Nebulization ultrasonic nebulizers

Despite the distinct advantages of pneumatic nebulizers, ultrasonic nebulizers may alternatively be used, in some instances, with success. In a recent application, a variation of ultrasonic nebulizer called spray nozzle-rotating disk FTIR interface was successfully applied to confirm the presence of methyltestosterone, testosterone, fluoxymesterone, epitestosterone, and estradiol and testosterone cyp-ionate in urine, after solid-phase extraction and reversed-phase LC separation (151). Using a commercial infrared microscopy spectrometer, usable spectra from 5 ng steroid deposits could be readily obtained. To achieve success with this interface, phosphate buffers in the mobile phase were not used because these nonvolatile salts accumulate on the collection disk and their spectra tend to swamp out small mass deposits. Another limitation of the method was that only nonvolatile analytes could be analyzed because volatile compounds simply evaporated off the collection-disk surface prior to scanning. 

Nebulizer jet nebulization ultrasonic nebulization. Generates small particles with higher delivery capacities than pMDIs and DPIs no coordination required. Inconvenient long inhalation times poor dose control lack of portability expensive. More compact and portable devices breath enhanced nebulizers dosimetric nebulizers. 

Warming may have a beneficial effect. For instance, the temperature of fluids atomized in air-jet nebulizers decreases by approximately 10-15°C during use, resulting in bronchoconstriction in some asthma suffers.Bronchoconstriction, which is most marked at 5°C, disappears at 37°C and thus may be minimized by using an ultrasonic device. Furthermore, when solutions of drugs with low solubility are to be nebulized, ultrasonic nebulizers, which warm the solutions, may be preferable to air-jet devices, which cool them and may cause precipitation. However, the heat generated may harm heat-labile materials such as diethylenetriaminepentoacetic acid ( mTc-/DTPA), " proteins, and some antibiotic solutions. Thus, ultrasonic nebulizers are specifically prohibited for aero-solization of recombinant human deoxyribonuclease (rhDNase). ... 

The major study that stimulated interest in the development of a commercially available inhaled tobramycin product was published in 1993 [27], In this trial, 71 cystic fibrosis patients with stable pulmonary disease were enrolled in a double-blind, placebo-controlled crossover study in which tobramycin 600 mg was nebulized (ultrasonic nebulizer) three times daily. This dose was based on a preliminary study, which showed that sputum concentrations would exceed 10 times the MIC of P. aeruginosa isolates. This concentration has been shown to overcome the competitive binding of tobramycin reported in the sputum of patients with cystic fibrosis. 

Devices used to generate therapeutic aerosols include jet nebulizers, ultrasonic nebulizers, MDIs, and dry-powder inhalers (DPIs). 

In this paper, an accurate method for determining the concentration of manganese and other metals in gasoline and diesel fuel by ICP without the use of chilled spray chamber, direct injection nebulizer, ultrasonic nebulizer with micro-porous membrane desolvator, thermostated condenser, or emulsification is discussed. 

Pneumatic nebulizer Ultrasonic nebulizer Pneumatic nebulizer Ultrasonic nebulizer... 

Pneumatic Nebulizer Ultrasonic Nebulizer Pneumatic Nebulizer Ultrasonic Nebulizer... 

ICP-OES has the advantage of multi-elemental detection capability and offers a wide linear dynamic range. However, the introduction of organic solvents, such as fuels cause plasma destabilization or even plasma extinction and the use of ICP accessories may be necessary, such as direct injection nebulizer, ultrasonic nebulizer with micro-porous membrane... 

There are two dominating principles used in nebulizing therapy ultrasonic nebu-lization and jet nebulization. Ultrasonic nebulizers are based on a piezoelectiic converter. The transducer vibrates at megahertz frequency and, in contact with liquids, can give high output of reasonably sized particles into a reservoir. Output... 

A second form of desolvation chamber relies on diffusion of small vapor molecules through pores in a Teflon membrane in preference to the much larger droplets (molecular agglomerations), which are held back. These devices have proved popular with thermospray and ultrasonic nebulizers, both of which produce large quantities of solvent and droplets in a short space of time. Bundles of heated hollow polyimide or Naflon fibers have been introduced as short, high-surface-area membranes for efficient desolvation. 

