JPS63109373A - Sampling method and apparatus therefor - Google Patents

Abstract

PURPOSE:To perform the sampling of a very small amount of a specimen with high accuracy, by connecting an air compressor to a sampling nozzle through a valve. CONSTITUTION:A sampling apparatus 1 is constituted of a sampling nozzle 2, a plunger pump 3, a pressure sensor 4, an air compressor 13 and a valve 14. When the leading end part 7 of the nozzle 2 reaches the position U of a specimen container 8, air is emitted from the leading end part 7 by the compressor 13. The pressure in piping 9 is measured by the sensor 4 through a three-way joint 10 and the output of the sensor 4 is inputted to a pressure signal discriminator 5. When the leading end part 7 reaches a liquid level L, the pressure in the piping 9 abruptly rises and a liquid level discriminating signal output 11 generates a liquid level detection signal and a nozzle transfer mechanism is stopped by the output 11 and a stop position S is stored. Next, the nozzle 2 rises over a definite distance to reach a position Y and the valve 14 is closed to stop the supply of air. Then, the nozzle 2 again falls to the position S and the plunger 6 of the pump 3 is drawn out and a desired amount of the specimen 12 is sampled in the nozzle 2.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for sampling reagents and samples in an automatic chemical analyzer, and an apparatus therefor.

(bl) Conventional technology In the field of automatic chemical analysis, a process is adopted in which a sample liquid is introduced into a measuring device that measures the concentration of a specific substance therein, and after the measurement is performed, it is discharged. In order to make a measurement, it is necessary to quantitatively collect a sample liquid into a measuring device.

This collection is sampling.

A common method for sampling a sample is to immerse a suction nozzle in a sample container and suction the sample using a suction pump.

In this case, the liquid level of the sample becomes a problem. However, dipping the nozzle more than necessary can lead to measurement errors, so it is important to detect the liquid level and immerse the nozzle to the minimum necessary level.

The reason for this is that when the nozzle is immersed, the sample adheres to its outer surface, and when this nozzle is immersed in the reaction liquid, it reacts in the same way as the sampled sample, leading to an increase in the amount of sample and resulting in an error. In addition, in the method of blowing out the sampled sample with air, etc., the nozzle does not need to be immersed in the reaction solution, so it seems that the sample attached to the outside of the nozzle does not affect the reaction solution. It is difficult to blow out completely and the sample may drip from the outside surface, which also causes errors.

For these reasons, it is necessary to sample without immersing the suction nozzle as much as possible.

For this purpose, it is necessary to detect the liquid level as described above.

Various methods have been known for detecting the liquid level. For example, there are methods in which an electrode is brought close to the liquid and an electric signal is emitted when it comes into contact with the liquid surface, and a method using glass fibers, etc. The liquid level can be detected using an optical method that measures the amount of light reflected from the liquid surface using There are methods to detect this.

Furthermore, there is also a method of separately providing a discharge pipe having the same shape as the suction nozzle, discharging air from the suction nozzle and the discharge pipe at the same time, and detecting the differential pressure therebetween.

(C) Problems to be Solved by the Invention Among the above methods, the electrode method has problems such as difficulty in inserting the electrode into a sample container with a small diameter, and malfunction due to liquid junction between the electrodes. There is a disadvantage that it occurs.

In methods that use a discharge pipe, it is necessary to provide a separate discharge pipe, which often makes it difficult to insert the nozzle and discharge pipe into the sample container.In addition, in methods that detect differential pressure, it is difficult to insert the nozzle and discharge pipe into the sample container. A detection pressure supply device consisting of a three-way valve for discharging air from the tip, a discharge pipe for differential pressure detection, a sample suction pump, and a pressure regulator is required, which increases cost, increases size, and requires additional equipment. The increase in the amount of data caused the reliability to decrease.

(d) Means for solving the problem In view of the above-mentioned current situation, the inventors have completed the present invention as a result of intensive research, and the nozzle for sample sampling can also be used as a nozzle for detecting the liquid level. It is characterized by: That is, by connecting a compressor or the like to the sampling nozzle, air is discharged or sucked from the sampling nozzle, and fluctuations in pressure in the sampling nozzle are detected, and when the sampling nozzle is close to or close to the surface of the liquid to be sampled. After detecting contact and measuring the level of cough fluid, a sample is sampled using the sampling nozzle.

