With the rapid development of science and technology, advanced analysis methods continue to emerge...
With the rapid development of science and technology, advanced analysis methods continue to emerge. Each analysis method has its strengths and limitations. The online hyphenation of analytical methods can complement each other. In addition, the hyphenated technology also has a synergistic effect, which can obtain certain functions that the two technologies do not have when used separately. Chromatography, as an analytical method, is an effective tool to realize the separation and analysis of mixtures in complex systems, but its qualitative and structural determination capabilities are poor. Chromatographic hyphenation technology is an analytical method that a hyphenation of two types of chromatography or a hyphenation of chromatography and spectroscopy (or mass spectrometry) to achieve online coupling. Chromatographic hyphenation technology combines the advantages of the chromatogram of component analysis and the spectrum of structure identification, which greatly enhances the research ability of mixtures. Chromatographic hyphenation technology can not only qualitatively identify the unknown components in the mixture, but also can be used for quantitative analysis. Due to the diversity of various chromatograms, spectroscopy and mass spectroscopy, chromatographic hyphenation technology includes a variety of coupling methods and technologies.
Chromatography is a fast and efficient separation technique, but it cannot identify every component separated. Mass spectrometry is a highly sensitive and efficient tool for qualitative identification and structural analysis, but it has no separation ability and cannot directly analyze mixtures. The combination of the two can give play to their respective advantages. The chromatograph is used as the sampling and separation system of the mass spectrometer, and the mass spectrometer is used as the detection system of the chromatograph. Chromatography-mass spectrometry technology has the high resolution of chromatography and the high sensitivity of chromatography, and it is an effective tool for qualitative and quantitative samples.
Chromatography has a high separation ability. Infrared spectroscopy has a strong identification ability. The combination of the two can have their own functions. Chromatography is used as a separation device, and infrared spectrometer is used as a qualitative detector. The dispersive infrared spectrometer used in the past has a slow scanning speed and cannot track the peak time of the chromatogram. Therefore, the combination of dispersive infrared spectrometer and chromatograph is difficult to achieve. The scanning speed and sensitivity of the Fourier Transform Infrared Spectrometer (FTIR) that appeared in the 1960s were greatly improved. Therefore, the FTIR and the chromatograph were successfully hyphenated through the interface device. The hyphenated use of chromatography and Fourier infrared spectroscopy is one of the important hyphenated techniques in modern analytical chemistry, realizing the real-time analysis of complex samples.
Nuclear Magnetic Resonance (NMR) can provide detailed structural information of organic substances and distinguish the subtle differences in the structure of different molecules. However, NMR can only analyze pure substances, and it is difficult to analyze mixtures. Chromatography is a separation method that can be used in conjunction with NMR. Chromatography can realize the separation and purification of the mixture before NMR detection. At present, the technology is not very mature and has few applications.
Chromatography has the characteristics of being able to separate different chemical components quickly and efficiently. Atomic spectroscopy is simple, fast, accurate and sensitive for the analysis of metal elements and some non-metal elements. The hyphenated technology of the two achieves complementary advantages. Chromatography-atomic spectroscopy technology is a commonly used separation and detection method, which can efficiently analyze element forms. Chromatography with different separation mechanisms is used to separate trace elements in different valence states and different forms, and then atomic spectroscopy is used to determine the content of these trace elements.
Chromatography is currently the most powerful method for the separation and analysis of complex components. For some samples with simpler components, a chromatographic column and a separation mode can usually be used to achieve good separation and analysis. But for some samples with more complex components, the situation is the opposite. The conventional one-dimensional chromatographic method cannot realize the separation and analysis of complex samples, trace components and harmful components in samples. The solution of these problems requires the use of chromatography-chromatography hyphenated technology. Chromatography-chromatography hyphenated technology, also called multidimensional chromatography, is a technology that combines different types of chromatograms or the same type of chromatograms but with different separation modes. Chromatography-chromatography hyphenated technology usually consists of a pre-separation column and a main separation column in series. The two columns are connected through an interface. The mobile phases used in the two columns can be the same or different.
Chromatographic hyphenation technology is diverse. For example, the hyphenation of chromatography and thermal analyzer can be used to study the thermal decomposition behavior of compounds. In addition, multi-machine technology, such as liquid chromatography-gas chromatography-infrared spectroscopy, can identify complex organic structural isomers.