JPH04238258A - Freezing point drop measuring method and freezing point drop measuring device - Google Patents

Abstract

PURPOSE:To obtain a small freezing point drop measuring device with excellent operability. CONSTITUTION:A main cooling block 11 cooling a sample liquid in a sample liquid chamber 12, an auxiliary cooling block 19 cooling a sample in an inlet pipe 14a feeding the sample into the sample liquid chamber 12 at a cooling speed faster than the cooling speed to cool the sample liquid in the sample liquid chamber 12, and a thermo-module cooling the main cooling block 11 and the auxiliary cooling block 19 are provided, the whole sample liquid is frozen by the crystal nucleus formed when the sample in the inlet pipe 14a is cooled in the supercooled state, and the temperature in the solid-liquid coexistence state formed by the coagulation latent heat at the time of freezing is measured.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to medical osmometers, etc. that measure the osmotic pressure of liquid samples, particularly body fluids such as plasma, spinal fluid, and tears that are subject to clinical tests, as well as dialysate and urine. The present invention relates to a freezing point depression measuring method and a freezing point depression measuring device.

0002

[Prior Art and Problems to be Solved by the Invention] Conventional freezing point depression measuring devices include a cooling tank that supercools a sample liquid to a state several degrees below its freezing point, a rod-shaped thermistor for detecting freezing point temperature, and a freezing point depression measuring device. A device is known that has a head consisting of an electromagnetic vibrating stirring bar, a measuring circuit for measuring the freezing point temperature detected by the head, a control section for overall control, and a display section for displaying the measurement results. There is.

[0003] In the freezing point depression measuring device described above, the head is inserted into a test tube containing a sample liquid and the test tube is immersed in a cooling tank to bring the sample liquid into a supercooled state. By rapidly vibrating the stirring rod in the head, the sample liquid is brought into a solid-liquid coexistence state, and the temperature of the sample liquid in the solid-liquid coexistence state is detected by a thermistor in the head. The osmotic pressure is calculated from the degree of freezing point depression measured by this freezing point depression measurement device (U.S. Patent Nos. 3 and 2).
03,226).

However, in the freezing point depression measuring method or freezing point depression measuring device using the above-mentioned head,
(1) The amount of sample solution must be adjusted manually, (2) Replenishment and replacement of refrigerant solution is necessary, and its handling is complicated; (3) Downsizing of test tubes and sample size It is difficult to reduce the amount of liquid, (4) it is difficult to miniaturize the device, and (5) it takes a long time to cool down the refrigerant liquid for cooling, so it is necessary to speed up osmotic pressure measurement. There were a number of technical problems that made it impossible to achieve this goal.

[0005] Another method for measuring freezing point depression is to cool the sample liquid to a supercooled state, and then further cool a portion of the sample liquid that is in the supercooled state to a supercooled state. There is a method in which ice crystal nuclei are generated in a portion, the ice crystal nuclei are used as a freezing stimulus to bring the entire sample liquid into a solid-liquid coexistence state, and the temperature is detected using a thermistor (Japanese Patent Publication No. 58-31541). Then, the osmotic pressure is calculated from the degree of freezing point depression thus measured.

However, the method for measuring freezing point depression described in the above-mentioned publication requires a cooler and its controller to supercool the sample liquid, and also requires a separate cooling device to cool a part of the sample liquid to a supercooled state. This method also requires a device and a controller, which poses an obstacle to achieving miniaturization of the measuring device.Moreover, the configuration is complicated, and measurement takes time.

SUMMARY OF THE INVENTION An object of the present invention is to provide a new freezing point depression measuring method and a freezing point depression measuring device that overcome the drawbacks of conventional freezing point depression measuring methods and freezing point depression measuring devices. That is, it is an object of the present invention to provide a freezing point depression measurement method that takes a short measurement time, has good operability, and can keep measurement costs low, and a freezing point depression measurement device that can implement the above-mentioned method with a compact configuration. This is the purpose.

