JPH0511846B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a liquid dispensing method, and in particular to high precision and high reliability sampling of minute amounts in which liquid samples, reagents, etc. are quantitatively dispensed by pipetting. The present invention relates to a liquid dispensing method suitable for a multi-item automatic analyzer, etc.

[Conventional technology]

Dispensing devices used for quantitative dispensing of liquid samples and reagents in multi-item automatic analyzers include, for example,
There is an apparatus discussed on pages 43 to 44 of ``Clinical Automated Analysis'' edited by Kyoichi Ozawa, published by Kodansha in 1985, and the case of dispensing a sample will be explained below. Connect two syringe pumps, a microsyringe and a millisyringe, and a purified water storage bottle to the probe for pipetting the sample in sequence, and connect the first one between the two syringe pumps and between the millisyringe pump and the storage bottle, respectively. ,
A second electromagnetic valve is provided, and the flow path system is filled with purified water. Of the two syringe pumps, the microsyringe pump is used for pipetting the sample, and suction and ejection of the sample with the probe is achieved by the operation of the piston within the microsyringe pump. In a multi-item automatic analyzer, the required sample is different for each analysis item, so it is necessary to change the amount of piston movement for each analysis item.This change is achieved by moving the piston using a computer-controlled pulse motor. This can be achieved by controlling the amount of movement. The millisyringe pump is used to clean the inner periphery of the probe after pipetting is completed, and discharges a certain amount of purified water sucked into the syringe from the probe via the first electromagnetic valve to clean the inner periphery of the probe. Next, a sample sampling operation using the sampling device having the above configuration will be explained. Before inhaling the sample, the probe sucks a small amount of air into its tip.
Thereafter, the microsyringe is moved to the sample position, its tip is dipped into the sample, and the required amount of sample is aspirated by the suction operation of the microsyringe. At this time, the first and second
The solenoid valve is in the closed state. The intake amount is set to be slightly larger than the amount to be exhaled. When the sample suction is completed, the probe rises, moves to the discharge position, descends into the reaction container, and discharges the amount of sample necessary for analysis by the discharge operation of the microsyringe. after that,
The probe moves to the cleaning position, discharges the extra sample that was drawn in, and then opens the first solenoid valve.
The discharge operation of the millisyringe pump discharges a certain amount of water to wash the inside of the probe, and the outside is also washed with washing water from the outside. After that, close the first solenoid valve, open the second solenoid valve, and suck the purified water in the syringe with the suction operation of the millisyringe pump.
Close the second solenoid valve. Additionally, a microsyringe pump sucks a small amount of air into the tip of the probe and waits for the next job. This small amount of air was added to prevent the sample from diluting with water.

The above-mentioned conventional sampling device has sufficient accuracy and
Although it has satisfied the reliability and fulfilled its role, it has become necessary to improve it in line with the progress and development of automatic analyzers in recent years. In other words, due to the diversification and increase in the number of clinical biochemical tests, there is a growing need for an increase in the number of analysis items and an increase in analysis processing capacity. However, there is a need for even higher speeds in order to realize smaller, more efficient devices. In addition, there is a high demand for improvement in device performance, and especially in sample sampling devices that directly affect device performance, there is a need to further miniaturize the dispensing amount, widen the range, and ensure accuracy. For example, the minimum sample amount required for analysis is 5 μ
However, some analysis items require a sample size of 20μ to ensure sensitivity. In addition, the cycle time for a series of device operations has almost doubled from 20 seconds to 12 seconds and then to 6 seconds, and the operation speed of sampling devices has also increased. It's getting faster proportionately. Previously, sample dispensing ranged from 5μ to 20μ, but now from 3μ or smaller to 20μ
It is necessary to maintain and improve the accuracy by dispensing up to two times or four times faster than before.

