JP2015031586A - Analyzer and liquid suction device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid suction device or an analyzer which is capable of accurately detecting a suction abnormal state even in the case with a trace of liquid to be dispensed or an analyte in which a temporary jam state occurs.SOLUTION: The liquid suction device includes a suction probe which sucks a liquid, a syringe which generates a pressure difference for sucking the liquid to the suction probe, a flow channel connecting the suction prove and the syringe, and a control unit which controls the operation for generating the pressure difference by the syringe. Further, the liquid suction device includes a pressure sensor which detects a pressure in the flow channel, storage means in which an output value of the pressure sensor is stored, and determination means which determines the presence or absence of liquid suction abnormality on the basis of a sum total of output values of the pressure sensor within a prescribed time after the start of liquid suction, which is based on output values stored in the storage means, and characteristics of process in which the output value of the pressure sensor is varied due to liquid suction.

Description

The present invention relates to a dispensing probe having a function of detecting a suction abnormality when a sample is sucked, a liquid suction device including the dispensing probe, and an analyzer including the liquid suction device.

  Automatic analyzers such as biochemical automatic analyzers and immune automatic analyzers include a sample dispensing mechanism that sucks a sample from a specimen container and discharges the sample into a reaction container (hereinafter referred to as dispensing). The sample dispensing mechanism generally includes a dispensing probe, a dispensing syringe connected to the dispensing probe through a flow path, a mechanism such as a motor for driving a plunger of the dispensing syringe, and a dispensing probe. It consists of a mechanism that moves to the position, immerses the tip of the dispensing probe in the sample liquid surface, and drives the plunger of the dispensing syringe by a predetermined amount, sucks a predetermined amount of sample and places the dispensing probe in the reaction vessel. The dispensing operation of moving and discharging the sample is performed.

  Serum and plasma are mainly used as samples, and solid matter called fibrin may be generated in the sample depending on the treatment state at the time of blood collection, the storage time after blood collection and the environment. In such a sample, solid matter is sucked when the sample is sucked, which causes clogging of the dispensing probe and insufficient amount of sample suction, leading to a decrease in analysis accuracy.

As a means to prevent clogging of the probe during dispensing and the occurrence of abnormal conditions associated therewith, a pressure sensor is provided in the dispensing channel connecting the dispensing probe and the dispensing syringe, and the pressure in the channel during sample suction Techniques have been reported for detecting sample dispensing anomalies based on fluctuations. For example, in Patent Document 1 (Japanese Patent Laid-Open No. 10-48220), a pressure sensor that detects a pressure in a suction path when sucking a sample is used, based on a pressure change at a point in time after a sample starts to be sucked. A method for detecting abnormal suction of a sample is described.

JP-A-10-48220

  In the method disclosed in Patent Document 1, when the amount of sample to be dispensed becomes a very small amount, the pressure fluctuation in the flow channel during sample suction becomes small, and it may be difficult to determine dispensing abnormality. .

  It is also difficult to determine a temporary suction abnormality. Temporary suction abnormality refers to a state in which solid matter is sucked in the middle of sample suction, but the solid matter is then sucked into the syringe and clogging is eliminated after a certain time. In this case, since the pressure fluctuation after a predetermined time is within the specified range, it cannot be determined that the dispensing is abnormal.

In view of the above problems, the present invention provides a suction device or analysis that can accurately detect an abnormal suction state even when the amount of a dispensed liquid is very small, or even in a specimen in which a temporarily clogged state occurs. The object is to provide a device.

  In view of the above problems, the present invention is characterized by the following configuration.

That is, a suction probe for sucking a liquid, a syringe for generating a pressure difference for causing the suction probe to suck a liquid, a flow path for connecting the suction probe and the syringe, and a pressure difference due to the syringe In the liquid suction device having the control unit for controlling the operation of the pressure sensor, the pressure sensor for detecting the pressure in the flow path, the storage means for storing the output value of the pressure sensor, and the output stored in the storage means Based on the value, whether or not there is an abnormality in liquid suction based on the sum of the output values of the pressure sensor within a predetermined time after the start of liquid suction and the characteristics of the process in which the output value of the pressure sensor fluctuates with liquid suction And a judging means for judging.

