• Sample submission form (pdf)

General Information

Samples may be delivered in person to A048 ASTeCC Building, or may be left, along with a completed analysis request form, in the sample submission box outside the laboratory. All samples should be submitted in small wide-mouthed containers appropriate to the type of sample. For example, samples to be dissolved in organic solvents such as methylene chloride should be placed in glass vials (with teflon-lined screw cap), while polar compounds for MALDI or ESI to be dissolved in water or methanol (acetonitrile)-water may be placed in small plastic microcentrifuge tubes. In all cases, contaminating materials such as salts, buffers, plasticizers, parafilm, and PVC should be avoided. Sample containers should be clearly labeled with a unique identifier (such as submitters initials and laboratory notebook/page number) that corresponds to the sample ID on the sample submission form. Note that taping an unlabeled container to the sample submission form does not constitute sufficient labeling.

Generally, DMSO is not a suitable solvent for mass spectrometry.

Sample Requirements

GC-MS

For "high concentration" samples, provide ca. 0.5 – 1 mg or a solution of 1mg/mL. For "low concentration" (i.e. splitless injection) detection limits for full mass range are on the order of 1 ng/uL or less per component. Our standard GC column is a DB-5ms. Avoid polar solvents.

Direct Probe

Usually used for characterization of single compounds, and particularly useful for samples that will not pass through a GC. These materials must have (EI/CI) sufficient volatility and thermal stability to evaporate from the sample probe under vacuum. Sub-milligram, or microliter quantities of mg/mL solutions are sufficient for analysis, with the lower limit set by the amount required to physically manipulate the sample. For analysis of air- or moisture-sensitive compounds, please contact the Facility manager.

MALDI

Similar to direct probe. Matrix compounds for MALDI are typically UV-absorbing crystalline solids – often aromatic carboxylic acids. FAB is no longer a routine method, having been replaced by MALDI or ESI for most samples.

ESI

Typically performed using solutions in acetonitrile/water or methanol/water, concentrations on the order of 10uM (10 pmol/uL) generally give usable spectra.

Fees

The Facility operates on a fee-for-service basis for all sample submitters. Contact the Facility for current pricing. Users without current funding are encouraged to apply for a Service Center Pilot Grant through the Office of Research.

Acknowledgment of Services

Please acknowledge the Facility in your publications that include mass spectral data; e.g. "Mass spectral data were obtained at the University of Kentucky Mass Spectrometry Facility." We appreciate receiving reprints of such publications.

UKMSF can help with the selection of methods for analysis and data interpretation. If you have any questions, please ask us.

High Resolution Mass Spectral Data for Formula Confirmation

(in part, from JASMS Instructions to authors; see also JEOL: Elemental Composition Calculations)

Exact-mass data are used to confirm identities of synthetic and natural products (e.g. for publication of novel compounds). As with any procedure, an understanding of the data objectives and limitations of the analysis is important. When valence rules and candidate compositions encompassing C _0-50 H _3-74, O _0-4, and N _0-4 are considered at nominal parent m/z of 118, there are no candidate formulae within 34ppm of each other. When the ion is of m/z 750.4 and formulae are in the range C _0-100 H _25-110, O _0-15, and N _0-15, there are 626 candidate formulae within 5ppm. Thus, for a measurement at m/z 118, an error of 34ppm uniquely defines a particular formula, whereas at m/z 750, an error (and precision) of 0.018ppm (unattainable at the current state-of-the-art) would be required to eliminate all extraneous possibilities. This underscores the utility of applying additional information to the analytical problem – for example fragment ions, isotope ratios, derivative products, or other methods such as nmr – to solve the question of compound identity.

Exact Masses of Some Common Elements and Their Isotopes:

Disclaimer: These data are for informational use only. No guarantees are made for the accuracy of the data presented.

• Link to WebElements periodic table -- http://www.webelements.com/