JP2869158B2 - Automatic sample introduction method and automatic sample introduction device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an automatic sample introduction method and an automatic sample introduction apparatus. In particular, when two-stage dilution is required in a liquid chromatograph or the like, a very small amount of sample can be sampled. The present invention relates to an automatic sample introduction method and an automatic sample introduction device which can be automatically performed without using a special dilution tank.

[Conventional technology]

For example, in an automatic sample introduction device of a liquid chromatograph, when the amount of a sample used for analysis is extremely small, it is difficult to directly sample a small amount of the sample. In such a case, as a previous step, a solution in which the sample was diluted in advance had to be prepared and sampled. For example, the amount of a sample necessary for analysis of glycohemoglobin performed in a clinical test or the like is about 0.05 to 0.1 μ, whereas the amount of a sample that can be accurately dispensed with a dispenser is 3 μm.
Since μ to 5 μ is the limit, a two-stage dilution method is adopted in which a sample is diluted 100 to 200 times before dilution and then sampled.

Conventionally, pre-dilution of a sample in such a liquid chromatograph has been performed manually. Recently, an automatic sample introduction device with an automatic pre-processing function controlled by a computer has been put into practical use, and a method for automatically performing the automatic sample introduction device has become widespread.

A typical example of a conventional automatic sample introduction device with an automatic pretreatment function will be described with reference to FIG. In FIG. 8, the automatic sample introduction device 1 is provided with a sample stage 2, a washing tank 3, a drain port 4, a dilution tank 5, and an injection port 6. The liquid sample to be measured is stored in each of a plurality of sample containers 7, arranged in a sample rack 8, and mounted on the sample stage 2. The nozzle 9 is configured to be connected to one of the syringe pump 12 and the diluent tank 13 via the thin tube 10 and the switching valve 11, and further to the X-axis direction and the Y-axis.
The axial drive mechanism 14 moves to the position of each sample container and each processing port to perform necessary work.

The analysis unit 15 is configured so that the reagents in the reagent tanks 17a and 17b flow to the separation column 19 via the sample introduction valve 18 by the pump 16. The sample introduction valve 18 is provided with a measuring tube 20, and the sample injected from the injection port 6 is held by the measuring tube 20 and introduced into the flow path of the analyzer 15. The sample separated by the separation column 19 is sent to a detector 21 and the detector 21 identifies sample components.

Sampling of a sample in the automatic sample introduction device having the above configuration is performed as follows. First, a predetermined amount of diluent is sucked into the syringe pump 12 from the diluent tank 13 in advance, and then the nozzle 9 is moved to the position of the sample container 7 to be analyzed, and a predetermined amount of sample is sucked into the tip of the nozzle 9. After that, the nozzle 9 is moved to the position of the dilution tank 5 to discharge the sample,
A predetermined amount of the diluting liquid is discharged from the rear side to prepare a sample solution having a predetermined dilution ratio. Next, the diluted sample is supplied to the nozzle 9
The nozzle 9 is moved to the position of the injection port 6 and discharged to be sent to the sample introduction valve 18, a predetermined amount of the sample is measured by the measuring tube 20, the sample introduction valve 18 is switched, and the flow of the analysis unit is changed. Introduce to the road.

In the above-mentioned conventional sampling method, the volume of the tube forming the flow path from the injection port 6 to the sample introduction valve 18 is reduced as much as possible, and the sample to be injected flows in a sufficiently large amount with respect to the volume of the tube and remains in the tube. Discarding the first sample area diluted by the washing solution and cutting out the sample area having a stable concentration with a measuring tube is a principle method for obtaining good sampling accuracy.

[Problems to be solved by the invention]

The aforementioned dilution sampling method using the automatic sample introduction device is a method in which the pre-dilution method, which was conventionally performed manually, is automated as it is, and has high dilution accuracy and can be widely used for flow-type automatic analysis other than liquid chromatography. This is a common method. However, this sampling method has the following problems: (1) a special dilution tank is required; (2) pre-dilution takes a long time and analysis takes a long time; In order to eliminate carryover, the dilution tank must be thoroughly washed every time one sample is processed, and a large amount of washing water is required. It is necessary to clean or replace the dilution tank.