According to the present invention, it is possible to accurately detect the occurrence of a temporary probe clogging that could not be detected in the past, and to analyze using a dispensing liquid that may have caused a suction abnormality. By executing this, it is possible to avoid reporting an erroneous analysis result.

It is a figure which shows the whole analyzer in this invention. It is a figure which shows the structure of the dispensing mechanism in this invention. It is a graph which shows a pressure output value temporal change in normal sample suction. It is a graph which shows the pressure output value time-dependent change (1st example) in abnormal sample attraction | suction. It is a graph which shows the pressure output value time-dependent change (2nd example) in abnormal sample attraction | suction. It is a figure which shows the normal / abnormal discrimination | determination flow of sample suction. Relationship between dispensing volume and threshold in this example

  Preferred embodiments for carrying out the present invention will be described below with reference to the drawings.

  As a preferred embodiment based on the present invention, the fluid in the flow path through the dispensing probe and the dispensing syringe is changed over time until the tip of the dispensing probe leaves the liquid surface after the suction from the start of the suction of the sample as the liquid to be dispensed. Storage means such as a memory for sequentially storing various pressure changes, a predetermined reference pressure and a sum of pressure values in a predetermined section after the start of suction are compared with a predetermined threshold, and a predetermined section after the start of suction Comparing the difference between the minimum and maximum pressure values of the sample with a predetermined threshold value, and providing calculation means such as a computer for determining the presence or absence of sample suction based on the comparison result, the volume of the sample to be sucked There is a means for calculating the threshold according to

  Hereinafter, examples of the present invention will be described more specifically. First, an outline of the analyzer and the analysis operation will be described with reference to FIG.

  A sample container 102 for holding a sample is installed on a rack 101 of the analyzer 100, and is moved to a sample dispensing position near the sample dispensing nozzle 103 by a rack transport line 117. A plurality of reaction containers 105 can be installed on the incubator disk 104, and the reaction containers 105 installed in the circumferential direction are arranged in a reaction container installation position, a reagent discharge position, a sample discharge position, a detection position, a reaction container discard position, Rotational motion for moving to a predetermined position is possible. The sample dispensing tip and reaction container transport mechanism 106 can move in three directions of the X axis, the Y axis, and the Z axis, and the sample dispensing tip and reaction container holding member 107, the reaction container stirring mechanism 108, and the sample dispensing chip. In addition, the range of the reaction container disposal hole 109, the sample dispensing tip mounting position 110, and a predetermined portion of the incubator disk 104 is moved to carry the sample dispensing tip and the reaction container.

  The sample dispensing tip and reaction vessel holding member 107 is provided with a plurality of unused reaction vessels and sample dispensing tips. The sample dispensing tip and reaction vessel transport mechanism 106 moves above the sample dispensing tip and reaction vessel holding member 107, descends, holds and raises an unused reaction vessel, and installs the reaction vessel on the incubator disk 104. Move above position and lower to install reaction vessel.

  The reagent disk 111 is provided with a plurality of reagent containers 118 holding reagents and diluents. A reagent disk cover 112 is provided above the reagent disk 111, and the inside of the reagent disk 111 is maintained at a predetermined temperature. A reagent disk cover opening 113 is provided in a part of the reagent disk cover 112. The reagent dispensing nozzle 114 can be rotated and moved up and down. The reagent dispensing nozzle 114 rotates and moves downward above the opening 113 of the reagent disk cover 112, and the tip of the reagent dispensing nozzle 114 is moved to the reagent or dilution in a predetermined reagent container. A predetermined amount of reagent or diluent is aspirated in contact with the liquid. Next, the reagent dispensing nozzle 114 is raised and moved above the reagent discharge position of the incubator disk 104 to discharge the reagent or diluent to the reaction vessel 105.

  Next, the sample dispensing tip and reaction vessel transport mechanism 106 moves above the sample dispensing tip and reaction vessel holding member 107, descends, holds and holds an unused sample dispensing tip, and then dispenses the sample. It moves above the tip mounting position 110 and descends to install the sample dispensing tip. The sample dispensing nozzle 103 can rotate and move up and down, moves to the upper side of the sample dispensing tip mounting position 110 and descends, and attaches the sample dispensing tip to the tip of the sample dispensing nozzle 103. The sample dispensing nozzle 103 equipped with the sample dispensing tip moves down above the sample container 102 placed on the transport rack 101 and sucks a predetermined amount of the sample held in the sample container 102. The sample dispensing nozzle 103 that sucks the sample moves to the sample discharge position of the incubator disk 104 and descends, and discharges the sample to the reaction vessel 105 on which the reagent or diluent is dispensed on the incubator disk 104. After sample discharge, the sample dispensing nozzle 103 moves above the sample dispensing tip and the reaction container discarding hole 109 and discards the used sample dispensing tip into the disposal hole.

