A retrospective view of mass spectrometry and natural products—sixty years of progress, with a focus on contributions by R. Graham Cooks

Abstract

Modern mass spectrometry as used by chemists has prospered for the past sixty years. During the first decade of this period, the primary compounds studied were from petroleum, although other organic compounds soon attracted interest. By the mid nineteen fifties, mass spectra were being recorded on thousands of compounds each year. Most of this activity was in industrial laboratories, although by 1960 the academic world had realized the potential of the technique. This retrospective, reviewing the past sixty years, is divided into four quarters. The first two quarters cover the thirty-year period to 1970, by the end of which R. Graham Cooks had begun to plant firm roots into mass spectrometry. The major feature of the third quarter is the development by Cooks and his students of tandem mass spectrometry using isobutane or ammonia chemical ionization mass spectrometry coupled to the mass-analyzed ion kinetic energy spectroscopy (MIKES) technique for the direct, rapid, and efficient analysis of complex biological matrices. A milestone in the work was the direct introduction of plant material into the mass spectrometry (MS) source. The fourth quarter of the review covers an explosive growth in the breadth of mass spectrometry. Work in the Cooks laboratory was focused on the application of a series of ion generation and sample introduction techniques, such as desorption chemical ionization, surface-induced dissociation, secondary ion mass spectrometry, and membrane introduction mass spectrometry, to analyze increasingly complex biological matrices. In contrast to the earlier MIKES technique on a sector spectrometer, tandem MS became more common using a triple quadrupole spectrometer, with the natural products being studied ranging in complexity from ethanol to proteins and DNA.