Comparison of the performances of a particle beam LC-MS interface obtained by standard and modified skimmers

Stainless steel skimmers were made in the technical workshop of our Department and mounted on a commercial Particle Beam interface. Their performances were compared with the standard ones, using three different compounds: benzidine, caffeine and perylene. Library searchable EI spectra were collected with a high quality match and remarkable improvements in the sensitivity were obtained (detection limit of 20 pg for perylene and benzidine), probably due to their better tightness that allowed to widen the skimmer orifices without significantly compromising the ion source vacuum. Also calibration curves showed a good linearity, in the concentration range 10-200 ng/ml.