Further, as a known document describing a conventional automatic sample introduction device for liquid chromatography, there is JP-A-63-71650. Also in this prior art, since it has a configuration that specially requires a mixing container that functions as a dilution tank,
It contains the problems described above.

Further, recently, the usefulness of liquid chromatographic analysis has been recognized in clinical examinations, and a dedicated machine for diagnosis has been put into practical use. However, a device for analyzing such specific items is not always strict. Many analyzes do not require sampling accuracy. For example, in the analysis of glycated hemoglobin, measurement is performed based on the ratio of separated components. Although the amount of sample required for analysis is extremely small, it does not always require strict sampling accuracy. In liquid chromatography, an internal standard solution is often added and measurement is performed on the basis of the internal standard solution, due to the problem of recovery efficiency of the separation column.

An object of the present invention is to realize an automatic dilution sampling means particularly useful for a dedicated machine for analyzing a specific item as described above, and has a simple configuration without using a special dilution tank. Another object of the present invention is to provide an automatic sample introduction method and an automatic sample introduction device capable of introducing a sample with a simple operation in a short time.

[Means for solving the problem]

The automatic sample introduction method according to the present invention, in order to achieve the above object, to a sample dilution introduction tube having a volume sufficiently larger than the amount of the sample to be introduced, from the inlet portion, to feed a certain amount of sample, Thereafter, a diluent is fed, the sample is dispersed in the diluent while the sample flows through the introduction tube, and a specific area of a sample concentration gradient formed in the flow in the introduction tube is formed. It comprises a procedure in which a sample portion is taken out using a flow path switching valve and fed to a flow path in which a carrier solution flows for analysis.

In order to achieve the above object, a first automatic sample introduction device according to the present invention has an injection port, a dispensing nozzle that sucks a sample in a sample container and injects the sample into the injection port, and is connected to the dispensing nozzle. An automatic sample introduction device that includes a pump that supplies a diluent to the dispensing nozzle from behind and a sample introduction valve that measures the sample injected from the injection port with a measuring tube and introduces the sample into an analysis unit. Providing a sample dilution introduction tube having a volume sufficiently larger than the amount of the sample to be injected between the injection port and the sample introduction valve, feeding a diluent from the rear of the injected sample, A sample portion in a specific area of the sample concentration gradient formed by dispersing the sample in the diluent injection with the flow in the tube is taken out by the sample introduction valve and introduced into the analysis section.

In order to achieve the above object, a second automatic sample introduction device according to the present invention includes a sample suction nozzle, a sample introduction valve for measuring a sucked sample with a measuring tube and introducing the sample into an analysis unit, and the sample suction nozzle. In the automatic sample introduction device having a suction pump for sucking the sample in the sample container and feeding the sample introduction valve, between the sample intake nozzle and the sample introduction valve,
A sample diluting introduction tube having a capacity sufficiently larger than the volume of the sample to be inhaled is provided, and a diluting solution tank into which the sample aspirating nozzle can be inserted is provided. A configuration in which a sample portion in a specific area of a sample concentration gradient formed by dispersing a sample in a diluent with the flow during the introduction is taken out by the sample introduction valve and introduced into the analysis unit. Is done.

[Action]

The moving sample introduction method according to the present invention is configured as an automatic dilution sampling method that does not use a specific dilution tank, and a sample introduction tube having a predetermined length and capacity is provided between an injection port and a sample introduction switching valve. The inlet tube also has the function of diluting the sample. When a sample is injected into the sample introduction tube, for example, in a state where the diluent is previously filled, the sample is injected from the injection port, and subsequently, the diluent is subsequently injected and fed. And a concentration gradient in the stream. Therefore, a specific area of this concentration gradient is measured by a measuring pipe of the sample introduction switching valve and introduced into the analysis unit, and a minute amount of sampling at a desired dilution ratio is performed. As described above, the sample is diluted in the flow of the thin tube, which is the flow path of the sample, and a very small amount of the sample is sampled.

