For an unknown fluorosurfactant, the first step is to determine its ionic type. This can be done using chemical methods initially, followed by confirmation using Infrared (IR) spectroscopy or Nuclear Magnetic Resonance (NMR). Subsequently, the active ingredients are measured. If necessary, the fluorine content can be determined using chemical methods, though the operation is cumbersome. Alternatively, chromatography can be used to determine the main content, but this requires standard samples and the establishment of a suitable separation method.

 

 

 

(1) Thorium Nitrate Titration Method: After decomposing the sample via the oxygen flask method or other techniques, organic fluorine is converted to hydrogen fluoride (HF). This is then titrated using a standard thorium nitrate solution under specific acidity conditions.

 

 

(2) Fluoride Ion-Selective Electrode Method: The advantages of using an ion-selective electrode are speed, sensitivity, and simplicity. Because the electrode responds selectively to the ion being measured, it avoids the hassle of separating interfering ions. It can also be used for direct measurement of opaque solutions and certain viscous liquids.

 

 

Chromatography is the most commonly used tool for quantitative analysis. It is a separation technique where the separation process of a sample mixture involves the continuous distribution of components between two phases within a chromatographic column. One phase is stationary (the stationary phase), while the other is a fluid (gas or liquid) that carries the sample mixture through the stationary phase (the mobile phase).

 

As the mixture carried in the mobile phase flows through the stationary phase, interactions occur. Due to differences in the nature and structure of the components in the mixture, the strength of the forces between the components and the stationary phase varies. As the mobile phase moves, the mixture undergoes repeated partitioning equilibria between the two phases. This results in different retention times for each component, causing them to elute from the stationary phase in a specific order. When combined with an appropriate post-column detection method, this achieves the separation and detection of each component in the mixture.

 

 

Although chromatography offers significant advantages in determining surfactant content, for the thousands of types of surfactants—particularly fluorosurfactants—many analytical methods remain to be developed. Conversely, while chemical analysis methods are cumbersome, they offer high versatility and remain irreplaceable analytical tools.

 

 

Before conducting structural analysis, it is necessary to separate the surfactant component from the sample. The ionic type is then qualitatively determined using the aforementioned methods. The sample is then analyzed using IR and NMR to obtain spectra, which are compared against standard spectra. This generally allows for the identification of whether the surfactant is anionic, cationic, or non-ionic. Standard spectra for amphoteric surfactants are relatively scarce.

 

(1) Ultraviolet-Visible (UV-Vis) Spectroscopy: This method can only identify substances containing chromophores such as unsaturated double bonds or aromatic hydrocarbons. It cannot identify saturated substances (as saturated single bonds do not absorb UV radiation) nor can it distinguish between isomers with similar structures.

 

(2) Infrared (IR) Spectroscopy: IR spectroscopy is simple, rapid, and the most useful tool for structural elucidation of surfactants, with wide applications. If the sample purity is sufficient, comparing the obtained IR spectrum with standard spectra can yield highly accurate results.

 

(3) Nuclear Magnetic Resonance (NMR) Spectroscopy: NMR spectroscopy—particularly including 1H, 19F, and Pub Time : 2026-01-08 14:47:53 >> News list