Application of TLC method in surfactants
Instrumental Analysis
Surfactant analysis focuses on the characterization of the structure using: IR, NMR, GCMS, MS, XRF, IC, acid-base titration.
Application of infrared spectroscopy
Testing infrared spectra provides structural information of compounds through the position relative intensity of absorption peaks and peak shape, etc. It is widely used for qualitative analysis of small molecules and polymer compounds, and can also be used for simple quantification.
It is a simple and fast analytical method.
The surface activities of polyoxyethylene ethers are all in the range of 1000~1250cm-1, and there are stretching vibration peaks of the -O-R group.
Several important parameters for the structure analysis of hydrogen spectrum
Chemical shift Coupling constant Peak shape (s, d, t, q) Integral area
1) Chemical shifts of common functional groups in the hydrogen spectrum
Factors affecting chemical shifts:
1) Shielding (antimagnetic) versus deshielding (paramagnetic) effects
2) Induced versus conjugated effects
3) Each anisotropy effect 4) Hydrogen bonding effect
5) Proton exchange effects 6) Solvent effects
2) Coupling constants
spin-spin coupling: the interaction of hydrogen nuclei on neighboring carbons coupling constant (Couplingconstant) J: the distance between the two cleavage peaks, unit: Hz coupling constant J is only related to the nature of the chemical bonding, and has nothing to do with the applied magnetic field
3) Split peaks of nuclear magnetism
Due to the spin-spin coupling between protons on neighboring carbon, it is therefore able to cause absorption peak splitting.
1) The coupling of a nucleus with n magnetically equivalent nuclei is such that n+1 spectral lines can be produced;
(2) The spacing of the spectral line splitting is their coupling constant J
(3) The multiple peaks are symmetrically distributed through their focus, with the center position being the chemical shift value
(4) The relative intensities of the multiple peaks are the coefficients of the quadratic expansion (a+b)n, and n is the number of equivalent nuclei.
4) Integral area
According to the step height of the integration diagram to see the ratio of the area surrounded by the following peaks, so as to know the number of hydrogen-containing group ratio
Example:
Mass spectrum
⇀ XRF test application range
1. Ceramics: ceramics, glass, cement elemental analysis;
2. Environment: soil, waste water, ash elemental analysis;
3. Chemical: elemental analysis in rubber, paint, plastic, plating solution;
4. Metal: alloy, ore, slag elemental analysis;
XRF advantages:
1. Simple sample preparation, solid, powder, liquid samples can be analyzed;
2. High analytical precision;
3. Determination process will not cause changes in the chemical state, can be repeated multiple measurements, good reproducibility of results.
1. Wide range of analytical objects
Gas chromatography is limited to the analysis of gases and compounds with low boiling points; HPLC is not subject to the limitations of volatility and thermal stability of the sample, and is suitable for substances with high boiling points, poor thermal stability and large molar mass. In principle, almost all organic and inorganic compounds can be analyzed in addition to the permanent gas.
Peculiar mobile phase plays a role in separation
Gas chromatography of the mobile phase only play a role in transportation, the components do not produce interaction force; HPLC mobile phase components to produce interaction force, equivalent to the addition of a parameter to control and improve the separation conditions.
Retention time is the basic basis for the characterization of chromatography, but the retention time of the same component is often affected by the flow rate of the mobile phase.
▲Based on the number of chromatographic peaks, the number of components contained in the sample can be judged
▲Based on the retention value of the chromatographic peaks, qualitative analysis can be carried out.
▲Based on the area or height of the peaks, quantitative analysis can be performed.
▲The retention value of a chromatographic peak and its area width are the basis for evaluating the separation efficiency of a chromatographic column.
▲The distance between two peaks of a chromatographic peak is the basis for evaluating the appropriateness of stationary phase (or mobile phase) selection.
1) Qualitative analysis of HPLC
Qualitative analysis is to determine the compounds represented by each peak, and the retention value can be used as a qualitative index.
(2) Quantitative analysis by HPLC
The task of quantitative analysis is to find out the percentage of each component in a mixed sample, and the basis of quantitative chromatographic analysis is that the amount of the measured component is proportional to its peak area.
①Normalization method ②Internal standard method ③External standard method
IC
Ion chromatography (Ion Chromatography, abbreviated as IC) is a kind of high performance liquid chromatography (HPLC), is a kind of liquid chromatography to analyze anions and cations.
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