A service of the School of Chemistry, Building 23, Monash University, Clayton, Victoria 3800, Australia.
Phillip Holt (03) 9905 9485. service/at/lcmsunit/dot/info
LCMS Unit News
June 2008, newly purchased HILIC column is on trial. These columns are useful for retaining very polar compounds (amino acids for example) that would not stick in reversed phase. A number of students have projects involving polar compounds and this column should solve LC/MS issues. For reference see this Phenomenex brochure.
The services offered by the LC/MS unit
What we can do for you.
Screen: Screen synthesis product mixtures to determine if the target product is present and how much.
Quantify: Quantify compounds relative to a standard.
Trace analysis: Environmental samples, or biological extracts can have trace quantity (ppb) compounds evaluated. See drug analysis on the examples of work done page.
Purification: Purification of compounds (up to 100mg) using reversed phase chromatography and mass triggered fraction collection. This means you only collect the desired product, and have less fractions to analyse later.
How to submit samples
For Monash University customers, fill in, print or electronically submit the submission form with your samples to lab G15, North wing, Building 23, Senior Chemistry. (It is marked combinatorial lab on the door). Customers also need to be aware of sample solubility considerations.
External customers can ring or email (see contact at top) to arrange sample and associated information delivery.
Picking up results
I'll ring you when they are ready. You can come to the lab to pick up and discuss the print outs. I can also email spectra and some chromatograms inside word documents. If required I can email spectra as text lists so you can import them into spreadsheets.
All data aquired and operating conditions of the instrument are archived onto CD-R. So if when you come to write your thesis/paper and you have no details of how work was carried out years before, come and see me and we can retrieve the information.
Costs
| Department | per MS | per LC/MS | per day |
|---|---|---|---|
| Chemistry | 25.00 | 40.00 | 250.00 |
| Other Monash | 35.00 | 60.00 | 350.00 |
| Outside Monash | 50.00 | 80.00 | 600.00 |
Purifications are charged at the day rate and can sometimes take longer than one day.
Training
Training for regular LC/MS users is available. Instruction can be organised when you arrange to drop off a batch of samples. You will be required to spend a couple of hours in the lab and be guided through sample preparation, system control and runnning.
Operational days
My normal weekly scheduled days are Tuesday, Wednesday and Friday.
Mondays and Thursdays are for other trained users to use the instrument.
Why use LC/MS ?
LC/MS is the Combination of two analytical techniques, liquid chromatography and mass spectrometry. You can obtain spectra and molecular mass identification for each peak eluted from the chromatography column. Straigtforward mass spectra of directly infused samples won't distinguish between, buffer components, contaminants and other components of a sample mixture.
By doing even simple LC separation first you can clean up the sample a little and remove interfering peaks from the spectrum of the required entity. The simplest form of this is desalting, where the buffer salts elute rapidly but the sample is slightly retained by a column. Interfering salts like phosphates can be diverted from the Mass Spectrometer and the sample switched back to enter the MS as it elutes from the column.
Distiguishing between in source fragmentation or sample chemical degradation is also much easier with LC/MS.
The Chromatography
We use Reversed phase C8, C18 or polymer columns. The solvents are water with methanol, isopropanol or acetonitrile. 0.1% formic acid is often added to the solvents to assist chromatography and ionisation. Samples are loaded with low levels of organic solvent and eluted with increasing percentages of organic in a gradient. See also the detailed information.
The Mass Spectrometry
The Micromass ZMD has an orthogonal (sample cone is to the side of the vapour stream) atmospheric pressure ionisation source. Sample entry to the source is via syringe pump or for LC/MS via a splitter, which reduces the flow from 1 mL/min to about 100uL/min.
ESI, electrospray ionization: The solvent with the sample is aspirated with hot nitrogen gas as it emerges through a high voltage orifice. Charge accumulates on the sample molecules as the solvent evaporates, and the resulting ions are skimmed off through the sample cone before being detected.
APcI, atmospheric pressure chemical ionization: similar to the above but the high voltage is applied near the cone to create a plasma of solvent ions that chemically transfer charge to the sample molecules. This is usually used when ESI fails to generate an ion.