In the paper, a novel carbon nanofiber paste electrode (CFPE) was fabricated and firstly used as a sensitive amperometric detector in capillary electrophoresis (CE) for the simultaneous determination of three β-blockers: sotalol, alprenolol and atenolol. Compared with the bare carbon paste electrode, the CFPE exhibited enhanced oxidation peak current responses to the analytes due to its excellent electrocatalytic activities, high conductivity and large effective surface area. Subsequently, effects of several important factors such as detection potential, pH and concentration of running buffer, separation voltage and injection time on the analysis were investigated. Under the optimum conditions, the three analytes could be separated and detected in a phosphate buffer (pH 8.5) within 11 min. The linear ranges were 0.1–100 μM for sotalol, 0.2–150 μM for alprenolol and 0.1–50 μM for atenolol and the detection limits were as low as 10−8 M magnitude (S/N=3). Moreover, the CFPE exhibited good repeatability and long-time stability. The proposed method was applied to determine the three β-blockers in spiked urine samples with satisfactory assay results. The good performance, low cost and straightforward preparation method of CFPE demonstrated that it could be used as a detector for CE–amperometric detection system for drug analysis.Highlights► Carbon nanofibers were produced by electrospinning technique. ► A carbon nanofiber paste electrode was fabricated by this electrospun material. ► This electrode was firstly used as a sensitive amperometric detector in CE. ► Proposed method was applied to determine three β-blockers in human urine.

The utility of novel latex nanoparticles as pseudostationary phases for electrokinetic chromatography with UV and mass spectrometric detection is demonstrated. The nanoparticles are synthesized using ab initio RAFT (reversible addition−fragmentation chain transfer) in emulsion polymerization, which yields small (63 nm) particles with a narrow size distribution, a hydrophobic core, and an ionic shell. The nanoparticles are shown to provide efficient and selective separations, with retention and separation selectivity dominated by hydrophobic interactions. The nanoparticles are highly retentive, such that they are effective at relatively low concentrations. Addition of the nanoparticles to the background electrolyte at these concentrations has a minor effect on the noise with UV detection, no measurable effect on the separation current, and minor effects on analyte ionization efficiency during electrospray ionization. The nanoparticles do not cause fouling or degradation of the electrospray−mass spectrometer interface even after several weeks of use. The combination of online sample preconcentration via sweeping and selective mass spectrometric detection yields low detection limits (10−16 ppb), particularly for more hydrophobic compounds.