Inductively coupled plasma-atomic emission characteristics

Because light emitted from inductively coupled plasma torches is characteristic of the elements present, the torches were originally introduced for instruments that optically measured the frequencies and intensities of the emitted light and used them, rather than ions, to estimate the amounts and types of elements present (inductively coupled plasma atomic emission spectroscopy. 

In reference 190, the authors describe the spectroscopic and X-ray crystallographic techniques they used to determine the pMMO structure. First, EPR and EX AFS experiments indicated a mononuclear, type 2 Cu(II) center hgated by histidine residues and a copper-containing cluster characterized by a 2.57 A Cu-Cu interaction. A functional iron center was also indicated by Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES). ICP-AES uses inductively coupled plasma to produce excited atoms that emit electromagnetic radiation at a wavelength characteristic of a particular element. The intensity of this emission is indicative of the concentration of the element (iron in this case) within the sample. 

Hydrous sodium titanate was prepared by the method of Dosch and Stephens (1). Titanium isopropoxide was slowly added to a 15 wt% solution of sodium hydroxide in methanol. The resulting solution was hydrolyzed by addition to 10 vol% water in acetone. The hydrolysis product is an amorphous hydrous oxide with a Na Ti ratio of 0.5 which contains, after vacuum drying at room temperature, approximately 13.5 wt% water and 2.5 wt% residual alcohol. The ion-exchange characteristics of the sodium titanate and the hydrolysis behavior of the nickel nitrate solutions were characterized using a combination of potentiometric titrations, inductively coupled plasma atomic emission (ICP) analysis of filtrates, and surface charge measurements obtained using a Matec electrosonic amplitude device. 

The choice of an analytical method depends on its performance characteristics (detection limits, accuracy and precision, speed etc). Other conditions to be reached are the concerned element, the concentration in the sample of interest, the variability of their concentration. The concentration of metal ions in studied Seaside Lakes were determined by flame atomic absorption spectrometry (FAAS) (Chirila et al., 2003a), inductively coupled plasma atomic emission spectrometry (ICP-AES) (Chirila et al., 2002), molecular absorption spectrometry in visible (Chirila and Carazeanu, 2001). These investigations were carried out in the biotope (sediment and water) and biocenosis (different plants and fish) from one ecosystem (Tabacarie Lake) and in water samples from the other Seaside lakes. 

Analysis of FTIR spectra of the ionomer(Figures 3 and 4) was also informative about the structure. It was reported previously that IR absorption bands at 1893 cm" and 1905 cm"l were characteristics of 4-methylstyrene (of > 50) and 4-bromomethyl styrene (of Exxpro elastomer, Figure 5). Such absorption bands were not found in the FTIR spectra of the above ionomers. However, new absorption peaks, characteristics of the quaternary phosphonium salts, at 1580, 1100, 100, 670-730 cm" were observed. The presence of both phosphorous and boron in the above ionomers was also confirmed in terms of the elemental analysis data, collected from the inductively coupled plasma/atomic emission spectroscopy(ICP/AES) technique. These results were in good agreement with the expected convertion of the respective phosphonium salts. 

Part III provides several conventional, environmental evaluation processes for surface finishing. In chapter The Necessity and Meaning , we describe the necessity and meaning of enviromnental evaluation for surface finishing. Also we discuss evaluation processes that have already been used. In chapter Frequently Used Evaluations for Effluents , the Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES) and the Inductively Coupled Plasma Mass Spectrometer (ICP-MS) are mainly described and discussed as conventional, but powerful analytical tools. In chapter Frequently Used Evaluations for Aerial and Solid Pollution , the conventional analyses for aerial and solid pollution are presented. These types of pollution have caused very serious problems. Therefore, various countermeasures have been devised for them. And even nowadays, new problems such as air pollutants called particulate matter are emerging. These air pollutants include solid particles and liquid droplets that come in various sizes. The small particles that are 2.5 pm or less are called PM2.5. In this chapter, we also focus oti gas chromatography/ion chromatography from the fundamental viewpoint. In chapter Dissolution Assay , the dissolution assay process is described. This type of analysis is used to measure the dissolution amounts and characteristics for many kinds of metal components of materials. 

Inductively coupled plasma atomic emission is more versatile than atomic absorption because emission does not require a lamp for each element. An element emits light at many characteristic frequencies. As many as 70 elements can be measured with simultaneous measurement of emission from each different element. In Color Plate 21, atomic emission entering from the top right is dispersed in the vertical plane by a prism and in the horizontal plane by a grating. The radiation forms a two-dimensional pattern that lands on a semiconductor detector similar to that in a digital camera. Each pixel receives a different wavelength and therefore responds to a different element. 

