An efficient liquid chromatography--mass spectrometry interface for the generation of electron ionization spectra

The use of a new LC-MS interface (cap-EI), part of a Waters Integrity system, capable of generating EI spectra at micro flow rates is presented. The cap-EI interface relies on the production of a fine aerosol by means of a nebulizer and supported by a nitrogen jet. Sensitivity, response linearity, reproducibility, and LC compatibility of the interface were thoroughly examined using testosterone, caffeine, a mixture of antiinflammatory drugs, and 3,4-dihydroxybenzoic acid as test compounds. The interface is fully compatible with LC requirements such as high-water- and/or -buffer-content mobile phases. Reproducibility, high sensitivity in scan mode, as well, to produce library-searchable EI spectra, 2 orders of magnitude linearity, together with an intrinsic simplicity of the entire system are the key features of cap-EI interface.