MASS SPECTROMETRY AND MOLECULAR WEIGHT DETERMINATION
Stephen J. Eyles, Coordinator

The Mass Spectrometry Facility at the University of Massachusetts was established in September 1997 with the purchase an ion trap mass spectrometer. Since then, the Facility has acquired three further instruments, which make the Facility one of the best-equipped in the area. Instrumentation available is as follows:

• Esquire-LC electrospray ion-trap (Bruker Daltonics, Inc.) equipped with HP1100 HPLC system.
  This system is designed for LC-MS applications, but can also easily be used for analysis of peptides, proteins and other biopolymers. With capabilities of MSn it is also a valuable structural tool.
  
  
• Reflex III MALDI-TOF (Bruker Daltonics).
  The "unlimited" mass range of a time of flight mass spectrometer enables the molecular weight and polydispersity of polymers to be analyzed.
  
  
• JMS700 MStation (JEOL) high resolution two-sector mass spectrometer. This instrument is equipped for EI, CI, FAB, ESI, and FD ionization methods. This instrument with its capabilities for accurate mass measurements of small molecules, its MS/MS capabilities, and its variety of ionization methods make it a powerful analytical tool.
  
  
• MS Engine (Hewlett-Packard) GC-MS system.
  This system can be used for separation of complex mixtures by gas chromatography and identification by mass spectrometry.
  
  

Additional information is located at the home page for the facility.

Molecular Weight Determination

In addition to the well-equipped mass spectrometry facility, two other shared facilities are available for molecular weight determination. A Beckman XL-I analytical ultracentrifuge equipped with absorbance and refractive index detectors are available for sedimentation velocity and equilibrium measurements.

This system can be used for determine molecular weight, sedimentation coefficients, association constant for intermolecular interactions, and a variety of other parameters. High and low temperature GPC systems equipped with multi-angle light scattering detectors are also available.

Gel permeation chromatography enables separations of mixtures and polydisperse samples with determination of the concentration and molecular weight of each species using a combination of refractometer, viscometer and multi-angle light scattering detectors.