Biomedical subjects

Xueming Chen

Publications and source records attributed to Xueming Chen.

4 recordsLinked to original sources

PubMed2006

In-capillary solid-phase extraction-capillary electrophoresis for the determination of chlorophenols in water.

A novel CE method combined with SPE in a single capillary was developed for analysis of chlorophenols in water. A frit of 0.5 mm was first made by a sol-gel method, followed by packing a SPE sorbent in the inlet end of the capillary. Two phenol derivatives, 2,4-dichlorophenol and 2,4,5-trichlorophenol, were used as the model compounds. By loading sample solutions into the capillary, the two chlorophenols were extracted into the sorbent. They were desorbed by injecting only about 4 nL of methanol. Finally, the analytes were separated by conventional CE. The technique provided a concentration enhancement factor of over 4000-fold for both chlorophenols. The detection limits (S/N = 3) of 2,4-dichlorophenol and 2,4,5-trichlorophenol were determined to be 0.1 ng/mL and 0.07 ng/mL, respectively. For replicate analyses of 5 ng/mL of 2,4-dichlorophenol, within-day and between-day RSDs of migration time, peak height and peak area were in the range of 1.8-2.0%, 4.0-4.4% and 4.1-4.6%, respectively. The method shows wide linear range, acceptable reproducibility and excellent sensitivity, and it was applied to the analyses of spiked river water samples. The capillary packed with the SPE sorbents can be used for more than 400 runs without performance deterioration.

Chlorophenols↗

PubMed2003

High-performance Ti/BDD electrodes for pollutant oxidation.

Deposition of stable boron-doped diamond (BDD) films on Ti substrates is believed to be very difficult. In the present study, the stability of Ti/BDD electrodes has been significantly improved by using an organic additive, CH2(OCH3)2. The improved electrodes had service lives of 175-264 h under accelerated life test conditions, which are 2.3-3.0 times longer than the service lives of electrodes prepared with the conventional H2 + CH4 mixture. Raman spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM) examinations demonstrated thatthe films had well-defined diamond features. The current efficiency (CE) obtained on Ti/BDD was 46.9-78.5% in oxidizing acetic acid, maleic acid, phenol, and dyes, which is 1.6-4.3-fold higher than that obtained on the typical Ti/ Sb2O5-SnO2 electrode. We used a Ti/BDD electrode prepared with H2 + CH4 + CH2(OCH3)2 for over 300 h; its activity remained superior. The successful development of stable and active Ti/BDD electrodes significantly increases the feasibility of industrial applications of anodic oxidation in wastewater treatment.

Boron↗

PubMed2002

Novel electrode system for electroflotation of wastewater.

Electroflotation (EF) is an attractive method in wastewater treatment. The heart of EF is the dimensionally stable oxygen evolution anode that is usually expensive. In this paper, we present a stable anode by coating IrOx-Sb2O5-SnO2 onto titanium. Accelerated life test showed that the electrochemical stability of the Ti/IrOx-Sb2O5-SnO2 anode containing only 2.5 mol % of IrOx nominally in the activated coating was even higher than that of the conventional Ti/IrOx anode. Its service life for electroflotation application is predicted to be about 20 yr. Voltammetric investigation demonstrated that the Ti/IrOx-Sb2O5-SnO2 anode could provide fast electron transfer. Moreover, the present anode was designed to be fork-like and arranged interlockingly at the same level as the cathode with a similar shape. Such an innovation in electrode configuration and arrangement allows bubbles produced at both electrodes to be dispersed into wastewater flow quickly and, therefore, enhances the effective contact between bubbles and particles, favorable for high flotation efficiency. In addition, the novel electrode system reduces the interelectrode gap to 2 mm, a spacing that is technically difficult for a conventional electrode system. This small gap results in a significant energy saving. Easy maintenance is found to be another advantage of this novel electrode system.

Coloring Agents↗

PubMed2002

[Investigation on the frequency specificity of the auditory brainstem response to tone burst in three different conditions].

OBJECTIVE: This study investigated and compared the effects of tone burst in three different conditions (linear-gated tone burst, linear-gated tone burst in broadband noise masking and Blackman-gated tone burst) on the frequency specificity of ABR. METHOD: The latencies of ABR wave V were recorded respectively on sixteen normal-hearing adults using 1, 2 and 4 kHz tone bursts in three types of stimuli at different intensities. RESULT & CONCLUSION: 1. Three types of tone bursts may evoke similar frequency-specific ABR when stimulus intensity was lower than 70 dB nHL for 1 kHz and any intensity for 2, 4 kHz. At the high-intensity(> or = 70 dB nHL) for lower frequency (1 kHz), however, linear-gated tone burst had poor frequency specificity due to the increased effects of spectral splatter. To improve the frequency specificity, linear-gated tone burst should be mixed with masking noise or using Blackman-gated tone burst directly. 2. Both linear-gated tone burst in broadband noise masking and Blackman-gated tone burst of 1 kHz, 2 kHz and 4 kHz at any intensity can produce frequency-specific ABR, but response amplitudes were smaller for the broadband noise masking condition than for the Blackman-gated one. Therefore the Blackman-gated tone burst is prefered.

Acoustic Stimulation↗