  The reaction container 105 in which the sample and the reagent are discharged is moved to the reaction container conveyance position by the rotation of the incubator disk 104, and is conveyed to the reaction container agitation mechanism 108 by the sample dispensing tip and the reaction container conveyance mechanism 106. . The reaction vessel stirring mechanism 108 rotates the reaction vessel to mix the sample and the reagent in the reaction vessel. After the stirring, the reaction container is returned to the reaction container transport position of the incubator disk 104 by the sample dispensing tip and the reaction container transport mechanism 106.

  The reaction solution suction nozzle 115 can be rotated and moved up and down, and the sample and the reagent are dispensed and mixed, and then moved above the reaction vessel 105 after a predetermined time on the incubator disk 104, and then moved down. Aspirate the reaction solution inside. Next, the detection reaction auxiliary reagent filled in the system reagent (detection reaction auxiliary reagent) reservoir 123 is aspirated, and the reaction liquid and the detection reaction auxiliary reagent are sent to the detection unit 116 to detect the measurement object. . Thereafter, the detection unit cleaning reagent filled in the system reagent (detection unit cleaning reagent) reservoir 124 is sucked and sent to the detection unit unit 116 to clean the detection unit. After the system reagents in the system reagent reservoirs 123 and 124 are aspirated, the system reagents are replenished from the system reagent supply nozzles 121 and 122, respectively.

The reaction container 105 in which the reaction liquid has been sucked moves to the reaction container discarding position by the rotation of the incubator disk 104, and the sample dispensing chip and reaction container disposal hole are removed from the incubator disk 105 by the sample dispensing chip and reaction container transport mechanism 106. It moves above 109 and is discarded from the disposal hole.
Next, the sample dispensing mechanism will be described with reference to FIG.

  The sample probe 103 is connected to a sample dispensing syringe 202 via a sample dispensing channel 203, and a pressure sensor 204 is provided therebetween.

  The control unit 119 controls the plunger drive motor via the motor drive circuit 201 and generates a pressure difference inside and outside the sample probe 103 by driving the plunger of the sample dispensing syringe 202 connected to the plunger drive motor in the vertical direction. The sample is sucked from the sample probe 103. Further, the control unit 119 controls the sample probe driving motor via the motor driving circuit 205 to drive the sample probe in the vertical and rotational directions, so that the tip of the sample probe is immersed in the sample. In this sample suction, the pressure sensor 204 outputs a voltage correlated with the pressure in the sample dispensing channel 203, amplified by the amplifier 206, converted into a digital signal by the A / D converter 207, and sent to the control unit 119. And various calculations and determination processes for detecting abnormal suction in sample dispensing are performed.

  Next, a method for determining a change with time in the pressure in the sample dispensing channel 203 converted into a digital signal and a suction abnormality in the sample suction will be described.

  FIG. 3 shows a change with time of an output value obtained by converting the pressure in the sample dispensing flow path 203 into a digital signal in normal sample suction. The time when the tip of the sample probe is immersed in the sample before the start of the plunger operation of the sample dispensing syringe is t0, and the output value of the pressure sensor at this time is p0.

  Assuming that the plunger operation start time of the sample dispensing syringe is t1, the output value of the pressure sensor indicates a change in which the pressure in the sample dispensing flow path 203 becomes negative from t1. Then, from t2 when the sample starts to be sucked into the sample probe, the pressure sensor value in the sample dispensing flow path 203 gradually returns from the negative pressure side toward p0 as the sample is sucked, and the suction of the sample is completed. In FIG.

  On the other hand, FIG. 4 shows a case where a sample with high viscosity or a sample containing solid matter (such as fibrin or foreign matter) such as clot cannot be sucked because the probe is clogged (the sample suction amount is insufficient). An example of such an abnormal sample suction is shown.

