Of course there are some potential competing processes might occur at same time, such as thermal degradation, oxidation, pyrolysis of analytes. Therefore, in order to get the better results and controlling side effects of competing oxidation and degradation, many parameters of AFI-MS could be optimized, such as: the choice of fuel, fuel flow, size of flame, sample introduction mode, sample introduction point in the flame and the distance between the flame and the inlet of MS.
In the process of AFI-MS analysis, the melting and boiling phenomena were not obvious, but it is believed that they are important factors for sample desorption step.
Most organic compounds responded fast in AFI-MS analysis and we found that normally the volatile organic compounds responded slightly faster than the solid samples with higher melt and boil point. The experimental results showed that the AFI-MS was an ideal method for mass spectrometric analyses of organic compounds and the applicability of AFI-MS technique has close relationship with the physicochemical properties of the analytes.
Because the fast sample desorption process in the outer flame has close relationship to the melting and boiling point and the vapour pressure in ambient condition of the analyte. The ionization process of the gaseous analyte mostly depended on the ionization energy and proton affinity.
The capabilities of AFI are demonstrated through rapid, direct, in-situ mass spectrometric analysis of sample in various states, such as volatile organic compounds e. Because most of these organic compounds could be desorbed and ionized with the help of flame, most of these organic compounds were protonated in AFI-MS; however, the compound with low ionization energy, such as ferrocene 6.
All data demonstrated that AFI-MS is a promising approach in the related research area since it is fast, simple and also carries great potential for portability.
As such, AFI-MS will be of interest to the analytical community at large, such as public security, environmental protection, therapeutic drug monitoring and food quality monitoring. Researches on the complicated combustion process in AFI-MS are still going on to harness its advantages for optimizing AFI-MS conditions and to reduce the competing side-processes, such as: degradation, oxidation, pyrolysis and combustion of analytes. In view of convenience and versatility, the AFI is potentially an attractive candidate to couple portable or miniature mass spectrometry to perform in-field analysis of target samples in their undisturbed environment and native states.
Such simple and high-efficiency AFI method might have a bright future in direct, high-throughput and on-site analysis.
Chemical reagents were directly used without any further purification. Food was purchased from local stores without any further treatment. All of food was directly exposed to the flame without any treatment. Drug tablets were bought from local pharmacy.
Coated tablets needed to scrape off a thin layer of the tablet and expose the subsurface active materials, whereas uncoated tablets were directly detected without any treatment. See the Supplementary Information.
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Analyst , — Shiea, J. This high-energy beam strips electrons from the sample molecules, leaving behind a positively charged radical species. Mass analyzers separate the ions according to their mass-to-charge ratios.
There are many types of mass analyzers. Each has its strengths and weaknesses, including:. For example, a time-of-flight TOF analyzer uses an electric field to accelerate the ions through the same potential and then measures the time they take to reach the detector. Since the particles all have the same charge, their velocities depend only on their masses, and lighter ions will reach the detector first. Another type of detector is a quadrupole. Here, ions are passed through four parallel rods, which apply a varying electric voltage.
As the field changes, ions respond by following complex paths. Depending on the applied voltage, only ions of a certain mass-to-charge ratio will pass through the analyzer. The ions are separated in the mass spectrometer according to their mass-to-charge ratio, and are detected in proportion to their abundance. A mass spectrum of the molecule is thus produced. It displays the result in the form of a plot of ion abundance versus mass-to-charge ratio. Ions provide information concerning the nature and the structure of their precursor molecule.
Analyzer: For resolving the ions into their characteristics mass components according to their mass-to-charge ratio. Detector System: For detecting the ions and recording the relative abundance of each of the resolved ionic species. With all the above components, a mass spectrometer should always perform the following processes:. Detect the ions emerging from the last analyzer and measure their abundance with the detector that converts the ions into electrical signals. Process the signals from the detector that are transmitted to the computer and control the instrument using feedback.
Mass spectrometry is fast becoming an indispensable field for analyzing biomolecules. Till thes, the only analytical techniques which provided similar information were electrophoretic, chromatographic or ultracentrifugation methods. Deflection is the magnetic bit. Here, the ions are deflected by a magnetic field, and the extent of deflection is again dependent on mass.
So, ions of different masses travel through the spectrometer at different speeds. The output will look something like in Figure 1. Figure 1. In a word, yes! Mass spectrometry provides accurate weight measurements for your bio- or other molecules, which can be used to:.
Mass spectrometry has enabled biology to move from identifying single proteins to proteome-wide characterization and quantification. With the development of this tool, researchers can now feasibly begin defining biochemical pathways on a kinetic basis, which will help us understand the mechanistic response of cells to changing environments. Drug companies and researchers are using the technique for drug discovery, for gaining information on drug metabolism, and for pharmacokinetic studies.
These uses also make mass spectrometry when coupled with other analytical techniques a powerful tool in forensic analysis.
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