CN105115929A - Method for determining surfactant critical micelle concentration based on terahertz time-domain spectroscopy technology - Google Patents

Abstract

The invention relates to a method for determining surfactant critical micelle concentration (CMC) based on the terahertz time-domain spectroscopy technology. The method comprises the steps that 1, a sample pool suitable for terahertz spectrum detection is prepared; 2, surfactant solution samples with different concentrations crossing four orders of magnitudes from 0.1 mM to 100 mM are prepared; 3, terahertz time-domain spectrum of a sample solution to be detected is measured and obtained, a relation spectrogram between the concentrations of the samples and terahertz absorption coefficients or refractive indexes are calculated and obtained through a formula, and the concentration, corresponding to a turning point of the spectrogram, of the surfactant sample is determined; 4, surfactant water solution samples which have a series of concentrations with smaller intervals are prepared according to the concentrations selected close to the determined sample turning point concentration; 5, terahertz time-domain spectra of sample solutions to be detected are measured and obtained again; 6, relation spectrograms between the concentrations of the samples to be detected and terahertz absorption coefficients or refractive indexes are calculated and obtained again, and the CMC of a surfactant is determined through spectrogram information. The method has the advantages of being rapid, free of marks, easy to operate, wide in application range, good in repeatability, high in result accuracy and the like.

Description

A kind of method based on terahertz time-domain spectroscopic technology determination critical micelle concentration of surfactant

Technical field

The invention belongs to Surfactants Analysis technical field, relate to a kind of method based on terahertz time-domain spectroscopic technology determination critical micelle concentration of surfactant (CriticalMicelleConcentration, CMC).

Background technology

Surfactant has multifrequency nature, as wetting, emulsification, foaming, dissolving, dispersion, washing, corrosion-resistant, antistatic etc., is widely used in multiple fields, as pharmaceutical chemistry, synthetic chemistry, material science, biology etc.Under certain concentration, i.e. CMC, surfactant starts to form thermodynamically stable micella, and meanwhile, significant change occurs various character.Therefore, the mensuration of CMC has very important significance in actual applications, is a focus of physical chemistry and analytical chemistry research.The CMC assay method of current development is that the sudden change of the physical quantity such as surfactant solution optical turbidity, surface tension, viscosity, coefficient of diffusion, conductivity when utilizing concentration to reach CMC is to determine CMC value.

THz wave refers to the electromagnetic wave of frequency within the scope of 0.1-10THz, between microwave and infrared between, have the features such as high permeability, low energy, instantaneity, acuteness, high s/n ratio, these features make Terahertz Dynamic Non-Destruction Measurement have very important application in a lot of method such as biomedicine, biological chemistry, chemical industry.THz wave covering dielectric nanosecond, this Bound moisture vibration just, diffusion and the time scale of solvent molecule low-frequency vibration, therefore THz spectral technique was applicable to the interaction detecting water and solute molecule in solution to the motion of psec yardstick.Because surfactant monomer and micella and water molecules state there are differences, cause surfactant solution to absorb THz wave and transfer.Patents and the bibliographical information of CMC of surfactant is not also detected up to now with terahertz time-domain spectroscopic technology.

Summary of the invention

In view of this, the object of the present invention is to provide a kind of based on terahertz time-domain spectroscopic technology determination critical micelle concentration of surfactant (CriticalMicelleConcentration, CMC) method, the method has quick, unmarked, simple to operate, applied widely, reproducible, result degree of accuracy advantages of higher.

For achieving the above object, the invention provides following technical scheme:

Based on a method for terahertz time-domain spectroscopic technology determination critical micelle concentration of surfactant, comprise the following steps:

S1: preparation is applicable to the sample cell that tera-hertz spectra detects;

S2: the surfactant solution sample preparing the variable concentrations across four order of magnitude: 0.1 to 100mM;

S3: measure and obtain the terahertz time-domain spectroscopy of testing sample solution; Utilize formulae discovery to obtain the concentration of sample and the relation spectrum of Terahertz absorption coefficient or refractive index, determine surfactant samples concentration corresponding to turning point occurs in image;

S4: select about the sample turnover concentration determined and prepare the water phase surfactant mixture sample of the less a series of concentration in interval;

S5: again measure and obtain the terahertz time-domain spectroscopy of testing sample solution;

S6: again calculate and obtain the concentration of testing sample solution and the relation spectrum of Terahertz absorption coefficient or refractive index, by the CMC of image information determination surfactant.