In the first automatic sample introduction device according to the present invention, the same injection port, sample introduction valve, and sample container and injection port of the automatic sample introduction device as those described in the conventional device are freely moved, and the sample is moved by the syringe pump. A dispensing nozzle for supplying and discharging the diluent and a control system for controlling the sampling, and further exhibits a diluting effect of the sample provided between the injection port and the sample introduction valve as a unique configuration of the present apparatus. And a sample dilution introducing tube. This sample dilution introducing tube is determined in advance on the basis of the amount of the sample to be injected and the dilution ratio for diluting in the introduction tube according to the analysis purpose, and its internal diameter and length are determined in advance and incorporated into the automatic sample introduction device according to the present invention. It is.

The second automatic sample introduction device according to the present invention is configured so that the injection port is eliminated, the position of the pump is changed, and the sample and the diluent are caused to flow into the introduction tube by the suction action.

The sampling in the automatic sample introduction device according to the present invention is performed in the following procedure.

(1) First, a certain amount of sample is sucked from the sample container by the dispensing nozzle.

(2) Next, the dispensing nozzle is inserted into the injection port, and a certain amount of the sample is injected into the sample dilution introducing tube by the syringe pump.
When the diluent is further fed from behind, the sample is dispersed in the diluent while flowing in the introduction tube.

(3) When a specific area of the concentration distribution of the sample flowing while dispersing reaches the sample introduction valve, the sample introduction valve is switched and introduced into the measuring tube of the sample introduction valve.

(4) When a predetermined sample area is held in the measuring tube,
The sample introduction valve is switched again to introduce the sample into the analysis unit.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows the first embodiment of the automatic sample introduction device according to the present invention.
An embodiment will be described. This embodiment shows an example in which the automatic sample introduction device is applied to a liquid chromatograph.

First, the configuration of the device will be described. In FIG. 1, the same elements described in FIG. 8 are denoted by the same reference numerals. In FIG. 1, an automatic sample introduction device 1 is provided with a sample stage 2, a washing tank 3, a drain port 4, and an injection port 6. A plurality of samples to be measured are accommodated in each of a plurality of sample containers 7, and the sample containers 7 are stored in sample racks 8.
And mounted on the sample stage 2. Nozzle 9
Is connected to a pump 12 via a thin tube 10 and a switching valve 11, and the pump 12 is configured to be selectively connected to one of the diluent tank 13 and the nozzle 9 by switching the switching valve 11. Have been. The nozzle 9 is moved to the position of each sample container or processing port by the drive mechanism 14 in the X-axis direction and the Y-axis direction, and performs necessary operations such as suction and discharge by the action of the pump.

In the analysis unit 15, the reagent tanks 17a, 17b,
One of the reagents 17c is configured to selectively flow to the separation column 19 via the sample introduction valve 18. solenoid valve
Reference numerals 22a, 22b, and 22c are provided for selecting reagents to be flown into the separation column 19 as the analysis proceeds. A sample diluting introduction tube 23 that produces a diluting action is provided between the injection port 6 and the sample introduction valve 18, and the sample diluted while passing therethrough is switched by switching the connection at the sample introduction valve 18. It is sent to the measuring tube 20 and is again introduced into the flow path 24 of the analyzer 15 by switching the sample introduction valve 18, sent to the separation column 19, and discharged to the drainage tank 25 via the detector 21. The introduction pipe 23 also functions as a dilutor. The sample components separated by the separation column 19 are measured while passing through the detector 21, and the measurement results are sent to a control unit 27 via an A / D converter 26, processed by the control unit 27, and processed by the display unit 28. And output to the printer 29.

