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Mass Spectrometry Service

The mass spectrometry (MS) laboratory is located in the basement of the Humphrey Raikes Building, Room B7, School of Chemistry.

Lab Instruments

MS laboratory is fully operational with the following cutting edge instruments:

GCxGC-TOF-MS/FID, LC-MS & UHPLC-QTOF-MS

 

What to expect from the MS results

Electrospray Ionization (ESI): A very mild ionization technique used for organic molecules. In ESI positive mode expect to see peaks corresponding to (M+H)+, (M+Na)+ and/or (M+K)+. If the molecule contains electrophilic carbons such as ketone/aldehyde it is common to see the addition of solvent masses (e.g. methanol or water) to these ion peaks. At high sample concentration, it is also possible to observe dimer and trimer peaks in the mass spectrum which can pick up a charge via the addition of H+, Na+, or K+. In ESI negative mode the most common type of ion observed is from loss of a hydrogen ion to give (M-H)- peak. Adducts with negative ions are also possible to give peaks corresponding to (M+Cl)- or (M+Br)-.

Electron Impact (EI): Used for organic molecules 50 - 1000 Da and melting point &tl; 250 oC. Ionization forms a radical cation and therefore expect to see a peak corresponding to the molecular mass (parent ion) along with stable fragments (e.g. base peak).

Laboratory capabilities

Synthesized organic compounds, complexes, plant and human metabolites, pesticides, pharmaceuticals, hydrocarbons, peptides and proteins, biological samples including fatty acids, archaeological samples, dyes, essential oils.

Samples for Analysis

These instruments provide staff, students and other users with a valuable service that allows analysis of a broad range of samples. We also accept external samples for analysis and prices for these services are available from Dr. Maya Makatini and Dr. Eric Morifi.


Dr. Maya Makatini
Room 203
maya.makatini@wits.ac.za
011 717-6708

Dr. Eric Morifi
Room 207/B7
eric.morifi@wits.ac.za
011 717 6761/16

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