JP5292359B2 - Sensing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sensing device capable of easily and accurately sensing an object to be sensed. <P>SOLUTION: In a sensing device which supplies a sample solution to an adsorption layer 46 while oscillating a crystal oscillator 4 so as to adsorb an object to be sensed in the sample solution and senses the object on the basis of the amount of change in an oscillation frequency of the crystal oscillator 4 after the adsorption time has passed, before the sample solution is supplied to the adsorption layer 46, the crystal oscillator 4 is oscillated to measure the oscillation frequency of the crystal oscillator 4 at a predetermined measurement interval, for example, every one second, and the oscillation frequency of the crystal oscillator 4 is stabilized until the measurement result reaches a level lower than or equal to a frequency allowance value predetermined on the basis of the measurement sensitivity of the object to be sensed throughout the same time as the measurement time. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a sensing device that adsorbs a sensing object in a sample fluid to an adsorption layer formed on an electrode provided on a piezoelectric piece, and senses the sensing object based on a change in the natural frequency of the piezoelectric piece. .

As a device for detecting trace substances in a solution or gas, there is a sensing device using a QCM (Quarts Crystal Microbalance) by a crystal resonator which is a piezoelectric resonator mainly composed of a crystal piece that is AT-cut as a piezoelectric piece. Are known. This type of sensing device adsorbs a trace substance to the crystal oscillator constituting the crystal oscillation circuit, and oscillates after the trace substance is adsorbed (resonance frequency) and before or after the trace substance is adsorbed. By detecting the difference between the oscillation frequency of the reference crystal resonator that is not present, the presence or concentration of a trace substance in the sample fluid is sensed. Examples of trace substances include dioxins, which are environmental pollutants in the atmosphere, and specific antigens in blood or serum. The sensing device senses these at extremely low concentrations, for example, ppb to ppt levels.
Such a sensing device is formed by, for example, forming an excitation electrode for oscillating the piezoelectric piece on the surface of the piezoelectric piece, and further laminating an adsorption layer such as an antibody that adsorbs a trace amount substance on the excitation electrode. Is done. Then, the oscillation frequency of the quartz resonator is measured by adsorbing the trace substance as described above, and the presence or concentration and the concentration of the trace substance in the sample fluid are calculated based on, for example, a calibration curve or threshold value obtained in advance. Is done.

By the way, the piezoelectric piece takes time from the start of oscillation until the oscillation is stabilized, and in particular when it is oscillated in the liquid phase, it takes a long time to stabilize. Further, when the piezoelectric piece is stably oscillated in the gas phase and placed in the liquid phase, it takes a long time to stabilize. Therefore, when sensing a trace amount of material, for example, before supplying the sample fluid to the adsorption layer, a standby time is provided to wait until the oscillation frequency of the piezoelectric piece stabilizes to a predetermined value, and this standby time has elapsed. It is necessary to start sensing (measuring) the sensing object later. However, it is extremely difficult to determine whether or not the oscillation frequency is stable. For example, the experience and determination of an operator are necessary to detect a trace amount of material with high accuracy in a short time. In other words, if measurement is started before the oscillation frequency of the piezoelectric piece settles, the detection accuracy of trace substances will deteriorate, and if a standby time longer than necessary is provided, the time required for measurement will be long. turn into. Furthermore, when the sample fluid is a liquid, a liquid such as a buffer solution is supplied to the piezoelectric piece before measurement to stabilize the oscillation frequency. However, in the liquid, the oscillation frequency of the piezoelectric piece is settled. Since it takes a longer time than gas, it is more difficult to determine whether the oscillation frequency of the piezoelectric piece has settled.
Patent Documents 1 and 2 describe a sensor and a system using a crystal resonator, but none of the above problems are studied.

JP-A-11-183479 Special table 2005-530177

  The present invention has been made based on such circumstances, and an object of the present invention is to provide a sensing device capable of sensing a sensing object simply and accurately.