The factors that affect the accuracy of sample dispensing by pipetting, that is, the sampling accuracy, are:
There are not only differences in the accuracy of the dispensed amount, but also changes in the concentration of the sample due to contact between the sample and purified water within the Lorabe.
The accuracy of the dispensed amount can be obtained by ensuring the shape and dimensions even when increasing the speed, but the dilution of the sample due to water is greatly affected by increasing the suction and discharge speeds. As is well known, the flow of fluid in a pipe has a velocity distribution in which the velocity is zero at the pipe wall in a cross section with respect to the flow direction and is twice the average flow velocity in the center due to the viscosity of the fluid. , this is the primary cause of thinning of the sample. For this reason, when pipetting a sample, it is observed that the sample becomes thinner near the interface between the sample and water due to contact between the sample and water. In other words, when a sample is sucked into the probe, the sample enters the flow of water at the center of the flow, and when it is expelled, the washing end of the water enters the flow of the sample, causing a dilution phenomenon of the sample. occurs. In conventional devices, in order to eliminate the effect of diluting the sample, as mentioned above, a small amount of air is interposed between the water and the sample, and the amount of sample to be aspirated is slightly larger than the amount to be discharged. was.
A second cause of thinning of the sample is wetting of the inner surface of the probe by the sample and water. Before the sample was aspirated, the inner surface of the probe was in contact with water, and even after the water flows to the syringe pump side to aspirate the sample, a thin layer remains on the inner surface due to wetness, and the sample flows over it. , thinning of the sample occurs. The effect of dilution of the sample caused by these factors on sampling accuracy becomes greater as the amount dispensed becomes smaller. For example, in the conventional example, when dispensing 3μ, the sampling accuracy is 2μ compared to when dispensing 20μ. ~3 times worse. It is also obvious that the sampling rate increases as the flow rate of the liquid in the probe increases.

If the above-mentioned conventional sampling device is applied to a device with a smaller sample dispensing amount and faster speed, it will not be possible to maintain or ensure its accuracy.To solve this problem,
Increasing the amount of air mentioned above will compromise accuracy when it comes to reducing the amount of sample, and increasing the difference between the suction and discharge amounts will go against the grain and be unacceptable. It's not a thing.

[Problem that the invention seeks to solve]

As is clear from the above explanation, conventional sampling devices have a limit in operating speed to ensure sample dispensing accuracy, and this device can be used to miniaturize and speed up sample dispensing. Regarding sample dilution, the suction and discharge speeds of the sample remain constant regardless of the amount dispensed, and therefore, there was a problem that sampling accuracy could not be ensured when dispensing a small amount of sample quantitatively. .

The purpose of the present invention is to minimize the required sample amount,
High-performance liquid dispensing that can ensure dispensing accuracy and improve device performance and reliability when used in multi-item automatic analyzers that have a wide range of applications and significantly increased dispensing speed. The goal is to provide equipment.

[Means for solving problems]

In order to achieve the above object, the present invention basically proposes the following liquid dispensing method. Note that the reference numerals attached to each element described below are the reference numerals used in the drawings of the embodiments for convenience, in order to facilitate understanding of the content of the invention.

That is, a probe 8 for pipetting a liquid to be dispensed such as a liquid sample or a reagent;
A piston 3 that sucks in and discharges the liquid to be dispensed.
A syringe pump 1 driven by a pulse motor 6, a valve 10 of a purified water supply system for filling purified water into the syringe pump 1, the probe 8, and the tube 7 connecting these, a pump 11, and purified water storage. Container 12 and drive circuit 1 for pulse motor 6
7 and a control system 16 that controls a drive circuit 17. When inhaling and dispensing the liquid to be dispensed, the probe 8 is provided with the syringe pump 1, the probe 8, and the tube 7 filled with purified water. It is carried out with a small amount of air layer interposed at the tip, and the control system 1
6 changes the rotational speed of the pulse motor 6 according to the dispensed amount based on the input data of the dispensed amount of the liquid to be dispensed (this change becomes larger as the dispensed amount increases) By controlling the drive circuit 17 using a relational expression or a table regarding the dispensing amount and pulse motor rotation speed characteristics prepared in advance, the suction and dispensing speeds of the liquid to be dispensed can be automatically adjusted according to the dispensing amount. Variable control.

[Effect]

The present inventors have discovered that the biggest factor affecting the sampling accuracy of liquids to be dispensed, such as liquid samples and reagents (hereinafter explained as a representative example of liquid samples), is dilution of the sample by purified water within the probe 8. However, as the volume of the sample becomes smaller and the flow rate of the liquid within the probe 8 increases, the thinning will increase as the amount of the sample becomes smaller and the flow rate of the liquid within the probe 8 increases. It was found that even if the flow rate is increased, there is no practical problem in sampling accuracy (effect of thinning of the liquid) (specifically, when the flow rate increases to near the upper limit of 20μ, the sampling accuracy decreases even if the flow rate is doubled). There is no practical impact on this), and the above dispensing method was developed with this in mind.

