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Method for determining critical micelle concentration of surfactant

A technology of critical micelle concentration and surfactant, applied in the direction of measuring devices, instruments, scientific instruments, etc., can solve the problems of poor accuracy, insensitivity, strong foaming of the solution, etc., achieve high accuracy and improve accuracy , the effect of easy operation

Inactive Publication Date: 2016-05-11
SOUTH CHINA UNIV OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

For example, the conductometric method is not sensitive to the turning point of surfactants with large cmc values ​​and low surface activity, and the presence of inorganic salts will greatly reduce the sensitivity of the measurement; the density method has little difference in the density of solutions with different concentrations. Not good; the operation of measuring the cmc value by the viscosity method is complicated, time-consuming, and the error is also large; the surface tension method will be subject to some restrictions when accurately measuring the surface tension of the surfactant solution, such as the capillary method to accurately measure the radius of the capillary, the solution Density and contact angle of solution on glass, drop volume method and drop weight method need to know the correction factor, maximum bubble pressure method solution will foam strongly
Moreover, the above method is not suitable for the determination of the critical micelle concentration of surfactants at high temperature

Method used

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  • Method for determining critical micelle concentration of surfactant
  • Method for determining critical micelle concentration of surfactant
  • Method for determining critical micelle concentration of surfactant

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0037] Determine the concentration of tracer toluene of the present invention with sodium dodecylbenzenesulfonate

[0038] 1. Preparation of stock solution

[0039] Pipette 0.1mL of toluene into a 10mL volumetric flask, and dilute to the mark with methanol, that is, the toluene concentration is 10g / L.

[0040] Weigh 1.86g of sodium dodecylbenzenesulfonate into three volumetric flasks, and then add 0.5L of distilled water into the volumetric flasks. Add 50 μL, 75 μL, and 100 μL of the prepared toluene-methanol solution to the volumetric flask respectively, that is, the concentration of toluene in the stock solution containing the surfactant is 1 mg / L, 1.5 mg / L, and 2 mg / L, respectively. Equilibrate the prepared stock solution at room temperature for 24 hours.

[0041] 2. Sample preparation

[0042] The three stock solutions prepared above were ultrasonically oscillated for 1 hour. Then weigh the same stock solution of different quality into 10 headspace bottles, and dilute ...

Embodiment 2

[0049] Effect of equilibration time on detection results

[0050] Get the sodium dodecylbenzenesulfonate stoste that contains toluene 1mg / L that example 1 prepares. Take 4.0g (lower than the critical micelle concentration of glycerol triacetate at this temperature) and 5.0g (higher than the critical micelle concentration of sodium dodecylbenzenesulfonate at this temperature) respectively into different headspace vials, and use distilled water Dilute to 5g. Analyze and detect under different headspace equilibration time, get figure 2 The curve shown. Depend on figure 2 It can be seen that when the concentration of the surfactant is lower than the critical micelle concentration, the equilibrium can be reached within 20 minutes. When it is higher than the critical micelle concentration, the required time is 40min to reach equilibrium. In order to ensure that the balance is fully achieved in the operation, the present invention selects a balance time of 40 minutes.

Embodiment 3

[0052] Method reproducibility and accuracy

[0053] The reproducibility evaluation of the method is to prepare 3 parallel samples according to the method described in Application Example 1 by detecting the critical micelle concentration of sodium lauryl sulfate at 40°C, and the relative standard deviation of the detection results is 3.5%. Therefore, it can be considered that this method has good reproducibility for the detection of the critical micelle concentration of surfactants at elevated temperatures.

[0054] The accuracy of the method is determined by detecting the critical micelle concentration of five surfactants, and comparing the measured results with the current data. The result analysis is shown in Table 1. It can be seen from Table 1 that the relative error between the results obtained by this method and the critical micelle concentration data in the current references is very small (relative error<9.0%). It shows that the tracer headspace gas chromatographic te...

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Abstract

The invention discloses a method for determining the critical micelle concentration of a surfactant and particularly provides a method for determining the critical micelle concentration of the surfactant by utilizing tracer agent headspace gas chromatography. The surfactant is added into a volumetric flask, and then 0.5 L of distilled water and a toluene-methanol solution are added into the volumetric flask to prepare a stock solution of the surfactant; different masses of the stock solution are respectively taken and put into 10 headspace bottles, dilution is performed by using 5 mL of distilled water, and sealing is performed by using press caps; the headspace bottles containing the surfactant solution are subjected to headspace gas chromatography and balanced in a headspace sampling device, and then gas-phase signal values of toluene are recorded through gas chromatography detection; drawing is performed based on the gas-phase signal values of the toluene and the corresponding concentrations of the surfactant in the headspace bottles. The method is quick in determination, objective and accurate in result and simple and convenient to operate, is especially suitable for determination of the critical micelle concentration at the rising temperature. The shortcomings of an existing method for detecting the critical micelle concentration of the surfactant are effectively overcome.

Description

technical field [0001] The invention relates to the technical field of critical micelle concentration detection, in particular to a method for measuring the critical micelle concentration of surfactants. Background technique [0002] Surfactants are widely used in various fields such as industry, agriculture and daily life, so the research on surfactants is very active. Micelles are an important concept in surface chemistry. When the concentration of surfactant molecules increases, its structure will change from single molecules to spherical, rod-like and lamellar micelles. The concentration of a surfactant whose solution begins to form micelles Called the surfactant's critical micelle concentration (criticalmicelleconcentration, cmc). Many physical and chemical properties of surfactant solutions, such as electrical conductivity, surface tension, osmotic pressure, vapor pressure, optical properties, detergency, density, viscosity, osmotic pressure, and light scattering inte...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N30/02
CPCG01N30/02G01N2030/025
Inventor 张舒心柴欣生
Owner SOUTH CHINA UNIV OF TECH