Further, in step sl, the sample cell of described preparation is divided into: two panels polythene strip with strike out square-outside and round-inside type hollow PET double faced adhesive tape, construction method is the liquid sample pool utilizing adhered by double sided plaster two panels polythene strip to form a hollow, concrete steps are first double faced adhesive tape and wherein a slice polythene strip bonds, and injection fluid sample, covers another sheet polythene strip, liquid thickness is determined according to PET double faced adhesive tape thickness, and the thickness of PET double faced adhesive tape can select 100um, 50um.

Further, in step s 2, described solution example to be measured is the surfactant solution of the concentration known be mixedly configured in proportion by surfactant to be detected and solvent; The concentration of the testing sample that first time is detected increases progressively successively from 0.1 to 100mM, gets the individual different concentration of 3-4 in each magnitude; The concentration of the testing sample that second time detects is determined according to first time testing result.

Further, in step s3, the liquid sample pool of sky and the liquid sample pool that sample is housed are placed in transmission-type terahertz time-domain spectroscopy device successively, the time-domain spectroscopy signal of the liquid sample pool obtaining sky respectively and the liquid cell that sample is housed; Using the former signal as with reference to signal, the latter carries out Fourier transform respectively as sample signal and obtains the information such as corresponding Terahertz frequency-domain waveform, amplitude; In order to reduce experimental error, the measurement of reference and sample signal all in triplicate;

The Terahertz absorption coefficient of surfactant solution or the calculating of refractive index are all the information acquisitions such as corresponding Terahertz frequency-domain waveform, amplitude obtained based on the Fourier transform of above reference signal and sample signal, and surfactant solution sample refractive index n (f) computing formula is as follows:

Wherein, I _refand I _srepresent respectively the reference signal that can catch and sample signal through energy, be respectively I _sand I _refthe phase information obtained after carrying out Fourier transform, c represents the light velocity, and d represents the thickness that Terahertz penetrates sample;

The computing formula of extinction coefficient κ (f) is as follows:

$\mathrm{\κ}\left(f\right)=\ln \[\frac{4n\left(f\right)}{\mathrm{\ρ}\left(f\right){\[n\left(f\right)+1\]}^2}\]\frac{c}{2\mathrm{\π}fd}$

Wherein ρ (f) is I _sand I _refthe amplitude ratio of Fourier transform,

The computing formula of surfactant solution absorption of sample factor alpha is as follows:

$\mathrm{\α}\left(f\right)=\frac{4\mathrm{\π}f\mathrm{\κ}\left(f\right)}{c}.$

Further, Terahertz frequency range is 0.3-1.7THz.

Beneficial effect of the present invention is: compared with prior art, the present invention utilizes the CMC of terahertz time-domain spectroscopic technology Surfactant to detect, and the method has quick, unmarked, simple to operate, applied widely, reproducible, result degree of accuracy advantages of higher.

Accompanying drawing explanation

In order to make object of the present invention, technical scheme and beneficial effect clearly, the invention provides following accompanying drawing and being described:

Fig. 1 is sample pool structure schematic diagram;

Fig. 2 is single dodecyl nine glycol ether (C of variable concentrations in embodiment 1 ₁₂e ₉) wave in time domain of aqueous solution;

Fig. 3 is the C of variable concentrations in embodiment 1 ₁₂e ₉the absorption coefficient figure of aqueous solution;

Fig. 4 is the C of variable concentrations in embodiment 1 ₁₂e ₉the index of refraction diagram of aqueous solution;

Fig. 5 is the C of variable concentrations in embodiment 2 ₁₂e ₉the absorption coefficient figure of PBS solution;

Fig. 6 is the C of variable concentrations in embodiment 3 ₁₂e ₉the absorption coefficient figure of HCl solution;

Fig. 7 is the absorption coefficient figure of lauryl sodium sulfate (SDS) aqueous solution of variable concentrations in embodiment 4;

Fig. 8 is the absorption coefficient figure of Tetradecyl Trimethyl Ammonium Bromide (TTAB) aqueous solution of variable concentrations in embodiment 5;

Fig. 9 is the schematic flow sheet of the method for the invention.

