Sample Preparation Guidelines

Mass Spectrometry General Lab Procedures for all Users

• Always acquire solvent blank and reference sample before commencing and after you have finished the analysis of your analytes. This applies to LC as well as direct induction projects.
• Compare two blanks before and after your analysis to ensure the instrument is cleaned from analytes. (If you injected highly concentrated samples, inject a few solvent blanks and inform the Lab Manager who will advise you on immediate clean up procedures.
• Dilute your sample to around 1- 100 ng/mL for the qualitative analysis. High concentration samples damage the instrument and give incorrect mass-to-charge measurements. Repeatedly injecting too high concentrated samples may result in reduced access to instruments.

Samples in Autosampler

• If you wish to keep the samples you ran overnight, please leave a note for the next user not to throw them away with instructions as to where to store the tray (room temp shelf or a fridge). Please ensure you pick up the samples next day or ensure they are labelled with your name, content, date and expiry date. By default, any samples left in autosampler will be thrown away.

Sample and users UHPLC column storage

• Samples, columns, etc. can be left in the assigned places in the MS Lab (room temp shelf, or the fridge, if appropriate) if labelled correctly with name, date and the sample content.

Instructions for sample preparation for MS analysis

• MS vials: 2 mL glass vial screw or snap lid.
• Solvent: HPLC-MS grade acetonitrile, methanol, water or mixtures of these.
• Volume: if less than 150 µL then use total or maximum recovery vials.
• Concentration (direct infusion): for molecules < 2000 Da, use 100 ng mL-1; for molecules > 2000 Da, use 1 µg mL-1.
• You must not use THF, DMSO, acetone, or DMF as solvent. Atmospheric pressure ionisation (API) – meaning ESI, APCI, APPI, ASAP ion source inlets – is severely compromised by the presence of involatile buffers and involatile salts. These must be removed from the sample or substituted by a volatile option, e.g. ammonium acetate. (still, do not leave high concentrated solution of those salts on idle systems for longer than a few hours).
• For high-resolution analysis (HR-MS) you must have a clean (low-res) LR-ESI-MS mass spectrum of the same sample and batch before submitting for HR analysis.

Contact facility staff for advice before preparing your sample. The way you prepare your sample can effect the quality of the final data.