagram showing injection by a six-way valve.

FIG. 3 shows the structure of a six-way valve.

FIG. 4 is a conventional sampling system using six three-way valves.

FIG. 5 is a sampling system according to the present invention.

[Explanation of symbols]

 1 Sample Fluid Inlet 2 Constant Volume Chamber 3 Sample Fluid Outlet 21 Carrier Fluid Inlet 22 Column 31 First Disk 32 Second Disk 51 Electromagnetic Valve Applied at Sampling 52 Electromagnetic Valve Applied at Sampling 53 Voltage Applied at Sampling Solenoid valve 54 A solenoid valve applied with a voltage at the time of injection 55 A solenoid valve applied with a voltage at the time of injection 56 A solenoid valve applied with a voltage at the time of injection 57 Column 58 An electromagnetic valve provided in front of the sampling section 59 A fixed capacity section

Claims (4)

[Utility model registration claims] 1. Sampling for switching between gas or liquid sampling into a fixed volume chamber and injection for injecting the gas or liquid in the fixed volume chamber into a carrier gas stream or a carrier liquid stream by combining an electromagnetic valve. In forming a part, the number of solenoid valves that apply a voltage during sampling and the number of solenoid valves that apply a voltage during injection are made substantially the same. 2. A two-way valve is provided at a sampling fluid inlet of a sampling part of a flow injection device for switching between gas or liquid sampling and injection for injecting the sampled gas or liquid into a carrier gas flow or a carrier liquid flow. The sampling system according to claim 1, wherein: 3. The sampling according to claim 2, wherein a time delay is provided between the operation of closing the two-way valve provided at the inlet of the sampling fluid of the sampling unit at the end of the sampling and the operation of switching to the injection. system. 4. The sampling system according to claim 2, wherein the two-way valve provided at the inlet of the sampling fluid in the sampling section is a normally open two-way valve.