Embodiment

The change of the Terahertz absorption coefficient of surfactant solution sample can reflect the state that surfactant molecule is residing in water.When surfactant molecule does not in the solution form micella, because solute concentration is lower, Terahertz absorption coefficient is calculated according to binary model, the absorption coefficient of solution contributes two parts to form by the absorption contribution of surfactant and the absorption of solvent, absorption coefficient due to surfactant is less than the absorption coefficient of aqueous solvent, so along with the increase of solute, the contribution proportion of water reduces, and the absorption coefficient of solution declines; After formation micella, according to ternary model, micella skin can be formed in conjunction with water layer, and Bound moisture has higher Terahertz absorption coefficient than free water, and more solute can form more micella, brings more Bound moisture, makes the absorption coefficient of solution increase.

Below in conjunction with accompanying drawing, the preferred embodiments of the present invention are described in detail.

Fig. 9 is the schematic flow sheet of the method for the invention, and as shown in the figure, method of the present invention comprises the following steps:

S1: preparation is applicable to the sample cell that tera-hertz spectra detects, as shown in Figure 1;

S2: the surfactant solution sample preparing the variable concentrations across four order of magnitude: 0.1 to 100mM;

S3: measure and obtain the terahertz time-domain spectroscopy of testing sample solution; Utilize formulae discovery to obtain the concentration of sample and the relation spectrum of Terahertz absorption coefficient or refractive index, determine surfactant samples concentration corresponding to turning point occurs in image;

S4: select about the sample turnover concentration determined and prepare the water phase surfactant mixture sample of the less a series of concentration in interval;

S5: again measure and obtain the terahertz time-domain spectroscopy of testing sample solution;

S6: again calculate and obtain the concentration of testing sample solution and the relation spectrum of Terahertz absorption coefficient or refractive index, by the CMC of image information determination surfactant.

In step sl, preparation sample cell be divided into: two panels polythene strip with strike out square-outside and round-inside type hollow PET double faced adhesive tape, construction method is the liquid sample pool utilizing adhered by double sided plaster two panels polythene strip to form a hollow, concrete steps are first double faced adhesive tape and wherein a slice polythene strip are bonded, inject fluid sample, covered by another sheet polythene strip, liquid thickness is determined according to PET double faced adhesive tape thickness, and the thickness of PET double faced adhesive tape can select 100um, 50um.

In step s 2, solution example to be measured is the surfactant solution of the concentration known be mixedly configured in proportion by surfactant to be detected and solvent; The concentration of the testing sample that first time is detected increases progressively successively from 0.1 to 100mM, gets the individual different concentration of 3-4 in each magnitude; The concentration of the testing sample that second time detects is determined according to first time testing result.

In step s3, the liquid sample pool of sky and the liquid sample pool that sample is housed are placed in transmission-type terahertz time-domain spectroscopy device successively, the time-domain spectroscopy signal of the liquid sample pool obtaining sky respectively and the liquid cell that sample is housed; Using the former signal as with reference to signal, the latter carries out Fourier transform respectively as sample signal and obtains the information such as corresponding Terahertz frequency-domain waveform, amplitude; In order to reduce experimental error, the measurement of reference and sample signal all in triplicate;

The Terahertz absorption coefficient of surfactant solution or the calculating of refractive index are all the information acquisitions such as corresponding Terahertz frequency-domain waveform, amplitude obtained based on the Fourier transform of above reference signal and sample signal, and surfactant solution sample refractive index n (f) computing formula is as follows:

Wherein, I _refand I _srepresent respectively the reference signal that can catch and sample signal through energy, be respectively I _sand I _refthe phase information obtained after carrying out Fourier transform, c represents the light velocity, and d represents the thickness that Terahertz penetrates sample;

The computing formula of extinction coefficient κ (f) is as follows:

$\mathrm{\κ}\left(f\right)=\ln \[\frac{4n\left(f\right)}{\mathrm{\ρ}\left(f\right){\[n\left(f\right)+1\]}^2}\]\frac{c}{2\mathrm{\π}fd}$

Wherein ρ (f) is I _sand I _refthe amplitude ratio of Fourier transform,

The computing formula of surfactant solution absorption of sample factor alpha is as follows:

$\mathrm{\α}\left(f\right)=\frac{4\mathrm{\π}f\mathrm{\κ}\left(f\right)}{c}.$

Terahertz frequency range is 0.3-1.7THz.