As is apparent from the above description, in the configuration of the automatic sample introduction device of the present invention, a special dilution tank is not used, and a sample dilution field having a predetermined length and capacity is provided between the injection port 6 and the sample introduction valve 18. A sample dilution introducing tube 23 to be formed was provided. When, for example, a diluent is filled in advance into the introduction tube 23, a sample is injected from the injection port 6, and subsequently, the diluent is continuously injected and fed, and the sample is diluted while flowing through the introduction tube 23. It is dispersed in the liquid and forms a concentration gradient in the stream and distributed. The specific area of this concentration gradient is
A small amount of sampling at a desired dilution ratio is performed by a method in which the sample is measured by the 18 measuring tubes 20 and introduced into the analysis unit.

Next, before describing the sampling procedure by the automatic sample introduction device 1 in detail, the principle of the automatic dilution sampling method according to the present invention will be described with reference to FIGS. 2A to 2C.

As shown in FIG. 2A, when a sample liquid 42 (position A) is injected into an elongated tube 41 in which a carrier liquid 40 flows as shown by an arrow,
The sample liquid is dispersed in the carrier liquid 40 while spreading as a laminar flow in the tube 41. If the horizontal axis represents the length of the tube (or the volume of the sample solution in the tube) on the horizontal axis and the concentration of the dispersed sample on the vertical axis, a curve as shown in FIG. 2B or 2C is obtained. 2A to 2C, the point A indicates the injection position, and the point B indicates the position of the center of dispersion of the sample 42 'when flowing by the length 1 in the tube 41. The dispersion has a normal distribution as shown in FIG. 2B when the flow path system is an ideal system having no dead space. The following equation is known as a theoretical equation representing this dispersion state (JOURNAL OF CHROMATOGRAPHIC SCIENCE VOL.9).

Here, r is the inner radius of the tube, l is the length of the tube, each unit is cm, Q is the flow rate of the liquid (sample liquid or the like), and the unit is cm ³ /
sec and D _M are the diffusion coefficients of the sample liquid in the unit of cm ² / sec, σ _T and σ
_T ² are constants defined in general as the standard error and variance of the normal distribution, the unit is cm ^3, cm ⁶ respectively.

The above equation is a theoretical equation derived by some assumptions and limiting conditions, and does not always correspond to an actual value in the channel system handled in the present invention. However, in a liquid chromatograph, a flow injection analysis method, or the like, the dispersion is changed by changing the inner radius r, the length 1, and the flow rate Q of the sample liquid, and accordingly, by appropriately controlling these values, a desired value can be obtained. It is widely known that variance can be obtained and reproduced with high accuracy.

With the peak position B of the dispersion curve in FIG. 2B as the origin, the amount of the sample liquid dispersed in the section of X _{1 to} X ₂ (the shaded portion in the figure) from the origin is expressed by the following equation.

Here, V ₀ is the amount of sample injected, and X is the coordinates of the dispersion curve in the tube flow direction. The function obtained by the indefinite integration of the above equation represents the volume of the sample liquid in the area from the origin to the distance X. Therefore, dilution ratio R of the sample to the carrier liquid in the area X ₁ to X ₂ is expressed by the following equation.

R = V _D / (X ₂ −X ₁ ) (3) In an actual flow path system, the distribution of dispersion is not always an accurate normal distribution. For example, dead space of a flow cell for performing measurement or other flow path systems Due to such factors, a tailing phenomenon as shown in FIG. 2C is often exhibited. Even in such a case, σ _T and σ _T ² can be obtained by calculation.
The description is omitted here because it becomes complicated.