The sensing device of the present invention comprises:
Using a piezoelectric sensor in which an adsorption layer is formed on an electrode provided on the piezoelectric piece, the sensing object in the sample liquid is adsorbed on the adsorption layer, and the sensing is performed based on a change in the natural frequency of the piezoelectric piece. In a device for sensing an object,
A liquid supply path for supplying liquid to the electrode;
A reference liquid that is provided on the upstream side of the liquid supply path and stores a reference liquid that does not contain a substance adsorbed on the adsorption layer, and that pushes the reference liquid to the electrode side through the liquid supply path. A supply section;
A storage part that is interposed in the liquid supply path and a reference liquid flow path through which the reference liquid flows and a reference liquid flow path through which the reference liquid flows are provided, and a flow path from the reference liquid supply part to the electrode, The reference liquid is configured to be switchable between a flow path for pushing the sample liquid in the storage section through the storage section to the electrode side and a flow path for the reference liquid to pass through the reference liquid flow path. Liquid switching part,
An oscillation circuit for oscillating the piezoelectric piece;
A frequency measurement unit for measuring the oscillation frequency of the oscillation circuit;
A data acquisition unit that acquires frequency time-series data by sampling the frequency measured by the frequency measurement unit at a preset time interval;
A storage unit for storing a measurement time set in advance to measure a change in frequency when the sample liquid is supplied to the piezoelectric sensor;
Sampling intervals sequentially for a group of sampling intervals of a length corresponding to the measurement time, each starting from the timing of each frequency sampling when the reference solution is supplied to the piezoelectric sensor via the reference solution passage The frequency stability is calculated every time, and when the calculated frequency stability falls below the allowable value corresponding to the measurement sensitivity, the supply of the sample liquid is permitted so that the flow path in the liquid switching part is switched to the storage part side. An output unit for outputting a signal ,
The measurement time is set based on a reference liquid supply rate when the reference liquid supply unit pushes out the sample liquid in the storage unit and a storage amount of the sample liquid in the storage unit .

ｙ_ｋ：各サンプリング区間毎のｋ番目のサンプリング時における周波数、ｍ：各サンプリング区間に含まれるサンプリング数（ｋ，ｍ：正数）
測定感度を選択することにより、測定感度に対応する許容値を求める許容値取得部備えていても良い。 The frequency stability is represented by the following formula, for example.
Frequency stability

y _k : frequency at the time of the k-th sampling for each sampling interval, m: number of samplings included in each sampling interval (k, m: positive number)
An allowable value acquisition unit that obtains an allowable value corresponding to the measurement sensitivity by selecting the measurement sensitivity may be provided.

As a specific configuration of the present invention, a sample solution supply unit that supplies a sample solution to the storage unit ,
A discharge unit for discharging the sample liquid and the reference liquid supplied to the piezoelectric sensor,
Examples of the calculation of the frequency stability and the detection of the sensing object in the sample liquid may be performed while flowing the reference liquid and the sample liquid in the atmosphere in which the piezoelectric sensor is placed.

  The present invention uses a piezoelectric sensor in which an adsorption layer is formed on an electrode provided on a piezoelectric piece, and adsorbs a sensing object in a sample solution to the adsorption layer, thereby changing the natural frequency of the piezoelectric piece. When sensing the sensing object based on this, the reference liquid is supplied before the sample fluid is supplied to the adsorption layer, and the oscillation frequency of the piezoelectric piece is measured at a preset measurement interval. Since the oscillation frequency of the piezoelectric piece is stabilized until it becomes equal to or less than a preset allowable value based on the measurement sensitivity of the sensing object over the same period of time, the sensing object can be sensed simply and accurately.

