JP2802344B2 - Method and apparatus for measuring osmotic pressure - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and a device for directly measuring the osmotic pressure of a solution.

(Prior Art) Methods for measuring the osmotic pressure of a solution include an indirect measurement method and a direct measurement method.

The indirect measurement method is a method of calculating the osmotic pressure by knowing the number of moles of solute contained in a unit volume of solution and fitting this number of moles to the formula of Van't Hoff. Is based on the freezing point method or the vapor pressure method.

On the other hand, the direct measurement method is performed using the apparatus shown in FIGS.

That is, the apparatus shown in FIG. 4 separates the solution chamber S1 and the solvent chamber S2 via the semipermeable membrane 100, and stands still until the infiltration of the solvent naturally reaches equilibrium. The apparatus shown in FIG. 5 is configured to convert the difference between the liquid surface heights (Δh) into reading pressures. The apparatus shown in FIG.
And the solvent chamber S2, and the pressure transducer 101 is used to measure the negative pressure on the solvent side when the outflow of the solvent is in an equilibrium state. Further, the apparatus shown in FIG.
The flow of solvent passing through the 100 was observed with a height h _a of the surface of the solution side, a zero flow of solvent addition h _a is in the cylinder 102 so as to be equal to the liquid level h _b solvents side Is sent to the solution chamber S1 via the pressure regulator 103 and the constant temperature bath 104, and waits until the gas reaches an equilibrium state.

(Problems to be Solved by the Invention) The above-described indirect measurement method has the following problems.

(1) In the measurement of the osmotic pressure by the freezing point depression method, a procedure in which the solution is supercooled, a sudden vibration (freezing stimulus) is applied thereto to cause freezing, and the temperature at this time is measured. To take the solution, a stable supercooled state (-
(6 to -7 ° C.), a highly accurate cooling bath and a device for applying vibration are required, and the device as a whole becomes complicated and expensive.

(2) In the measurement of the osmotic pressure by the freezing point depression method, it is necessary to accurately measure the freezing point of the solution (measurement error ± 0.01 ° C.), and an expensive temperature sensor is required. In addition, since the freezing point is measured in a supercooled state, the true freezing point is not theoretically measured. Depending on the sample, there are also problems in the measurement technique such as freezing before applying the freezing stimulus and freezing not occurring even when the freezing stimulus is applied.

(3) In the osmotic pressure measurement by the freezing point depression method, an accurate osmotic pressure cannot be measured because a solute precipitated at a low temperature is not included in the osmotic pressure conversion.

(4) In the osmometer based on the vapor pressure drop method, the dew point is determined by the vapor pressure, and this dew point temperature is measured by a thermocouple, converted into a change in vapor pressure, and further converted into osmotic pressure. . For this reason, it is necessary to control the temperature in the measurement chamber with high accuracy, and to use a highly accurate and expensive device for converting a signal from the thermocouple into temperature.

(5) In any case of the osmotic pressure measurement by the freezing point drop method or the vapor pressure drop method, the osmotic pressure is not directly measured, but the molar concentration of the solution is measured, and the Van't Hoff equation is used. Conversion is performed and the osmotic pressure is obtained indirectly. Van't Hoff's equation is applicable only to a dilute (less than 0.2 mol) low molecular weight solution, and does not apply to a concentrated solution or a polymer solution such as a protein. For this reason, there is a theoretical problem in using the Van't Hoff equation when converting the freezing point drop or vapor pressure drop into osmotic pressure in a concentrated solution or polymer solution.

Further, the direct measurement method shown in FIGS. 4 to 6 has the following problems.

(6) In the apparatus shown in FIG. 4, since it takes a long time (at least several days to about one week) to reach an equilibrium state, sufficient attention must be paid to decay of the solution and deformation of the membrane. is there. This is because the solution concentration in the vicinity of the membrane 100 in the solution chamber decreases due to the intrusion of the solvent from the solvent chamber S2 to the solution chamber S1, and it takes an enormous amount of time to make the concentration of the entire solution chamber uniform by diffusion. . In addition, since the concentration of the solution in the solvent chamber is reduced as a whole by the infiltration of the solvent, there is also a problem that the value of the obtained osmotic pressure is lower than the true osmotic pressure. In order to minimize these problems, the diameter of the liquid column is generally as small as possible with respect to the membrane area. However, if the column diameter of the liquid column is too small relative to the total volume of the solution chamber, the temperature of the device will be very sensitive to the height of the liquid column in the capillary, so the device must be at least ± 5 /
It must be kept in a 1000 ° C thermostat.

(7) In the apparatus shown in FIG. 5, since the negative pressure in the solvent chamber S2 is measured, the measurement range is very narrow, from 0 to 100 mmHg.

(8) In the apparatus shown in FIG. 6, the penetration of the solvent, which is a problem in the apparatus shown in FIG. 4, can be avoided to some extent. However, it still takes a long time (about 24 hours) to reach equilibrium, and during that time, humans constantly observe the height of the liquid column,
The pressure regulator must be adjusted.

