NEW IONIZATION STRATEGIES IN PARTICLE-BEAM LIQUID-CHROMATOGRAPHY MASS-SPECTROMETRY BASED ON THE PRINCIPLE OF SURFACE-IONIZATION

The potential of surface ionization (SI) as an ionization technique in particle-beam (PB) LC-MS was investigated. Using a laboratory-built s urface ionization probe with a platinum tip, several ionization phenom ena were observed, i.e., thermal surface ionization (TSI), hypertherma l surface ionization (HSI) and alkali metal addition. Although TSI exp eriments suggest that kinetic energy is added to the molecules in the PB, the increase in kinetic energy is still insufficient to induce eff icient HSI. TSI in combination with LC-PB-MS leads to highly improved detection limits of tetraalkylammonium salts. The use of the SI probe as a thermionic emitter of alkali metal ions for the formation of alka li metal adduct ions leads to sensitive detection of crown ethers and to a considerably extended upper mass limit for polyethylene glycol sa mples in comparison with standard ammonia chemical ionization conditio ns.