It is the schematic which shows the whole structure of the sensing apparatus of this invention. It is a perspective view which shows an example of the sensor unit of the said sensing apparatus. It is a disassembled perspective view which shows said sensor unit. It is a top view which shows an example of the crystal oscillator used for said sensor unit. It is a longitudinal cross-sectional view which shows said quartz resonator. It is a perspective view which shows the flow-path formation member used for said sensor unit. It is a longitudinal cross-sectional view which shows said sensor unit. It is a schematic diagram which shows a mode that a buffer solution and a sample solution are supplied to said sensor unit. It is the schematic which shows the measurement part 10 in a sensing apparatus. It is a characteristic view which shows the characteristic acquired when a sample fluid is sensed with said sensing apparatus. It is a schematic diagram which shows an example of the tolerance used for calculation performed in said measurement part. It is a schematic diagram which shows the frequency data obtained in a measurement part. It is a schematic diagram which shows an example of the calculation method performed in the control part of said sensing device. It is the schematic which shows the flow at the time of sensing a sensing target object in said sensing apparatus. It is the schematic which shows a mode that a sensing target object is sensed by said sensing apparatus.

  As shown in FIG. 1, an embodiment of the sensing device of the present invention includes a sensor unit 2, a liquid supply system 1 that supplies a liquid (sample liquid or buffer solution) to the sensor unit 2, and a discharge from the sensor unit 2. A liquid discharge system 90 for storing the liquid to be stored, and a frequency measuring unit 10 for driving the quartz sensor 7 as a piezoelectric sensor attached to the sensor unit 2 and processing the obtained oscillation output. As shown in FIGS. 2 and 3, the sensor unit 2 includes a support 21, a sealing member 30, a wiring board 3, a crystal resonator 4, a flow path forming member 5, and an upper cover 24 stacked in this order from the lower side. Has been configured.

  The crystal sensor 7 is configured by providing a crystal resonator 4 that is a piezoelectric resonator on a wiring board 3. For example, as shown in FIG. 4, the crystal resonator 4 is configured by providing excitation electrodes 42 and 43 on both surfaces of a disk-shaped crystal piece 41 that is a piezoelectric piece. The excitation electrode 43A and the second excitation electrode 43B are arranged apart from each other, and a common excitation electrode (common electrode) 42 for the two excitation electrodes 43A and 43B is arranged on the surface side. Therefore, as shown in FIG. 5, the first vibration region 4A is formed by the first excitation electrode 43A and the common electrode 42, and the second vibration region 4B is formed by the second excitation electrode 43B and the common electrode 42. It will be. The first excitation electrode 43 </ b> A and the second excitation electrode 43 </ b> B are 2 described later provided in the measurement unit 10 via the conductive paths 32 and 34 of the wiring board 3 when the crystal sensor 7 is attached to the sensor unit 2. The common electrode 42 is connected to the ground side of the oscillation circuits 6A and 6B through the conductive path 33 of the wiring board 3 while being connected to the two oscillation circuits 6A and 6B. Connection terminals 35 to 37 connected to the respective conductive paths 32 to 34 are formed in the end region of the wiring board 3.

As shown in FIGS. 3 and 7, the crystal resonator 4 is mounted so as to close the through-hole 31 formed in the wiring board 3. As shown in FIG. Are attached to the sensor unit 2 in a state where the front surface side and the back surface side are pressed by the flow path forming member 5 made of an elastic body shown in FIG.
And in the area | region corresponding to the 1st excitation electrode 43A in the common electrode 42 of the quartz sensor 7, as shown in FIG. 5, the adsorption layer (reactive substance) which consists of an antibody for adsorbing the antigen which is a sensing object, for example ) 46 is formed. Therefore, for example, when a sensing object in the sample liquid is adsorbed on the adsorption layer 46, the oscillation frequency in the first vibration region 4A is lowered due to the mass load effect, while in the second vibration region 4B, the common electrode 42 senses it. Since the object is not adsorbed, by comparing the oscillation frequencies of the regions 4A and 4B before and after the adsorption of the sensing object, the temperature around the sensor unit 2, the viscosity of the sample liquid, and other than the sensing object contained in the sample liquid Therefore, it is possible to detect the change (decrease) in the oscillation frequency corresponding to the amount of the sensing object adsorbed on the adsorption layer 46 while suppressing the influence of disturbance such as adhesion of the substance.