[0008]

[Means for Solving the Problems] In the method according to the invention according to claim 1 for solving the above problems, the cooling rate for cooling a part of the sample liquid is lower than the cooling rate for cooling the remaining part of the sample liquid. A portion of the sample liquid and the remainder are cooled at the same time to freeze the sample liquid, and the temperature of the sample liquid, which has entered a solid-liquid coexistence state due to the latent heat of solidification released when the sample liquid freezes, is measured by a measuring means. A freezing point depression measuring method according to claim 2, characterized in that, in the freezing point depression measuring method according to claim 1, a part of the sample liquid is cooled to an overcooled state. An ice crystal nucleus is formed in a part of the sample liquid, and the entire sample liquid is frozen at the same time as the ice crystal nucleus is formed.The temperature of the sample liquid in a solid-liquid coexistence state is controlled by the latent heat of solidification released during this freezing. In the invention according to claim 3, in the freezing point depression measuring method according to claim 1, the solid-liquid temperature is determined from the temperature of the sample liquid immediately before freezing and the temperature of the sample liquid in a solid-liquid coexistence state. Correct the temperature of the coexistence state.

The apparatus according to the invention according to claim 4 includes a sample liquid chamber containing a sample liquid, an auxiliary cooling block that cools the sample liquid in the inlet portion of the sample liquid chamber to a supercooled state, and a sample liquid chamber. A cooling means including a main cooling block for cooling a sample liquid in a room and a cooler for simultaneously cooling the auxiliary cooling block and the main cooling block, a detection means for detecting the temperature of the sample liquid, and a detection means for detecting the temperature of the sample liquid. This is a freezing point depression measuring device characterized by having a calculation means for calculating the temperature of a sample liquid based on the result.

0010

[Operation] The operation of each invention will be explained below.

In the method according to claim 1, the part of the sample liquid and the remaining part of the sample liquid in the sample liquid chamber are cooled so that the cooling rate of the part of the sample liquid in the sample liquid chamber is faster than the cooling rate of the remaining part of the sample liquid. are cooled at the same time. The cooling period is until ice crystal nuclei are spontaneously formed in a portion of the cooled sample liquid. When these ice crystal nuclei are formed, the entire sample liquid freezes. Then, the sample liquid enters a solid-liquid coexistence state due to latent heat of solidification released during freezing. The detection means detects the temperature of the sample liquid in a solid-liquid coexistence state and sends it to the measurement means. Thereby, the measuring means can measure the temperature.

In the method according to claim 2, a portion of the sample liquid is cooled to an overcooled state. Ice crystal nuclei spontaneously form in a portion of the sample liquid that has been cooled to an overcooled state. This formation of ice crystal nuclei causes the entire sample liquid to freeze. The subsequent steps are as described in claim 1 above.

In the method described in claim 3, the temperature of the sample liquid is measured both immediately before freezing and in the solid-liquid coexistence state, and the temperature in the solid-liquid coexistence state is corrected by the temperature immediately before freezing to obtain an appropriate value. At this time, the freezing point temperature can be corrected using the following correction formula.

[0014]T(X,Y)=(Ty・K1−K2
−Tx )·K3 +Ty where T(X, Y) is the corrected freezing point temperature, Ty is the measured freezing point temperature, and Tx is the temperature just before freezing. K1, K2, and K3 are constants, and can be determined from the temperature just before freezing and the freezing temperature of a calibration liquid whose freezing point temperature is measured at least three times.

In the apparatus according to claim 4, when the main cooling block and the auxiliary cooling block are simultaneously cooled by one cooler, the sample liquid in the inlet of the sample liquid chamber is cooled to an overcooled state by the auxiliary cooling block. , ice crystal nuclei are formed spontaneously. The entire sample liquid rapidly freezes due to these ice crystal nuclei, and the entire sample liquid becomes in a solid-liquid coexistence state. The temperature of the solid-liquid coexistence state is detected by the detection means, and the freezing point is calculated by the calculation means from the detection result.

Normally, the temperature of the solid-liquid coexistence state detected by the detection means is defined as the freezing point, but the same sample may have different solid-liquid coexistence states depending on the concentration of the sample liquid, the presence of impurities, and other reasons. Temperature may be detected. In such a case, the detection means may measure the temperature of the sample liquid immediately before freezing and the freezing point temperature, and the calculation means may calculate the accurate freezing point using the correction formula.