The theoretical equation of dispersion in the capillary has been described above. However, in an actual apparatus, it is difficult to obtain an accurate value of the diffusion coefficient of the sample liquid or the carrier liquid due to differences in the assumptions and the limiting conditions in the above equation (1). Actual values often do not always agree with the calculated values of the theoretical formulas due to problems inherent to the device such as road space dead spaces. Therefore, when a sample solution is flowed and diluted in an actual apparatus, an experiment is performed by assembling the apparatus based on conditions preliminarily estimated from a theoretical equation or the like, and an actual distribution curve or σ _T , X ₁ , X ₂ It is desirable to determine such a value.

Next, the sampling procedure in the automatic sample introduction method according to the present invention will be described in steps. This sampling is the same as the condition described above, and the length l and the internal volume Vp
Concentration of the sample using the dilution inlet tube 23, the sample solution from the injection port 6 and injected by V _0, passing a carrier liquid for dilution at a flow rate Q, the sample dispersed in the state of FIG. 2B or the 2C Figure A case will be described in which the analysis unit 15 samples the portion between X _{1 and} X _{2 in} the distribution. The description will be made by using the state of the sample flowing at the time of switching the sample introduction valve shown in FIGS. 3A to 3C.

(1) First, the sample introduction valve 18 is connected as shown in FIG. 3A,
The nozzle 9 is moved to the position of the injection port 6, the tip of the nozzle 9 is inserted into the injection port 6, the syringe pump 12 is operated, and the carry-over of the sample that has flowed through the sample dilution introducing tube 23 is performed. After sufficient washing so that no residue remains, the diluent is filled in the introduction tube 23.

(2) then moves to the position of the sample container 7 to be analyzed the nozzle 9, to suck the sample solution in a predetermined amount V ₀ at the tip of the nozzle 9.

(3) The nozzle 9 is moved again to the position of the injection port 6, inserted into the injection port 6, the sample is injected by operating the cylinder pump 12, and the diluent is flowed from behind at the flow rate Q at the flow rate Vp +
Only X ₁ to deliver.

(4) The sample is dispersed in the diluent in the state shown in FIG. 2B or 2C while flowing through the introduction tube 23. Since the internal volume of the introduction pipe 23 is Vp, the center of the dispersed sample is at the connection point between the sample dilution introduction pipe 23 and the sample introduction valve 18 when the diluent flows at the flow rate Vp.
When it reaches 33 and Vp + X ₁ flows, the X ₁ part is the connection point 33
To reach. The state is shown in FIG. 3A. The 3A filled portion in view is the area of the distribution curve X ₁ to X _2, part of the preceding sample is flowing the portion of the discharge passage 35 from the connecting passage 34.

(5) In this state, the sample introduction valve 18 is switched in the direction of the arrow in FIG. 3A, and the carrier liquid is further fed by X ₂ -X ₁ .
X ₁ to X ₂ the area of the distribution curve as shown in Figure 3B connection passage 36
From the measuring pipe 20. This is the area which is held in a state in which the sample quantity V _D necessary for analysis as described above was diluted.

(6) When the sample introduction valve 18 is switched again to the state shown in FIG. 3C, the sample liquid held in the measuring tube 20 and the connection passage 36 is introduced into the flow path 24 of the analysis section. During this time, the nozzle 9 moves to the washing port 3 to wash its outer wall,
12 sucks a new diluent from the diluent tank 13 and stands by for sampling of the next sample.

By the above procedures (1) to (6), the sample injected from the injection port 6 can be diluted to a desired concentration, and a desired amount of the sample can be sampled in the analysis unit.

FIG. 4 is a program example of the sampling procedure described above.
FIG. 4 (A) is a bar graph showing the working process over time, and FIG. 4 (B) is the function of the sample introduction valve 18, the nozzle 9, and the cylinder pump 12 which operate according to the working process. FIG.

The features of the apparatus and method according to the present invention are that the sample dilution introduction pipe 23 is provided in the sample solution injection channel, and the sample solution generated by dispersing the sample solution in the diluent in the flow is thereby provided. Sampling a sample portion of a specific area of the concentration gradient. That is, as described above, in the sample introduction device of the conventional method, the flow path from the sample injection port to the sample introduction valve is made as small as possible, and a sufficient amount of the sample to be replaced with the cleaning liquid remaining in the flow path is injected. Then, the basic method was to introduce it into a measuring tube. On the other hand, the present invention is characterized in that the sample diluting introduction tube 23 having a volume sufficiently larger than the amount of the sample to be injected is provided, and the sample is positively diluted.

