Orthogonal injection

Chernushevich, I.V., Ens, W., and Standing, K. G., Orthogonal injection topics for analyzing biomolecules, Anal. Chem. News Features, 7/1, 452A, 1999. 

Krutchinsky, A.N. Loboda, A.V. Spicer, V.L. Dworschak, R. Ens, W. Standing, K.G. Orthogonal Injection of MALDl Ions into a TOF Spectrometer Through a Colli-sional Damping Interface. Rapid Commun. Mass Spectrom. 1998, 72, 508-518. 

Orthogonal injection provides a high-efficiency interface for sampling ions from continuous beam to a TOF analyser. The TOF analyser allows simultaneous transmission of all ions and therefore all the ions formed are analysed. However, the duty cycle is far from 100 % for the oa-TOF spectrometer and it is lower than for the TOF spectrometer. This is due to the orthogonal accelerator that samples to the analyser only a part of the ions produced in the source. The duty cycle, despite this fact, is between 5 and 50 %. This is a considerable improvement over the conventional techniques described for coupling a continuous source to a TOF spectrometer. 

Another important advantage of orthogonal injection is its ability to minimize the initial velocities in the TOF direction and, simultaneously, to reduce the dispersion of these velocities. This is due to the formation of a parallel ion beam with orthogonal orientation to the flight tube. This favourably affects mass resolution, mass accuracy and mass calibration stability. This makes easier to achieve resolutions of more than 10000. 

Laiko W, Dodonov AF. Resolution and spectral-line shapes in the reflecting time-of-flight mass spectrometer with orthogonally injected ions. Rap Comm Mass Spectrom 1994 8 720-6. 

IV Chemushevich, W Ens, KG Standing. Orthogonal-injection TOFMS for analyzing biomolecules. Anal Chem 71 452A—461A, 1999. 

Although the interface of a TOF spectrometer with ESI has been traditionally difficult, orthogonal injection has recently proven to be a good method to enable the ESI method to be coupled with a TOF spectrometer [475]. This also gives possibilities of studying biomolecular complexes. ESI has also recently been coupled to ion mobility spectrometry, which enables a higher resolution in comparison with... 

Only part of the continuous ion beam can be sampled, as the excised ion packet must traverse the analyzer before another set of ions is introduced. The duty cycle of the orthogonal injection process limits the sensitivity of orthogonal TOF instruments. 

Guo, C. Huang, Z. Gao, W. Nian, H. Chen, H. Dong, J. Shen, G. Fu, J. Zhou, Z. A Homemade High-Resolution Orthogonal-Injection Time-of-Flight Mass Spectrometer With a Heated Capillary Inlet. Rev. Sci. Instrom. 2008, 79, 013109-1-013109/8. 

Figure 3 A schematic diagram of an orthogonal-injection TOF instrument with an electrospray ionization source. Collisional cooling is used in a quadrupole ion guide to produce a beam with a small energy spread, and a small cross section. The pressure in the ion guide is typically tens of millitorr the main TOF chamber is under high vacuum, typically torr. Ions are pulsed into...

Chernushevich IV, Ens W and Standing KG (1999) Orthogonal-injection TOFMS fot analyzing biomolecules. Analytical Chemistry 71. 

Chuenushevich, I. V. Ens, W. Standing, K. J. Orthogonal injection TOFMS far analysing biomolecules. Anal. Chem. 1999, 71, 452A—461A. 

K. G. (1998) Orthogonal injection of matrix-assisted laser desorption/ionization ions into a time-of-flight spectrometer through a colUsional damping interface. Rapid Commun. Mass Spectrom., 12, 508-18. 

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