[0017]

EXAMPLES Examples of the present invention will be described in detail below.

The freezing point depression measurement apparatus 1 shown in FIG. 4, a detection means 5 and a cooling means 15 attached to the storage means 2, and a measurement means 6 that takes in the detection results of the detection means 5 to measure and correct the temperature of the sample liquid.
A pump driving section 7 that drives the pump 3 under the control of the measuring means 6, a drain bottle 8 that stores the sample liquid discharged from the storing means 2, and various operational information for the measuring means 6. It is equipped with an operating means 9 for sending a message, and a display means 10 such as a liquid crystal display.

As shown in FIGS. 2 and 3, the housing means 2 includes an approximately L-shaped main cooling block 11 made of a corrosion-resistant material having high thermal conductivity and low specific heat, such as silver. Equipped with:

This main cooling block 11 has a vertical piece 11
The sample liquid chamber 12 is formed inside the vertical piece 11a. Further, a thermistor 13 constituting the detection means 5 is inserted from the upper side of the sample liquid chamber 12 .

An inlet pipe 14a communicating with the pump 3 is inserted into the lower side of the sample liquid chamber 12, and a drain pipe 14a communicating with the drain bottle 8 is inserted into the horizontal piece 11b communicating with the sample liquid chamber 12. A tube 14b is inserted therethrough.

Furthermore, the main cooling block 11 includes a thermo module 16a that utilizes the Peltier effect as a main cooling section constituting the cooling means 15, a cooling plate 17, and thermo modules 16b and 16c connected in cascade with the thermo module 16a. It is attached to the heat sink 18 via the heat sink.

Furthermore, below the main cooling block 11,
Further, an auxiliary cooling block 19 is closely disposed on the surface of the thermo module 16a so as to surround the inlet pipe 14a. The auxiliary cooling block 19 is made of a material having higher thermal conductivity and lower specific heat than the material constituting the main cooling block 11.

As shown in FIG. 1, the measuring means 6 includes a control section 21 that performs overall control and determines the temperature value based on the detection signal of the thermistor 13, and a storage section 22 that includes ROM, RAM, etc. , a resistance voltage conversion circuit 23 that converts the output signal of the thermistor 13 into a voltage value and outputs it, and A that converts the voltage value signal from the resistance voltage conversion circuit 23 into a digital signal and sends it to the control section 21. /D converter 24 and an I/O port that is connected to the control section 21 and outputs a measurement signal measured based on various control signals from the control section 21 and a detection signal of the thermistor 13.
25, the cooling means 15, a polarity switch 26 for switching the polarity of the resistance voltage conversion circuit 23, and a thermo module 1.
It is equipped with a DC power supply 27 for 6a, 16b, and 16c.

Furthermore, the control section 21 controls the pump driving section 7 via the I/O port 25.

Next, the freezing point depression measuring device 1 having the above-described configuration will be described.
A method of measuring freezing point depression using the method will be explained with reference to FIGS. 4 and 5.

When the operator issues a command to start measurement from the operating means 9, this command is taken into the control section 21, and the control section 21 then sends a control signal to the pump drive section 7 via the I/O port 25. (Step A shown in FIG. 4).

The pump driving section 1 drives the pump 3 for a predetermined period of time based on the control signal, and as a result, a predetermined amount (for example, 0.2 ml) of the sample liquid contained in the sample bottle 4 flows into the inlet pipe 14a. The sample is sent into the sample chamber 12 through the . After this, the pump 3 stops driving.

[0029] The control unit 21 also controls the I/O ports 25,
A control signal to start cooling is sent to the cooling means 15 via the polarity switch 26 (step B shown in FIG. 4).

At this time, the state in which the cooling means 15 cools the sample liquid is indicated by "CS" in FIG.

With the cooling operation of the cooling means, the sample liquid in the sample liquid chamber 12 is cooled by the main cooling block 11 as shown by the characteristic X shown in FIGS. 4 and 5, and this state is maintained by the thermistor 13. Further, the detection result is sent to the control section 21 via the resistance voltage conversion circuit 23 and the A/D converter 24 to obtain a temperature value, and this temperature value is displayed on the display means 10.

