Sample stacking (SS) is actually a technique to concentrate solutes by some special principles and/or techniques, highly useful for the introduction of samples in capillary electrophoresis (CE) and/or mass spectrometry (MS) of diluted solutes with especially a salted background.Although several SS approaches have been available such as solid phase extraction (SPE), electric field amplification (EFA), sweeping, transient isotachophoresis (t-ITP) and so forth, few can directly be hyphenated to either CE or MS.To explore some other techniques that may be better than the existed is rhus necessary and has been conducted in this laboratory by mainly using CE as a testing model.A novel method has hence been obtained called acid-base titration anti-salt stacking (ATAS) and shown applicable to direct CE of biological fluids.