Department of Chemistry   University of Oxford

 

Accurate Mass Sample Submission Service

The sample submission service provides high resolution mass spectra and accurate mass data for novel compounds using a range of ionisation techniques.

Accurate Mass Service

If your sample gives an identifiable low resolution spectrum (ie appropriate m/z peaks corresponding to [M+H]+, [M+Na]+, [M-H]-, etc.) and you require an accurate mass measurement for elemental composition, you may submit the sample to the accurate mass service as follows:

  • Log the submission by completing the next available row on the accurate mass ESI Excel spreadsheet (yellow, ground floor accurate mass login computer).
  • Fill in a small molecules sample submission form ensuring the 'Electrospray Accurate Mass Analysis box is ticked towards the bottom of the page. Take the ESI number from the Excel spreadsheet and write it in the space provided next to the tick box towards the bottom of the form. Write the open access ID (found on the top right hand corner of the result pdf) in the appropiorate place on the form. Samples will not be run without an open access ID unless otherwise agreed with a member of the MS staff.
  • Place the form in the accurate mass ESI tray (yellow), in the ground floor open access mass spec room.
  • Label the sample vial with the sample number shown on the Excel spreadsheet and paper form using a sticky label. NOTE permanent markers are easily washed off with common solvents. Only clearly labelled vials will be accepted.
  • Place the sample vial in the accurate mass ESI sample tube rack labelled 'Accurate Mass Samples' in the fridge at the position indicated on the Excel spreadsheet.

The sample will be measured ESI MS as soon as possible. Samples and sample submission form will no longer be returned to submitters other than by special arrangment in one of cases. Please see a member of MS staff prior to sample submission if you require these forms or sample returned. Results will be sent by email either as a pdf or Word document. Requests for follow-up accurate measurements should be made on the same form.

Sample Preparation (important!)

Mass spectrometers are very much more sensitive to sample concentration than NMR and when samples are too concentrated (for example when an NMR solution has not been sufficiently diluted) the mass spectrometer's detector becomes saturated which will provide provide innacute mass data. unlike NMR, the sample injected is ionised and then transmitted inside the insturment through a very small inlet and if sample is too concentrated, the inlet gets contaminted compromising analysis of subsequent samples. At the very least this leads to the instrument needing to be shut down for the system to be cleaned. Please ensure you make up samples very carefully paying attention to the following conentrations ranges and solvents:

A basic rule for small sample preparation (<1500amu) is to aim for between 5 and 10 micrograms of analyte per millilitre of solvent. Where samples are an unknown concentration they should not be run on the system unless it is possible to serially dilute the sample to a level you can be confident is below 10ug/mL.

Sample preparation

1. Dissolve the sample in an organic solvent (eg DCM, CHCL3, EtOAc, MeCN, MeOH) or H2O at 1mg/mL.

2. Dilute 50 to 100 times with MeOH (if necessary use 50:50 MeOH/MeCN (low polarity) or water (high polarity).

3. Placed the solution in a 2mL sample vial with a screw or snap cap lid (available from stores).

 

Trained users are encouraged to use the trained user instruments (GCT GC/MS, LCT LC/MS, UPLC/MS MALDI-TOF and ZMD LC/MS) to analyse samples.

Please note that due to the high demand placed on this service, accurate mass measurements are performed on novel compounds only. Samples are generally measured next-day (negative ion samples may take 2 or 3 days) and date-stamped forms returned to the appropriate Group tray in Lab 20.062. Measurements can be processed using the Accurate Mass Processing PC, again located in Lab 20.062.

Submission Forms for Accurate Mass Samples

Sample preparation for small molecules and biopolymers

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


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