  Similar to FIG. 3, the output value from the plunger operation start time t1 to the time t2 at which the sample starts to be sucked into the probe indicates a change in which the inside of the sample dispensing flow path 203 becomes negative pressure. The output value change with time during this period is almost the same as the normal sample suction in FIG. However, at the time t3 when the suction of the sample is expected to be completed in the normal sample from t2, the increase in the output value accompanying the suction of the sample is moderate, and the output value after t3 shows less than p0. This indicates that the sample suction does not complete normally due to the balance between the pipe friction resistance between the sample and the sample probe and the negative pressure in the dispensing flow path, and the suction amount is insufficient with respect to the set value. . Note that the output value at t2 and the value of t3 vary depending on the sample dispensing amount.

  FIG. 5 shows an example of abnormal sample suction in which a clot is temporarily clogged with a probe and the sample suction is temporarily inhibited in a sample containing a solid matter such as a clot.

  Similar to FIG. 3, the output value from t1 to t2 shows a change in which the inside of the sample dispensing flow path 203 becomes negative pressure. The output value change with time during this period is almost the same as the normal sample suction in FIG. Then, at the time t3 when the sample suction is expected to be completed in the normal sample from t2, the increase in the output value accompanying the sample suction is moderate and indicates less than p0. However, when the clogging of the probe is resolved thereafter, the output value of the pressure sensor gradually increases after t3, and the output value shows a value substantially equal to p0 by the time t4 when the sample probe leaves the sample. In this case, the sample dispensing volume is generally maintained at the set value, but the aspirated sample may contain solids, and it is treated as abnormal sample aspiration in consideration of the influence on the subsequent analysis results. Things are appropriate.

  Next, a calculation method for determining the difference between normal sample suction as shown in FIG. 3 and abnormal sample suction as shown in FIGS. 4 and 5 will be described.

  First, as step 1, the total value (S) of the difference between p0 and the output value from t2 to t4 when the difference between the output values starts to occur between normal sample suction and abnormal sample suction is calculated. That is, the area of the region surrounded by the line indicating p0, the line indicating t2, the line indicating t4, and the line indicating the output value. By using this total value, high discrimination resolution is ensured even when the amount of sample dispensed is small and the pressure fluctuation is small in normal suction as shown in FIG. 3 and abnormal suction as shown in FIG. can do.

  However, in normal suction as shown in FIG. 3 and abnormal suction such as temporary clogging as shown in FIG. 5, if the sample dispensing amount is very small, p0 and output from t2 to t4 are output. It may be difficult to discriminate only with the total value (S) of the difference of values.

  Therefore, as step 2, the characteristics of the process in which the inside of the sample dispensing channel 203 returns from the negative pressure side toward p0 as the sample is sucked from t2 are taken into consideration. This characteristic indicates the difficulty of returning from negative pressure to p0 during abnormal sample suction. For example, in the section from t3 to t4, the maximum value and the minimum value of the output value of the pressure sensor are extracted, There is a method for calculating the difference value (P). Since the pressure sensor output value at the time of sample suction in which a temporary clogging abnormality occurs as shown in FIG. 5 is less likely to return to p0 by the amount of clot clogging, the calculated difference value is The absolute value is larger than the difference value in normal suction as shown in FIG.

  Alternatively, only the minimum value in the section from t3 to t4 can be used as an index. As described above, at the time of abnormal sample suction in which temporary clot clogging has occurred, the pressure value is unlikely to return from negative pressure to p0, so the extracted minimum value is smaller than the minimum value in normal suction.

  There is also a method of using time until a predetermined pressure is reached. For example, the output value at the time t3 when the sample suction is expected to be completed when the normal sample is sucked can be stored as a reference output value, and the time required to reach the reference output value can be used as an index. Alternatively, the time required to approach the initial pressure value p0 before the syringe operation can be used as an index. If these times are used as indices, the time required for abnormal suction is longer than that for normal suction.

  As described above, in addition to the determination method (first determination method) using the total value (S) of the difference between p0 and the output value from t2 to t4, an index indicating the difficulty in returning from the negative pressure to p0. By performing the discriminating method based on this (second discriminating method), it is possible to maintain a high discriminating resolution even in the case of a minute dispensing amount that has been difficult to discriminate in the past or abnormal suction that causes a temporary clogging state. It becomes possible.

