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The charm of plasma technology: How to create ions using electrical discharge?
In today's scientific exploration, ionization technology is gradually showing its unique value in mass spectrometry analysis. In particular, plasma technology can not only analyze samples quickly, but also directly generate ions without the need for sample pretreatment. The charm of this technology lies in its efficiency and convenience. Let us explore in depth the operating principles and applications of this technology.
The basis of extraction technology
An important branch of ambient ionization is solid-liquid extraction, in which a charged spray is first introduced into the sample surface to form a liquid film. This causes molecules on the sample surface to enter the solvent, and when the primary droplets hit the surface, secondary droplets are produced. These secondary droplets are the source of ions for mass spectrometry analysis.
"Desorption electrospray ionization (DESI) is a classic ambient ionization source that uses an electrospray source to create charged droplets that interact directly with solid samples."
In addition to DESI, there is desorption atmospheric pressure photoionization (DAPPI), which uses a combination of hot solvent vapor and ultraviolet light to directly analyze samples of particles on the surface. This process not only improves the accuracy of the analysis, but also expands the range of samples that can be analyzed.
Application of plasma basic technology
Plasma is based on the principle of electrical discharge, which can produce reactive ions in flowing gas and chemically ionize volatile substances in the sample. Some techniques use Leiner or thermal excitation in a helium discharge to allow ionization in the gas phase, and these ions can react with the analyte to generate the ions required for mass spectrometry.
"The intrinsic protonation process by ambient water clusters in a helium discharge is an important pathway for plasma ionization."
This method is not limited to the detection of positive ions. For some samples, negative ion mode can also be used. This is particularly effective when detecting molecules with higher gas-phase acidity, such as carboxylic acids.
Advantages of Laser-Assisted Ionization
Laser-assisted ambient ionization involves first desorbing or vaporizing a sample using a pulsed laser and then interacting that material with a spray or plasma to create ions. This approach increases the flexibility of sample analysis and expands the types of compounds that can be analyzed.
"Laser desorption electrospray ionization (ELDI) combines the advantages of UV and IR lasers to effectively desorb materials into the electrospray cloud to generate highly charged ions."
This method was combined with mass spectrometry for the first time in metal analysis, and its application areas have been continuously expanded in subsequent research.
Emerging two-step non-laser methods
In the non-laser two-step ionization method, material removal and ionization are separate steps. For example, probe electrospray ionization (PESI) combined with a sharp solid needle, which can improve high salt tolerance and greatly reduce sample consumption, represents a new possibility.
Gas Phase Ionization and Chemical Reactions
Analytes generated from the gas phase, whether breath, odors or volatile organic compounds (VOCs), can now be effectively detected with increasing sensitivity. This process is usually achieved through gas-phase chemical reactions, using charging agents to collide with analyte molecules to transfer their charge.
"Secondary spray ionization (SESI) uses nanoelectrospray running at ultra-high temperatures to generate small droplets that evaporate quickly, making it effective for analyzing volatile substances."
This method shows its unique advantages in the analysis of tracking mixed gases and other low-volatile substances.
Comprehensive technical comparison
With the advancement of technology, environmental ionization technology has been classified into various technologies such as "extraction", "plasma", "double step", "laser", "acoustic", etc. Each method has its own characteristics. and application scenarios.
Today, the combination of plasma and other ionization technologies provides a more comprehensive solution for scientific research and industrial applications. The use of these technologies in the analysis of a variety of samples will make future research more accurate and efficient. When we think about the applications and potential of these technologies, do you also feel the infinite possibilities of technology in changing our world?
