Michael P. Balogh

Almost a half-century later, we enjoy far greater access to the experience of others via the internet. This month's column addresses some elementary aspects of the mass spectrum, discusses tools employed by experienced practitioners, and provides some glimpses into current advances in the science and art of deriving unambiguous answers from unknown spectra.

Basics of the mass spectrum: The sine qua non for practitioners is, of course, mastery of the language of MS, which takes the form of spectral output. Jim Clark, a retired chemistry teacher in the U.K., has developed an accessible, comprehensive, and useful resource that captures a wealth of experience from his years teaching. His Web site ( http://www.chemguide.co.uk/), aimed more at beginning students than advanced ones, serves as a quick refresher for the scientist–practitioner who does not regularly use MS. Many of the examples in the first section of this column are adapted from Clark's work updated with our current appreciation of accurate mass and atmospheric pressure ionization practice. Take from it what you will and apply as needed.

Deriving the unambiguous answer:Defining the unique qualities of the spectrum gives us a basis for de novo assessments. As comfortable as we can be with the fidelity of isotope prediction, it does not mean we can apply rules to flawlessly derive the only possible unambiguous formula from an acquired ion. Kirsten Hobby (see http://kisotopic.com/) worked to develop a software tool (referred to as iFit in MassLynx software, Waters Corp., Milford, Massachusetts) to compare an acquired spectrum with its theoretical equivalent. Hobby's comments from a few years ago on the limits and utility of what he designed to help derive an answer are compared with thoughts from Richard Denny, current architect of MassLynx spectral "fitting" tools.