The inner diameter and length of the sample dilution introducing tube 23 are determined in advance from the amount of the sample to be injected into the injection port 6 and a desired dilution ratio,
Built into the device. Since the value does not always match the above formula, it is desirable to determine the value after confirming the actual value by experiment. In order to increase the dilution ratio, the larger the inner diameter and the length of the introduction tube, the more effective. However, if the internal volume of the introduction tube is large, it takes time to clean the tube, and the amount of the cleaning liquid used increases. Although skirt portion and dilution (FIG. 2B and the 2C reference to X ₁ to X ₂ in the diagram) for sampling of the dispersion curve becomes larger, as compared to when sampling portion of the peak of the dispersion curve, the sampling accuracy Decrease. Conversely, if the peak portion of the dispersion curve is sampled, the sampling accuracy is improved, but the dilution ratio is reduced, and an increase in the ratio requires an introduction pipe with a large capacity. It is necessary to determine a flow path system suitable for the purpose in consideration of these relationships. From the experiment according to the present embodiment, the inside diameter of the sample dilution introducing tube 23 is 0.5 to 1 mm, the length is 0.5 to 2 m, the pump flow rate is 1 to 3 ml / min, and the amount of the sample to be injected is 3 to 10 μm.
Is appropriate, and the flow path conditions are determined in this range, and by appropriately selecting the sampling area of the dispersion curve, it is several tens times to
Sampling can be performed at a dilution factor of several hundred times.

 Next, a modified embodiment of the present invention will be described.

FIG. 5 shows a second embodiment of the present invention, in which only essential parts are shown. Other configurations are the same as those of the first embodiment. In this embodiment, the measurement pipe 20 of the sample introduction valve 18 is connected to the sample dilution introduction pipe 23.
The sample is injected from the injection port 6 in the state where the sample is connected to the sample tube.
This is a method in which the feed is stopped at the time of entering 20 and the sample introduction valve 18 is switched to be introduced into the analysis unit 15. Although the area to be cut is limited by the volume of the measuring tube 20, there is an advantage that the sampling time can be reduced.

FIG. 6 shows a third embodiment of the present invention, in which only essential parts are shown. Other configurations are the same as those of the first embodiment. In this embodiment, a small-volume stirrer 30 having a built-in rotor of a magnet stirrer is provided in the sample diluting introduction tube 23, and it takes a long time to clean the flow path, but a high dilution ratio can be obtained. Has advantages.

FIG. 7 shows a fourth embodiment of the present invention. In this embodiment, the injection port 6 required in the first embodiment is not provided, and the arrangement position of the cylinder pump 12 is also changed to the opposite side with respect to the sample introduction valve 18, so that sampling is performed by suction. I have. The diluting liquid in the diluting tank 13 is supplied to the diluting liquid port 31 by an ironing pump 32 and is always filled. The sample is sucked at the tip of the nozzle 9 and then the nozzle 9
Is inserted into the diluent port 31, and the diluent following the sample is sucked by the syringe pump 12 to flow into the sample diluting introduction tube 23,
When the area of the desired concentration gradient of the dispersed sample reaches the measuring tube 20, the sample introduction valve 18 is switched to introduce the sample into the analysis unit. Also in this method, the same effect as in the method of injecting from the injection port as in the above embodiment can be obtained.

All of the above-described modified embodiments are included in the scope of the present invention.

