Resolution, in mass spectrometry

Resolving Power and Resolution In Mass Spectrometry The resolving power of a mass spectrometer describes the smallest mass differences which can be separated by the mass analyser (Webb, 2004b). Resolution and resolving power in MS today are defined differently depending on the analyser or instrument type, and is often stated without the indication of the definition employed. The new fUPAC definitions of terms used in MS provide a precise definition. 

Webb, K. (2004b) Resolving Power and Resolution in Mass Spectrometry, Best Practice Guide, VlMMMS/2004/01, LGC Ltd., Teddington, November 2004, www.lgc.co.uk (accessed 14 May 2014). 

Figure 3.14 Illustration of the two most common definitions of resolution in mass spectrometry (a) full width at half maximum (FWHM) and (b) 10% valley definition. Note that the two partially overlapping peaks in (b) have been chosen to have the same heights but this definition would apply equally well to two peaks with different heights.

The luciferin produces a blue oxidation product during its purification process. In the DEAE chromatography of luciferin, this blue compound is eluted before the fractions of luciferin. The fractions of the blue compound were combined and purified by HPLC on a column of Hamilton PRP-1 (7 x 300 mm) using methanol-water (8 2) containing 0.1% ammonium acetate. The purified blue compound showed absorption peaks at 234, 254, 315, 370, 410, 590 (shoulder) and 633 nm. High-resolution FAB mass spectrometry of this compound indicated a molecular formula of C l C Nai m/z 609.2672 (M - Na + 2H)+, and mlz 631.2524 (M + H)+]. These data, together with the HNMR spectral data, indicated the structure of the blue compound to be 8. 

There are a number of different mass separation devices - analysers - used in mass spectrometry and each has its own advantages and disadvantages. Those most likely to be encountered by users of LC-MS are described briefly below, while more detailed descriptions may be found elsewhere [2-4]. One property that is important in defining the analytical capabihties of a mass analyser is the resolution which it may achieve. 

Resolution is a term encountered in many areas of analytical science and refers to the abihty to differentiate between closely related signals. In mass spectrometry, these signals are the m/z ratios of the ions, with the resolution being defined mathematically as follows ... 

Resolution A term which indicates the ability of a device/technique to sepa-rate/distingnish between closely related signals. In chromatography, it relates to the ability to separate componnds with similar retention characteristics, and in mass spectrometry to the ability to separate ions of similar m/z ratios. 

Balogh, M. P. Debating resolution and mass accuracy in mass spectrometry. Spectroscopy 2004,19, 34-40. 

KJinkert I, McDonnell LA, Luxembourg SL, et al. Tools and strategies for visualization of large image data sets in high-resolution imaging mass spectrometry. Rev. Sci. Instrum. 2007 78 053716. 

Resolution (or resolving power) plays an important role in mass spectrometry for applications requiring the characterization of very similar chemical species. The ability to detect and accurately measure the m/z ratio of a particular ion depends directly on the resolving power of the mass analyzer. For example, if a sample contains two isobaric compounds (i.e., having the same nominal molecular mass but different elemental formulae) the difference in the exact masses of the molecular ions will be much less than 1 m/z unit. Any mass analyzer possessing a nominal resolving power (e.g., RP< 1000) will register only one peak in the mass spectrum of such a binary mixture. Attempts to measure the... 

Notwithstanding the efforts of groups attempting to precisely define acceptable practices and requirements, [20] confusion still exists on the differences between definition of the terms high resolution and accurate mass. [21] High resolution, as in any context, implies the ability to make confident measurements of small differences. In mass spectrometry, high resolution implies the ability to measure the small differences deriving from different elemental compositions, which have the... 

The net effect of all this controversy was to stifle the application and development of what is, fundamentally, an extremely useful and practical technique. This is unfortunate, because in the last ten years advances in mass spectrometry, particularly the advent of high resolution MC-ICP mass... 

Plumb R. Dear G. Mallet D. Ayrton J. Direct analysis of pharmaceutical compounds in human plasma with chromatographic resolution using an alkyl-bonded silica rod column. Rapid Communications in Mass Spectrometry, 2001, 15,986-993. 

Dramatic advances in mass spectrometry and improvements in the various steps within the experimental hydrogen exchange procedures have resulted in the development of automated systems for high-throughput, high-resolution H/D exchange analysis [6, 8, 40-44]. 

Trends in mass spectrometry focus on the improvement of instrumentation, of several techniques in order to minimize sample volume, to improve sensitivity and to reduce detection limits. This is combined with increasing the speed of several analyses, with automation of analytical procedures and subsequently reducing the price of analysis. A minimizing of sample volumes means a reduction of waste volume with the aim of developing green chemistry . Furthermore, new analytical techniques involve a development of quantification procedures to improve the accuracy and precision of analytical data. Special attention in future will be given to the development of hyphenated mass spectrometric techniques for speciation analysis and of surface analytical techniques with improved lateral resolution in the nm scale range. 

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