•To the best of our knowledge, the maximum numbers of BAs were simultaneous separated by CE in this work.•Different structures (aliphatic, aromatic and heterocyclic) of BAs could be detected by UV in one analytical process.•The formation of negative and positive peaks was theoretically predicted.•Thirteen BAs were detected without any preconcentration and derivatization, and the LOD and resolution were studied in detail.Biogenic amines (BAs) play significant roles in indicating human health or food quality. Aiming to simultaneously determine three structures (aliphatic, aromatic and heterocyclic) of underivatized BAs, we explored a simple and rapid capillary electrophoresis (CE) method only coupled with conventional UV detector for the separation of thirteen key BAs. The strategy is to choose a UV absorbing probe as co-ion in the background electrolyte (BGE), and different BAs could be characterized by positive or negative peaks according to the fact that their UV absorptivity coefficients at a certain wavelength are better or worse than that of the UV absorbing probe. After the detailed investigation of critical parameters as pH, the concentration of Imidazole (Im) and α-cyclodextrin (α-CD), the optimized BGE consisted of 12.0 mmol/L Im as the UV probe and 10.0 mmol/L α-CD as the additive (at pH 4.50 adjusted with acetic acid). With such condition, the targets of thirteen BAs were baseline separated in 9.0 min and appeared at nine positive peaks and four negative peaks at 200 nm. The obtained LODs and LOQs (S/N = 3 or 10) were in the range of 0.36–3.67 and 1.2–12.2 μmol/L, respectively. The interday RSDs of migration time and peak area were less than 0.7% and 4.7% (n = 6), respectively. To the best of our knowledge, this is the first report on separating diverse structures of BAs by using Im as UV absorbing probe. The thirteen BAs were simultaneously detected by direct and indirect UV detection in a CE process. To verify the applicability, this method was used to analyze BAs in commercial beer samples. The recoveries of all BAs except carnosine (not identified by the interference) ranged from 70.4 to 119.6%, and four aliphatic and aromatic amines were satisfactorily identified and quantified.

Pressure-assisted electrokinetic injection (PAEKI) was applied for negatively charged verteporfin (VER) overloading and inline stacking, which targeted highly sensitive enantioseparation by CE. The essential step of PAEKI is a constant pressure used to counterbalance the electroosmotic flow (EOF), consequently, the large amount of analyte could be permitted into capillary and concentrated at the motionless boundary of the sample zone and background electrolyte (BGE). Aiming to know the balance, the velocity of the whole BGE in capillary by the impetus of pressure (0.2–2.0 psi), and the velocity of EOF depending on the length of sample plug and voltage (5.0–20 kV) was investigated, respectively. The velocity of bulk flow in capillary has good linearity with the pressure or applied voltage. Through the pattern of EOF marked peak and analyte peaks (dissolved in pure water), the constant pressure (0.8 psi) vs. the added voltage (−10.3 kV) during PAEKI was confirmed to immobilize the bulk flow of BGE, thus the sample injection time could sustain 2.0 min without compromising separation efficiency. The obtained LOD (S/N = 3) of each isomer at UV detection (428 nm) was around 10.3 μg/L, which was improved to 116 and 39-fold in comparison with normal hydrodynamic injection (HDI) and electrokinetic injection (EKI). The LOD is far below the reported value with LIF detection of VER. The RSD (n = 5) of migration time and peak area was, respectively, around 3.5% and 5.7% for the proposed PAEKI method. Finally, PAEKI was used for the detection of VER in artificial urine to investigate the matrix interference.