Ultrasonic field separators

General sonochemical studies of both chromium and manganese have been reported separately due to strong oxidising nature of these ions. However, comparative strength of their oxidising powers, in an ultrasonic field, is of some technical... 

Procedure Effects of ultrasound on the following reaction can be seen clearly, when the reactions are carried out both in the ultrasonic field as well as under normal conditions. The yield in most of the reactions increased due to cavitation and mass flow but a decrease could also be sometimes expected due to volatility of one of the reagents. The average increase/decrease in the yield of product, reported here, is an average of two sets of reactions carried out separately under sonicated and mechanical stirring conditions. 

An early comparison of US and dielectrophoretic separations revealed the lower size limits of microparticles (0.65 pm for single particles and 14 nm for particle ensembles) manipulated by dielectrophoresis to be similar to those for ultrasonic fields (0.25 pm in intermediate volume suspensions to 40 nm in microchamber assemblies). Unlike US-assisted separations, dielectrophoretic separations require either very low volumes to avoid heating in salt-containing suspensions or desalination prior to separation in the field [111]. 

US applications, where the ultrasonic field can induce potential oscillations [169]). Somewhat less common is the use of split cell arrangements where a glass separator [145] or a polymer coating [170] is used to separate the compartments in which the ultrasonic tip and the electrodes are immersed. 

Clarification of surface water samples is achieved by using a laminar flow filtration chamber (Fig. 3.17C). The concentrated particles and clarified water are removed through separate outlets. The filter operates vertically, with a continuous flow of water sample being fed upward from the base of the system into the ultrasonic field. Particles concentrate along the central axis of the chamber and allow the clarified material to be drawn out of the filter at the edges. 

Various mathematical models have been put forth to describe the rate of bubble growth and the threshold pressure for rectified diffusion.f ° The most widely used model quantifies the extent of rectified diffusion (i.e., the convection effect and bubble wall motion) by separately solving the equation of motion, the equation of state for the gas, and the diffusion equation. To further simplify the derivation, Crum and others made two assumptions 1) the amplitude of the pressure oscillation is small, i.e., the solution is restricted to small sinusoidal oscillations, and 2) the gas in the bubble remains isothermal throughout the oscillations.Given these assumptions, the wall motion of a bubble in an ultrasonic field with an angular frequency of co = 2nf can be described by the Rayleigh-Plesset equation ... 

Acoustic separation Acoustophoresis Position manipiilaticHi of particles by ultrasonic fields Ultrasonic particle separation... 

In ICP-AES and ICP-MS, sample mineralisation is the Achilles heel. Sample introduction systems for ICP-AES are numerous gas-phase introduction, pneumatic nebulisation (PN), direct-injection nebulisation (DIN), thermal spray, ultrasonic nebulisation (USN), electrothermal vaporisation (ETV) (furnace, cup, filament), hydride generation, electroerosion, laser ablation and direct sample insertion. Atomisation is an essential process in many fields where a dispersion of liquid particles in a gas is required. Pneumatic nebulisation is most commonly used in conjunction with a spray chamber that serves as a droplet separator, allowing droplets with average diameters of typically <10 xm to pass and enter the ICP. Spray chambers, which reduce solvent load and deal with coarse aerosols, should be as small as possible (micro-nebulisation [177]). Direct injection in the plasma torch is feasible [178]. Ultrasonic atomisers are designed to specifically operate from a vibrational energy source [179]. 

Although most scaled up US-assisted systems have traditionally been chemical systems, there is a growing trend to exploit US energy for assisting physical processes in the biochemical field such is the case with a large-scale acoustic filter for perfusion of cell cultures [36] or a novel h-shaped ultrasonic resonator for the separation of biomaterials [37]. 

The capabilities of ultrasonic radiation forces for manipulating suspended particles have been the subject of a broad spectrum of experimental research. The effectiveness of particle-liquid separation by ultrasonic radiation forces depends on the acoustic distribution in a standing-wave field. In a US standing wave, suspended particles of appropriate... 

In a previously mentioned work by Kirlew et al., electrophoretic separations of Se, Se As As, and dimethylarsinic acid were performed using various ultrasonic nebulizer (USN) interfaces. Using the optimized CE interface conditions and a borate run buffer at pH 8, a separation was accomplished within 10 min. Electrokinetic injections gave better sensitivities for the analytes as compared to hydrostatic sample injection. In the Kirlew study, arsenate and selenite ions had very similar migration times, but these analytes were easily resolved by the multielement capability of the ICP-MS detector. An electropherogram of this work is shown in Fig. 5. In an application to field samples. Van Holderbel ... 

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