LC-MS

Our major current interest is in developing LC-MS as a tool for the John Innes Centre. We have an Agilent (Hewlett-Packard) 1100 HPLC system with mass spectroscopic detector. (pictured right). This system can carry out conventional hplc analysis and includes a diode array detector. It is therefore possible to recreate an hplc method that is already in use elsewhere, in order to extend it by collecting mass spectra throughout the hplc run. The mass detector can use electrospray (AP-ESI) or atmospheric pressure chemical ionisation (APCI), and has a range of 50 to 2000 m/z.

LC-MS combines the good features of HPLC with the good features of mass spectroscopy, and overcomes the weaknesses of each. The weakness of hplc is that it is hard to be certain a particular peak contains only one chemical, and if you see a new peak, how on earth do you begin to assess what it might be? Actually the situation is worse than this: in most practical applications you can expect that some of your hplc peaks are NOT pure. There are good statistical reasons why. Mass spectroscopy is also not perfect: it measures mass, so it is weak on isomers.

We have just bought an ion-trap LC-MS system from Thermo-Fischer (Thermo-Finnigan), an LCQ DecaXP. It is now installed and running. It has a very sensitive mass detector, and provides all the facilities of the Agilent system, but also selection and fragmentation of ions. It is very suitable for identification of unknowns; we're still in the process of learning what this versatile instrument can do.

This web-site also contains information about:

• How LC-MS works
• Interpretation of mass spec data