  2, 3, and 7, 26 is a liquid supply pipe, 27 is a liquid discharge pipe that is a discharge means, and the liquid supplied from the liquid supply pipe 26 is between the flow path forming member 5 and the crystal unit 4. It is configured to be discharged from the liquid discharge pipe 27 through the liquid supply region 53 which is a flow path of As shown in FIG. 1, the liquid supply system 1 includes a buffer solution supply unit 91 and a sample solution supply unit 92 that respectively supply a buffer solution and a sample solution as a reference solution to the crystal sensor 7. . The buffer solution supply unit 91 includes a buffer solution storage unit 93 that stores a buffer solution such as a phosphate buffer, a buffer solution holding unit 94 such as a syringe pump, and a first valve 95 that includes, for example, a three-way valve. The buffer solution holding unit 94 sucks and holds the buffer solution from the buffer solution storage unit 93, and then, as shown in FIG. 8A, the flow path of the first valve 95 is switched to change the buffer solution holding unit 94. The buffer solution can be supplied to the quartz sensor 7 from the top.

  The sample solution supply unit 92 includes a sample solution storage unit 96 that stores a sample solution such as blood and serum, and a second valve 97 formed of, for example, a six-way valve. As shown in FIG. The column 98 provided in the second valve 97 is filled with the sample solution in the sample solution storage unit 96, and then, as shown in FIG. The sample liquid is pushed out and supplied to the crystal sensor 7. In FIG. 1, reference numerals 91 a and 99 denote a buffer solution supply path extending from the first valve 95 to the crystal sensor 7 via the second valve 97 and a waste liquid portion forming the liquid discharge system 90. Is supplied, the buffer solution passes through the second valve 97 without passing through the column 98, and the excess sample solution overflowing from the column 98 is discarded to the waste liquid part 99.

  Next, the measurement unit 10 will be described with reference to FIG. In FIG. 9, 6A is a first oscillation circuit for oscillating the first vibration region 4A of the crystal resonator 4, and 6B is a second oscillation for oscillating the second vibration region 4B of the crystal resonator 4. These oscillation outputs (frequency signals) are configured to be alternately taken into the measurement unit 10 by the switch unit 80. The measurement unit 10 may detect the frequency by a frequency counter which is a known circuit. For example, as described in Japanese Patent Application Laid-Open No. 2006-258787, the measurement unit 10 performs A / D conversion on the frequency signal to generate a carrier. A method that uses a method of generating a rotation vector that rotates at the frequency of the frequency signal and obtaining the speed of the rotation vector by processing with a move, or using a measurement unit using such digital processing Is preferable because the frequency detection accuracy is high.

  The frequency signal obtained in this way is sampled, for example, every 1 sec by a program (which is stored in the program storage unit but shown as a program) 11 and stored in the storage unit 13 as time-series data 12. In FIG. 9, reference numerals 15 and 18 denote a control unit and a bus, each of which is a computer. The program 11, the storage unit 13, the CPU 14, for example, an input means 16 for an operator to input later-described measurement time, frequency allowable value, and the like. A display unit 17 for displaying the measurement result of the frequency and the sensing object is provided. The storage unit 13 stores measurement time and frequency tolerance.

