Reflectron time-of-flight

Mass analyzer/ Feature Linear Quadrupole Quadrupole ion trap Linear time-of-flight Reflectron time-of-flight... 

Time-of-flight reflectron mass spectrometry with some form of time-delay extraction has become popular for large-molecule characterizations. Resolutions of up to 15,000 can be routinely achieved over very broad mass ranges, extending up to about 300,000 Da. As noted previously, time-of-flight analysers are particularly compatible with laser-based ionization techniques that produce very short bursts of ions. They are also very fast, with mass spectra often obtainable in about 25 p,s. Finally, time-of-flight analysers have been paired with a quadrupole to produce a hybrid two-dimensional mass spectrometry system that has found widespread use in protein analyses. This device will be discussed in more detail in the section on two-dimensional mass spectrometry. 

Schematic diagram of a time-of-flight reflectron mass analyzer.

Time-of-flight (TOF) instmments utilize the times taken by ions to pass (fly) along an evacuated tube as a means of measuring m/z values and therefore of obtaining a mass spectmm. Often a reflectron is used to direct the ions back along the TOF tube. 

Figure 3.7 Schematic of a time-of-flight mass analyser, involving the use of a reflectron .

Reflectron An ion lens nsed in the time-of-flight mass analyser to increase the distance travelled by an ion and thereby increase the resolntion of the instmment. 

The chemical compositions of the isolated Au SR clusters were investigated by mass spectrometry [15,16,18, 22,32-35]. TEM was used to confirm that the species detected by the mass spectrometer represents the clusters in the sample. Figure 3a is a schematic representation of the top view of the mass spectrometer, which consists of five stages of differentially pumped vacuum chambers. The apparatus accommodates two t5 pes of ion sources, electrospray ionization (ESI) and laser-desorption ionization (EDI), and a time-of-flight (TOE) mass spectrometer with a reflectron. Details of the apparatus and the measurement protocols are described below. 

Figure 6.15 Schematic design of a reflectron time-of-flight mass spectrometer...

The ECAP incorporates an electrostatic lens in the time-of-flight spectrometer in order to improve the mass resolution by compensating for small spreads in the energies of the ions evaporated from the specimen under the pulsed electric field. A lens design by Poschenrieder or a reflectron type of electrostatic lens is used for this purpose, and is standard equipment for metallurgical or materials applications of APFIM. These typically improve the mass resolution at full width half maximum (FWHM) from m/Am 250 to better than 2000. 

Mamyrin, B. A. Karataev, V. I. Shmikk, D. V. Zagulin, V. A. Mass reflectron New nonmagnetic time-of-flight high-resolution mass spectrometer. Zh. Eksp. Teor. Fiz. 1973, 64, 82-89. 

Chien, B. M. Michael, S. M. Fubman, D. M. Enhancement of resolution in matrix-assisted laser desorption using an ion-trap storage/reflectron time-of-flight mass spectrometer. Rapid Comm. Mass Spectrom. 1993, 7,837-843. 

Figure 2.10 Time of flight analyzer drift tube (a) and reflectron (b)...

B. A. Mamyrin, V. I. Karataev, D. V. Shmikk, and V. A. Zagulin. The Mass-Reflectron, a New Non-Magnetic Time-of-Flight Mass Spectrometer with High Resolution. Sov. Phys. JETP, 37(1973) 45-48. 

R. J. Cotter, W. Griffith, and C. Jelinek. Tandem Time-of-Flight (TOF/TOF) Mass Spectrometry and the Curved-Field Reflectron. J. Chromatogr., B855(2007) 2-13. 

T. J. Cornish and R. J. Cotter. A Curved-Field Reflectron for Improved Energy Focusing of Product Ions in Time-of-Flight Mass Spectrometry. Rapid Commun. Mass Spectrom., 7(1993) 1037-1040. 

B.A. Mamyrin, Laser assisted reflectron time-of-flight mass spectrometry, hit. J. Mass Spectrom. Ion Proc., 131 (1994) 1-19. 

In this instrument, the final stage of the triple quadrupole is replaced by an orthogonal time-of-flight (ToF) mass analyser, as shown in Figure 3.10. The configuration is typical of the latest generation of ToF instruments in which a number of reflectrons, in this case two, are used to increase the flight path of the ions and thus increase the resolution that may be achieved. 

Reflectron time-of-flight mass spectrometers can be used to generate fragment spectra. Before the introduction of delayed extraction, it was observed that the ions had a tendency to disassemble into fragments while they were traveling to the reflectron (Spengler et al., 1992). This behavior is called postsource decay (PSD). The ions collide with matrix ions in the gas phase when they are accelerated with several kilovolts. Their decay occurs in the first field-free drift region. 

---