Instrumentation atomic fluorescence spectrometry

See also Atomic Absorption Spectrometry Principles and Instrumentation. Atomic Emission Spectrometry Principles and Instrumentation. Atomic Fluorescence Spectrometry. Gas Chromatography Pyrolysis Mass Spectrometry. Liquid Chromatography Normal Phase Reversed Phase Size-Exclusion. Polarography Inorganic Applications Organic Applications. Polymers Synthetic. Thin-Layer Chromatography Overview. Voltammetry Organic Compounds. 

See also Atomic Absorption Spectrometry Principles and Instrumentation. Atomic Emission Spectrometry Principles and Instrumentation. Atomic Fluorescence Spectrometry. 

Table B.2 Instrumental conditions for hydride generation atomic fluorescence spectrometry.

F. R. Prell, Jr.. J. T. McCaffrey. M. D. Seltzer, and R. G. Michel. "Instrumentation for Zeeman Electrothermal Atomizer Laser Excited Atomic Fluorescence Spectrometry,"... 

Atomic Fluorescence Spectrometry. A spectroscopic technique related to some of the types mentioned above is atomic fluorescence spectrometry (AFS). Like atomic absorption spectrometry (AAS), AFS requires a light source separate from that of the heated flame cell. This can be provided, as in AAS, by individual (or multielement lamps), or by a continuum source such as xenon arc or by suitable lasers or combination of lasers and dyes. The laser is still pretty much in its infancy but it is likely that future development will cause the laser, and consequently the many spectroscopic instruments to which it can be adapted to, to become increasingly popular. Complete freedom of wavelength selection still remains a problem. Unlike AAS the light source in AFS is not in direct line with the optical path, and therefore, the radiation emitted is a result of excitation by the lamp or laser source. 

Laser-excited atomic fluorescence spectrometry is capable of extremely low detection limits, particularly when combined with electrothermal atomization. Detection limits in the femtogram (10 g) to attogram (10 g) range have been shown for many elements. Commercial instrumentation has not been developed for laser-based AFS, probably because of its expense and the nonroutine nature of high-powered lasers. Atomic fluorescence has the disadvantage of being a singleelement method unless tunable lasers with their inherent complexities are used. 

More recently for ultratrace determination and speciation of antimony compounds the so-called hyphenated instrumental techniques have been applied which combine adequate separation devices with suitable element-specific detectors. They include high-performance liquid chromatography (HPLC) connected on-line with heated graphite furnace (HGF) AAS (HPLC-HGF-AAS), hydride-generation atomic fluorescence spectrometry (HPLC-HG-AFS) or inductively coupled plasma (ICP) mass spectrometry (MS) (HPLC-ICP-MS) capillary electrophoresis (CE) connected to inductively coupled plasma mass spectrometry (CE-ICP-MS) and gas chromatography (GC) coupled with the same detectors as with HPLC. Reliable speciation of antimony compounds is still hampered by such problems as extractability of the element, preservation of its species information, and availability of Sb standard compounds (Nash et al. 2000, Krachler etal. 2001). Variants of anodic stripping voltammetry for speciation of antimony have also been applied (Quentel and Eilella 2002). 

Human biological materials to be investigated include (a) hard calcified tissues, e.g. bone, teeth, other calcified formations (b) semi-hard tissue, e.g. hair, nails (c) soft body tissues and (d) various biological fluids and secretions in the human body. The treatment of each of these materials varies from one material to another and, as stated earlier, is often determined by the instrumental method to be employed for measuring the analytical signal, the elements to be determined and the concentration levels at which these are present. For the purposes of this discussion, it shall be generally assumed that the analytical techniques employed include atomic absorption spectrometry both with (F-AAS) as well as with a furnace (GF-AAS), neutron activation analysis (NAA), flame emission spectrometry (FES) voltammetric methods and the three inductively coupled plasma spec-trometric methods viz. ICP-atomic emission spectrometry, ICP-mass spectrometry and ICP-atomic fluorescence spectrometry. The sample preparation of biological methods for all ICP techniques is usually similar (Guo, 1989). 

Figure 3 Instrumental methods for the determination of arsenic compounds (Abbreviations AAS, atomic absorption spectrometry APS, atomic fluorescence spectrometry CE, capillary electrophoresis GC, gas chromatography HG, hydride generation ICP-AES, inductively coupled plasma-atomic emission spectrometry ICP-MS, inductively coupled plasma-mass spectrometry INAA, instrumental neutron activation analysis LC, liquid chromatography MS, mass spectrometry).

Atomic fluorescence spectrometry (AES) is an analytical method used to determine the concentration of elements in samples. The sample is converted to gaseous atoms, and the element of interest is excited to a higher electronic energy level by a light source. Following excitation, the atoms are deactivated by the emission of a photon. The measured fluorescence is this emission process. Instrumentation for AES... 

