Chu Chu,Linmin Lian,Caijing Liu,Jing Li,Hui Mao,Luyi Jiang,Jizhong Yan
Electrokinetic supercharging, a convenient and powerful online preconcentration technique in capillary electrophoresis, was introduced and evaluated for the determination of two alkaloids, berberine and jatrorrhizine, in mice fecal samples for the first time. The method depended on using a bare fused silica capillary (50 cm × 50 μm i.d.) and applying the voltage of 25 kV with UV detection at 205 nm. Parameters that affect the separation and preconcentration efficiency have been optimized. The optimum conditions used were as follows: background electrolyte consisting of 40mM sodium dihydrogenphosphate containing 30% methanol (v/v); hydrodynamic injection of 20mM KCl (50 mbar × 150 s) as the leading electrolyte; electrokinetic injection of the sample (+15 kV, 120 s) followed by the hydrodynamic injection of 30mM dodecyl trimethyl ammonium chloride (50 mbar × 12 s) as the terminating electrolyte. The results showed that the detection sensitivity of berberine and jatrorrhizine was, respectively, improved up 2740- and 2928-fold compared with normal injection, providing limits of detection lower than 3 ng/mL with good repeatability in areas (relative standard deviation < 3%). In summary, the developed method proved its ability in analyzing trace alkaloids in complicated biological samples.
The analysis of anionic compounds via the sensitive FLM-EKS method remains challenging due to their inverse migration behaviors to EOF in the capillary. A highly sensitive ionic liquid coating-based online preconcentration methodology via electrokinetic supercharging (EKS) coupled to a free liquid membrane (FLM) was first proposed and successfully used to determine vanillic acid (VA), salvianic acid A sodium (SAAS) and ferulic acid (FA) in a complex sample matrix. EKS was recognized as the first step preconcentration, and its separation conditions were optimized. Then, the second preconcentration step, namely FLM, which was performed by simple injection of a short water-immiscible solvent plug as a membrane interface prior to electrokinetic injection (EKI) of the sample, was further investigated to increase the stacking efficiency. The influences of multifarious parameters on FLM-EKS performance were examined, and the optimal FLM-EKS conditions were identified: a buffer electrolyte of 20 mM Tris-HOAc (pH = 6) with 5% (v/v) methanol; hydrodynamic injection (HI) of a leading electrolyte (50 mM NH 4 Cl, 30 s, 0.5 psi) followed by the HI of 2-nitrophenyl octyl ether (NPOE) as the FLM (5 s, 0.5 psi); EKI of the sample (120 s, −10 kV) and there with the HI of terminator (20 mM N-cyclohexyltaurine, CHES, 40 s, 0.5 psi). The newly developed method yielded analytes with 2006–2862-fold enhancement compared to the normal injection, there by producing detection limits of 1.5–5.0 ng mL −1 with satisfactory repeatability below 2.92%, which provides 1.5–2.0 times higher stacking efficiency than that obtained by EKS only. Feasibility in real sample analysis was demonstrated by using Naoxintong capsules and rat feces, which suggests that the presented methodology has a high potential for the reliable and sensitive determination of trace anionic components in complex sample matrices.
危险品化学品经营许可证（带存储）