JPH0619361B2 - Blocking detection method for automatic dispensing device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for detecting clogging of an automatic pipetting device, and more particularly to a method for detecting clogging by a solid substance in a liquid sample adsorbing to a nozzle tip.

[Prior Art] It is indispensable to dispense a desired amount of sample by inhalation in a sample test or the like. Generally, a device for injecting a predetermined amount of sample by inserting a nozzle tip connected to a suction pump into the sample is available. Widely used.

In particular, in recent years, an automatic dispensing apparatus has been developed that can continuously perform each dispensing step without human intervention, and is very suitable for processing many kinds of samples in a short time.

Usually, the sample to be dispensed is often a body fluid collected from a living body such as serum or plasma, and the dispensed sample is mixed with a reagent or the like and subjected to a predetermined test.

[Problems to be Solved by the Invention] However, serum and plasma, which are generally objects of automatic dispensing, are actually used in a state in which blood or the like is centrifuged.

Centrifugation agents, blood clots, etc. are mixed in the serum particularly in such a treatment state, so if this is directly applied to the dispenser for the dispensing action, these extremely small nozzle tip suction ports will not contain these substances. Separation agents or blood clots, which are solid bodies, are adsorbed to cause an occlusion state, and it is difficult to continue smooth sample suction and collection work.

In order to avoid such inconvenience, in the past, it was necessary to perform a pre-treatment such as transferring the sample to another tube before applying it to the pipetting machine, which hinders the rapid progress of the pipetting treatment work, which is extremely difficult. There was a problem of inconvenience.

OBJECT OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to adsorb a solid substance contained in a liquid sample during suction of the liquid sample to a nozzle tip suction port. If a solid substance that may block the nozzle tip suction port is contained in the non-specimen by simply and quickly detecting the occurrence of a blockage caused by An object of the present invention is to provide a method for detecting blockage of an automatic dispensing device that can realize the above.

[Means for Solving the Problems] In order to achieve the above object, the present invention is an automatic method for inserting a nozzle tip at the tip of an air hose connected to a suction pump into a sample tube to absorb and collect a predetermined amount of liquid sample. In the blockage detection method of the dispensing device, the air hose internal pressure level that changes with the suction time when collecting the liquid sample in the sample tube is sampled at a predetermined cycle, and the change rate of the detected pressure level value from the previous detection value is specified. When the above is the case, it is characterized by detecting and determining that the suction port of the nozzle tip is in a closed state.

[Operation] According to the method of the present invention configured as described above, the occurrence of so-called clogging in which the nozzle tip suction port for collecting a liquid sample is blocked by the solid substance contained in the sample is connected to the suction pump. The pressure change in the air hose can be promptly detected by using the pressure change as an index.

That is, during suction and collection of the liquid sample in the sample tube, the internal pressure of the air hose becomes negative, and the internal pressure of the air hose gradually decreases with the passage of time.

Then, when the suction work is normally performed, the internal pressure of the air hose returns to the atmospheric pressure when the sampling is completed, but the suction port of the nozzle tip is in a closed state where solid matter in the sample, for example, fibrin, is adsorbed. When the above occurs, the above-mentioned internal pressure of the air hose is not returned to the atmospheric pressure, and a sudden decrease in the internal pressure appears at the same time when this blockage occurs.

Therefore, by sampling the air hose internal pressure level that changes with the suction time during the liquid sampling in this sample tube at a predetermined cycle, it is possible to promptly detect the blocked state of the nozzle tip suction port that appears as a sudden decrease in internal pressure. can do.

Then, the suction operation is stopped at the same time as the detection of the blocked state, and the adsorbed substance can be separated from the nozzle tip suction port by immediately ejecting the sucked liquid sample slightly, and only a desired pure liquid sample is collected. be able to.

[Embodiment] A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 schematically shows the principle configuration of an automatic dispensing apparatus to which the method of the present invention is applied. A nozzle tip 14 is connected to the tip of an air hose 12 connected to the suction pump 10. The nozzle tip 14 is inserted into a sample tube 16 such as a test tube filled with a liquid sample in advance, and a predetermined amount is inserted. Take a liquid sample by inhalation.

A feature of the present invention is that the occurrence of an occlusion state caused by adsorption of a blood clot, which frequently occurs when serum or plasma is used as a poor liquid, or a drug added during centrifugation, to the tip of the nozzle tip. It is configured to detect accurately and quickly with a simple structure and to immediately remove the adsorbed substance from the nozzle tip portion so that the normal sampling operation can be continued.

Conventionally, there is almost no measure against such blockage of the nozzle tip suction port during the sampling and sampling operation, and even if the nozzle tip becomes clogged after the dispensing work, the worker is The actual condition is that it is left unattended until it is consciously recognized, and normal inhalation work cannot be continued.

For this reason, when a liquid sample that causes clogging is targeted, pretreatment such as filtering it beforehand is required, and it is possible to avoid inefficiency of dispensing work due to extremely troublesome labor and extension of working time. There wasn't.

Under such a situation, in the method of the present invention, attention is paid to the fact that a large pressure fluctuation occurs in the air hose at the same time when the nozzle tip suction port is closed, and when this is detected reliably and the occurrence of clogging is found, it is already sucked. By returning a small amount of the liquid sample to the sample tube, the adsorbed substance is removed, and normal suction sampling can be performed again.

