Preparation and Submission
Preparation
Samples for EI, or APPI (solid probe) analysis must be neat, solvent-free, and reasonably pure. It must be possible to introduce them into a fine capillary tube. These ionization methods can tolerate impurities provided that the impurity peaks do not overlap the sample peaks. Samples may be either solid or liquid; however, highly volatile liquid samples will require special procedures - please consult Xiao Feng.
For ESI and APCI the sample may either be neat or in solution. If neat, the sample should be solvent-free and pure, but both ionization methods can handle moderate mixtures. If a solution, the sample should be at a low concentration (less than 10-4 M) in methanol, water or acetonitrile (mixtures are OK). Other solvents may work for APCI - please contact Xiao Feng. There must be no excess salt in your sample, especially for ESI. Buffers such as phosphate and HEPES are fatal to these techniques.
Place your sample into a small screw-top vial. Use an inert cap liner, such as aluminum foil or Teflon, for screw-top vials, since a solvent will leach plasticizers from plastic caps. The amount of sample required varies with ionization technique and instrument. Normally, 1 mg is enough for ESI.
Impure samples likely produce poor spectra. In addition to providing “extra” peaks in a mass spectrum, which may be confusing, they may mask the sample peaks in several ways. Impurity peaks may totally overlap sample peaks. In the case of samples that are volatilized into the ion source, a more volatile impurity will appear first and appear to be the sample, perhaps leading to premature halting of data acquisition. Impurities may compete with samples for ionizing reagents or interfere in other ways, sometimes totally suppressing the sample ions (especially in ESI).
Submission
To submit samples for mass spectrometric analysis, you must fill out and submit a sample submission form:
For the internal Dalhousie users:
Submission Form for INTERNAL DALHOUSIE SAMPLES ONLY
For the external Dalhousie users:
Submission Form for SAMPLES EXTERNAL to DALHOUSIE
Paper Form:
Submission Form pdf
* Due to COVID-19, please fill out the form and send a copy by email.
For Dalhousie users, bring the completed forms and samples to Room 537 or 328 (the Mass Spec Lab), or drop off your samples and forms in the box outside Room 328.
Users from outside Dalhousie University should mail the completed submission forms with samples, securely packaged, to:
Xiao Feng
Chemistry Stores, Rm. 1020
Chemical Storage Facility
6245 Castine Way
P.O. Box 15000
Dalhousie University
Halifax, NS B3H 4R2
To comply with WHMIS regulations, all samples must be labeled with the user’s name, sample identifier, and hazards.