  The measurement time is a time required to acquire a change (decrease) in frequency due to the sensing object in the sample being adsorbed to the quartz sensor 7 when the sample is supplied to the quartz sensor 7. As shown in FIG. 10, when the sample solution is supplied to the quartz sensor 7, the time until the frequency decreases and stabilizes varies depending on the concentration of the sensing object. In this apparatus, the measurement time is, for example, in the column 98. Corresponds to the time (for example, 5 minutes) required for the sample liquid to pass through the quartz sensor 7. Then, for example, the frequency of the first vibration region 4A at a predetermined time point after this time has elapsed uniformly, or the first vibration region 4A when the slope of the frequency decrease curve becomes smaller than a predetermined value. Is evaluated as the frequency when the sensing object of an amount corresponding to the concentration of the sensing object in the sample liquid is adsorbed to the quartz crystal sensor 7 (adsorption layer 46). In addition, when creating a calibration curve that represents the correspondence between the concentration of the sensing object in the sample liquid and the decrease in frequency, that is, the sensing object is sensed for the sample liquid with a known concentration. When measuring the amount of decrease in the frequency corresponding to the concentration of the substance, it is known in advance that the stabilization time required for the frequency to decrease and stabilize is shorter than the passage time of the sample liquid in the column 98. When the sampling is finished when the time has elapsed and the frequency at this time is used as the frequency after the adsorption of the sensing object, the stable time becomes the measurement time.

Further, the allowable frequency value is a sufficiently small value corresponding to the stabilization (σ ² (τ)) as an index for stabilizing the frequency, as will be described later, when determining whether or not the frequency is stable. It is a threshold value for determining whether or not. For example, as shown in FIG. 11, the allowable frequency value varies depending on the set measurement sensitivity (resolution). For example, when the oscillation frequency of the crystal unit 4 is 30 MHz, the measurement sensitivity is, for example, The noise (error range) allowed in the measurement time at 5 Hz is set to 0.5 Hz (0.0167 ppm for a 30 MHz crystal sensor), for example, and the allowable value of σ ² (τ) corresponding to this error range is 1.67 × 10 ⁻⁸ (0.0167 ppm) or less. Here, a table of allowable frequency values corresponding to the measurement sensitivity as shown in FIG. 11 is stored in the storage unit 13, and the program 11 uses this table to determine the allowable frequency values based on the measurement sensitivity input or selected by the operator. You may make it acquire a value. Alternatively, the ratio of noise to the measurement sensitivity (0.1 in this example) is stored in the storage unit in advance, and noise (error range) that is allowed by multiplying the measurement sensitivity by the ratio of noise when the measurement sensitivity is selected. You may ask for.

ｙ_ｋ：各サンプリング区間毎のｋ番目のサンプリング時における周波数、ｍ：各サンプリング区間に含まれるサンプリング数（ｋ，ｍ：正数） The program 11 supplies a sample solution to the crystal sensor 7 based on the time series data 12 in addition to a step group for sampling the time series data 12, a step group for switching the valves 95 and 97. This includes a step group for obtaining the above-described decrease in frequency. Further, the program 11 includes a step group for determining the stabilization of the frequency when the buffer solution is supplied to the crystal sensor 7. The determination of the stabilization of the frequency will be described below. Whether or not the oscillation frequency of the crystal unit 4 has been stabilized is calculated based on, for example, the Allan Deviation formula of the following formula (1).

y _k : frequency at the time of the k-th sampling for each sampling interval, m: number of samplings included in each sampling interval (k, m: positive number)

In this equation (1), y _k is the frequency at the time of the k-th sampling for each sampling section, and m is the number of samplings (k, m: positive number) included in each sampling section. For example, an oscillation frequency difference (y _{k + 1} −y _k ) is calculated every second after sampling is started by supplying a buffer solution, and a value obtained by squaring the oscillation frequency difference is measured until the measurement time elapses ( A measurement result σ ² is calculated which is the result of adding and dividing by 2 m (until obtaining m frequencies). Then, as shown in FIG. 12, the measurement result σ ² is updated every second after the measurement time elapses after sampling is started, that is, a new sampling start point is set every one second, and the sampling period is sequentially set. Σ ² (t ₁ ), σ ² (t ₂ ), σ ² (t ₃ ), σ ² (t _j ), and σ ² (t _{j + 1} ) are acquired every time. Thus, as shown in FIG. 13, the measurement result σ ² decreases to a predetermined value as the oscillation frequency stabilizes with the passage of time from the start of sampling. When the measurement result σ ² (more specifically, the standard deviation σ as described below) becomes smaller than the above-described frequency tolerance, it is determined that the frequency has stabilized, and a sample solution supply permission signal is output to The supply of the sample solution is started by switching the second valve 97 described above from the buffer solution side to the sample solution side. In this example, a part of the step group of the program 11 corresponds to an output unit that outputs a sample liquid supply permission signal.