On the other hand, the sample liquid in the inlet pipe 14a is cooled by the auxiliary cooling block 19 at a faster cooling rate than the main cooling block 11, as shown by characteristic Y shown in FIG.

When the temperature of the sample liquid in the sample liquid chamber 12 reaches Tx shown in FIG. In the operation of block 19, Tz (temperature in supercooled state,
For example, it is cooled down to about -18°C. Ice crystal nuclei are spontaneously generated in the sample liquid that has been cooled to an overcooled state by the inlet pipe 14a, so that the entire sample liquid rapidly freezes. At this time, the sample liquid enters a solid-liquid coexistence state due to the latent heat of solidification, and its temperature gradually rises due to the release of latent heat accompanying freezing, once reaches a plateau (temperature flat area), and then gradually decreases.

The temperature Ty when the plateau is reached is detected by the thermistor 13 as the equilibrium temperature of the solid-liquid coexistence state, is calculated by the control unit 21 to which the detection signal is input, is displayed by the display means 10, and is stored in the memory. Part 22
is memorized.

The rapid temperature change from Tx to Ty allows the measuring means 6 to know that the sample liquid is in a fixed coexistence state, and the temperature Tx just before freezing can be used as a correction parameter.

After this, the cooling means 15 is controlled to be in the OFF state (Step C shown in FIG. 3).

Next, when the above-described measurement of the freezing point temperature Ty is completed, the control section 21 controls the heating of the cooling means 15 as indicated by "HS" in FIG.

Then, when the temperature of the sample liquid exceeds 0° C., the controller 21 controls the thermo module 16 of the cooling means 15.
a, 16b, and 16c are turned off, and at the same time, the sample liquid is discharged into the drain bottle 8 (step E shown in FIG. 4).

Next, the process of forming the above-mentioned solid-liquid coexistence state of the sample liquid will be numerically explained.

For example, the latent heat of solidification of 0.2 ml of sample liquid is 0.2 ml×79.7 cal=15.94 cal.

It is also assumed that the amount of heat required to change the sample liquid by 1°C is 0.2 cal/°C.

[0042] The volume of the silver main cooling block 11 is set to 0.
．． 5cm3, the specific heat of silver is 0.054cal/g/℃,
If the specific gravity of silver is 10.49 g/cm3, the amount of heat required to change the temperature of the sample liquid block by 1°C is 0.054
×0.5×10.49=0.283 cal/°C.

Now, when the temperature of the sample liquid and the main cooling block 11 is -22°C, assuming that the sample liquid freezes and enters a solid-liquid coexistence state and reaches equilibrium at -2°C, the heat of solidification at this time is: (22-2)×0.2+(22-2)×0.
283=9.66 cal.

Since this heat of solidification is lower than the latent heat of solidification (approximately 15.94 cal) of the entire sample liquid, the entire sample liquid does not freeze and enters a solid-liquid coexistence state.

Regarding the heat capacity of the main cooling block 11 mentioned above, reducing this heat capacity means that the amount of heat required to raise the supercooled sample liquid and the main cooling block 11 to the freezing point temperature is reduced. This means that the latent heat of solidification is lower than the latent heat of solidification of the entire sample liquid.

Although the heat capacities of the inlet pipe 14a, outlet pipe 14b, and thermistor 13 mentioned above can be ignored, the heat capacities of the thermo modules 16a, 16b, and 16c cannot be ignored, and the amount of heat for the above-mentioned temperature increase is naturally equal to the increase temperature. The larger the number, the greater the number, so it is necessary to keep the heat capacity of the main cooling block 11 small with some margin.

Next, referring also to FIG. 5, temperature correction of the freezing point temperature Ty will be explained.

The temperature Tz at which natural freezing occurs varies depending on the concentration of the sample liquid, the degree of impurities, etc., and this influences the temperature Tx just before freezing and the freezing point temperature Ty.

For example, when measuring a sample solution with the same concentration twice, the temperature immediately before freezing is Tx1 as shown in FIG.
, Tx2, and therefore the freezing point temperature also changes as Ty
There may be cases where there is a difference such as 1 and Ty2.

For this reason, the freezing point temperature correction value T(x,y) is determined using the following (1).

