In 1850, Runge separated the salt solution on paper. In 1869, Goppalsroeder analyzed dyes and animal and plant pigments on long paper, and chromatography began its prototype. After more than 100 years of development, until the establishment of gas chromatography, it should be a milestone in modern chromatography, but for analysts, gas chromatography is far from the analysis requirements, and more than half of the compounds in nature cannot reach gas chromatography. The required characteristics of easy gasification and thermal stability until the emergence of high performance liquid chromatography. In the 1960s, high performance liquid chromatography was further improved and became another milestone in analytical chemistry, especially the diode array detector The application of HPLC allows us to obtain the HPLC-UV three-dimensional spectrum of each component. In the late 1980s, another qualitative liquid chromatography detector appeared, that is, mass spectrometry. Its appearance makes the analysis workers more accurate. Qualitative and quantitative compounds, in the early days of liquid chromatography-mass spectrometry, some technical obstacles have always appeared in the connection technology, because the classic gas ionization method is not suitable for compounds with high polarity, low volatility, easy thermal decomposition, and large molecular weight. Until the emergence of atmospheric pressure ionization (API) interface technology, it included electrospray ionization technology (ESI) and atmospheric pressure chemical ionization technology ( APCI), these two interface technologies are the mildest ionization technology nowadays. The difference is that the method of generating gas phase ions at atmospheric pressure is different. This technology better and more effectively combines liquid chromatography and mass spectrometry. In recent years, HPLC -The rapid development of MS combined technology has gradually replaced gas chromatography as the most important analytical method in the future.
1 Working principle of HPLC-MS combined system
1.1 Principle of liquid chromatography part of HPLC-MS combined instrument
The HPLC-MS combined instrument is divided into two separate parts: liquid chromatography and mass spectrometry. For the liquid chromatography system, the chromatography column is generally a reversed-phase ODS column and a short chromatography column with a length of 10 mm to 50 mm. In order to obtain a stable and accurate The mobile phase therefore requires a lower flow rate, and at lower flow rates, the efficiency of the ionization process increases. In order to shorten the inspection time, we often use a relatively large flow rate, which requires a column with a small internal diameter to improve the separation efficiency of the components, and at the same time requires a power pump to provide a large flow pressure. The reduction in the efficiency of the ionization part can be compensated to some extent by improving the spraying process and increasing the evaporation rate of the charged mist droplets.
The mobile phase of the liquid chromatography part is a special consideration. For commonly used reversed-phase chromatography, the C18 column is generally selected. In order to obtain a better retention effect for the components of the mobile phase, non-dissociation is often used. The state exists in the mobile phase, and the presence of ions in the mobile phase can better facilitate the formation of gas-phase ions in the mass spectrometer. Therefore, we need to adjust various conditions to make the mobile phase suitable for both separation and mass spectrometry. Ionization. In each adjustment condition, it is important to use a buffer to adjust the pH of the mobile phase. It should be noted that a volatile buffer should be used to obtain better ionization efficiency. For HPLC-MS combined technology, in order to obtain better To detect the effect and improve the sensitivity, you can also use a variety of methods, such as increasing the flow rate of the mobile phase, derivatization after the column, and adding ion pairs to further improve the detection efficiency.
1.2 The principle of electrospray ionization (ESI) technology
Electrospray ionization technology is commonly used in the actual HPLC-MS combination. Its principle is that under normal pressure, the mobile phase flowing out of the liquid phase system enters a capillary tube. The capillary tube has a very high voltage and a high voltage of several thousand volts. And with the help of auxiliary means such as sheath fluid, highly charged mist-like droplets are generated. The droplets continue to break up into smaller droplets under the action of high voltage and high temperature, and the mass and charge redistribution of small droplets The evaporation and fragmentation process continues, and finally becomes ions, which enter the mass analyzer along the direction of the voltage.
1.3 The principle of atmospheric pressure chemical ionization (APCI) technology
In APCI, the sample solution is sprayed into the high-temperature evaporator by the action of an atomizer. Both the solvent and the solute become steam, and then pass through the needle-shaped corona discharge electrode. After high-pressure discharge, the vaporized sample molecules are chemically ionized to generate a gas phase. ion. The ions formed after the molecules of the analyte are ionized enter the mass analyzer of the mass spectrometer under the combined action of pressure difference and potential difference. Atmospheric pressure chemical ionization is suitable for small molecules with low polarity.