(Means for Solving the Problems) In order to solve the above problems, the present invention is directed to a method for measuring osmotic pressure according to claim 1, wherein the method comprises the steps of: A solvent chamber connected to each other by a semi-permeable membrane and having an air vent above the chamber, and a solution chamber having an air vent that can be opened and closed above the chamber are formed so that air above the solution chamber escapes from the air vent. The solution is completely filled up to the upper part of the solution chamber and up to the air vent, and thereafter, the air vent is closed to seal the solution chamber, and then the solvent is injected into the solvent chamber, and thereafter, an equilibrium state is established. Then, the pressure in the solution chamber when the pressure rise in the solution chamber stopped was measured, the difference between the measured pressure in the solution chamber and the atmospheric pressure was read, and this pressure difference was used as the osmotic pressure.

According to claim 2, in the device for directly measuring the osmotic pressure of the solution, a semi-permeable membrane is provided vertically in a longitudinally intermediate portion of a horizontal cylindrical space formed in the device main body, and the semi-permeable membrane is provided. On both sides, a solution chamber and a solvent chamber are formed so as to be interconnected by the semipermeable membrane, and an openable air vent is provided at the top of the solution chamber so as to communicate with the chamber. A solution inlet is provided in the lower half of the chamber, and a pressure sensor is disposed in the solution chamber such that the tip thereof faces the chamber,
In the upper part of the solvent chamber, an air vent is provided so as to communicate with the chamber, and a solvent inlet is provided in the lower half of the solvent chamber,
The surface of the semipermeable membrane on the solvent chamber side was supported by a porous plate.

(Operation) After the solution chamber is completely filled with the solution, the solution chamber is closed to prevent the volume of the solution chamber from increasing, and the solvent is injected into the solvent chamber in this state. Then, the pressure in the solution chamber increases while preventing the solvent in the solvent chamber from entering the solution chamber.
Then, in a short time, an equilibrium state is reached and the pressure rise stops, so the pressure at this point is measured, and the rise is defined as the osmotic pressure of the solution.

(Example) Hereinafter, an example of the present invention will be described with reference to the accompanying drawings.

1 is a longitudinal sectional view of the osmotic pressure measuring device according to the present invention, FIG. 2 is a side view in the direction A of FIG. 1, and FIG. 3 is a side view in the direction B in FIG.

The measuring device is composed of a main body 1 and a pair of cells 1a and 1b
And nut 3. That is, in the cells 1a and 1b, recesses 4 and 5 each having a substantially cylindrical shape with an axis opening on one surface sideways (horizontally) are formed, and the openings of these recesses 4 and 5 are opposed to each other so that A laterally cylindrical chamber is formed, and the semipermeable membrane 6 is sandwiched vertically (vertically) between opposed opening lines of the recesses 4 and 5 which are longitudinally intermediate portions (axially intermediate portions) of the chamber. a pair of cells 1a, a solution chamber S1 in the cell 1a on by combining 1b the butt via the O-ring O _1, O _2, to define a solvent housing S2 in the cell 1b to.

Here, the side surface of the solvent chamber S2 of the semipermeable membrane 6 is backed up by a hard porous support plate 7. In this manner, the semipermeable membrane 6 is prevented from swelling toward the solvent chamber S2 and the solution chamber S1 is prevented.
Can be kept constant.

Valves 8 and 9 are attached to the outer portion of the main body 1, a pipe 10 extending upward is connected to the valve 8, and a tank 11 for storing a solution is provided at an upper end of the pipe 10, and the valve 9 extends upward. A pipe 13 is connected, and a tank 13 for storing a solvent is provided at an upper end of the pipe 12. When the valve 8 is opened, the solution is supplied into the solution chamber S1 through the solution inlet 14 formed in the cell 1a, and when the valve 9 is opened, the solvent is supplied through the solvent inlet 15 formed in the cell 1b. Is supplied into the solvent chamber S2. The solution inlet 14 and the solvent inlet 15 are each a solution chamber.
Opening is in the lower half of the cylindrical side surface of S1 and solvent chamber S2.

An air vent 1 is provided at the upper end of the solution chamber S1 and the solvent chamber S2.
6, 17 are open, and a valve 18 is provided in the air vent 16 of the solution chamber S1.

Further, a mounting hole 20 for the pressure sensor 19 is formed in the cell 1a. The mounting hole 20 has a portion holding the pressure sensor 19 as a circular hole 20a, and a portion facing the tip of the pressure sensor 19 and becoming a part of the solvent chamber S1 as a tapered hole 20b gradually expanding. In this way, the portion where the pressure sensor 19 faces is a tapered hole 20b, the solution inlet 14 is opened in the lower half of the side surface of the solution chamber S1, that is, the upwardly inclined surface, and the air vent 16 is further opened in the upper end of the solution chamber S1. As described above, the solution chamber S1 has a laterally-cylindrical shape as described above. Therefore, the ceiling of the solution chamber S1 has a convex upward curved surface, and when the solution chamber S1 is filled with the solution, one of the solution chamber S1 is formed. No air bubbles remain in the part. Therefore, in the osmotic pressure measurement, a measurement error due to the contraction of the bubble does not occur.

A method for measuring the osmotic pressure using the apparatus having the above configuration will be described below.