That is, according to the present invention, inhaling a liquid sample,
When dispensing, first fill the syringe pump 1, probe 8, and tube 7 with purified water by controlling the purified water supply system, and then
This is done with a small amount of air interposed at the tip. In this case, the control system 16 inputs data regarding the amount of liquid sample to be dispensed, and uses this data to adjust the amount of liquid sample to be dispensed. Since the rotation speed of the pulse motor 6 is changed according to the relational expression and table set in advance, the suction and discharge speeds of the liquid sample can be adjusted so that the smaller the amount of the dispensed amount, the less the degree of collapse of the air layer inside the probe 8. The effect of dilution of the liquid sample on the purified water can be prevented by controlling the liquid sample to a small value, and the suction and discharge speeds can be controlled more greatly as the amount to be dispensed increases (the more the effect of dilution of the purified water disappears). . In particular, near the maximum dispensed volume, inhalation,
Discharge speed can be doubled compared to conventional methods.

As a result, it is possible to realize a multi-item automatic analysis system that always takes into consideration sampling accuracy and high speed dispensing operation according to the amount of liquid sample dispensed.

〔Example〕

The present invention will be explained in detail below using the embodiments shown in FIGS. 1 and 2.

FIG. 1 is a configuration diagram showing an embodiment of a liquid dispensing device of the present invention. In FIG. 1, reference numeral 1 denotes a microsyringe pump, which is composed of a cylinder 2, a piston 3, and a seal 4 for the piston 3. 5 is a rack and pinion mechanism; 6 is a pulse motor; the rotary motion of the pulse motor 6 is converted into linear motion by the rack and pinion mechanism to drive the piston 3; 7 is a flexible tube, 8 is a probe, 9 is a probe moving mechanism that gives rotation and vertical movement to the probe 8, 10 is a solenoid valve, and the cylinder 2 stores purified water through the solenoid valve 10 on one side and the pump 11, etc. It is connected to a bottle 12, and the other end is connected to a probe 8 by a flexible tube 7, and the purified water from the storage bottle 12 is filled up to the tip of the probe 8. 13 is a sample container containing a sample, 14 is a reaction container, 1
5 is an input device for inputting analysis items, amounts of samples and reagents, etc., 16 is a control circuit that controls the pulse motor 6 at a rotation speed (rotation angle) according to the input sample dispensing amount, and 17 is a control circuit. This is a drive circuit that drives the pulse motor 6 using signals from the pulse motor 16.

Quantitative dispensing of a sample using the liquid dispensing device having the above configuration, that is, the liquid sample sampling device, can be performed as follows. First, the piston 3, which was located at the top dead center, is slightly lowered to suck a small amount of air into the tip of the probe 8. Then, the probe 8 is moved to the position of the sample container 13 by the probe moving mechanism 9, and the probe 8 into the sample. Here, the pulse motor 6 is operated with the output of the control circuit 16 at an amount and speed corresponding to the suction amount V, which is the predetermined dispensing amount V ₀ that has been input and stored in advance by the input device 15 and an extra amount V ₁ to be inhaled. Rotate at f, pull out the piston 3 from the cylinder 2, and remove the probe 8.
Inhale the sample into the tube. After that, the probe 8 is raised and moved to the position of the reaction vessel 14, and the probe 8 is moved to the position of the reaction vessel 14.
The sample is discharged from the probe 8 by rotating the pulse motor 6 in a direction in which the piston 3 is pushed in by an amount corresponding to a predetermined dispensing amount V ₀ at a speed f set at the time of suction. After the discharge is completed, the probe 8 is moved to the cleaning position (not shown), the piston 3 is returned to the top dead center, and the remaining sample V ₁ is discharged,
The solenoid valve 10 is opened and the pump 11 is operated for a predetermined period of time to discharge purified water from the tip of the probe 8 to clean the inner surface of the probe 8.
The outer surface of is also washed with water, and the solenoid valve 10 is closed.

In this state, wait for the next dispensing request.

