Preparative Mass Spectrometry with Electrospray Ionization
In the early 1940s, E. O. Lawrence developed a mass spectrometry-based separation approach to enrich radioactive uranium 235 U from the natural isotopic distribution of uranium. 1 -3 This method used Calutron 3 mass spectrometers to separate ions according to their mass-to-charge ratio (m/z), and once separated, the ions were collected. As part of the Manhattan Project, Lawrence applied this preparative mass spectrometry approach to the purification of radioactive 235 U, which was then used to construct the first nuclear weapon. Since those early experiments more efficient (non-mass spectrometric) means of generating and separating uranium isotopes have been established, yet separating compounds based on mass is certainly an intriguing idea which has not lost its appeal. The question of whether modern mass spectrometry can be further developed as a practical separation and collection device has been addressed here with electrospray ionization mass spectrometry. In the experiments described, a monodisperse polymer was generated from a synthetically derived polydisperse version of the polymer. This simple example served to illustrate some of the advantages and disadvantages of using electrospray mass spectrometry as a preparative tool for molecular separation and purification.
The science of mass spectrometry has undergone dramatic changes in the past decade, expanding its utility as the mass range and sensitivity of the instrumentation have increased. More specifically, electrospray ionization 4 mass spectrometry (ESI-MS) has been applied in many diverse ways extending far beyond routine molecular mass determination, especially in the chemical and biochemical sciences. One area where ESI-MS has been found to be interesting and useful is in the study of non-covalent interactions. For instance, it was recently demonstrated 6 that non-enveloped viruses (which are non-covalent complexes containing proteins and genetic material) can be non-destructively introduced into the