  Hereinafter, a normal / abnormal determination flow of sample suction will be described with reference to FIG. From the pressure value acquired at the time of sample dispensing, the S value is calculated as a discriminant value from the sum of the differences between the initial pressure value (p0) and the output value. In addition, based on the pressure waveform in the sample dispensing flow path 203 acquired at the time of sample dispensing, determination is made that shows the characteristics of the process of returning from the time point (t2) when the pressure value is reduced to the initial pressure value (p0). As a value, a P value is calculated. Note that P may be, for example, the difference between the minimum value and the maximum value of the pressure value in the time region from t2 to t4, or may be the minimum value of the pressure value in the time region from t3 to t4. Further, it may be a time until a predetermined pressure value is reached.

  As a first determination method, the calculated S value is S <F1 with respect to a predetermined threshold value (F1), and as a second determination method, the calculated P value is set with respect to a predetermined threshold value (F2). When | P | <F2, it is determined that the sample is normally sucked and the analysis is continued.

  On the other hand, when the S value is S ≧ F1 with respect to the predetermined threshold value (F1), it is an abnormal suction that is not sucked by an appropriate amount due to clogging or the like based on the first determination method. Judge and stop the analysis.

  Furthermore, even if S <F1 with respect to the threshold value (F1) and no abnormality is detected by the first determination method, if the P value is out of the predetermined threshold value (F2) range, It is determined that the sample suction is abnormal based on the determination method. For example, in the case where an abnormality is determined based on the difference between the maximum value and the minimum value or the minimum value in the process in which the output value of the pressure sensor within a predetermined time region varies, | P | ≧ F2 or | P | When ≦ F2, it is determined that the sample is abnormally sucked, and the analysis using the sample is canceled.

  Next, a method for calculating the threshold value (F1) will be described below.

  F1 can be determined according to the set dispensing amount, and high discrimination resolution can be ensured by using F1 according to the set dispensing amount. For example, in the set dispensing amount u1, u2, u3, normal sample suction S values obtained in advance by experiment are n1, n2, n3, abnormal sample suction S values are m1, m2, and m3. The median values (n1 + m1) / 2, (n1 + m2) / 2, and (n3 + m3) / 2 of the abnormal samples are set as threshold values (F1) f1, f2, and f3.

  The dispensing amount (U) and the threshold value (F1) are approximated lines as shown in FIG. 7, and can be expressed by a relational expression of F1 = aU + b or F1 = aU ^ 2 + bU + c. When the set dispensing amount (U) is u ′, the threshold value (F1) is the value f ′ calculated by the above formula. The S value (x ′) obtained by sample aspiration is compared with F ′. If f ′> x ′, it is determined as normal and the analysis is continued. If f ′ ≦ x ′, an appropriate amount of aspiration is obtained. It is determined that the abnormal suction is not performed, and the subsequent analysis is canceled.

  Next, a method for calculating the threshold value (F2) will be described below.

  The difference value between the maximum value and the minimum value of the pressure value in the time region from t3 to t4 of normal sample suction obtained by experiments in advance is q, and the fluctuation range r of the difference value q is acquired. The threshold value F2 can be calculated in advance using, for example, q + r as a threshold value. However, when only the minimum value in the section from t3 to t4 is used as an index, or when the time to reach a predetermined pressure is used as an index, the set value is set as necessary as in the above-described threshold (F1). It can be determined according to the dosage.

  Note that these threshold values are preferably calculated in advance for each device and stored in a storage device (not shown) in the device. As a normal sample, it is desirable to use a sample that does not contain a solid substance such as a clot and has a viscosity in a normal range. As an abnormal sample, it is desirable to use, as a pseudo sample, a high-viscosity solution prepared by adding glycerol, for example, as having an abnormally high viscosity compared to a normal sample. The normal sample and the abnormal sample are sucked in advance, and the pressure generated in the probe pipe at that time is measured. Based on the obtained pressure waveform, the pressure waveform and threshold values (F1, F2, etc.) of the reference normal sample ) Is calculated.

In the present embodiment, the abnormality determination at the time of sample aspiration has been mainly described. However, the present invention can also be applied to dispensing of a reagent solution or a reaction solution, for example, as long as it can cause a clogged state. is there.

