Sample Preparation Guides

Required Procedures 

1. DO keep sample amounts low. For most applications on the LTQ instruments sensitivity is on the order of pmols. Keep concentrations in the low hundreds of nanograms per milliliter. If you are working with a new sample and don’t know how it will behave, start with a very low concentration and go higher until you see a signal. 

2. DO make the sample as clean as possible. Purity and amount are the two big determinants for getting good mass spectrometry results. 

3. DO work with volatile solvents and buffers. Volatile buffers will pass through the mass spectrometer. Non-volatile buffers, salts etc., leave residue in the source, in the capillary and in the mass spectrometer necessitating costly, time-consuming clean outs. 

4. DO ask questions. Li and Postdoc advisors are happy to consult with all the users regarding any and all aspects of mass spectrometry. We are glad to help with or consult about the experiments, since cleaner samples means higher quality data for all the users. It is always better to ask than risk damaging columns or instruments by using inappropriate techniques or reagents. 

5. DO centrifuge your samples before loading them in the vials for mass spectrometric analysis. Particulates clog columns leading to high back pressures. Filtration is another option but centrifugation is preferred.

 


Forbidden Procedures 

1. DO NOT operate the instruments without appropriate training. Training for the walk-up is offered frequently by appointment. If you require mass spectrometry for your project and you have not been trained, ask another member of your lab or another lab to run the samples for you until you complete the training. 

2. DO NOT use trifluoroacetic acid (TFA). While TFA is an excellent pairing reagent and gives nice peak shape for HPLC, it dramatically reduces ionization of most compounds at the source. 

3. DO NOT try to analyze samples with high concentrations of mineral salts (Na, K etc.). Excess non-volatile buffer components can be deposited on the source during ionization and reduce sensitivity. They can also build up in other parts of the instrument and cause problems. 

4. DO NOT spike samples with Na or K. 

5. DO NOT analyze samples with high concentrations of solvents/conditions (e.g. hexanes and high pH) that are not recommended in the column care guide. You could damage or dissolve the matrix, ruining the column. 

6. DO NOT analyze samples with corrosive compounds present. Perchloric acid and other corrosives will damage or destroy the stainless steel parts of the HPLC system. 

7. DO NOT attempt to fix or recalibrate the instruments without contacting the facility managers or Post Doc Super Users. Incorrectly calibrating or tuning the instrument will affect data collection in all experiments after you. If you believe the instrument is not working correctly, please report the problem.

File: Sample Preparation guidelines R3, Rev 4/7015