We consider the determination of the concentration of elements in various materials studied in agricultural and environmental applications, by the use of the following methods atomic absorption spectroscopy (AAS) using a flame (FAAS) or a graphite furnace (GFAAS) as an atom cell inductively coupled plasma atomic emission spectroscopy (ICPAES) inductively coupled plasma mass spectrometry (ICPMS) and X-ray fluorescence (XRF). The analytical characteristics of the methods as normally practised are compared with the requirements of fitness for purpose in the examination of soils and sediments, waters, dusts and air particulates, and animal and plant tissue. However, there are numerous specialized techniques that cannot be included here. 

In Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES), a gaseous, solid (as fine particles), or liquid (as an aerosol) sample is directed into the center of a gaseous plasma. The sample is vaporized, atomized, and partially ionized in the plasma. Atoms and ions are excited and emit light at characteristic wavelengths in the ultraviolet or visible region of the spectrum. The emission line intensities are proportional to the concentration of each element in the sample. A grating spectrometer is used for either simultaneous or sequential multielement analysis. The concentration of each element is determined from measured intensities via calibration with standards. 

In a flame, as the concentration of atoms increases, the possibility increases that photons emitted by excited atoms in the hot region in the centre will collide with atoms in the cooler outer region of the flame, and thus be absorbed. This self-absorption effect contributes to the characteristic curvature of atomic emission calibration curves towards the concentration axis, as illustrated in Fig. 4.4. The inductively coupled plasma (ICP) tends to be hotter in the outer regions compared with the centre—a property known as optical thinness—so very little self-absorption occurs, even at high atom concentrations. For this reason, curvature of the calibration curve does not occur until very high atom concentrations are reached, which results in a much greater linear dynamic range. 

Atomic emission spectroscopy can be employed, generally with an inductively coupled plasma for thermal excitation. The sample is introduced into the plasma as a mist of ultrafine droplets, and the monochromator and detector are set to measure the intensity of an atomic emission line characteristic of the element. This technique is powerful, general, sensitive, linear, and able to measure over 70 elements, and, as a result, is widely used. Response is typically linear over four orders of magnitude in concentration with relative standard deviations of 1 to 3%. In low-salt aqueous solutions, detection limits range from 10 to 1000 nanomolar without preconcentration. Significant problems with saline samples remain, but use of Babington nebulizers alleviates these problems somewhat. 

There is also a standard test method for determination of major and minor elements in coal ash by inductively coupled plasma (ICP)-atomic emission spectrometry (ASTM D-6349). In the test method, the sample to be analyzed is ashed under standard conditions and ignited to constant weight. The ash is fused with a fluxing agent followed by dissolution of the melt in dilute acid solution. Alternatively, the ash is digested in a mixture of hydrofluoric, nitric, and hydrochloric acids. The solution is analyzed by (ICP)-atomic emission spectrometry for the elements. The basis of the method is the measurement of atomic emissions. Aqueous solutions of the samples are nebulized, and a portion of the aerosol that is produced is transported to the plasma torch, where excitation and emission occurs. Characteristic line emission spectra are produced by a radio-frequency inductively coupled plasma. A grating monochromator system is used to separate the emission lines, and the intensities of the lines are monitored by photomultiplier tube or photodiode array detection. The photocurrents from the detector... 

Name four characteristics of inductively coupled plasmas that make them suitable for atomic emission and atomic mass spectrometry. 

Argon plasmas are used in optical emission spectrometry (cf. section 14.3.1) to atomize and ionize elements in order to provoke the emission of characteristic spectral lines. Hence, it is not surprising that the same plasma torches are employed to ionize inorganic samples in mass spectrometry. Thermal ionization is induced at high temperatures in a gaseous sample with microwave or an inductively coupled plasma. 

The AED employs a microwave-induced He plasma to dissociate eluted analyte molecules to their component atoms and excite them to emit at characteristic wavelengths. This is very similar to the mechanism in the argon plasma inductively coupled plasma source (cf. Section 7.3.1). A spectrometer with a diode array detector (Figure 7.26b and c) isolates and measures the intensity of sensitive emission lines unique to each element. Depending on the relative sensitivity and proportion of atoms in the molecules, separate element response channels may display peaks in several element-selective chromatograms. These data may be combined with retention... 

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