Embodiment 1:

Utilize terahertz time-domain spectroscopic technology to non-ionic surfactant C ₁₂e ₉solution C MC carries out the method detected, and it comprises the following steps:

1, the sample cell being applicable to Terahertz and detecting is built: utilize the bonding two panels transparent plastic sheet of PET double faced adhesive tape, circular chamber splendid attire C ₁₂e ₉the volume of solution is about 17.7 μ l;

2, C is prepared ₁₂e ₉aqueous sample: by C ₁₂e ₉mix in proportion with deionized water, be configured to the surfactant solution sample mother liquor of concentration known, dilution obtains the solution example a series of to be measured of concentration range 0.1mM to 100mM in proportion;

3, the detection of solution example and signal transacting: utilize terahertz time-domain spectroscopy device to adopt transmitted light path with empty sample cell for reference, each sample duplicate measurements three times are detected to solution example.Time domain beamformer is carried out Fourier transform and obtain its amplitude collection of illustrative plates, phase place collection of illustrative plates etc., according to formulae discovery absorption coefficient, refractive index, the result mapping in the frequency range 0.3-1.7THz utilizing variable concentrations corresponding, obtains turnover concentration;

4, again C is prepared according to turnover concentration ₁₂e ₉solution example: at least 7 concentration point are set about the turnover concentration that step 3 obtains, configure solution example to be measured with the method that step 2 is identical;

5, C is determined ₁₂e ₉cMC: identical with step 3, the graph of a relation of rendered surface surfactant concentration and absorption coefficient or refractive index, determine the concentration that in image, curve is transferred (absorption coefficient and concentration relationship figure) or intersection (refractive index and concentration relationship figure) is corresponding, be CMC.Fig. 2 is the C of variable concentrations in embodiment 1 ₁₂e ₉the wave in time domain of aqueous solution; Fig. 3 is the C of variable concentrations in embodiment 1 ₁₂e ₉the absorption coefficient figure of aqueous solution; Fig. 4 is the C of variable concentrations in embodiment 1 ₁₂e ₉the index of refraction diagram of aqueous solution.

Embodiment 2:

The present embodiment provides one to utilize terahertz time-domain spectroscopic technology to C under hypersaline environment ₁₂e ₉the method that solution C MC detects, operation steps is identical with embodiment 1, and just testing sample is ionic surfactant C ₁₂e ₉pBS solution.Fig. 5 is the C of variable concentrations in embodiment 2 ₁₂e ₉the absorption coefficient figure of phosphate buffer (PBS).

Embodiment 3:

The present embodiment provides one to utilize terahertz time-domain spectroscopic technology to C under sour environment ₁₂e ₉the method that solution C MC detects, operation steps is identical with embodiment 1, and just testing sample is ionic surfactant C ₁₂e ₉acid solution.Fig. 6 is the C of variable concentrations in embodiment 3 ₁₂e ₉the absorption coefficient figure of hydrochloric acid solution.

Embodiment 4:

The present embodiment provides a kind of method utilizing terahertz time-domain spectroscopic technology to detect anionic surface active agent SDS solution C MC, and operation steps is identical with embodiment 1, and just testing sample is ionic surfactant SDS.Fig. 7 is the absorption coefficient figure of the SDS aqueous solution of variable concentrations in embodiment 4.

Embodiment 5:

The present embodiment provides a kind of method utilizing terahertz time-domain spectroscopic technology to detect cationic surfactant TTAB solution C MC, and operation steps is identical with embodiment 1, and just testing sample is ionic surfactant TTAB.Fig. 8 is the absorption coefficient figure of the TTAB aqueous solution of variable concentrations in embodiment 5.

What finally illustrate is, above preferred embodiment is only in order to illustrate technical scheme of the present invention and unrestricted, although by above preferred embodiment to invention has been detailed description, but those skilled in the art are to be understood that, various change can be made to it in the form and details, and not depart from claims of the present invention limited range.

