Sakchai Satienperakul

Determination of sulfite by pervaporation-flow injection with amperometric detection using copper hexacyanoferrate-carbon nanotube modified carbon paste electrode

A pervaporation-flow injection (PFI) method was developed for the determination of sulfite in selected food samples using a copper hexacyanoferrate-carbon nanotube (CuHCF-CNT)-modified carbon paste electrode. The electrochemical behavior of the modified electrode was observed using cyclic voltammetry in comparison to a CuHCF-modified carbon paste electrode and a bare carbon paste electrode at a scan rate of 100mVs(-1) in 0.10M KNO(3). The bare carbon paste electrode gave the lowest response to sulfite, while the presence of CuHCF made the detection of sulfite possible through electrocatalytic oxidation by the hexacyanoferrate in the modified electrodes. The presence of CNT in the CuHCF-CNT-modified sensor gave the most remarkable current for the detection of sulfite and was then used as a working electrode in the amperometric flow-through cell in the pervaporation flow injection system. The PFI method involves the injection of a standard or sample sulfite solution into a sulfuric acid donor stream to generate sulfur dioxide gas and evaporate into the headspace of the pervaporation unit. The sulfur dioxide diffuses through the PTFE hydrophobic membrane into a potassium nitrate acceptor stream and reverts to the sulfite form, which, subsequently, is transported to the electrochemical flow cell where it is analyzed amperometrically at a CuHCF-CNT-modified electrode at +0.55V (vs. Ag/AgCl). The detection was determined to be applicable in the sulfite concentration range of 0.5-50mgL(-1). The sensitivity, detection limit, and sample throughput were determined to be 2.105nALmg(-1), 0.40mgL(-1) and 11h(-1), respectively. The developed PFI method, coupled with the CuHCF-CNT-modified carbon paste electrode, was applied in the determination of sulfite content in sulfite-containing food products. The results agreed well with those obtained through the officially recommended differential pulse polarographic method.

Characterization of bismuth vanadate (BiVO4) nanoparticle prepared by solvothermal method

ABSTRACT Bismuth vanadate (BiVO4) nanoparticle was prepared by solvothermal method. The starting precursors were used as bismuth nitrate pentahydrate (Bi(NO3)3•5H2O), ammonium metavanadate (NH4VO3) and absolute ethanol (C2H5OH). Solution I: Bi(NO3)3•5H2O was dissolved in 2.0 M nitric acid (HNO3) and absolute ethanol (C2H5OH). Solution II: NH4VO3 was dissolved in 2.0 M ammonium hydroxide (NH4OH) and absolute ethanol (C2H5OH). The mixed solutions were stirred for 5 min and left into Teflon-lined stainless steel autoclave treatment at 200°C for 3 and 5 h. The yellow final solution was filtered and dried at 100°C for 24 h. All BiVO4 nanoparticle samples were characterized by X-ray diffractometer (XRD), field emission scanning electron microscope (FESEM), energy dispersive X-ray spectrometer (EDXS) and Fourier transform infrared spectrometer (FTIR).

BiVO 4 Powder Synthesized via the Solvothermal Method

Bismuth vanadate (BiVO4) powder was synthesized via the solvothermal method at 100200 °C for 26h by using acetic acid as solvent without calcination steps. The phase transition of BiVO4 powder was studied by Xray diffraction (XRD). The morphology and chemical composition of BiVO4 powder were investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The functional groups of BiVO4 powder was identified by Fourier transform infrared spectroscopy (FTIR).

Sequential injection analysis for the determination of fluoroquinolone antibacterial drug residues by using eosin Y as complexing agent

A sequential injection analysis (SIA) method was developed for the rapid and sensitive determination of fluoroquinolone residues, including norfloxacin, ciprofloxacin and enrofloxacin, in fish samples. The method is based on the reaction between fluoroquinolone drug and eosin Y in Britton-Robinson buffer (pH 2.0), forming pink colored complexs with maximum absorptions at 522, 525 and 527 nm for norfloxacin, ciprofloxacin and enrofloxacin, respectively. Linearity ranges were found to be 0.05-10.0 mg L-1 (r2 = 0.9996), 0.1-10.0 mg L-1 (r2 = 0.9995) and 0.05-10.0 mg L-1 (r2 = 0.9997) for norfloxacin, ciprofloxacin and enrofloxacin, respectively. The detection limit was found to be in the range of 0.013-0.019 mg L-1. The method was tested and validated for various parameters according to main guidelines. The proposed SIA method was successfully applied for the determination of fluoroquinolone drug residues in fish samples with the sampling rate of 47 h-1. The results demonstrated that the method is accurate, precise and reproducible, while being simple, rapid, economical and less time consuming. It can be suitably applied for the estimation of fluoroquinolone drug residues in routine quality control.

Characterization of Diatomite, Leonardite and Pumice

This research studies compositions of diatomite, leonardite and pumice for utilization appropriate to the properties of materials. Chemical compositions of these materials were characterized by X–ray fluorescence spectrometry (XRF) and energy dispersive X–ray spectrometry (EDXS). The silica was major component of these materials. The morphology was investigated by scanning electron microscopy (SEM). Diatomite was cylindrical in shape, leonardite was sheet or flake in shape and pumicewas prismatic in shape. The structure was studied by X–ray diffraction (XRD). It was found that the mineral composition of diatomite, leonardite and pumice showed cristobalite low, quartz and anorthite, respectively. The functional groups were identified by Fourier transform infraredspectrometry (FTIR). The functional group of siloxane was obtained and dominated vibration in these materials. And the vibration of carboxylic, alcoholic and carbonyl groups were obtained in leonardite.

Microwave-Assisted Synthesis and Characterization of Zinc Oxide Micropowder

Zinc oxide micropowder was synthesized by a microwave-assisted method. Zinc nitrate and ammonium hydroxide were used as the starting precursors with the mole ratio of 1:1. The white precipitated powder was formed after adding ammonium hydroxide until the pH of final solution was 9 and treated with the microwave radiation power at 1000 Watt for 2-6 min. The phase of zinc oxide micropowder was examined by X-ray diffraction (XRD). A single phase of hexagonal structure was obtained. The morphology and chemical composition of zinc oxide micropowder were investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The particle was plate-like in shape with the range of particle size of 0.1-0.5 µm. The elemental composition of zinc oxide showed the characteristic X-ray energy value as follows: zinc of Lα = 1.012 keV, Kα = 8.630 keV and Kβ = 9.570 keV and oxygen of Kα = 0.525 keV, respectively.