Ultrasonic atomisation

A wealth of other data can be obtained from the use of US as an analytical method. Sonoelectrochemical analysis of trace metals [220] and organic compounds [221] has been reported. Ultrasonic atomisation [222] is used in many fields where a dispersion of liquid particles is required. Ultrasonic nebulisation (USN) is used for analysis of organic solutions in conjunction with ICP-AES/MS [223,224] and MIP-AES [225],... 

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]. 

Freitas, S., Merkle, H. P., and Gander, B. (2004), Ultrasonic atomisation into reduced pressure atmosphere—envisaging aseptic spray drying for microencapsulation, /. Controlled Release, 95,185-195. 

Rodriguez L, Passerini N, Cavallari C, Cini M, Sancin P, Fini A (1999) Description and preliminary evaluation of a new ultrasonic atomiser for spray congealing processes. International Journal of Pharmaceutics 183 133-143. 

The on-line interface of flow manifolds to continuous atomic spectrometric detectors for direct analysis of samples in liquid form typically requires a nebuliser and a spray chamber to produce a well-defined reproducible aerosol, whose small droplets are sent to the atomisation/ionisation system. A variety of nebulisers have been described for FAAS or ICP experiments, including conventional cross-flow, microconcentric or Babington-type pneumatic nebulisers, direct injection nebuliser and ultrasonic nebulisers. As expected, limits of detection have been reported to be generally poorer for the FIA mode than for the continuous mode. 

While possible to obtain satisfactory products with the pneumatic nebuliser, the experimental difficulties due to clogging and the strong dependence on many interrelated variables indicated that another type of atomiser should be investigated. An ultrasonic nozzle, in which high frequency electrical energy is converted into vibratory mechanical motion at the same frequency, was therefore examined. The ultrasonic nozzle was chosen because the average droplet size was small, about 25 microns, and... 

Using a solution-spray technique,124 an aqueous solution of HAuCU and titanium tetrachloride was atomised by an ultrasonic device to produce a mist without separation of the components this was then calcined, and the fine particles collected on a glass filter at the outlet. Samples of 1 wt.% Au/TiC>2 contained 4 nm particles when the spray reaction temperature was... 

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