Mass spectrometry, like all chemical analytical methods, works best when performed within a narrow range of analytical parameters. Operating outside of this range normally results in severe degradation of performance. It is therefore vitally important that you prepare samples for mass spectral analysis in the correct manner for the particular analytical method you have selected.

Listed below are sample preparation guidelines for each of the techniques employed at JHU chemistry, along with links to downloadable (in .pdf format) sample submission forms for the VG-70S high resolution mass spectral service. If you have further questions regarding sample preparation, please contact the facility for advice before submitting your sample.

VG70S (EI/CI/FAB)

We normally request ~0.5 mg of sample for FAB and direct probe EI /CI analyses (though we can often make do with less when only a small amount of sample exists – please seek advice prior to submission). This may seem like a lot of material, but these techniques are not as sensitive as other techniques such as GCMS or Electrospray. More sample is always preferable (particularly for accurate mass measurements) and any unused sample will be returned to you after analysis.

EACH individual sample must be submitted with a correctly completed sample submission form indicating the service required. Samples should be purified and dried prior to submission, and submitted for analysis as crystals or as an oil in glass screw-top 1DRAM vials (or other alternative containers where appropriate – please contact the MS facility for advice prior to submission) that are CLEARLY labeled with the investigators Name, Research Group and a systematic sample ID (please, no complete chemical names). Do not submit solutions. Sample vials must be securely attached to the completed submission form. Loose sample vials will NOT be accepted (the exception being for samples that require cold storage prior to analysis - please deposit these samples in the refrigerator in Rm. B14 and mark the submission form for these samples "In Fridge" ). Samples should be deposited in the appropriate trays in room B14, which is normally open from 9-5, Monday -Friday. There is one tray for EI/CI samples and one for FAB samples. Blank submission forms are also located in Rm. B14  or may be downloaded from this link as a pdf file.  Samples without completed submission forms, forms which are incomplete or incorrect, or are submitted in inappropriate containers will NOT be accepted for analysis. Radioactive, Highly Toxic or other “Dangerous” samples requiring specialist handling will NOT be accepted.

Samples for EI or CI analyses are normally introduced using a heated direct insertion probe and so it is important that the vaporization point of these samples is noted on the submission form in order to obtain the correct sample volatization rate to achieve good quality data. Samples for direct probe EI or CI should volatilize at temperatures below 350C under high vacuum conditions. Samples for FAB analyses are dissolved in an appropriate solvent and mixed with a matrix (usually m-nitrobenzyl alcohol) deposited on a target. Please specify an appropriate solvent to dissolve your sample (NOT water) that is miscible with the matrix. Common solvents employed are Methanol, Ethyl Acetate, Chloroform and dichloromethane. However, if you require the use of a specialist solvent and/or matrix, please indicate this. Failure to specify a suitable solvent may result in delayed analysis.

Finnigan LCQ (ESI)

Most samples for the ESI instrument are introduced via syringe pump. They must be purified and dissolved in an appropriate carrier mixture. Carriers are normally semi-polar solvents such as MeOH or CH3CN, along with 0.1 - 1% volatile modifier. Organic carriers are often mixed 1:1 with deionized water, but the exact ratio of the organic / aqueous content can be varied, though it should NOT contain >80% water. Organic solvents should be HPLC grade. Typical modifiers utilized are Acetic Acid, Ammonium Acetate, Ammonium Formate, Ammonium Hydroxide, Triethylamine (TEA) and Trifluoroacetic acid (TFA). Non-volatile modifiers such as phosphates, borates, or similar salts should NOT be used as they cause spray problems. Acidic modifiers are typically used when obtaining positive ion spectra, and typically result in the formation of protonated species. Basic modifiers should be used when obtaining negative ion spectra. The maximum concentration of the sample of interest in the solvent mixture should be less than the 1ug/mL or 10-20micromolar) and the entire solution should be filtered prior to introduction to remove any insoluble material which would otherwise block the sample introduction line. 1-2 mL of solution is normally sufficient for analysis.

Shimadzu (GC-MS)

Samples should be prepared by dissolution in a volatile solvent at concentrations of ~0.5ug/ml.  Typically, non- or moderately polar volatile solvents are used such as methanol, acetone, pentane, hexane, etc. Do NOT use water. Samples should be prepared in a glass ½ DRAM screw-top vial. Several mL of solution is normally sufficient. It is important that you ensure your sample components are volatile at temperatures of less than 300 degC, otherwise they will remain on the column and contaminate it.

Kratos SEQ (MALDI)

The scientific literature contains many different methods of preparing samples for MALDI mass spectra and you will have to chose the method that is best fro your particular samples. However, in general, you need to mix deposit your sample on the target plate in a 1:10 sample:matrix ratio. Typical matrices used are α-cyano-4-hydroxycinnamic acid and sinapinnic acid. A quick method of MALDI sample preparation is to prepare a solution mixture containing 0.1mg/ml of sample and 1mg/mL of matrix. 0.5uL of the mixture is deposited on the target and allowed to dry. Several repeat depositions may often give improved spectra. Each user should have their own MALDI target which can be obtained from the Chemistry department stockroom.