Many designs of nebulizer are commonly used in ICP/MS, but their construction and mode of operation can be collated into a small number of groups pneumatic, ultrasonic, thermospray, APCI, and electrospray. These different types are discussed in the following sections, which are followed by further sections on spray and desolvation chambers. 

For a longitudinal disturbance of wavelength 12 pm, the droplets have a mean diameter of about 3-4 pm. These very fine droplets are ideal for ICP/MS and can be swept into the plasma flame by a flow of argon gas. Unlike pneumatic forms of nebulizer in which the relative velocities of the liquid and gas are most important in determining droplet size, the flow of gas in the ultrasonic nebulizer plays no part in the formation of the aerosol and serves merely as the droplet carrier. 

The transfer efficiencies for ultrasonic nebulizers (USN) are about 20% at a sample uptake of about 1 ml/min. Almost 100% transfer efficiency can be attained at lower sample uptakes of about 5-20 pl/min. With ultrasonic nebulizers, carrier gas flows to the plasma flame can be lower than for pneumatic nebulizers because they transfer sample at a much higher rate. Furthermore, reduction in the carrier-gas flow means that the sample remains in the mass measurement system for a longer period of time which provides much better detection limits. 

Ultrasonic nebulizers are almost free of clogging from solute, have better detection limits, and have become popular despite their high cost relative to the pneumatic forms. A typical construction of an ultrasonic nebulizer is shown in Figure 19.17. 

To accommodate smaller liquid flows of about 10 pl/min, micro-ultrasonic nebulizers have been designed. Although basically similar in operation to standard ultrasonic nebulizers, in these micro varieties, the end of a very-small-diameter capillary, through which is pumped the sample solution, is in contact with the surface of the transducer. This arrangement produces a thin stream of solution that runs down and across the center of the face of the transducer. The stream of sample... 

Thermospray nebulizers are somewhat expensive but can be used on-line to a liquid chromatographic column. About 10% of sample solution is transferred to the plasma flame. The overall performance of the thermospray device compares well with pneumatic and ultrasonic sprays. When used with microbore liquid chromatographic columns, which produce only about 100 pl/min of eluant, the need for spray and desolvation chambers is reduced, and detection sensitivities similar to those of the ultrasonic devices can be attained both are some 20 times better than the sensitivities routinely found in pneumatic nebulizers. 

Nebulizers are used to introduce analyte solutions as an aerosol spray into a mass spectrometer. For use with plasma torches, it is necessary to produce a fine spray and to remove as much solvent as possible before the aerosol reaches the flame of the torch. Various designs of nebulizer are available, but most work on the principle of interacting gas and liquid streams or the use of ultrasonic devices to cause droplet formation. For nebulization applications in thermospray, APCI, and electrospray, see Chapters 8 and 11. 

There is a very wide range of designs for nebulizers, but most are based on some form of gas/liquid sprayer or on ultrasonics. 

For ultrasonic nebulizers, the liquid is fragmented into droplets by an acoustic standing wave, usually produced by a piezoelectric transducer. 

Kennedy describes a method using an ultrasonic nebulizer to generate a fog of water droplets w hich is used in the same way as smoke to visualize airflows. Several types of nebulizers are available but they require an electrical connection and are not hand-held. Food dye can be added to the water to produce colored fog. The nebulizers are expensive (about 1500 ECU) but have negligible operating costs. Although the amount of smoke produced is small, it is nontoxic and nonirritating. 

As a starting material, TTBP (Titinium tetraisoproxide, Aldrich Chem. Co. ltd., 98%) was dissolved in distilled water by adding nitric acid. Total titanium ion concentration was fixed at 0.5M. The precursor solution was converted into droplets by ultrasonic nebulizer of 1.7MHz. These droplets were transported to the reaction region by carrier gas. 

ICP-MS (inductively coupled plasma mass spectrometry) is frequently used for determining ultratrace amounts of technetium [9]. In spite of the high cost of the equipment, this detection method is far superior to other radiometric methods as regards sensitivity. When a double focussing high-resolution system is used (HR-ICP-MS) and an ultrasonic nebulizer is introduced [10], the detection limit is in the order 0.002 mBq. The ICP-MS method has been successfully applied to the determination of environmental "Tc as well as to other long-lived radionuclides of neptunium and plutonium in the environment. 