T(x,y)=(Ty・K1−K2−Tx)・K3+T
y... (1) Note that the values of K1, K2, and K3 are obtained from the past several calibration data.

That is, for example, if the freezing point temperature is -1.85
Create a calibration solution of 1000mOsm/kg at 8℃,
The data when calibrated three times is (Tx1, Ty1), (
Tx2, Ty2), (Tx3, Ty3),
By combining the following equations (2), (3), and (4), K
1, K2, and K3 can be found.

−1.858 = (Ty1K1−K2−Ty1)・K3
+Ty1...(2)-1.858 =(Ty2K
1-K2-Tx2)・K3 +Ty2...(3)-
1.858 = (Ty2・K2 −K2−Tx3)・K
3 +Ty3 (4) In addition to the embodiments described above, the present invention can be modified in various ways within the scope of its gist.

[0054]

[Effects of the Invention] The present invention described in detail above provides the following effects.

According to the present invention, (1) the freezing point is measured by sucking the sample liquid into the sample liquid chamber and cooling it, so there is no need to manually adjust the amount of the sample liquid, and (2) the refrigerant Since the sample liquid is cooled by a thermo module etc. without using liquid, replenishment of refrigerant liquid,
There is no need for complicated maintenance operations such as replacement, in other words, it is maintenance-free. (3) Since the sample liquid chamber is used instead of a test tube containing a thermistor or stirring rod, the amount of sample liquid can be minimized. (4) It is easy to downsize the device; (5) Cooling is performed in a short time because the cooling operation is performed using a thermo module, etc. without cooling the refrigerant liquid for cooling. Therefore, by adopting this freezing point depression measuring method, it is possible to speed up the osmotic pressure measurement. This eliminates the need for a cooler and its controller to cool the sample liquid to a supercooled state, as well as other coolers and its controller to cool the sample liquid from the supercooled state to the supercooled state.
It is possible to provide an excellent method for measuring freezing point depression, which allows the device to be made more compact, and a small-sized freezing point depression measuring device capable of realizing the method.

[Brief explanation of the drawing]

FIG. 1 shows a block diagram of an embodiment device of the present invention.

FIG. 2 is a front view showing a sample liquid chamber and cooling means in the apparatus.

FIG. 3 is a sectional view taken along line II in FIG. 2;

FIG. 4 is a diagram illustrating the principle of an embodiment method of the present invention.

FIG. 5 is an explanatory diagram when temperature correction is performed in the embodiment method of the present invention.

[Explanation of symbols]

1 Freezing point depression measuring device 2. Containment means 5 Detection means 6 Measurement means 12 Sample liquid chamber 15 Cooling means.

Claims (4)

[Claims] Claim 1: The sample liquid is frozen by simultaneously cooling a part of the sample liquid and the remaining part so that the cooling rate for cooling the part of the sample liquid is faster than the cooling rate for cooling the remaining part of the sample liquid. A method for measuring freezing point depression, characterized in that the temperature of a sample liquid, which has entered a solid-liquid coexistence state due to the latent heat of solidification released when the liquid freezes, is measured by a measuring means. 2. Forming ice crystal nuclei in a portion of the sample liquid by cooling a portion of the sample liquid to an overcooled state, freezing the entire sample liquid at the same time as the formation of the ice crystal nuclei, and freezing the entire sample liquid. 2. The freezing point depression measuring method according to claim 1, wherein the temperature of the sample liquid that has entered a solid-liquid coexistence state is measured due to the latent heat of solidification released at the time. 3. The freezing point depression measuring method according to claim 1, wherein the temperature in the solid-liquid coexistence state is corrected from the temperature of the sample liquid immediately before freezing and the temperature of the sample liquid in the solid-liquid coexistence state. 4. A sample liquid chamber containing a sample liquid, an auxiliary cooling block that cools the sample liquid in the inlet portion of the sample liquid chamber to a supercooled state, a main cooling block that cools the sample liquid in the sample liquid chamber, and A cooling means equipped with a cooler that simultaneously cools the auxiliary cooling block and the main cooling block, a detection means for detecting the temperature of the sample liquid, and an arithmetic means for calculating the temperature of the sample liquid based on the detection result of the detection means. A freezing point depression measuring device comprising: