Simultaneous determination of phytohormones containing carboxyl in crude extracts of fruit samples based on chemical derivatization by capillary electrophoresis with laser-induced fluorescence detection.
ABSTRACT An efficient and sensitive capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) method has been developed for the simultaneous determination of phytohormones containing carboxyl group, including gibberellic acid, indole-3-acetic acid, abscisic acid, jasmonic acid, indole butyric acid, 1-naphthalene acetic acid and 2,4-dichloro-phenoxy acetic acid, based on the chemical derivatization with 6-oxy-(acetypiperazine) fluorescein. Using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide as the condensing reagent, the derivatization reaction completed at 60°C in 60 min and the derivatization limits could reach 20 nmol L(-1). The formed derivatives of seven phytohormones have been separated and quantified within 20 min. The linearity was found in the range of 0.01-1 μmol L(-1) and the limits of detection were 1.6-6.7 nmol L(-1) (S/N=3). The proposed method has been applied to analyze the crude extract of 0.5 g banana samples directly without further purification and the recoveries varying from 90.7 to 106.1%.
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ABSTRACT: The minimum fluidization velocity of beds has been determined experimentally in beds of 0.089 m and 0.29 m diameters, respectively. The particles studied had sizes ranging from 100 lm to 1 mm in diameter, and densities from 1128 to 11400 kg/m 3 . Three distributors were used in the experimental scheme, each perforated by holes of 0.8 mm in diameter but with varying hole densities, as well as a porous plate. It was found that the minimum fluidization velocity was affected by both the diameter and distributor used. The effect of vertical tubular inserts on the minimum fluidization velocity was investigated in the 0.29 m diameter bed. The experimental data in the large bed, using four distributors, were parameterized within experimental error.Chemical Engineering & Technology - CHEM ENG TECHNOL. 01/2001; 24(2).
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ABSTRACT: In the present study, a new correlation for the determination of the minimum fluidization velocity in 2D fluidized beds was developed. The proposed correlation was based on the experimental results obtained in 2D fluidized beds with different particle sizes, bed thicknesses and bed heights. Thus, the proposed correlation depends only on the nondimensional variable t/dp, where t is the bed thickness and dp is the particle size. The proposed correlation was compared with other experimental results that can be found in the literature, and two different trends were observed. Namely, one set of experimental results was in accordance with the proposed correlation, while the other set deviated from the theoretical results. In particular, the minimum fluidization velocities of the experimental results were greater than the predicted values of the proposed correlation. In view of the differences in the experimental conditions, the observed discrepancies may be attributed to the effects of electrostatic charge and particle shape. In addition, the experimental fluidization–defluidization curves were compared to the theoretical results of Jackson's model, and the parameters were fitted to the experimental data. However, Jackson's model is based on a 1D bed; thus, general parameters could not be obtained for a bed with a fixed particle size and thickness due to the two dimensional voidage distribution in the bed and bed cohesion effects, which are a result of electrostatic forces and are not considered in Jackson's model.Powder Technology - POWDER TECHNOL. 01/2011; 207(1):145-153.
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ABSTRACT: Detailed local flow structures are investigated in bubbling and turbulent fluidized bed with FCC particles. The operating conditions ranges from 0.06 to 1.4 m/s. Extensive experiments are carried out using a newly developed optical fiber probe system, which can measure the solids concentration and velocity at multi-points. The results reveal that with increasing Ug, local solids concentrations go through three evolution stages, reflecting a gradual regime transition process. Under all operating conditions, upflowing and descending particles co-exist at all measuring locations. The upflowing particle velocity is strong function of both superficial gas velocity and spatial position. However, the descending particle velocity mainly depends on superficial gas velocity. The bed radial symmetry and the effects of static bed height on the local flow structures are also investigated.Graphical abstractInstantaneous particle concentration and velocity were measured simultaneously to detail the local flow structures during the transition to turbulent fluidization. With increasing gas velocity, the local transition is found to be a gradual process, starting from the top of the bed. With increasing solids inventory, the local transition velocity is a function of the distance from the bed surface.Powder Technology. 01/2008; 180(3):339-349.