Nebulisers ultrasonic

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]. 

Berman et al. [735] and McLaren [738] attempted to determine the foregoing nine elements in seawater by a combination of ion exchange preconcentration on Chelex 100 [129,736-738], and ICP-AES using ultrasonic nebulisation. Preconcentration factors of between 25 and 100 were obtained by this technique. 

Warnken et al. [956] have reported an online preconcentration - ultrasonic nebulisation - ICP-MS method that achieved detection limits of 0.26,0.86,1.5, 10, and 0.44 ng/1 for manganese, nickel, copper, zinc, and lead in seawater. This online preconcentration method compares favourably to the state of-the-art off-line methods. 

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. 

M. Grotti, E. Magi and R. Frache, Multivariate investigation of matrix effects in inductively coupled plasma atomic emission spectrometry using pneumatic or ultrasonic nebulisation, J. Anal. At. Spectrom., 15(1), 2000, 89-95. 

Wang, S.R. and Jiang, S.J. (1991) An ultrasonic nebuliser as the sample introduction device for high-performance liquid-chromatography combined with inductively coupled plasma atomic emission spectrometry./. Chinese Chem. Soc., 38, 327-332. 

K. L. Yang, S. J. Jiang, Determination of selenium-compounds in urine samples by liquid chromatography-inductively coupled plasma-mass spectrometry with an ultrasonic nebuliser, Anal. Chim. Acta, 307 (1995), 109-115. 

Falter, R., Wilken, R.D. Determination of carboplatinum and cisplatinum by interfacing HPLC with ICP MS using ultrasonic nebulisation. Sci. Total Environ. 225, 167-176 (1999)... 

Figure 9.48 Schematic diagrams of (a) a Venturi-type nebuliser and (b) an ultrasonic nebuliser.

Varner A, Busse W 1996 Are you undertreating inflammation in asthma Journal of Respiratory Disease 17 656-668 Viel L 1999 Therapeutic efficacy of inhaled fluticasone propionate in horses with chronic obstructive pulmonary disease. In Proceedings of the 45th American Association of Equine Practitioners Annual Convention, Albuquerque, NM, pp. 306-307 Votion D, Ghafir Y, Munsters K et al 1997 Aerosol deposition in equine lungs following ultrasonic nebulisation versus jet aerosol delivery system. 

Figure 2.9 Overview of sample introduction methods and hyphenated techniques used in ICP-AES. (A) Pneumatic concentric (sometimes called the Meinhard nebuliser) (B) Babington (C) fritted disc (D) Hildebrand nebuliser (E) cross flow (G) standard ultrasonic nebuliser for aqueous and non-aqueous solvents (H) electro-thermal graphite ( ) electro-thermal carbon cup (K) graphite tip filament (L) laser ablation (M) hydride generation (P) flow injection...

The membrane desolvator is very effective in reducing the solvent loading further when used in conjunction with the ultrasonic nebuliser. This will allow a range of solvents to be used for ICP-AES that would otherwise quench the plasma by almost totally removing the solvent from the sample and only allowing the dried particles containing the elements of interest to enter the source. 

Figure 2.19 Schematic diagram of the percentage of droplet mist successfully going to the plasma source. Line (a) is 2% for standard nebulisers and line (b) is 20% for ultrasonic nebulisers...

CETAC Technologies. Ultrasonic Nebulisation of Liquid Samples for Analytical ICP Atomic Spectroscopy, South Shields CETAC. 

Typical plastics used in electronic and electrical appliances are polyethylene, polypropylene or polyethene terphthalate, and these are studied here as part of the RoHS requirement for the presence of toxic metals. This method is to show that analysis of these plastics used in electrical and electronic equipment is essential, especially if the origin of the plastic is unknown and the supplier is unable to state whether or not they are free of these metals. The metals are measured against calibration standards curves for each metal and may also include additional attachments for improving limits of detection such as ultrasonic nebulisers for Cd, Pb and Cr and the cold trap method for Hg. 

All samples are analysed for Cd, Pb, Cr against standard calibration curves prepared from 0.0, 0.5, 2.5, 5.0 and lO.Oppm of each metal in 0.25 M HNO3. The ultrasonic nebuliser is used for the determination of Cd, Pb and Cr while the continuous cold vapour trap method is used for the determination of Hg. The recovery of each metal is determined for each metal. The Hg forms the vapour ion of the metal in solution after reduction with SnCl2(Sn2+ + Hg2+ > Sn4+ + Hg°) and the metallic mercury is swept to the plasma torch by the argon gas. This method is sensitive for Hg and has the advantage that it removes the analyte from the main solution and has very low limits of detection. 

The concentration of metals that are detrimental to catalysts added can vary between 20.0 ppm for Fe to 100 ppm for Ni and lOOOppm for V. The presence of these metals necessitates the need for analysis of these metals to determine their concentrations prior to the cracking process. The best method to analyse these oil samples needs to be rapid and accurate. Careful selection of the method either from experience or by trial and error may be applied depending on the metal and the concentration. Sample dissolution in a solvent or solvent mixture is considered the easiest but may not be suitable for low limits of detection. Destructive sample preparation methods, i.e. oxygen bomb combustion, microwave acid digestion followed by pre-concentrating may be required for trace analysis and/or with the aid of a hyphenated system, e.g. ultrasonic nebuliser. Samples prepared by destmctive methods are dissolved in aqueous solutions that have very low matrix and spectral interferences. 

The benefit of sample preparation techniques using microwave acid digestion and bomb combustion is that the sample is totally enclosed during the decomposition. These methods remove matrix interference and generate aqueous solutions, which can be analysed using ICP-OES. Sub-trace concentrations can be detected when hyphenated attachments are used, e.g. ultrasonic nebuliser, hydride generation or continuous cold vapour method. These methods are essential where trace levels of toxic elements are present that need to be identified and quantified. 

The metals As, Cd, Cr, Pb and Se are analysed against multi-element standards of 0.0, 0.1, 0.25, 0.5 and 1.0 ppm prepared in 0.1 M HN03 using ICP-OES with the CETAC 5000AT ultrasonic nebuliser attachment. The element Hg is measured using the continuous cold vapour method. 

The analysis of petroleum products for the presence of toxic metals is an environmental requirement and results of analysis must be made known to all concerned bodies including the public. In order to establish the true concentrations present, a reliable method must be employed in order to be certain of the results. A sensitive method must be available and the use of an ICP coupled with an ultrasonic nebuliser, hydride generation or cold vapour method for Hg offer the most sensitive and reliable methods available. If analysing for lower levels of these metals, a mass spectrograph with hyphenated attachments may be required. 

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