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Mass Spectrometry: The Only Method with Many Ionization Techniques
Published in Ali Pourhashemi, Sankar Chandra Deka, A. K. Haghi, Research Methods and Applications in Chemical and Biological Engineering, 2019
Francisco Torrens, Gloria Castellano
The ion source is the element of the mass spectrometer that ionizes the material to be analyzed. Later, MF or EF transport the ions to the total analyzer. The ionization techniques were fundamental to determine which type of samples can be analyzed by MS. The electron and molecular ionization are used for gases and vapors. Two techniques, frequently used with liquid and solid biosamples, include ionization by electrospray (after Fenn) and desorption/ionization by matrix-assisted light amplification by stimulated emission of radiation (laser) desorption ionization (MALDI, after Karas, and Hillenkamp). The sources of inductively coupled plasma (ICP) are used, above all, for the analysis of metals in an extensive range of samples. Other techniques include the ionization via fast atom bomb (FAB), thermospray, atmospheric-pressure chemical ionization (APCI), secondary-ion MS (SIMS), and so on.
Capillary Electrophoresis
Published in Grinberg Nelu, Rodriguez Sonia, Ewing’s Analytical Instrumentation Handbook, Fourth Edition, 2019
The MS detector is commercially available and is a powerful detector used in CE due to its sensitivity, universality, and ability to obtain structural information. To obtain the identity of sample components, capillary electrophoresis can be directly coupled with mass spectrometers. In most systems, the capillary outlet is introduced into an ion source that uses electrospray ionization (ESI). The resulting ions are then analyzed by the mass spectrometer. MS detector limits of detection are typically 10−8–10−9 M [27]. The mass spectrometer requires volatile buffer solutions, which will affect the range of separation modes that can be employed and the degree of resolution that can be achieved. Interfaces requiring the use of a sheath flow are the coaxial sheath-flow interface or the liquid-junction interface. Sheathless interfaces include the low flow electrospray or nanospray device [129]. The disadvantages of the MS detector are cost and interferences in the analysis. CE-MS requires the direct coupling of the ionization method to a liquid-phase separation technique to permit MS detection. There are challenges in achieving stability, reproducibility, and sensitivity of CE-MS for routine use. However, improvements have been made in the reliability and reproducibility of the interface. Applications of CE-MS have been applied for the analysis of peptides [130], drug analysis [131], food analysis [132], proteomics [133], and small chiral and achiral compounds [134].
Measurement of Partial Pressure at Vacuum Conditions
Published in Igor Bello, Vacuum and Ultravacuum, 2017
Ion Sources with Electron Impact Ionization: One of the most frequently used techniques to obtain ions is the method employing the electron impact ionization. Some molecules of a sample are ionized by collisions with energetic electrons in an ion source. It should be noted that more than hundred types of ion sources currently exist. These ion sources have been developed for different purposes. However, for MS, ion sources based on the concept designed by Nier1002 have been used particularly in spectrometers operating with sector magnetic fields. These ion sources producing relatively low fragmentation of parental molecules are rather simple. A small amount of sample molecules in a gas phase enters an ionization space where these molecules are intercepted by an electron beam in transversal direction. Thermionic electrons emitted from a cathode are extracted via a slit electrode by an extraction electrode to form a ribbon electron beam. The electron beam passes between the first and second electrodes of an axial set of electrodes for acceleration and focusing of ions. The electron beam reaches an anode via a slit that screens the anode. The positive ions, formed along the electron beam path and between these two axial electrodes, drift under a week electric field to a zone from where they are extracted in the axial direction. The extracted and accelerated ions are focused by a set of electrodes of an ion optical system to form an ion beam whose energy is on the order of keV.
Pilot-scale demonstration of phytoremediation of PAH-contaminated sediments by Hydrilla verticillata and Vallisneria spiralis
Published in Environmental Technology, 2019
PAHs in the extracts were analyzed by GC-MS in a selected ion monitoring mode. The GC-MS system consists of an Agilent 6890N gas chromatograph equipped with an Agilent 7683B injector, a fused-silica HP-5 capillary column (30.0 m length, 250 µm i.d., 0.25 µm film thickness) and a mass-spectrometer detector (Agilent 5975C). The temperatures of both the injector and detector were kept at 250°C. The injection volume was 1 μl and the purge time was set to 0.50 min. Helium was used as a carrier gas at a constant flow rate of 1.0 ml/min. The initial oven temperature was 100°C and then increased at a rate of 20°C/min until 280°C with a holding time of 2 min. The total time was 11 min. The MS conditions for the electron ionization were as follows: The ion energy was 70 eV and the ion source temperature was 230°C.
Aerobic Biodegradation of DDT by Advenella Kashmirensis and Its Potential Use in Soil Bioremediation
Published in Soil and Sediment Contamination: An International Journal, 2018
Chiraz Abbes, Ahlem Mansouri, Naima Werfelli, Ahmed Landoulsi
The extracted samples were analyzed by gas chromatography (7890 A) coupled with a single quadric pole mass spectrometer (Agilent, USA, Santa Clara, CA, 5975C). A one mL sample was injected and separated on an HP_5MS capillary GC column (Agilent, 30 m, 0.25 mm i.d., 2.5 mm film), split injection (injector temperature 280°C, split 1/8 for samples and 1/20 for standard samples); oven temperature programmed from 80°C (three min) to 280°C (11 min) at 10°C/min; carrier gas ¼ Helium, flow rate one mL/min. MS was performed in electron ionization mode, with electron energy 70eV, ion source temperature 230°C and quadrupole temperature of 150°C. Data were learned in full scan (m/z 30e650) and scan acquisition modes with solvent delay of four min, and analyzed using the Enhanced Chem Station software program, Agilent.
Removal of prometryn from hydroponic media using marsh pennywort (Hydrocotyle vulgaris L.)
Published in International Journal of Phytoremediation, 2018
J. Ni, S. X. Sun, Y. Zheng, R. Datta, D. Sarkar, Y. M. Li
All extracted samples were analyzed using GC-MS (Agilent 7890B-5977A MSD) at the Southwest Forestry University precision instrument-sharing platform. The samples were introduced into the machine using an Agilent automatic sample injector (Agilent 7693A, G4513A, China). The capillary column was 30 m × 0.32 mm ID × 0.25 µm HP-5MS (Agilent Technology 19019J-413, USA). Splitless injection was performed at 260°C, injection volume was 1.0 µL. The carrier gas was Helium (at a flow rate of 1.0 mL/min). A temperature gradient was employed, by raising temperature up to 180°C at 25°C/min from 70°C and maintaining it for 1 min. This was followed by raising the temperature to 220°C at 5°C/min, followed by raising the temperature to 280°C at 20°C/min and maintaining it for 3 min. Chromato Solution Light Chemstation software was employed to acquire and process chromatographic data obtained from GC. Mass spectrometry was done by electron ionization (EI) at 70 eV, the temperature of ion source was 230°C, interface temperature was 280°C, temperature of the quadrupole was 150°C. Solvent delay time was 3.75 min. Full scan mode (SCAN) with selected ion monitoring (SIM) mode simultaneously with scan range of (m/z) 50–350 was used. SIM was m/z 241, 184, 226, 199; quantitative ion was m/z 184. The structure identifications were based on the interpretation of the fragmentation pathways.