Here, the term "sample" refers to an object whose concentration, etc., of a specific substance contained therein is to be measured, and is often blood, urine, or the like.

"Sampling" refers to sucking a sample from a sample container using a nozzle or the like and introducing the sample into the concentration measuring section.

"The nozzle approaches" refers to the point in time when the nozzle tip approaches the sample liquid surface and the pressure resistance for suction or discharge becomes large. The actual distance is about 1 to several mm, but this varies depending on the inner diameter of the nozzle and the amount of air sucked and discharged. Therefore, when the inner diameter and the discharge amount are determined, the relationship between the distance and the pressure fluctuation is determined, and if this is memorized, it becomes possible to detect a point in time when the distance approaches.

"Contact" means that the nozzle tip comes into contact with the sample liquid surface.

The "pressure detection device" refers to a pressure sensor such as a so-called diffusion type semiconductor, and any device may be used as long as it can measure fluctuations in its value, that is, the rise of a pressure curve.

"Compressor etc." refers to an air compressor, a vacuum pump, etc., which is connected to the sampling nozzle via a valve to discharge or suck air from the sampling nozzle when detecting the liquid level.

"Sample suction pump" refers to a piston-type or diaphragm-type reciprocating pump that is used only when aspirating a sample.

The present invention supplies air to the sampling nozzle using an air compressor or the like, exhausts the air from the tip of the nozzle, and measures the internal pressure of the sampling nozzle with a pressure sensor. This is a method in which the point in time (the rising point of the pressure curve) is set at or near the liquid level. Whether it is at this liquid level or near it can be distinguished by the degree of pressure fluctuation, and as it approaches the liquid level, air discharge decreases and the pressure curve rises. When the nozzle is moved closer to the liquid level, the nozzle comes into contact with the liquid level, the nozzle opening is closed, and the pressure curve rises more rapidly. The point at which this sudden rise occurs is considered the liquid level.

However, if the amount of air discharged is very small and the pressure fluctuations at nearby points are small and difficult to detect, the pressure may increase only when the liquid level is reached. This is a problem with the air discharge amount and the performance of the pressure detector, etc., and cannot be determined.

In this way, the liquid level is stored in the storage device, and when the nozzle is immersed in the liquid, the nozzle is pulled up once and then the nozzle is immersed to a predetermined depth. The reason for this increase in temperature is that since air is discharged from the nozzle, air bubbles remain at the tip of the nozzle when measuring the liquid level, and if the sample is sucked in as it is, the amount of sample decreases by the amount of bubbles, resulting in an error in the amount of sample. This is to become. The amount of suction may be set by taking the amount of air bubbles into account, but this poses a problem because the size of the air bubbles is not constant, causing variations.

Furthermore, in order to detect the liquid level by detecting pressure fluctuations within the sampling nozzle, it is also possible to similarly detect the liquid level by suctioning air from the tip of the nozzle.

That is, this is a method in which air is sucked from the tip of the nozzle and the nozzle is brought close to the liquid surface while measuring the internal pressure of the nozzle with a pressure detector, and the liquid level or the vicinity of the liquid level is detected based on pressure fluctuations.

Air suction is performed by separately providing a vacuum pump or the like.

(e) Examples Hereinafter, the present invention will be explained in detail based on examples shown in the drawings.

FIG. 1 shows an embodiment of the sampling device (11) according to the present invention, in which a sampling nozzle (2),
It is composed of a plunger pump (3), a pressure sensor (4), a pressure signal discriminator (5), an air compressor (13), and a valve (IIO).

Here, the procedure from liquid level detection to sampling will be described in detail below.

First, the nozzle (2) begins to move down by a nozzle transfer mechanism (not shown). The nozzle tip (7) is the sample container (8)
When the position U is reached, air is discharged from the nozzle tip (7) by the air compressor (13). Note that nozzle positions U and B are the highest and lowest positions of the sample liquid level. The pressure increase in the pipe (9) can be almost ignored until the nozzle tip (7) reaches the liquid level.