  Here, in the above equation (1), since σ is an average value indicating an error, if the allowable value of noise (error) when the measurement sensitivity is 5 Hz as described above is defined as 0.5 Hz, the variance is Therefore, σ can be interpreted in a broad sense as σ≈0.5. That is, since the standard deviation (σ) is used in the above equation (1), this standard deviation is handled as an allowable value in the measurement sensitivity. Such determination of frequency stabilization is performed, for example, for the oscillation frequency of the first vibration region 4A or for the oscillation frequencies of both the first vibration region 4A and the second vibration region 4B. In FIG. 12, the sampling interval is schematically drawn as 9 seconds, and the time when the oscillation of the crystal unit 4 is started before the buffer solution is supplied is shown as t0.

  Next, the operation of the sensing device will be described with reference to FIG. First, the crystal unit 4 is accommodated in the sensor unit 2, and the sensor unit 2 is hermetically integrated as shown in FIG. 2, and the vibration region is connected via the connection terminals 35 to 37 formed on the wiring board 3. 4A and 4B are electrically connected to the oscillation circuits 6A and 6B, respectively. Then, for example, the operator inputs (selects) a measurement time (amount of sample liquid stored in the column 98) and a frequency tolerance or measurement sensitivity according to the sample liquid to be measured (step S1). ). When inputting the measurement sensitivity, the ratio of noise to the measurement sensitivity (0.1 in the above example) is stored in advance in the storage unit, and the allowable value is obtained by multiplying the measurement sensitivity by this ratio.

  Next, the oscillation circuits 6A and 6B start oscillation of the crystal unit 4 (vibration regions 4A and 4B) at a predetermined frequency, for example, 30 MHz, and the buffer solution is supplied from the buffer solution supply unit 91 via the valves 95 and 97. Supply to the supply area | region 53 (step S2). The oscillation frequencies of the vibration regions 4A and 4B are sampled by the measurement unit 10 and are lowered to a predetermined value when a buffer solution is supplied. The oscillation frequency of the crystal unit 4 at this time fluctuates up and down as shown in FIG. 10 because the oscillation state is unstable immediately after oscillation, and then stabilizes as time passes. Then, as shown in FIG. 13 described above, whether the standard deviation σ is stable below the frequency allowable value over the same time as the measurement time for measuring the sensing object by the frequency stabilization program 14. Whether or not the sensing object is measured is determined until the oscillation frequency of the crystal unit 4 is stabilized, so that a waiting time is provided. When it is determined that the frequency has stabilized (step S4), sensing of the sensing object is started as follows.

  Subsequently, the sample solution is supplied in advance into the column 98 of the second valve 97, and the flow path of the second valve 97 is switched while the crystal unit 4 is oscillated, so that the buffer 98 is supplied from the buffer solution supply unit 91 to the column 98. A buffer solution is supplied to (Step S5). The sample solution in the column 98 is pushed out by the buffer solution and supplied to the liquid supply region 53. When the sensing object comes into contact with the adsorption layer 46 of the crystal unit 4 shown in FIG. 15A, as shown in FIG. 15B, the sensing object is detected on the adsorption layer 46 by, for example, antigen-antibody reaction or chemical reaction. An object is adsorbed, and the oscillation frequency of the crystal unit 4 (vibration region 4A) decreases due to the mass load effect, and this frequency data is acquired (step S6). Thereafter, by supplying the sample liquid to the liquid supply region 53 over the measurement time, as shown in FIG. 10 described above, the adsorption layer 46 detects an amount corresponding to the concentration of the sensing object in the sample liquid. The object is adsorbed, and the oscillation frequency of the crystal unit 4 (vibration region 4A) is lowered to a predetermined value. The frequency data obtained at this time is measured in units of, for example, a preset measurement sensitivity, for example, 5 Hz, and the error range (noise) in the measurement time is suppressed to 0.5 Hz or less. Thereafter, when the measurement time elapses, the solution supplied to the liquid supply region 53 is switched from the sample solution to the buffer solution. In this example, the frequency immediately before the sample solution in the column is supplied to the crystal unit 4 (the frequency that is in the state of the buffer solution) and the sample pass through the crystal unit 4 to push out the sample solution. The difference from the frequency immediately after switching to the buffer solution is obtained. For this reason, the measurement time is from immediately before the sample solution reaches the quartz crystal resonator 4 to immediately after it passes.