Here, the suction and discharge speed of the sample is determined by the amount dispensed, which is determined by the control circuit 1.
Do it in 6. The details will be explained using FIG. 2.
FIG. 2 is a block diagram showing one embodiment of the control circuit 16 of FIG. 1. In FIG. 2, 18 is a basic clock generation circuit consisting of a crystal oscillator, etc., and 19 is an arithmetic unit that determines the rotational speed f and movement amount n of the pulse motor 6 according to the suction amount V of the sample, and is composed of a computer, for example. , the rotational speed f is determined by calculating the following equation.

Here, v: the amount of sample suction or discharge per pulse given to the pulse motor 6.

t: Predetermined dispensing time 20 is a pulse generator that generates a pulse train having a rotational speed f and a movement amount n, and divides the frequency ₀ of the basic clock into f/ ₀ to obtain the rotational speed f.

21 is a distribution circuit that distributes the pulse train obtained by the pulse generator 20 to each phase winding of the pulse motor 6. All of these can be constructed using known circuits or computers.

According to equation (1), the moving speed of the liquid within the probe 8 can be controlled at a speed approximately proportional to the amount V of sample inhaled, and near the minimum dispensed amount, which is most susceptible to the effect of diluting the sample, The dispensing speed can be increased near the maximum dispensing amount where the moving speed is extremely low, and therefore no dilution occurs and is hardly affected by dilution, enabling high-speed operation. I can do it. In order to obtain the rotational speed f according to the suction amount V, in addition to using the calculation unit 19, the suction amount V is divided into several stages in an appropriate range, and the rotational speed f is determined for each of the stages. , this may be prepared as a table.

Note that the control circuit 16 can be realized by changing the contents of the computer section of the conventional device, and does not cause any economic burden.

In addition, although the above explanation was only about sample dispensing, reagent dispensing also includes miniaturization,
The need for faster processing is exactly the same as for samples.
It goes without saying that the same effect can be obtained even when the present invention is applied to reagent dispensing.

〔Effect of the invention〕

As described above, according to the present invention, the suction and discharge speeds of liquids to be dispensed, such as liquid samples and reagents, within the probe are adjusted to achieve both sampling accuracy and high-speed dispensing operation according to the amount of the dispensed liquid. Since the present invention can be automatically and variably controlled while maintaining the accuracy, it can be applied to a multi-item automatic analysis system, etc., and contribute to speeding up the system operation and increasing the accuracy of analysis.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the liquid dispensing device of the present invention, and FIG. 2 is a block diagram showing an embodiment of the control circuit of FIG. 1... Micro syringe pump, 2... Cylinder, 3... Piston, 6... Pulse motor, 8...
...Probe, 9...Probe moving mechanism, 12...
Purified water storage bottle, 13... Sample container, 14...
Reaction container, 15... Input device, 16... Control circuit, 17... Drive circuit, 18... Basic clock generation circuit, 19... Arithmetic unit, 20... Pulse generator, 21... Distribution circuit.

Claims (1)

[Scope of Claims] 1 A probe for pipetting a liquid to be dispensed such as a liquid sample or a reagent, and a piston for sucking in and discharging the liquid to be dispensed with the probe are driven by a pulse mode. syringe pump,
A valve, a pump, a purified water storage container of a purified water supply system for filling purified water in the syringe pump, the probe, and a tube connecting these, a drive circuit for the pulse motor, and a control system for controlling the drive circuit. When inhaling and dispensing the liquid to be dispensed, the syringe pump, the probe, and the tube are filled with the purified water, and a small amount of air space is interposed at the tip of the probe. At the same time, the control system changes the rotational speed of the pulse motor according to the dispensed amount based on the input data of the dispensed amount of the liquid to be dispensed (this change becomes larger as the dispensed amount becomes larger). By controlling the drive circuit using a relational expression (which is a change in rotational speed) or a table prepared in advance regarding the dispensing amount vs. pulse motor rotational speed characteristics, the suction and discharge speed of the liquid to be dispensed can be changed to the dispensing amount. A liquid dispensing method characterized by automatic variable control depending on the situation. 2. Claim 1 is characterized in that the control system controls the rotational speed of the pulse motor so that the suction and discharge speeds of the liquid to be dispensed change in proportion to the amount dispensed. liquid dispensing method. 3. In claim 1, the control system controls the rotational speed of the pulse motor so that the suction and discharge speeds of the liquid to be dispensed are changed in stages according to the amount to be dispensed. Characteristic liquid dispensing method.