Fused silica microcolumn LC‐MS and MS/MS using an aeronebulized interface

An aeronebulized interface has been developed for use with 0.15–0.25-mm i.d. slurry-packed fused silica columns. The interface was built in a removable probe that uses tha direct inlet on a triple quadrupole mass spectrometer for easy switching between LC, GC, or the solids probe. The probe is indirectly heated by the ion source, and premature evaporation of the mobile phase, acetonitrile/water, is prevented by controlled water cooling. A standard EI/CI ion source was used in the chemical ionization mode using methane to control the pressure in the source. Several variables that influence the performance of the interface were evaluated using various drugs as model compounds. Typically, 50,000 to 70,000 theoretical plates could be generated. The minimum detectable quantities were generally in the low picogram range. The best result was 3 pg using negative ion SIM, corresponding to a concentration of 8 × 10−8 M in the injected sample.