2 Application of HPLC-MS combined technology in fiber dye analysis
Fiber is one of the important carriers of dyes. The main components of fibers are relatively simple and easy to check, and there are few types. The dyes in fibers are very different because of the wide variety of dyes and the use of some dye additives. In recent years, the analysis technology for fiber dyes has developed rapidly. High-performance liquid chromatography and spectroscopy have gradually become general techniques for dye detection. HPLC-MS combined technology is a more prominent detection technology in recent years. It is highly efficient and exclusive. Sex and reliability are unmatched by other methods. The use of HPLC-MS combined technology can identify textile fiber dye extracts and provide information on the chemical structure of the dye, thereby providing a basis for accurate dye type identification.
Huang M et al. Compared 7 kinds of dye extracts of different kinds with almost identical absorption spectra when detected by ultraviolet-visible spectroscopy, and the maximum absorption wavelength difference was within 5nm, and these 7 pairs of commercial dyes used HPLC-MS Combined technology detection has achieved very good results, and the resulting mass spectrum has obvious differences, so the superiority of this method over spectroscopy is determined; Winkeler et al. [3] studied allergic dyes on socks. A variety of complex dyes were measured by HPLC-MS. Two ion sources, ESI and APCI, were used to determine respectively. It was concluded that 20% of the samples tested contained allergic dyes. The experiment adopted the positive ion mode and detected all the dyes. , And all the dyes except indigo 124 can be detected by the negative ion mode. This method separately measured the orange 37/36 dye, which showed more detailed chemical structure information, and at the same time obtained the chlorine atom structure according to the isotope peak. The pretreatment in the method is also very simple and practical. The methanol solution is used to extract the sample in the ultrasonic bath to obtain a good effect. Increasing the flow rate to 250 μL / min can be measured within 5 minutes. As a result, the time of the experimental work was shortened; Tae-kyung Kim [4] used HPLC-MS to determine the half-fading fiber dye when analyzing the color change of the wool fiber, and determined that the dye was cinnamic acid blue 113 with a di-coupled group , The mass spectrum after decomposition has 326.1 peak which is exactly the same as the mono-group. Therefore, it is judged that the color change of the fiber is caused by the decomposition of the di-group into the mono-group. Analysis to study the principle of fiber color change has achieved good results; Sutthivaiyakit [5] et al. Further used HPLC-MS combined with secondary mass spectrometry technology to further improve the accuracy of the determination. In the experiment, secondary mass spectrometry determined a precursor ion and For two product ions, the dye 18 aromatic amines were measured by APCI mode. The linear range was 0.1μg / mL ~ 0.3μg / mL, 50μg / mL ~ 80μg / mL, and the correlation coefficient was more than 0.99. It has good qualitative effect on benzidine dyes.
3 Significance of HPLC-MS combined technology for fiber dye analysis
3.1 Significance of material evidence identification
Clothing fibers are easily left at the crime scene and are one of the most important physical evidences. Using HPLC-MS combined technology to analyze the dye on the fiber can identify the type of fiber dye, provide the basis for the police to find the source of the fiber, help solve the case, and provide the basis for identification for the court. Therefore, the analysis of fiber dyes using HPLC-MS combined technology is of great significance in the detection of cases and the disclosure of the truth of cases.
3.2 The significance of textile quality supervision
There is a very close relationship between textiles and human health. Some people call certain diseases "disease from the wardrobe", which has caused people to pay attention and attention to the safety of textiles [6]. The analysis of dyes on textiles by HPLC-MS combined technology can monitor the banned azo dyes, carcinogenic dyes and sensitizing dyes to avoid the abuse of these disease-causing dyes, thereby realizing the supervision of textile quality and protecting consumers Personal health.
In short, the HPLC-MS combined technology has been recognized by the majority of analysts due to its unique qualitative and quantitative effects. With the maturity of its technology and the reduction in cost, it will definitely become the main analytical tool in the future. Play a greater role in detection and analysis.
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