The CESI 8000 High Performance Separation-ESI Module with OptiMS technology consists of the first commercial CESI sprayer combined with new capillary electrophoresis instrumentation specifically designed for mass spectrometry (MS). OptiMS Technology combines an intrinsically low flow CE separation with electrospray ionization (ESI) within a capillary in which the electrophoretic separation and the ESI are integrated in a single dynamic process. This new process is referred to as CESI, as the CE separation and ESI are combined into one. This gives researchers a robust, high-sensitivity interface of capillary electrophoresis (CE) with mass spectrometry (MS) while providing a broad range of analyte coverage that is complementary to LC-MS and GC-MS. CE works at its best with polar and charged analytes such as drugs, drug metabolites, organic acids, amino acids, low molecular weight amines, peptides, intact proteins, protein complexes, nucleic acids and nucleosides. Molecules often missed or altogether undetectable by technologies, like reversed phase LC-MS, now become visible.