High-Resolution Mass Spectrometry

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Abstract
High resolution mass spectra can be obtained in seconds from submicrogram quantities of compounds of molecular weights as high as 1000 to 2000, including steroids, alkaloids, polysaccharides, and peptides. The monoisotopic molecular weight of the molecule can be measured to accuracies of a few parts per million, and from these measurements the elemental composition of the compound can be calculated directly. In addition to the molecular ion, the spectrum also displays the mass and relative abundance of fragment ions produced by unimolecular decompositions of the sample molecule. The elemental compositions of the fragment ions can also be determined and used to elucidate the molecular structure. An understanding of the mechanisms of such decompositions enables the researcher to reassemble the fragment ions into logical structures. The small sample requirements and the speed with which high-resolution spectra can be obtained make such spectra very valuable for identifying pure components separated by gas chromatography. Recent techniques make possible rapid, fully automatic reduction of data obtained at high resolution, and calculation of elemental compositions and suitable display of spectra by a computer. Abundant additional information is obtainable under other ionizing conditions, and the availability of such information, plus the increasing use of the computer for special interpretation and search, promises continuing progress in this field.