JP2003035648A - Method for measuring surface tension and interface tension - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for measuring interface tension and surface tension of a low concentration surfactant, a highly volatile solvent, a corrosive sample, or the like, accurately with high reproducibility using an equipment for measuring surface tension or interface tension of a liquid sample. SOLUTION: In a liquid drop measuring method using a liquid sample feeder fixed with a shielding part for preventing intrusion of a sample into the gap between a push rod and the inner wall of a tubular body, residual liquid drop is removed forcibly after a liquid drop is formed and measured and then next analysis is started.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a tension between liquid molecules existing on the surface of a liquid sample in a gas phase, that is, a surface tension, or a sample existing in an interface between a surrounding liquid and a liquid sample in a liquid phase. The present invention relates to a method for measuring surface tension and interfacial tension, which can accurately and reproducibly measure tension between liquid molecules, that is, interfacial tension.

[0002]

2. Description of the Related Art As a device for measuring the surface tension of a liquid, a device by a liquid drop method as disclosed in JP-A-8-152396 is considered. However, as a result of the liquid sample being dropped being exposed to the outside air, this device continuously evaporates the sample component from the surface of the liquid droplet during the measurement of the surface tension, and the weight of the sample component continuously changes with time. As a result of the decrease, it has a drawback that the surface tension cannot be measured accurately.

The inventor of the present invention has long been aware of this drawback, and in order to solve this, the surface Vol. 34,
No. 3, 26-36 (1996), a saturated vapor pressure atmosphere of the sample component is formed around the sample droplet under the measurement temperature condition to evaporate the continuous component from the droplet. We developed a surface tension measuring device characterized by installing a sample container to prevent it, and completed a patent application for the device (Japanese Patent Application No. 2000-162529).

[0004]

However, even when such a device is used, when measuring low-concentration surfactants, highly volatile solvents, corrosive samples, etc., there is a problem that the measured values do not match. It was happening. Furthermore, the experimental values also fluctuated, and there were cases where reproducibility was poor.

Specifically, the method of measuring the surface tension and the interfacial tension of a liquid sample by the liquid drop method forms a liquid drop in the liquid sample portion of the liquid feeding device, and This is done by measuring the time when the droplets drop or float and the volume of the droplets after the temperature and the adsorption of the components have reached equilibrium. When measuring a sample such as a simple aqueous solution, a small amount of the sample residue that has reached the equilibrium and remains at the liquid sample outlet of the liquid delivery device affects the size of the droplets during the next measurement. There is a problem that the size is carelessly reduced.

The present invention has been made in view of the above-mentioned problems of the prior art, and accurately collects reproducible experimental data for any sample such as a low-concentration surfactant. The present invention relates to a method for measuring the interfacial tension and surface tension of a liquid sample.

[0007]

The present invention has been made to solve the above-mentioned problems, and the characteristics of the method for measuring surface tension and interfacial tension of the present invention are as follows: And a sample having a liquid sample outlet, a push rod for discharging the liquid sample to the outside of the cylinder through the liquid sample outlet of the cylinder, and a sample being prevented from entering the gap between the push rod and the inner wall of the cylinder. A method for measuring the interfacial tension and surface tension of a liquid sample by the liquid drop method, which uses an interfacial tension and surface tension measuring device for a liquid sample, which is equipped with a liquid delivery device for forming a liquid drop having a shielding portion The next measurement is performed after the droplet residue that remains at the tip of the liquid sample outlet of the liquid delivery device after the droplets have been formed and dropped or floated is extruded through the push rod and removed.

Further, the features of the method for measuring surface tension and interfacial tension of the present invention are that a liquid sample inlet, a liquid sample holding portion, and a liquid sample outlet are provided, and a liquid sample outlet portion of the liquid sample is used. Of a liquid sample having a liquid delivery device for forming droplets, which includes a push rod for discharging the sample to the outside of the cylinder through a shield, and a shield for preventing the sample from entering the gap between the push rod and the inner wall of the cylinder. In a method of measuring the interfacial tension and surface tension of a liquid sample by a droplet method using an interfacial tension and surface tension measuring device, the tip of the liquid sample outlet part of the liquid delivery device after forming and dropping or floating a droplet After dropping one or more drops of the residual liquid remaining in the above through the push rod,
The next liquid sample is increased to just before the dropping, and it is held until the adsorption equilibrium time is reached and adsorption is equilibrated.

[0009]

The method for measuring the surface tension and interfacial tension of a liquid sample according to the present invention is novel by eliminating the liquid droplets remaining in the liquid sample portion of the liquid feeding device before forming new liquid droplets. It is possible to form droplets only with a simple liquid sample and to make the amount of components contained in the sample constant, and as a result, it is possible to make the surface adsorption amount of sample components constant at all times.