The pressure in the pipe (9) is measured by a pressure sensor (4) via a three-way joint (10), and the sensor output is connected to a pressure signal discriminator (5) consisting of a sensor amplifier, a differentiation circuit, and a comparison circuit. ing.

When the nozzle tip (7) reaches the liquid level, the pressure inside the pipe (9) increases rapidly, and the liquid level determination signal output (11) generates a liquid level detection signal. To speed up the response of liquid level detection, install piping (9), three-way joint (10), and pressure sensor (4).
It is also necessary to reduce the internal volume of the nozzle (2) as much as possible. The nozzle transfer mechanism is stopped by the liquid level detection signal output (11) and the stop position S is memorized.
For example, when a pulse motor is used as the driving means, this can be done by storing the number of driving pulses. Then, the nozzle (2) rises a certain distance to position Y,
By closing the valve (14), the supply of air is stopped (in this case, the air compressor (13) may also be stopped). Then, use the nozzle again (
2) is lowered to the previous S position, and the plunger pump (3) is lowered to the previous S position.
) is pulled out and the desired amount of sample (1
2) is sampled into the nozzle (2). At this time, the position of the nozzle tip (7) can be set to any position other than S, and can be set to the optimum position for sample suction. After sample sampling, nozzle (2
) rises and moves to the intended transfer destination, and the plunger (6) is pushed out to release the sample (12) in the nozzle (2).
) is discharged in preparation for the next sampling.

Next, the liquid level can also be detected by suctioning air from the nozzle tip (7). That is, this is done by connecting a vacuum pump (not shown) to the nozzle (2) instead of the air compressor (13). This vacuum pump lowers the nozzle (2) while sucking air from the nozzle tip (7).
7) outputs a liquid level detection signal based on the pressure fluctuation when the liquid level reaches the liquid level, and is a method of detecting the liquid level in substantially the same manner as in the above-described embodiment. However, in this case, the sample (12) may be sucked into the nozzle (2) when detecting the liquid level, so after stopping air suction by the vacuum pump, open the nozzle (2). It is better to push out the plunger (6) a little to eject the sample before raising it. This is because if you push out the sample after raising the nozzle (2), the sample ( 1
2) may not drip, and the initial pressure when suctioning the sample (12) next changes, which deteriorates sampling accuracy.

ff) Effects of the Invention As described above, the sampling method and device according to the present invention connects an air compressor, a vacuum pump, etc. to the sampling nozzle via a valve, thereby discharging or suctioning air from the nozzle, thereby suppressing fluctuations in the internal pressure of the nozzle. The sampling nozzle detects the liquid level by detecting the liquid level, and can be modified very easily to conventional sampling equipment.The operation method is also simple and reliable, and the sampling nozzle Since it also serves as a nozzle for surface measurement, sampling from small-diameter sample containers is possible, and it can be applied to any sampling device. Furthermore, there is very little sample adhesion to the outer surface of the nozzle tip, making it possible to sample a minute amount of sample with high precision. Furthermore, the output from the pressure sensor has the extremely beneficial effect that it is possible to monitor nozzle clogging, plunger pump leakage, etc. during sample suction and discharge.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of a sampling device according to the present invention. ■... Sampling device 2... Nozzle 3... Plunger pump 4... Pressure sensor 5... Pressure signal discriminator 6... Plunger 7... Nozzle tip 8... Sample container 10 ...Three-way joint 12...Sample 13...Air compressor 14...Valve

Claims (1)

[Claims] 1. Air is discharged or sucked from the sampling nozzle by a compressor connected to the sampling nozzle, and the sample to be sampled by the sampling nozzle is detected by detecting pressure fluctuations within the sampling nozzle. A sampling method comprising: detecting proximity to or contact with a liquid surface, measuring the liquid level of the liquid, and sampling the sample using a sample suction pump. 2. A sample suction pump, a sampling nozzle, a compressor, etc. connected to the sampling nozzle via a valve to discharge or suck air from the sampling nozzle, and detect pressure fluctuations in the sampling nozzle when air is discharged or sucked. A liquid level detection device comprising a pressure sensor.