Abstract
It is a widely held, but erroneous, supposition that mass spectrometry cannot analyze stereochemistry.  Another misconception (prevalent outside the field) is that mass spectrometry does a poor job of quantitating mixtures.  Work from this laboratory over the past two decades has been directed towards demonstrating that conventional MS/MS techniques can be used to measure ratios of acyclic diastereomers in mixtures.

A well-known example of stereochemical discrimination is the difference between the simple EI mass spectra of cis and trans-1,2-dichloroethylene.  The cis isomer loses HCl to a much greater extent than does the trans.  The same type of discrimination can be observed between diastereomers of deuterated sec-phenoxyalkanes.  Two stereoisomers exhibit the same peaks in EI, but with different intensities.  Pairs of isomers, which differ only with respect to the placement of deuterium relative to the functional group, display large enough differences for mixtures to be quantitated.

Stereochemistry can be analyzed in electrosprayed ions, as well.  Diastereomeric amino acids and peptides and be distinguished using MS/MS.  For instance, a number of naturally occurring peptides contain a single D-amino acid in a chain containing 40-50 residues.  Enzymatic digests show measurable differences between all-L oligopeptides and those that contain one D-residue.  Potential applications of these results range from microbiology to neuroscience.

Background
Professor Thomas Morton received his AB degree from Harvard in 1968 [majored in Classics (Greek) and Fine Arts].  He completed his PhD in organic chemistry at Caltech under the joint direction of R.G. Bergman & J.L. Beauchamp in1972.  He served on the chemistry faculties of Brown & Brandeis Universities from 1972 to 1981.  He has been a faculty at UC Riverside since 1981.