Claims (5)

1. based on a method for terahertz time-domain spectroscopic technology determination critical micelle concentration of surfactant, it is characterized in that: comprise the following steps:

S1: preparation is applicable to the sample cell that tera-hertz spectra detects;

S2: the surfactant solution sample preparing the variable concentrations across four order of magnitude: 0.1 to 100mM;

S3: measure and obtain the terahertz time-domain spectroscopy of testing sample solution; Utilize formulae discovery to obtain the concentration of sample and the relation spectrum of Terahertz absorption coefficient or refractive index, determine surfactant samples concentration corresponding to turning point occurs in image;

S4: select about the sample turnover concentration determined and prepare the water phase surfactant mixture sample of the less a series of concentration in interval;

S5: again measure and obtain the terahertz time-domain spectroscopy of testing sample solution;

S6: again calculate and obtain the concentration of testing sample solution and the relation spectrum of Terahertz absorption coefficient or refractive index, by the critical micelle concentration of image information determination surfactant.

2. the method based on terahertz time-domain spectroscopic technology determination critical micelle concentration of surfactant according to claim 1, it is characterized in that: in step sl, the sample cell of described preparation is divided into: two panels polythene strip with strike out square-outside and round-inside type hollow PET double faced adhesive tape, construction method is the liquid sample pool utilizing adhered by double sided plaster two panels polythene strip to form a hollow, concrete steps are first double faced adhesive tape and wherein a slice polythene strip are bonded, inject fluid sample, another sheet polythene strip is covered, liquid thickness is determined according to PET double faced adhesive tape thickness, the thickness of PET double faced adhesive tape can select 100um, 50um.

3. the method based on terahertz time-domain spectroscopic technology determination critical micelle concentration of surfactant according to claim 1, it is characterized in that: in step s 2, described solution example to be measured is the surfactant solution of the concentration known be mixedly configured in proportion by surfactant to be detected and solvent; The concentration of the testing sample that first time is detected increases progressively successively from 0.1 to 100mM, gets the individual different concentration of 3-4 in each magnitude; The concentration of the testing sample that second time detects is determined according to first time testing result.

4. the method based on terahertz time-domain spectroscopic technology determination critical micelle concentration of surfactant according to claim 1, it is characterized in that: in step s3, the liquid sample pool of sky and the liquid sample pool that sample is housed are placed in transmission-type terahertz time-domain spectroscopy device successively, the time-domain spectroscopy signal of the liquid sample pool obtaining sky respectively and the liquid cell that sample is housed; Using the former signal as with reference to signal, the latter carries out Fourier transform respectively as sample signal and obtains the information such as corresponding Terahertz frequency-domain waveform, amplitude; In order to reduce experimental error, the measurement of reference and sample signal all in triplicate;

The Terahertz absorption coefficient of surfactant solution or the calculating of refractive index are all the information acquisitions such as corresponding Terahertz frequency-domain waveform, amplitude obtained based on the Fourier transform of above reference signal and sample signal, and surfactant solution sample refractive index n (f) computing formula is as follows:

Wherein, I _refand I _srepresent respectively the reference signal that can catch and sample signal through energy, be respectively I _sand I _refthe phase information obtained after carrying out Fourier transform, c represents the light velocity, and d represents the thickness that Terahertz penetrates sample, and f represents frequency;

The computing formula of extinction coefficient κ (F) is as follows:

$\mathrm{\κ}\left(f\right)=\ln \[\frac{4n\left(f\right)}{\mathrm{\ρ}\left(f\right){\[n\left(f\right)+1\]}^2}\]\frac{c}{2\mathrm{\π}fd}$

Wherein ρ (f) is I _sand I _refthe amplitude ratio of Fourier transform, n (f) represents refractive index, and f represents frequency;

The computing formula of surfactant solution absorption of sample factor alpha is as follows:

$\mathrm{\α}\left(f\right)=\frac{4\mathrm{\π}f\mathrm{\κ}\left(f\right)}{c}.$

5. the method based on terahertz time-domain spectroscopic technology determination critical micelle concentration of surfactant according to claim 4, is characterized in that: Terahertz frequency range is 0.3-1.7THz.