Nebulizer/atomizer

E. Puskel, Z. Mester, P. Fodor, Determination of selenoamino acids by high-performance liquid chromatography-hydraulic high pressure nebulization-atomic fluorescence spectrometry, J. Anal. Atom. Spectrom., 14 (1999), 973-976. 

A number of devices are available for the delivery of medications for inhalation therapy. Among these are the nebulizer, atomizer, and insufflator, which operate under Bernoulli s Principle. 

A Woller, Z Mester, P Fodor. Determination of arsenic species by high-performance liquid chromatography-ultrasonic nebulization atomic fluorescence spectrometry. J Anal At Spectrom 10 609-613, 1997. 

Nebulizers, the atomizers that produce a fine mist, are classified into three main commercialized types air-jet (pneumatic), ultrasonic, and vibrating-mesh. Air-jet nebulizers atomize liquid into droplets using a high-velocity gas passing through... 

Flame atomization assembly equipped with spray chamber and slot burner. The inset shows the nebulizer assembly. 

Precision For absorbances greater than 0.1-0.2, the relative standard deviation for atomic absorption is 0.3-1% for flame atomization, and 1-5% for electrothermal atomization. The principal limitation is the variation in the concentration of free-analyte atoms resulting from a nonuniform rate of aspiration, nebulization, and atomization in flame atomizers, and the consistency with which the sample is heated during electrothermal atomization. 

Flame Sources Atomization and excitation in flame atomic emission is accomplished using the same nebulization and spray chamber assembly used in atomic absorption (see Figure 10.38). The burner head consists of single or multiple slots or a Meker-style burner. Older atomic emission instruments often used a total consumption burner in which the sample is drawn through a capillary tube and injected directly into the flame. 

For inductively coupled plasma atomic emission spectroscopy (ICP-AES) the sample is normally in solution but may be a fine particulate solid or even a gas. If it is a solution, this is nebulized, resulting in a fine spray or aerosol, in flowing argon gas. The aerosol is introduced into a plasma torch, illustrated in Figure 3.21. 

Specific advancements ia the chemical synthesis of coUoidal materials are noteworthy. Many types of genera ting devices have been used to produce coUoidal Hquid aerosols (qv) and emulsions (qv) (39—43) among them are atomizers and nebulizers of various designs (30,44—50). A unique feature of produciag Hquid or soHd coUoids via aerosol processes (Table 3) is that material with a relatively narrow size distribution can be routinely prepared. These monosized coUoids are often produced by relying on an electrostatic classifier to select desired particle sizes ia the final stage of aerosol production. 

Recently it has been shown that rotating coiled columns (RCC) can be successfully applied to the dynamic (flow-through) fractionation of HM in soils and sediments [1]. Since the flow rate of the extracting reagents in the RCC equipment is very similar to the sampling rate that is used in the pneumatic nebulization in inductively coupled plasma atomic emission spectrometer (ICP-AES), on-line coupling of these devices without any additional system seems to be possible. 

Electrothermal vaporization can be used for 5-100 )iL sample solution volumes or for small amounts of some solids. A graphite furnace similar to those used for graphite-furnace atomic absorption spectrometry can be used to vaporize the sample. Other devices including boats, ribbons, rods, and filaments, also can be used. The chosen device is heated in a series of steps to temperatures as high as 3000 K to produce a dry vapor and an aerosol, which are transported into the center of the plasma. A transient signal is produced due to matrix and element-dependent volatilization, so the detection system must be capable of time resolution better than 0.25 s. Concentration detection limits are typically 1-2 orders of magnitude better than those obtained via nebulization. Mass detection limits are typically in the range of tens of pg to ng, with a precision of 10% to 15%. 

Strictly speaking, the size of an atom is a rather nebulous concept The electron cloud surrounding the nucleus does not have a sharp boundary. However, a quantity called the atomic radius can be defined and measured, assuming a spherical atom. Ordinarily, the atomic radius is taken to be one half the distance of closest approach between atoms in an elemental substance (Figure 6.12). 

An inductively coupled plasma formed by passing argon through a quartz torch is widely used for the mass spectroscopic analysis of metal compounds separated by online HPLC.6 Samples are nebulized on introduction into the interface. Plasma impact evaporates solvent, and atomizes and ionizes the analyte. Applications include separation of organoarsenic compounds on ion-pairing F4PLC and vanadium species on cation exchange. 

But what about the elements How many were there Could the elements then known to man not be further expanded. Could they only be found on Earth Did God create them in the beginning or were they the result of some process of evolution Even the existence of atoms was doubted. The nebulous concepts and the countless deadends led to the eminent French chemist Jean B. A. Dumas writing in 1837 to state that "If I had the power, I would strike the word "atom" from science". 

For the majority of applications, the sample is taken into solution and introduced into the plasma as an aerosol in the argon stream. The sample solution is pumped by a peristaltic pump at a fixed rate and converted into an aerosol by a nebulizer (see atomic absorption spectrometry). Various designs of nebulizer are in use, each having strengths and weaknesses. The reader is directed to the more specialist texts for a detailed consideration of nebulizers. There is an obvious attraction in being able to handle a solid directly, and sample volatilization methods using electric spark ablation, laser ablation and electrothermal volatilization have also been developed. 

Rate offuel flow. This affects the rate of nebulization and the residence time of the atoms within the flame. 

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