Mass spectrometry and isotopes: A century of research and discussion

Abstract

In 1815, the British physician William Prout had advanced the theory that the molecular masses of elements were multiples of the mass of hydrogen. This "whole number rule" (and especially deviations from it) played an important role in the discussion whether elements could be mixtures of isotopes. F. Soddy's discovery (1910) that lead obtained by decay of uranium and of thorium differed in mass was considered a peculiarity of radioactive materials. The question of the existence of isotopes came up when the instruments developed by J.J. Thomson and by W. Wien to study cathode and canal rays by deflection in electric and magnetic fields were steadily improved. In 1913, Thomson mentioned a weak line at mass 22 accompanying the expected one at mass 20 when he analyzed the mass spectrum of neon. Subsequently Aston obtained the mass spectrum of chlorine with masses at 35 and 37. Still in 1921, Thomson objected heavily to the idea of isotopes. The isotope problem was finally settled, but more accurate mass measurements showed that even isotopic weights differed to some extent from the whole numbers. Based on earlier ideas of P. Langevin and J.-L. Costa, F.W. Aston and A.J. Dempster developed the idea of packing fractions and mass defects due to the transformation of a portion of the matter comprising the atomic nucleus into energy. While the determination of the exact isotopic masses had improved over the years, the accurate determination of isotopic abundances remained a problem as long as photographic recording was used. Here especially A.O. Nier pioneered using dual collectors and compensation measurements. This was the prerequisite for the discovery that isotopic ratios varied somewhat in nature. M. Dole discovered the fractionation of oxygen isotopes by photosynthesis and respiration. Today 13C/12C-ratios are employed to detect adulterations of food and in doping analysis, and 14C/13C-ratios obtained by accelerator mass spectrometry are used for dating historical objects, just to give some examples.

Mass Spectrometry and Gas‐Phase Chemistry of Anilines

“…Attempts to correlate mass spectrometric data with structure can only be described as elegant, though many times it is very complex, puzzling and arbitrary. The insight of the many pioneers in this endeavor, such as those from the groups of McLafferty 21 , Beynon 22 and Budzikiewicz 23 , led to a number of rational mechanisms for ion dissociation. These rationalizations were masterfully summarized in textbooks and reviews by McLafferty and Turecek 5 , Biemann 24 , Budzikiewicz, Djerassi and Williams 4,25 and others.…”

Microdosing studies using accelerated mass spectrometry as exploratory investigational new drug trials

“…AMS has frequently been used in environmental research, the exploration of natural resources, earth sciences, and the investigation of natural materials (Arjomand, 2010). AMS can quantify such elements (isotopes) as 10 Be, 14 C, 26 Al, 36 Cl, 41 Ca, and 129 I in addition to the target isotope, 14 C, and its measurement accuracy can be secured within a tolerance of the measurement error at units of 10 −12 to 10 −18 (Budzikiewicz and Grigsby, 2006).…”

Computational Challenges in Deciphering Genomic Structures of Bacteria

“…So we need to constantly remind ourselves about this when attempting to bridge the gap! In the rest of the article, I will discuss the information that is potentially derivable from genome sequence alone in the foreseeable future, which will need to be integrated, when attempting to understand the whole picture, with information derivable based on other experimental data such as (a) microarray gene expression data [76][77] for inference of the transcription subsystem and associated regulatory subsystem in a cell, (b) tiling arrays [78][79] for identification of cis regulatory elements of operons, (c) ChIP on chip data [80] for identification of interaction partners between transcription regulators and their cis regulatory elements, (d) proteomic data measuring the presence and the quantities of proteins under specific conditions typically collected using mass spectrometry techniques [81][82] , (e) metabolomic data measuring the metabolites as the results of metabolic reactions and their quantities using mass spectrometry or nuclear magnetic resonance (NMR) techniques [83][84] , (f) protein interaction data generated using techniques like yeast two-hybrid arrays [85] or pull-down approaches [86][87] , (g) protein and complex structures generated using X-ray crystallography [88][89] , NMR or electronic cryo-microscopy techniques [90][91] , which can provide detailed information such as how a protein executes a particular reaction, and (h) imaging data for tracing the movements of bio-molecules inside a cell, as well as information derived through systems level modeling and simulational studies as outlined earlier.…”