100: Analyzing apparatus 101: Rack 102: Sample container 103: Sample dispensing nozzle 104: Incubator disk 105: Reaction container 106: Sample dispensing chip and reaction container transport mechanism 107: Sample dispensing chip and reaction container holding member 108: Reaction Container stirring mechanism 109: Sample dispensing tip and reaction vessel disposal hole 110: Sample dispensing tip mounting position 111: Reagent disc 112: Reagent disc cover 113: Reagent disc cover opening 114: Reagent dispensing nozzle 115: Reaction liquid suction nozzle 116: detection unit 117: rack transport line 118: reagent container 119: control unit 121: system reagent (detection reaction auxiliary reagent) supply nozzle 122: system reagent (detection part washing reagent) supply nozzle 123: system reagent (detection reaction auxiliary reagent) ) Reservoir 24: System reagent (detector wash reagent) reservoir 201: motor driving circuit (sample dispensing syringe)
202: Sample dispensing syringe 203: Sample dispensing flow path 204: Pressure sensor 205: Motor drive circuit (for sample probe)
206: Amplifier 207: A / D converter 300: Pressure output value in normal sample suction 400: Pressure output value in abnormal sample suction (first example)
500: Pressure output value in abnormal sample suction (second example)

Claims (8)

A suction probe for sucking a liquid;
A syringe for generating a pressure difference for causing the suction probe to suck liquid;
A flow path connecting the suction probe and the syringe;
In a liquid suction device having a control unit for controlling an operation for generating a pressure difference by the syringe,
A pressure sensor for detecting the pressure in the flow path;
Storage means for storing an output value of the pressure sensor;
Based on the output value stored in the storage means, the sum of the output values of the pressure sensor within a predetermined time after the start of liquid suction and the characteristics of the process in which the output value of the pressure sensor fluctuates as the liquid is sucked. And a determination means for determining whether or not there is a liquid suction abnormality.
The liquid suction device according to claim 1,
The section in which the determination means calculates the sum of the pressure sensor output values is the time required to finish sucking a desired amount of liquid from the time when the pressure in the flow path starts to rise from the negative pressure, or the desired amount The liquid sucking device is characterized in that it is the time until the dispensing probe is completely sucked and the dispensing probe is detached from the liquid surface.
The liquid suction device according to claim 1,
As a characteristic of the process in which the pressure sensor output value fluctuates, the determination means is from the time when the pressure in the flow path starts to rise from the negative pressure to the time when the dispensing probe starts to detach from the liquid level. A liquid suction device that makes a determination based on a difference between a maximum value and a minimum value of the pressure sensor.
The liquid suction device according to claim 1,
The liquid suction device according to claim 1, wherein the determination means makes a determination based on a time from the start of liquid suction until a predetermined pressure is reached as a characteristic of a process in which the pressure sensor output value fluctuates.
A suction probe for sucking a liquid;
An analysis unit for analyzing using the liquid sucked by the suction probe;
A syringe for generating a pressure difference for causing the suction probe to suck liquid;
A flow path connecting the suction probe and the syringe;
A control unit for controlling an operation for generating a pressure difference by the syringe;
A pressure sensor for detecting the pressure in the flow path;
Storage means for storing an output value of the pressure sensor;
Based on the output value stored in the storage means, the sum of the output values of the pressure sensor within a predetermined time after the start of liquid suction and the characteristics of the process in which the output value of the pressure sensor fluctuates as the liquid is sucked. Determination means for determining the presence or absence of liquid suction abnormality based on,
The analysis device, wherein the control unit stops the analysis based on a determination result of the determination unit.
The analyzer according to claim 5, wherein
The section in which the determination means calculates the sum of the pressure sensor output values is the time required to finish sucking a desired amount of liquid from the time when the pressure in the flow path starts to rise from the negative pressure, or the desired amount The analyzer is characterized in that it is the time until the dispensing probe is sucked and the dispensing probe is detached from the liquid surface.
The analyzer according to claim 1, wherein
As a characteristic of the process in which the pressure sensor output value fluctuates, the determination means is from the time when the pressure in the flow path starts to rise from the negative pressure to the time when the dispensing probe starts to detach from the liquid level. An analyzer according to claim 1, wherein the determination is based on a difference between a maximum value and a minimum value of the pressure sensor.
The analyzer according to claim 1, wherein
The analyzer is characterized in that, as a characteristic of a process in which the pressure sensor output value fluctuates, a determination is made based on a time from the start of liquid suction until a predetermined pressure is reached.