Negative ion mode mass spectrometry - Journal of Chemical ...

Negative ion...Somsubhra Ghosh et al.The resulting electrical field within the space defined by the four rods are used for resolve ions injectedinto the field. Ions entering this quadrupole electric field undergoing oscillatory trajectories, and at anygiven combination of applied fields, only one m/z ratio attains a stable trajectory that carries it through theanalyzer;and other ions are collected on the rods. By varying the dc or rf fields, different m/z ratios arebrought to focus.Fig. 5: Shows Schematic diagram of Quadrupole mass analyzer (13)(b)Time –of-flight analyzer: Ion separation is based on the principle that ions of different masses,possessing equal kinetic energy, have different velocities. If there is a fixed distance for the ions to travel,the time of travel will vary with their mass, the lighter ions travelling faster and reaching the detector in ashorter period of time. According to this concept, the kinetic energy of an ion accelerated through anelectrical potential V will beZv =mv 2 /2 (Equation 1)and the velocity of the ion is the length of the flight path L divided by the time t. It takes the ion to travelover that distance:substituting the equation 2 in equation 1Zv=mL 2 /2t 2Thus, it follows thatv=L/t (Equation 2)m/z=2Vt 2 /L 2(Equation3)The TOF mass analyzer requires very fast electronics to accurately measure ion flight times that may besubmicrosecond. Furthermore, the ions in a TOF system must be created in short, well defined pulses sothat the ions all start their journey toward the detector at the same moment.1467 J. Chem. Bio. Phy. Sci. Sec. C, 2012, Vol.2, No.3, 1462-1471.

Negative ion...Somsubhra Ghosh et al.Fig. 6: Shows Schematic diagram of Q-TOF Mass analyzer(c) Ion trap mass analyzer: Ion traps are ion trapping devices that make use of a three-dimensionalquadrupole field to trap and mass-analyze ions.It was invented by Wolfgang Paul (Nobel Prize1989) . ItOffers good mass resolving power. The ion trap consists of two hyperbolic end-cap electrodes and adoughnut-shaped ring electrode (by which end cap electrodes are connected). An alternating current (AC)or (DC) and an RF potential is applied between the ring and endcaps electrodes. In the ion trap analyzer,ions of all m/z values are in the trap simultaneously, oscillating in concentric trajectories. Sweeping theRF potential results in the removal of ions with increasing m/z values by putting them unstable trajectorycauses them to be ejected from the trap in the axial direction toward the detector.Fig. 7:Schematic diagram of Ion trap mass analyzerFig. 8: Shows Schematic diagram of Ion trap mass analyzer1468 J. Chem. Bio. Phy. Sci. Sec. C, 2012, Vol.2, No.3, 1462-1471.

