Department of Chemistry   University of Oxford

 

High Resolution Sample Submission Service

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

High Resolution Service

If you know for certain that your compound will not ionise with electrospray ionisation (open access) or your open access analysis failed you may submit your sample to the mass spec service for alternative methods of ionisation. Please pay close attention to the following guidelines:

If your Open Access ESI measurement was unsuccessful (or you know that the sample will not ionise by ESI) submit the sample as follows:

  • Log the submission by completing the next available row on the General Submission Excel spreadsheet (white, ground floor accurate mass and alternative ionisation sample login computer).
  • Fill in the General Submission form which can be downloaded here 'Submission Forms for Mass Spec Service' ). Take the sample's MSS number from the Excel spreadsheet and write it into the correct space towards the bottom of the form, making sure you tick the EI/CI/FI or MALDI tick box to request alternative ionisation analysis.
  • If an unsuccessful open access spectrum was run put the ID number of this run (found on the top right hand corner of the results pdf) on the form where indicated. Leave this line blank if no open access sample was run due to the sample being unsuitable. Place the completed form in the 'General Submissions' tray.
  • Label the sample vial with the MSS number shown on the Excel spreadsheet using a sticky label. NOTE permanent markers onyl are easily washed off with common solvents. Only clearly labelled vials will be accepted.
  • Place the sample vial in the General Submissions sample tube rack (blue) in the fridge.

The sample will be measured by ESI, CI, EI, FI or MALDI as soon as possible and the date stamped request form returned to the appropriate Group tray in Lab 20.062 (open access lab). 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, but bear in mind that accurate mass determination by CI, EI or FI requires additional, manually intensive measurements to be performed on the sample and will lead to a delay in the return of your spectrum. Accurate mass measurements will be performed on novel compounds only. DO NOT use yellow (accurate mass ESI) forms for this purpose

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 hands-on 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.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


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