First, with valve 8 and valve 18 open, vent
The solution is injected from the solution inlet 14 while releasing the air from the solution 16. When the solution is completely filled up to the upper part of the air vent 16, the valve 8 and the valve 18 are closed, and the solution chamber S1 is closed. Next, with the valve 9 open, the solvent inlet 15
, The solvent is injected into the solvent chamber S2. Solvent level is valve 18
Is reached, the valve 9 is closed to stop the injection of the solvent. Thereafter, the pressure sensor 19 observes an increase in the pressure in the solution chamber, and waits for the increase in the pressure to stop and reach an equilibrium state. Finally, read how much the pressure in the solution chamber S1 has increased with respect to the atmospheric pressure (the pressure immediately after the injection of the solvent),
This is defined as the osmotic pressure of the solution.

(Effects of the Invention) The present invention has the following effects because of the configuration and method as described above.

(1) The pressure rise in the solution chamber can be directly measured as the osmotic pressure without relying on the conversion using the Van't Hoff equation (formula that can be satisfied only with a low-concentration low-molecular solution).

(2) The structure of the device is extremely simple, and can be downsized. Therefore, cleaning and maintenance can be easily performed.

(3) Since it is composed of inexpensive parts, the price of the entire apparatus can be kept low.

(4) The temperature of the entire system can be controlled only by immersing the portion below the air vent valve in a constant temperature bath, and the temperature control of the apparatus is extremely easy.

(5) Unlike an indirect measurement using a freezing point drop method or a vapor pressure drop method or a conventional diaphragm type osmotic pressure measuring device, a change in the ambient temperature does not directly lead to a measurement error. Therefore, strict temperature control is not required.

(6) There is no penetration of the solvent into the solution chamber, and the osmotic pressure can be accurately measured in a very short time (10 hours or less) as compared with the conventional apparatus.

(7) The measurement range of the osmotic pressure can be expanded within the range of the strength of the cell constituting the main body.

(8) After injecting the solution and the solvent, the measurement is completed only by leaving it to stand. Therefore, the labor required for measurement can be significantly reduced as compared with the conventional apparatus shown in FIG.

(9) A part of the mounting hole of the pressure sensor is formed as a tapered hole, and the solution inlet is opened in the lower half of the solution chamber inclined upward,
In addition, by opening the air vent at the top of the solution chamber,
No bubbles remain in the solution chamber, and accurate measurement can be performed.

(10) By backing up the surface of the semipermeable membrane on the solvent chamber side with a porous plate, the semipermeable membrane does not swell to the solvent chamber side, and the volume of the solution chamber can be kept constant and accurate measurement can be performed. .

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an osmotic pressure measuring device according to the present invention, and FIG.
1 is a side view in the direction A of FIG. 1, FIG. 3 is a side view in the direction B of FIG. 1, and FIGS. 4 to 6 are views showing a conventional measuring apparatus. In the drawings, reference numeral 1 denotes an apparatus main body, 1a and 1b denote cells, 4 and 5 denote recesses forming a horizontal cylindrical chamber, 6 denotes a semi-permeable membrane, 7 denotes a porous support plate, and 18 denotes an air port of the solution chamber. A valve, 14 is a solution inlet, 15 is a solvent inlet, 16 and 17 are air vents, 19 is a pressure sensor, 20 is a mounting hole for a pressure sensor, S1 is a solution chamber, and S2 is a solvent chamber.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-B-48-17113 (JP, B1) (58) Field surveyed (Int. Cl. ⁶ , DB name) G01N 13/04

Claims (2)

(57) [Claims] 1. A solvent chamber which is connected to each other by a semipermeable membrane on both sides of a semipermeable membrane disposed vertically in a main body and has an air vent above the chamber, and an air vent which can be opened and closed above the chamber. A solution chamber is formed by partitioning the solution chamber, and while the air above the solution chamber is allowed to escape from the air vent, the solution is completely filled up to the upper part of the solution chamber and up to the air vent, and then the air vent is closed to close the solution. The chamber is closed, and then the solvent is injected into the solvent chamber.After that, the pressure in the solution chamber when the pressure rise in the solution chamber is stopped when the equilibrium state is reached is measured. Read the difference from the atmospheric pressure,
An osmotic pressure measuring method, wherein the pressure difference is used as an osmotic pressure. 2. An apparatus for directly measuring the osmotic pressure of a solution, wherein a semi-permeable membrane is disposed vertically at an intermediate portion in a longitudinal direction of a horizontal cylindrical space formed in the apparatus main body. On both sides of the membrane, a solution chamber and a solvent chamber are formed so as to be interconnected by the semipermeable membrane, and an openable air vent is provided at the top of the solution chamber so as to communicate with the chamber, In addition, a solution inlet is provided in the lower half of the solution chamber, and a pressure sensor is disposed in the solution chamber so that the tip thereof faces the chamber. An air vent port is provided in the upper part of the solvent chamber. Is provided so as to communicate with the chamber, a solvent inlet is provided in the lower half of the solvent chamber, and a surface of the semipermeable membrane on the solvent chamber side is supported by a porous plate. Osmotic pressure measuring device.