A pressure sensor 18 is connected on the way to monitor the internal pressure of the air hose 12, and the output of the pressure sensor 18 is amplified by a DC amplifier 16 and then supplied to a limiter 22 to be digitally converted by an A / D converter 24. To be converted.

The suction pump 10 to the limiter 22 constitute one channel, and normally a plurality of channels arranged in parallel can be simultaneously driven and controlled, and a large number of internal pressures of the air hoses 12 can be monitored at the same time. In this embodiment, for convenience of explanation, only a single channel is shown.

The detection signal digitized in the A / D converter 24 is analyzed by the liquid sensing unit 26, and the result is analyzed by the host M.
When the occurrence of the blocked state of the nozzle tip 14 is found by the action described later while being supplied to the PU 28,
The nozzle / pump stop signal will be output to the suction pump 10 drive unit.

The liquid sensing unit 26 outputs a designation signal of a channel to be monitored and controlled to the A / D converter 24 based on a command from the host MPU 28, and can monitor only a desired channel among a plurality of channels.

FIG. 2 is a graph showing the relationship between the internal pressure of the air hose 12 and the sample suction time when a solid state in the liquid sample, such as fibrin, is adsorbed to the suction port of the minute nozzle tip 14 and a closed state occurs.

As described above, the method of the present invention catches a sudden drop in the internal pressure of the air hose 12 during suction to maintain the suction action.

If it is simply considered here, if the internal pressure of the air hose 12 at the time of intake falls to the conversion limit of the A / D converter 24, it may be unconditionally determined that the blockage has occurred.
This causes a problem that the time of detecting the closed state is delayed and the adhered substance is deeply sucked into the nozzle tip 14.

Therefore, when the pressure change becomes large to some extent, it is considered that the closed state occurs. However, with this alone, there is a possibility that the pressure change at the start of the inhalation action may be erroneously determined to be the occurrence of the closed state, so the detection action is not performed at the start of the inhalation action.

In the graph of FIG. 2, the check for blockage is started after a certain time has passed from the start of the inhalation action, and the air hose 1
Monitor the pressure inside 2. In some cases, the blockage may occur immediately after the start of the inhalation action of the liquid. Therefore, in order to cope with such a case, the check is started immediately when the internal pressure of the air hose drops by a certain level from the level at the start of the inhalation.

That is, in the illustrated example, the blockage check is started at the same time when either the time t _{0 has} elapsed from the start of the suction work or the internal pressure of the air hose 12 decreases by p ₀ or more.

If the sampling action proceeds normally without the suction port being blocked, the pressure change curve gradually decreases the internal pressure of the air hose 12 as shown by the chain line in the figure, and a predetermined amount of sample is sucked. At the time of completion, the trajectory draws a trajectory that the internal pressure quickly returns to atmospheric pressure.

On the other hand, if a solid substance such as fibrin is adsorbed to the nozzle tip tip suction port during suction and falls into a closed state, the suction operation by the suction pump 10 continues even though the tip is blocked. The internal pressure of 12 shows a rapid decrease as shown in the figure.

Therefore, the slope of the graph at this time, that is, Δ during the time Δt
When the pressure changes by more than p, it is considered that the blockage state occurs. Then, at the same time as the detection of the closed state, the driving of the suction pump 10 is stopped, and a small amount of the liquid already sucked into the nozzle tip 14 is returned toward the non-specimen tube 16. Is washed away and returned to the inside of the sample tube 16, the adsorbed substance is removed, and the sample is put into a state in which the normal sample inhaling action can be performed again.

It should be noted that t ₀ may be set to a time during which the pressure change at the start of suction stabilizes, and p ₀ may be designated as a level difference slightly higher than the pressure at t ₀ .

Further, it should be noted that Δt becomes a substantially fixed value when the device is determined, and if Δt is small, the detection reaction is improved, but at the same time a malfunction easily occurs.

[Effects of the Invention] As described above, according to the method of the present invention, the internal pressure of the air hose to which the nozzle tip is connected is monitored for the occurrence of so-called clogging in which the nozzle tip suction port is blocked by the solid substance in the liquid sample. By grasping and recognizing quickly, the suction action is temporarily stopped at the same time as the occurrence of the blockage state is detected, the adsorbed substance is washed away by returning a small amount of the liquid sample that has already been sucked, and the normal sample placement action is performed again. Since it was configured to continue, for example, serum or plasma after centrifugation can be directly used for dispensing without any pretreatment, and even if an obstruction occurs, this can be quickly removed, It is possible to continue the desired dispensing work.

[Brief description of drawings]

FIG. 1 is a principle block diagram of an automatic dispensing device to which the method of the present invention is applied, and FIG. 2 is a graph showing the relationship between the air hose internal pressure and the suction time when blockage occurs. 10 ... Suction pump 12 ... Air hose 14 ... Nozzle tip 16 ... Specimen tube 18 ... Pressure test 20 ... DC amplifier 22 ... Limiter 24 ... A / D converter 26 ... Liquid sensing unit 28 ... Hose MPU.

Claims (1)

[Claims] 1. A method for detecting obstruction of an automatic pipetting device, wherein a nozzle tip at the end of an air hose connected to a suction pump is inserted into a sample tube to absorb and collect a predetermined amount of liquid sample. The air pressure inside the air hose that changes with the suction time is sampled in a predetermined cycle, and the suction port of the nozzle tip is blocked when the rate of change of the detected pressure level value with respect to the previous detection value is a predetermined value or more. A method for detecting blockage of an automatic pipetting device, characterized in that