Negative ion...Somsubhra Ghosh et al.(b) It is an accurate method for the determination of molecular mass of the components and its elementalcomposition.(c) It also used to investigate reaction mixtures (gases, liquids and solids) and also used in understandingreaction kinetics and mechanisms of unimolecular decomposition reactions (16) .(d) Using solid phase extraction (SPE) and liquid chromatography/tandem mass spectrometry(LC/MS/MS), 46 pesticides in positive ion mode and 14 pesticides in negative ion mode wereanalyzed (17) .(e) Sugar and sugar alcohols such as sorbitol and glucose were successfully analyzed by massspectrometry using atmospheric pressure ionization in negative ion mode (18) .(g) ) ESI in the negative ion mode has been employed to determine the structure of glycosides ofanthraquinones [67,68], coumarins [67], flavonoids [4,31,67,69,70], iridoids [67,71], aromatics [30,67],cardenolides [29],isoflavonoids [57] and triterpenes [67,72] (19) .(h) Chemical warfare agents, explosives, dyes are analyzed by using both positive and negative ion modeby using liquid chromatography-Mass spectrometry (20) .(i) By using negative chemical ionization we can measure the MDA(3,4-Methylene dioxyamphetamine),MDMA(3,4-Methylene dioxy methamphetamine), MDEA(3,4-Methylene dioxy ethyl amphetamine) inblood (21) .CONCLUSIONMass spectrometer is operated in positive and negative ion mode. Generally now a days positive ion modeis used in many cases and Negative ion mode spectroscopy is also being used in some specific andsensitive cases, in such cases negative ion mode is more efficient than the positive ion mode .In future itcan be used in other fields also.REFERENCES(1) K. R. Jennings, Philosophical Transactions A., 1979,293:125-133.(2) D. Pavia, Spectroscopy, 2007, page no.401-419.(3) K. S Graham, Applications of liquid chromatography: Mass spectrometry to cytochromep450 inhibition screening and the measurement of plasma free Metanephrines, Universityof Wales Swansea 2005.(4) J. J. Pitt, Clin Biochem Rev, 2009, 30(1): 19-34.(5) Available at: http://www.colby.edu/chemistry/instruments/ElectrosprayIntro.pdf, Electrosprayion mass spectrometry.(6) D. F Smith, Petroleomics applications of fourier transformion cyclotron resonance massspectrometry:Crude oil and bitumen analysis, The Florida state university college of artsand sciences, Oct, 2007.(7) K. A. Schug, Pseudo-molecular ion formation by aromatic acids in negative ionization modeelectrospray ionization mass spectrometry, Oct, 2002.(8) R. Ekman, J. Silberring, A. M.W. Brinkmalm, A. Kraj, D. M. Desiderio, N. M. Nibbering,1470 J. Chem. Bio. Phy. Sci. Sec. C, 2012, Vol.2, No.3, 1462-1471.

Negative ion...Somsubhra Ghosh et al.Mass spectrometry: Instrumentation,interpretation and applications, (WileyInterscience, NewYork) 2008.(9) M. Dashtiev, E. W¨afler, U. R¨ohling, M. Gorshkov, F. Hillenkamp, R. Zenobi.,International Journal of Mass Spectrometry, 2007, 268:122-130.(10) Available at: http://www.freepatentsonline.com/5204530.html, Noise reduction in negativeionquadrupole mass spectrometry, April 20, 1993.(11) Y. R. Sharma, Elementary Organic Spectroscopy; Principles And Chemical Applications, S.Chand & Company Ltd, 2007, 279-290.(12) D. Wishart, Mass spectrometry: Methods & theory.(13) K. A. Connors, A text book of Pharmaceutical Analysis, Wiley- India, New Delhi, 2007, 306-307.(14) Available at: http://www.whoi.edu/cms/files/wjenkins/2005/9/Notes07_5343.pdf, Principlesof mass spectrometry, AMS, and ion optics.(15) M. Fabrizi, C. Pagura, A. Tolstogouzov, S. Daolio, M. Ferretti, E. Magnone and G. L.Olcese, Rapid Commun. Mass Spectrom; 1998,12, 675–682.(16) G. D. Rao, A text book of pharmaceutical analysis, volume -2,30 th july, 2002, pageno.140 - 146.(17) Chin-Kai Meng , Determination of pesticides in water by SPE and LC/MS/MS in bothpositive and negative ion modes,September ,2008.(18) H. Kumaguai, Application of Liquid Chromatography/Mass Spectrometry to the Analysis ofSugars and Sugar-Alcohol, 2001.(19) M. Kubota, K. Yoshida, A. Tawada, M. Ohashi, J. Mass Spectrom. Soc. Jpn., 2002, 50 (2),58-66.(20) G. M. Cabrera, Phytochemistry: Advances in Research, 2006,1-22.(21) ) F. T. Peters, N. Samyn, C.T. Lamers, W.J. Riedel, T. Kraemer, G.D. Boeck, H.H. Maurer,Clinical Chemistry, 2005, 51(10), 1811-1822.*Correspondence Author: Somsubhra GhoshNalanda College of Pharmacy, Nalgonda, Andhra Pradesh, India1471 J. Chem. Bio. Phy. Sci. Sec. C, 2012, Vol.2, No.3, 1462-1471.