The results of experiments conducted using the surface tension and interfacial tension measuring device of the present invention will be described below based on the examples shown in FIGS. 1 to 5 and Tables 1 and 2.

[0011]

Example 1 FIG. 1 shows an overall view of a measuring apparatus of the present invention and a system used for an experiment. 1 is a measuring device of the present invention, 2 is a detecting device for detecting passage of liquid droplets, 3 is an automatic micrometer controller for quantitatively dropping a liquid sample, and 4 is a personal computer for recording data.

In this example, an aqueous solution of anionic surfactant sodium dodecyl sulfate (SDS) was used as the liquid sample. The results of measurement using an aqueous solution having a sample concentration of 7.431 mmol / kg as a sample are shown in FIG. 4 and Table 1.
As is clear from the results, according to the present invention, the stability of the data is significantly improved as compared with the method of removing the remaining droplets as in the prior art.

[0013]

Second Embodiment Next, another embodiment will be described. However, the overall configuration of the measuring device and the system used for the experiment is
Since it is the same as the first embodiment, the description thereof is omitted here.

In this example, an aqueous solution of anionic surfactant sodium dodecyl sulfate (SDS) was used as a liquid sample. The results of measurement using an aqueous solution having a sample concentration of 4.802 mmol / kg as a sample are shown in FIG. 5 and Table 2.
In this example, measurement was performed according to the following steps. 1) Droplet residue is removed once or more at the start of measurement. 2) The droplet residue is removed once or more after the temperature equilibration treatment. 3) Increase the amount of droplets held at the time of adsorption equilibrium to the point just before dropping with reference to the immediately preceding dropping amount. 4) Hold the droplet for the adsorption equilibrium time to equilibrate adsorption. 5) The liquid is pushed out until the liquid drops are dropped. 6) Droplet residue removal was performed at least once. 7) Repeat steps 3) to 5) for measurement. As is clear from the results, according to the present invention, the stability of the data is significantly improved as compared with the method of removing the remaining droplets as in the prior art.

[Table 1]

[Table 2]

[0015]

As described above, the method of the present invention is
In the method for measuring the interfacial tension and surface tension of a liquid sample by the liquid drop method, the liquid drop residue remaining at the tip of the liquid sample outlet part of the liquid feeding device after the liquid drop is formed and dropped or floated By forcibly extruding and removing it via the next measurement, it is possible to form droplets only with the new liquid sample by performing the next measurement, and as a result, it becomes possible to always perform stable measurement.

Further, according to the present invention, the measurement accuracy and reproducibility of a sample such as an anionic surfactant which tends to adhere to the glass surface, which cannot be accurately measured by the conventional drop volume method, are improved.

[Brief description of drawings]

FIG. 1 Surface tension and interfacial tension measurement system of the present invention

FIG. 2 Details of the measuring device of the present invention

FIG. 3 is a detail of the liquid delivery device of the present invention.

FIG. 4 Example of the present invention (high concentration of SDS)

FIG. 5: Example of the present invention (SDS low concentration)

[Explanation of symbols]

1 constant temperature water tank 2 Drop drop detector 3 Electric micrometer controller 4 PC 5 Temperature control device 11 Liquid feeder 11a Liquid sample inlet 11b Liquid sample holder 11c Liquid sample outlet 11d cylinder 11e push rod 11f Shield 12 Sample container 13 Holder 14 constant temperature bath

Claims (3)

[Claims] 1. A cylinder (11d) having a liquid sample inlet (11a), a liquid sample holder (11b) and a liquid sample outlet (11c), and a liquid sample outlet (1) for the liquid sample.
A push rod (11e) that discharges to the outside of the cylinder through 1c),
Interfacial tension and surface of a liquid sample equipped with a liquid delivery device (11) for forming droplets, which includes a shield (11f) that prevents the sample from entering the gap between the push rod (11e) and the inner wall of the cylinder. In a method for measuring the interfacial tension and surface tension of a liquid sample by a liquid drop method using a tension measuring device, a liquid sample outlet part (11c) of the liquid sending device is formed after a liquid drop is formed and dropped or floated. A method for measuring the interfacial tension and surface tension of a liquid sample, characterized in that the next measurement is performed after the droplet residue remaining on the tip is extruded through the push rod (11e) and removed. 2. The method for measuring the interfacial tension and surface tension of a liquid sample according to claim 1, wherein the extrusion amount is one drop or more. 3. The liquid sample according to claim 1, wherein after the liquid droplet is pushed out by the push rod, the liquid sample is increased to the level just before the dropping, and is held until the adsorption equilibrium time is reached, and the adsorption equilibrium is measured. Method of Interfacial Tension and Surface Tension of Various Liquid Samples