Inductively coupled plasma-atomic sources

Heavy Metals, Isotope Dilution, Spark Source Mass Spectrometry, and Inductively Coupled Plasma Atomic Emission Spectrometry... 

Chemical composition of fresh HTs was determined in a Perkin Elmer Mod. OPTIMA 3200 Dual Vision by inductively coupled plasma atomic emission spectrometry (ICP-AES). The crystalline structure of the solids was studied by X-ray diffraction (XRD) using a Siemens D-500 diffractometer equipped with a CuKa radiation source. The average crystal sizes were calculated from the (003) and (110) reflections employing the Debye-Scherrer equation. Textural properties of calcined HTs (at 500°C/4h) were analyzed by N2 adsorption-desorption isotherms on an AUTOSORB-I, prior to analysis the samples were outgassed in vacuum (10 Torr) at 300°C for 5 h. The specific surface areas were calculated by using the Brunauer-... 

One of the more recent branches of atomic spectrometry, although perhaps the most exciting one, is atomic mass spectrometry, which has had a very important impact on science and technology. At present, atomic mass spectrometry is ordinarily performed using inductively coupled plasma ion sources and either a quadrupole or a scanning sector-field mass spectrometer as an analyser. The remarkable attributes of such a combination, being an indispensable tool for elemental analysis, include ... 

One of the most challenging aspects of atomic spectrometry is the incredibly wide variety of sample types that require elemental analysis. Samples cover the gamut of solids, liquids, and gases. By the nature of most modem spectrochemical methods, the latter two states are much more readily presented to sources that operate at atmospheric pressure. The most widely used of these techniques are flame and graphite furnace atomic absorption spectrophotometry (FAAS and GF-AAS) [1,2] and inductively coupled plasma atomic emission and mass spectrometries (ICP-AES and MS) [3-5]. As described in other chapters of this volume, ICP-MS is the workhorse technique for the trace element analysis of samples in the solution phase—either those that are native liquids or solids that are subjected to some sort of dissolution procedure. 

Inductively Coupled Plasma Atomic Emission Spectrometry Liquid samples offer the best opportunity for aspiration into the plasma sources with minimal pretreatment. Therefore, introduction of solubilized samples into the ICP torch has received and still is receiving much attention [11D18]. 

This article focuses primarily on traditional low-temperature flame photometry. High-temperature flame photometry has evolved into separate techniques, typically identified by their temperature sources (e.g., inductively coupled plasma-atomic emission spectrometry, ICP-AES ). Some references to other related analytical tools, including high-temperature flame photometry, are made here to establish perspective. 

Knowledge of the atomic spectra is also very important so as to be able to select interference-free analysis lines for a given element in a well-defined matrix at a certain concentration level. To do this, wavelength atlases or spectral cards for the different sources can be used, as they have been published for arcs and sparks, glow discharges and inductively coupled plasma atomic emission spectrometry (see earlier). In the case of ICP-OES, for example, an atlas with spectral scans around a large number of prominent analytical lines [329] is available, as well as tables with normalized intensities and critical concentrations for atomic emission spectrometers with different spectral bandwidths for a large number of these measured ICP line intensities, and also for intensities calculated from arc and spark tables [334]. The problem of the selection of interference-free lines in any case is much more complex than in AAS or AFS work. 

The X-ray diffraction (XRD) patterns were obtained by Philips X pert Pro X-ray diffractometer equipped with a Cu-K source at 40 kV and 40 mA. The crystalline sizes of R particles were calculated from Scherrer s equation [15]. Transmission electron microscopy (TEM) images were obtained using the G2 FE-TEM Tecnai microscope at an accelerating voltage of 200 kV. The content of platinum and carbon in the sample was determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES, RF source Jobin Yvon 2301, 40.68 MHz). 

The measurements were performed using a Thermo Elemental IRIS Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES). A 2 kW crystal-controlled radio frequency (RF) generator operating at 27.12 MHz powers the plasma source. An Echelle optical system with a 381-mm focal length diffracts the light from the plasma source before it is focused onto the Charge Injected Device (CID) camera detector [4]. 

The inductively coupled plasma ion source was developed to accomplish exactly the opposite of the two soft ionization methods just described. Molecules are reduced to their atomic (i.e. elemental) components through the application of intense energy. Masses corresponding to elements of interest (e.g. 30.974 for phosphorus) are then specifically monitored. 

Inductively coupled plasma atomic emission spectrometry (ICP-AES) involves a plasma, usually argon, at temperatures between 6000 and 8000 K as excitation source. The analyte enters the plasma as an aerosol. The droplets are dried, desol-vated, and the matrix is decomposed in the plasma. In the high-temperature region of the plasma, molecular, atomic, and ionic species in various energy states are formed. The emission lines can then be exploited for analytical purposes. Typical detection limits achievable for arsenic with this technique are 30 J,g As/L (23). Due to the rather high detection limit, ICP-AES is not frequently used for the determination of arsenic in biological samples. The use of special nebulizers, such as ultrasonic nebulization, increases the sample transport efficiency from 1-2% (conventional pneumatic nebulizer) to 10-20% and, therefore, improves the detection limits for most elements 10-fold. In addition to the fact that the ultrasonic nebulizer is rather expensive, it was reported to be matrix sensitive (24). Inductively coupled plasma atomic emission spectrometry is known to suffer from interferences due to the rather complex emission spectrum consisting of atomic as... 

The inductively coupled plasma (ICP) source is used largely for specific element identification and evolved from the ICP atomic emission spectrometer it is probably more commonly employed in LC/MS than GC/MS. In GC/ MS, the ICP ion source is used in the assay of... 

ICP-MS is advantageous over RIMS and AMS due to fast and relatively inexpensive multielement determination, precise and accurate isotopic analysis at the trace, and ultratrace concentration levels in any material. Another advantage of ICP-MS compared to other atomic mass spectrometric techniques is the simple sample preparation and introduction of aqueous solutions into the normal-pressure inductively coupled plasma ion source. 

Atomic absorption spectrometry (AAS) has been widely used. Although flame AAS was useful in the past [45], electrothermal AAS is now preferred [30,46-48] as well as a simultaneous multielement atomic absorption continuum source coupled with a carbon furnace atomizer (SIMAAC) [49] or inductively coupled plasma atomic emission spectrometry (ICPAES) [39]. 

Research into the development of environmental methods might consider the use of AA detection. Perhaps some of the more interesting detectors are those that use inductively coupled plasma (ICP) as an energy source and either atomic emission (AE) or mass spectrometry (MS) as the detector. ICP-AE and ICP-MS are well-developed analytical tools. One of the major advantages of these techniques is that a mixture of metals can be analyzed without the need for separation. Thus, workers who use these instruments normally do not think about their use as detectors. However, ICP-AE and ICP-MS cannot determine the oxidation or chemical state of a particular metal ion (Chapter 13). Some samples are quite important from a toxicological and environmental standpoint since the toxicity of a metal may depend on its oxidation state. For example, Cr(IIl) is not toxic (and even considered an essential element), but Cr(VI) is extremely toxic. An inductively coupled plasma atomic emission [81] detector was used to detect rare earth metals. 

Figure 1.5 Polychromator system for inductively coupled plasma atomic emission spectrometer. Source Author s own files)...

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