Three different reactors were used to deposit CuInS2 films via AACVD. Reactor A, shown schematically in Fig. 6.11a, was primarily used in the parametric studies described below. This is a horizontal, atmospheric pressure, hot-wall reactor with a plate-type 2.5-MHz ultrasonic nebulizer from Sonaer Ultrasonics. The precursor (1.5-3.5g) was dissolved into distilled toluene (50-400 ml) and fed into the nebulizer using a syringe pump. The nebulizer... 

More recent determinations of serum iron have been reported by Schmidt 57), who simply diluted with lanthanum chloride solution, and by Tavenier and Hellen-doorn58), who deproteinized samples in the latter study, iron in the protein precipitate is analyzed to correct the serum iron level. Uny etal. 59) determined serum iron, using ultrasonic nebulization of the sample to increase the sensitivity. Olson and Hamlin 6°) have determined serum iron and total iron-binding capacity. Proteins are precipitated and iron (III) is released by heating with trichloroacetic acid. 

Ultrasonic Atomization Nebulizers 1-5 (55kHz, 0.12 1/min) 30-60 (50 kHz) l-200[88] Medical spray. Humidification. Spray drying. Acid etching. Printing circuit. Combustion Very fine and uniform droplets, Low spray rates Incapable of handling high liquid flow rates... 

Finally, periodic cleaning of the burner head and nebulizer is needed to ensure minimal noise level due to impurities in the flame. Scraping the slot in the burner head with a sharp knife or razor blade to remove carbon deposits and removing the burner head for the purpose of cleaning it in an ultrasonic cleaner bath are two commonplace maintenance chores. The nebulizer should be dismantled, inspected, and cleaned periodically to remove impurities that may be collected there. 

Montaser A, Tan H, lishi II, Nam SFI, CaiM (1991) Argon inductively coupled plasma mass spectrometry with thermospray, ultrasonic, and pneumatic nebulization. Anal Chem 63 2660-2665 Montaser A, Minnich MG, Liu FI, Gustavsson AGT, Browner RF (1998) Fundamental aspects of sample introduction in ICP spectrometry. In Inductively Coupled Plasma Mass Spectrometry. Montaser A (ed), Wiley-VCH, New York, p 335-420... 

Bensimon M, Bourquin J, Parriaux A (2000) Determination of ultra-trace elements in snow samples by inductively-coupled plasma source sector field mass spectrometry using ultrasonic nebulization. J Anal Atom Spectrom 15 731-734... 

In addition to high LC flow rates, solutions of high conductivity, and/or high surface tension are unsuitable for use with conventional ESI. An ultrasonic nebulizer can reduce such problems because it mechanically creates the spray. Unfortunately, the ultrasonically created droplets are comparatively large and this hin-... 

Fig. 11.4. Different sprayers for ESI. (a) Pure electrospray, (b) ESI with sheath liquid, (c) pneumatically assisted ESI, and (d) ultrasonic nebulizer. Adapted from Ref. [5] (p. 109) by permission. John Wiley Sons, Inc. 1997.

As described in Section 3.3 in more detah, particles in the aerosol cloud should preferably have an aerodynamic diameter between 0.5 and 7.5 pm. Currently three different types of devices are used to generate aerosol clouds for inhalation nebulizers (jet or ultrasonic), (pressurized) metered dose inhalers (pMDIs) and dry powder inhalers (DPIs). The basic function of these three completely different devices is to generate a drug-containing aerosol cloud that contains the highest possible fraction of particles in the desired size range. 

For ultrasonic nebulizers the relation between viscosity and droplet size is more obvious. As could be expected on theoretical grounds, droplet size was found to be proportional to viscosity [57]. As a consequence, viscous solutions might not be aerosolized at all [58,59]. 

A theoretical study of factors which affect pneumatic nebulizers (nebulizer geometry, capillary diameter, temperature fluctuations, gas pressure, solution viscosity, etc.] has been published by Heineman (24). Ultrasonic nebulization (which produces both smaller droplets and a narrower droplet size distribution] continues to attract attention (93, 95). 

Five basic nebulizer designs, known to be used on ICP systems are cross flow, concentric, flow shear, ultrasonic, and FAA. The cross flow and concentric designs are most commonly supplied with commercial systems. FAA nebulizers were supplied with early multi-element systems and there are some commercial suppliers who provide ultrasonic nebulizers. 

Ultrasonic nebulizers, conceptually, are ideally suited for the production of aero-... 

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