  After that, in step S7, the frequency at the time when it is determined that the buffer solution is supplied to the quartz crystal sensor 7 and the frequency is stabilized, and when the measurement time elapses or a predetermined time elapses, or the slope of the frequency decrease curve The difference from the frequency at which becomes a predetermined value is obtained. That is, the difference in frequency in the first vibration region 4A (detection region) of the crystal unit 4 and the difference in frequency in the second vibration region 4B (reference region) of the crystal unit 4 are obtained. As described above, the frequency difference of the second vibration region 4B is due to disturbance such as temperature change, viscosity of the sample liquid, or adhesion of substances other than the sensing target contained in the sample liquid. By subtracting the difference of the second vibration area 4B from the difference of the first vibration area 4A, the frequency difference caused only by the adsorption of the sensing object is obtained, which compensates for the frequency fluctuation due to the disturbance. This value is used, for example, for preparing the above-mentioned calibration curve, or is evaluated as the concentration or presence of the sensing object in the sample solution in light of a calibration curve prepared in advance.

According to the above-described embodiment, the sample liquid is supplied to the adsorption layer 46 while the crystal oscillator 4 is oscillated to adsorb the sensing object in the sample liquid, and based on the amount of change in the oscillation frequency of the crystal oscillator 4. In sensing the sensing object, before supplying the sample solution to the adsorption layer 46, the buffer solution is supplied and the oscillation frequency of the crystal unit 4 is measured at a predetermined measurement interval, for example, every second. Since the oscillation frequency of the crystal unit 4 is stabilized until σ ² (τ) is equal to or lower than a preset frequency tolerance based on the measurement sensitivity of the sensing object over the same time as the measurement time, sensing is performed. An object can be easily and accurately detected.
Further, since the Allan Deviation formula is used as described above in determining the stabilization of the oscillation frequency, the stabilization of the frequency can be easily and reliably determined.

  Further, when sensing the sensing object, the frequency decrease corresponding to the concentration of the sensing object can be accurately calculated by measuring the oscillation frequency while supplying the sample liquid. It is possible to detect accurately, and since two vibration areas 4A and 4B are provided on one crystal resonator 4, one vibration area 4A is used for measurement and the other vibration area 4B is used for reference. Since the influence of the ambient temperature of the unit 2 is suppressed, the sensing object can be sensed with high accuracy.

In the above example, the two vibration regions 4A and 4B are provided to suppress the influence of the temperature around the sensor unit 2, but only one vibration region may be provided. Further, the oscillation frequency was measured while supplying the buffer solution and the sample solution. However, if the buffer solution and the sample solution are dropped on the excitation electrodes 43A and 43B, the oscillation frequency may be measured in a closed system.
In the above, the buffer solution is an example of a reference solution. The reference liquid needs to be a liquid that does not contain a substance that is adsorbed on the adsorption layer of the piezoelectric sensor. For example, pure water may be used. When blood or serum is used as the sample solution, it is preferably a buffer solution. However, when pollutants in environmental water such as rivers are examined as sensing objects, pure water is preferred as a reference solution.
Further, the presence / absence and concentration of the sensing object are calculated by the measurement unit 10 as described above. For example, the oscillation frequency obtained in each vibration region 4A, 4B is displayed on the display unit 17, and the operator displays the oscillation frequency. The presence / absence and concentration of the sensing object may be obtained by comparing the read result with the above-described calibration curve and threshold value. In addition, the switching from the buffer solution to the sample solution is performed by the measurement unit 10 (control unit 15) after the frequency is stabilized. For example, the display unit 17 displays whether or not the frequency is stabilized, and displays this. The operator may switch the second valve 97 based on the above.

