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Determination of formaldehyde in aquatic products by micellar electrokinetic capillary chromatography with 2,4-dinitrophenylhydrazine derivatization

Xu L. N, Gai F. Y, Mu G. F, Gao Y., Liu C. J., Luan F.

Acta Chromatographica

2012

Vol. 24, no. 4

519--528

Formaldehyde in aquatic products was determined by micellar electrokinetic capillary chromatography (MEKC) after derivatization with 2,4-dinitrophenylhydrazine. Separation was carried out at 25 °C and 25 kV, using a fused silica capillary (75 µ internal diameter; 50.5 cm effective length) and an ultraviolet detector set at 360 nm. The optimal background electrolyte was 20 mM sodium tetraborate and 20 mM sodium dodecyl sulfate at pH 9.0 with 3 s hydrodynamic injection at 30 mbar. Electrophoretic analysis took approximately 6.5 min. The correlation coefficient of the calibration curve was 0.999 over the concentration range 2.0–100.0 mg L-1 and the LOD and LOQ values were 0.57 and 1.89 µg mL-1, respectively. The recoveries were from 83.7% to 97.2% with steam distillation as the sample pretreatment method.

TiO2 supported on SiO2 photocatalysts prepared using ultrasonic-assisted sol-gel method

Yang X. L., Liu C. J., Liu Y. Q., Li X., Xu Y. H.

Materials Science Poland

2011

Vol. 29, No. 3

189--194

Guangdong TiO2-SiO2 (TiO2 supported on SiO2) photocatalysts were prepared using an ultrasonic-assisted sol-gel method. These photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and photoluminescence spectra (PL). Their photocatalytic activities were investigated by the method of methyl orange oxidation. It was found that the photocatalytic activity of TiO2-SiO2 was optimal when the molar ratio of hexadecyl trimethyl ammonium bromide to titanium butoxide was 1:10. The average crystallite size of TiO2-SiO2 was smaller than that prepared by the stirring method. Furthermore, for pure anatase phase samples, it was shown that the lower the photoluminescence intensity, the higher the photocatalytic activity.

Progressive failure modelling of transverse cracking in cross-ply laminates with double-edge-semicircular notches

Liu C. J., Nijhof A. H. J., Ernst L. J., Marissen R.

Engineering Transactions

2002

Vol.50, iss.4

287-303

A local-global progressive failure finite element (FEM) model was created in combination with the maximum strain criterion on an individual layer scale to study the formation of transverse cracks in cross-ply laminates with double-edge-semicircular notches. It is assumed that the laminate is made of homogeneous orthotropic layers before the occurrence of the matrix failure. Then, the average reduced layer stiffness as a function of the applied load is separated from the reduced laminate stiffness. Additionally, a maximum strain strength criterion is applied on a very local scale of a single layer to induce the local matrix failure. The initiation, propagation and multiplication of the transverse cracks starting from the notch are predicted in this way. The influences of the laminar thickness and the notch-width aspect ratios were also studied. Furthermore, the stress distribution and redistribution caused by the initiation and propagation of the transverse cracks were calculated. In addition to the stress concentration caused by the circular notch, an extra stress concentration in the 0° layers is induced by the transverse cracks in the 90° layers. This stress redistribution will in turn initiate more local failures in the 0° layers or at the interface between the longitudinal and transverse layers. The simulated results show a good agreement with experimental observations.