〔The invention's effect〕

As is apparent from the above description, according to the present invention, dilution is performed in the sample introduction flow path, and there is no need to provide a special dilution tank as in the conventional method. Pre-dilution function enables sampling of very small amounts of sample, making it suitable not only as a sample introduction device such as a liquid chromatograph dedicated to specific items of routine work such as clinical tests, but also as an option for a general-purpose liquid chromatograph Is wide.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a first embodiment of the automatic sample introduction device according to the present invention, FIGS. 2A to 2C are diagrams for explaining the dilution method in the present invention in principle, and FIGS. FIG. 3C is a diagram for explaining the operation of the sample introduction valve, FIG. 4 is a time chart showing a sampling procedure, FIG. 5 is a main part configuration diagram showing a second embodiment of the present invention, and FIG. FIG. 7 is a block diagram of a main part showing a third embodiment of the present invention, FIG. 7 is an overall block diagram showing a fourth embodiment of the present invention, and FIG. 8 is a block diagram of a conventional automatic sample introduction device. [Explanation of Symbols] 1 ... Automatic sample introduction device 6 ... Injection port 7 ... Sample container 9 ... Nozzle 12 ... Syringe pump 13 ... Diluent tank 16 ... Pump 18 ... Sample introduction valve 19 ... Separation column 20… Measurement tube 21… Detector 23… Introduction tube for sample dilution 42 …… Injected sample 42 '…… Specific area sample

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masato Ito 882 Ma, Katsuta-shi, Ibaraki Pref.Naka Works, Naka Plant (72) Inventor Yoshio Fujii 882 Mao, Katsuta-shi, Ibaraki Pref. Inside the Naka Plant (72) Inventor Tadafumi Kuroishi 882 Ma, Katsuta-shi, Ibaraki Prefecture Inside Naka Plant, Hitachi Ltd. (72) Inventor Exit Kisaburo 882, Ma, Katsuda City, Ibaraki Prefecture Inside Naka Plant, Hitachi Plant 56) References JP-A-63-71650 (JP, A) JP-A-61-190863 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01N 30/06 G01N 35/08

Claims (3)

(57) [Claims] 1. A fixed amount of a sample is fed from an inlet to a sample dilution introducing tube having a volume sufficiently larger than the amount of a sample to be introduced, and then a diluent is fed. Dispersing the sample in the diluent while flowing in the introduction tube, taking out a sample portion of a specific area of the sample concentration gradient formed in the flow in the introduction tube using a flow path switching valve, An automatic sample introduction method characterized in that the sample is supplied to a flow path of a carrier solution for analysis. 2. An injection port, a dispensing nozzle for sucking a sample in a sample container and injecting the sample into the injection port, and connected to the dispensing nozzle to feed a diluting liquid to the dispensing nozzle from behind. In an automatic sample introduction device including a pump and a sample introduction valve that measures the sample injected from the injection port with a measuring tube and introduces the sample into the analysis unit, the sample is injected between the injection port and the sample introduction valve. A sample diluting inlet tube having a volume sufficiently larger than the volume of the sample to be supplied, and a diluent is fed from behind the injected sample, and the sample is dispersed in the diluent with the flow in the inlet tube. An automatic sample introduction device characterized in that a sample portion in a specific area of a sample concentration gradient formed by the above is taken out by the sample introduction valve and introduced into an analysis section. 3. A sample suction nozzle, a sample introduction valve for measuring a sucked sample by a measuring tube and introducing the sample into an analysis section, and a sample in a sample container is sucked by the sample suction nozzle and sent to the sample introduction valve. An automatic sample introduction device having a suction pump for supplying a sample, wherein a sample dilution introduction pipe having a capacity sufficiently larger than the amount of the sample to be sucked is provided between the sample suction nozzle and the sample introduction valve, and the sample suction is performed. A sample formed by providing a diluent tank into which a nozzle can be inserted, sucking and feeding the diluent from behind the sucked sample, and dispersing the sample in the diluent with the flow between the introductions A moving sample introduction device, wherein a sample portion in a specific area of a concentration gradient is taken out by the sample introduction valve and introduced into an analysis section.