  Further, when the oscillation frequency of the crystal unit 4 is stabilized using the liquid sample liquid, the liquid buffer solution is supplied to the liquid supply region 53. In the case of sensing a sensing object in the gas, for example, in the gas The sensor unit 2 may be used for detecting dioxins, alcohol, and the like. In that case, when the oscillation frequency of the crystal unit 4 is stabilized, for example, a clean gas is used instead of the buffer solution.

DESCRIPTION OF SYMBOLS 1 Liquid supply system 2 Sensor unit 4 Crystal oscillator 4A, 4B Vibration area 7 Crystal sensor 10 Measuring part 41 Crystal piece 42 Excitation electrode 43 Excitation electrode 46 Adsorption layer 90 Liquid discharge system

Claims (4)

Using a piezoelectric sensor in which an adsorption layer is formed on an electrode provided on the piezoelectric piece, the sensing object in the sample liquid is adsorbed on the adsorption layer, and the sensing is performed based on a change in the natural frequency of the piezoelectric piece. In a device for sensing an object,
A liquid supply path for supplying liquid to the electrode;
A reference liquid that is provided on the upstream side of the liquid supply path and stores a reference liquid that does not contain a substance adsorbed on the adsorption layer, and that pushes the reference liquid to the electrode side through the liquid supply path. A supply section;
A storage part that is interposed in the liquid supply path and a reference liquid flow path through which the reference liquid flows and a reference liquid flow path through which the reference liquid flows are provided, and a flow path from the reference liquid supply part to the electrode, The reference liquid is configured to be switchable between a flow path for pushing the sample liquid in the storage section through the storage section to the electrode side and a flow path for the reference liquid to pass through the reference liquid flow path. Liquid switching part,
An oscillation circuit for oscillating the piezoelectric piece;
A frequency measurement unit for measuring the oscillation frequency of the oscillation circuit;
A data acquisition unit that acquires frequency time-series data by sampling the frequency measured by the frequency measurement unit at a preset time interval;
A storage unit for storing a measurement time set in advance to measure a change in frequency when the sample liquid is supplied to the piezoelectric sensor;
Sampling intervals sequentially for a group of sampling intervals of a length corresponding to the measurement time, each starting from the timing of each frequency sampling when the reference solution is supplied to the piezoelectric sensor via the reference solution passage The frequency stability is calculated every time, and when the calculated frequency stability falls below the allowable value corresponding to the measurement sensitivity, the supply of the sample liquid is permitted so that the flow path in the liquid switching part is switched to the storage part side. An output unit for outputting a signal ,
The measurement time is set based on a reference liquid supply speed when the reference liquid supply unit pushes out the sample liquid in the storage unit and a storage amount of the sample liquid in the storage unit. apparatus. The sensing device according to claim 1, wherein the frequency stability is expressed by the following equation.

yk: frequency at the time of the kth sampling for each sampling interval, m: number of samplings included in each sampling interval (k, m: positive number)   The sensing device according to claim 1, further comprising an allowable value acquisition unit that obtains an allowable value corresponding to the measurement sensitivity by selecting the measurement sensitivity. A sample solution supply part for supplying a sample solution for the reservoir,
A discharge unit for discharging the sample liquid and the reference liquid supplied to the piezoelectric sensor,
4. The calculation of the frequency stability and the detection of a sensing object in the sample liquid are performed while flowing a reference liquid and a sample liquid in an atmosphere in which the piezoelectric sensor is placed, respectively. A sensing device according to claim 1.

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