Hi there,
I'm going to have an Interview for a job at Agilent soon.
Therefor I need to know again how thermospray and electrospray works. Unfortunately I have lent away my documentation. So I would be glad if some of you could help.
Additionally it would be nice if you could tell me witch techinque is used in Agilent LC-MS systems.
Thanks.
CU, Dominik

Thermospray is an older technique, and no longer in common use. I'm young enough to have never used it in the lab, so everything I learned about it was from books, much of which I've since forgotten. Fairly high concentrations of ammonium acetate are added post-column, then this mix is sprayed into a heated chamber at partial vacuum. Somehow, a proton transfer happens, producing even-electron (M+H)+ ions. I don't remember how the mechanism is explained, or if other types of ions can form.

In electrospray, LC eluent is sprayed into a chamber at atmospheric pressure, through a needle which is held at a high voltage relative to its surroundings. At lower LC flow rates, the high voltage causes the liquid to leave the needle in a spray of fine droplets. At higher LC flow rates, the spray becomes unstable, so a concentric gas flow is used to assist the spray. The droplets have a net charge from being sprayed through the needle at high voltage (to put it simply). As the droplets evaporate and are reduced to smaller volume, the repulsive force of the charge exceeds the surface tension of the droplet, and the droplet explodes into smaller droplets. This cycle repeats itself. There is some controversy as to what happens to actually produce gas phase ions. One theory is that when the droplets reach a certain (small) size, the coulombic explosion is no longer favorable, and instead ions desorb from the droplet surface into the gas phase. Electrospray works well for compounds with polar functional groups, and particularly well for compounds with acidic or basic sites. Ions formed are usually protonated or deprotonated, but other types of ions can be formed as well.

Don't forget about APCI....