A range of chromatographic techniques coupled to element specific detectors has been used in speciation studies to separate individual organometallic species (e.g., butyltins, arsenic species) and to separate metals bovmd to various biomolecules. The combination of a chromatographic separation with varying instrumental detection systems are commonly called coupled, hybrid, or hyphenated techniques (e.g., liquid chromatography inductively coupled plasma-mass spectrometry (LC-ICP-MS), gas chromatography-atomic absorption spectroscopy (GC-AAS)). The detection systems used in coupled techniques include MS, ICP-MS, atomic fluorescence spectrometry (AFS), AAS, ICP-atomic emission spectrometry (ICP-AES), and atomic emission detection (AED). 

Inductively Coupled Plasma. Atomic Fluorescence Spectrometry. Atomic Mass Spectrometry Inductively Coupled Plasma. Chemiluminescence Liquid-Phase. Enzymes Enzyme-Based Electrodes. Fluorescence Instrumentation. Ion-Selective Electrodes Overview. Optical Spectroscopy Detection Devices. Sensors Overview. Voltammetry Overview. 

This technique comprises a group of quantitative instrumental analytical methods based on the capacity of free atoms of both emitting and absorbing radiation at a specific wavelength. The radiation lies within the range for ultraviolet and visible light. A distinction is made between atomic emission spectrometry (AES), atomic absorption spectrometry (AAS), and atomic fluorescence spectrometry. The most commonly applied techniques are flame-AAS, graphite furnace-AAS, and ICP-AES. With ICP, excitation takes place in a plasma at a temperature of 7000 K. 

Atomic Absorption and Atomic Fluorescence Spectrometry 230 9A Sample Atomization Techniques 230 9B Atomic Absorption Instrumentation 237 9C Interferences in Atomic Absorption Spectroscopy 241... 

See also Atomic Absorption, Theory Atomic Emission, Methods and Instrumentation Atomic Fluorescence, Methods and Instrumentation Inductively Coupled Plasma Mass Spectrometry, Methods. 

Emission, Methods and Instrumentation Atomic Fluorescence, Methods and Instrumentation Fluorescence and Emission Spectroscopy, Theory Geology and Mineralogy, Applications of Atomic Spectroscopy Inductively Coupled Plasma Mass Spectrometry, Methods Proton Microprobe (Method and Background) X-Ray Emission Spectroscopy, Applications X-Ray Emission Spectroscopy, Methods X-Ray Fluorescence Spectrometers X-Ray Spectroscopy, Theory. 

The basic instrumentation used for spectrometric measurements has already been described in the previous chapter (p. 277). Methods of excitation, monochromators and detectors used in atomic emission and absorption techniques are included in Table 8.1. Sources of radiation physically separated from the sample are required for atomic absorption, atomic fluorescence and X-ray fluorescence spectrometry (cf. molecular absorption spectrometry), whereas in flame photometry, arc/spark and plasma emission techniques, the sample is excited directly by thermal means. Diffraction gratings or prism monochromators are used for dispersion in all the techniques including X-ray fluorescence where a single crystal of appropriate lattice dimensions acts as a grating. Atomic fluorescence spectra are sufficiently simple to allow the use of an interference filter in many instances. Photomultiplier detectors are used in every technique except X-ray fluorescence where proportional counting or scintillation devices are employed. Photographic recording of a complete spectrum facilitates qualitative analysis by optical emission spectrometry, but is now rarely used. 

Theory Instruments In energy dispersive x-ray fluorescence spectrometry, a sample is bombarded by x-rays that cause the atoms within the sample to fluoresce (i.e., give off their own characteristic x-rays) and this fluorescence is then measured, identified and quantified. The energy of the x-rays identify the elements present in the sample and, in general, the intensities of the x-ray lines are proportional to the concentration of the elements in the sample, allowing quantitative chemical... 

Molybdenum may be identified at trace concentrations by flame atomic absorption spectrometry using nitrous oxide-acetylene flame. The metal is digested with nitric acid, diluted and analyzed. Aqueous solution of its compounds alternatively may be chelated with 8—hydroxyquinobne, extracted with methyl isobutyl ketone, and analyzed as above. The metal in solution may also be analyzed by ICP/AES at wavelengths 202.03 or 203.84 nm. Other instrumental techniques to measure molybdenum at trace concentrations include x-ray fluorescence, x-ray diffraction, neutron activation, and ICP-mass spectrometry, this last being most sensitive. 

Numerous methods have been published for the determination of trace amounts of tellurium (33—42). Instrumental analytical methods (qv) used to determine trace amounts of tellurium include atomic absorption spectrometry, flame, graphite furnace, and hydride generation inductively coupled argon plasma optical emission spectrometry inductively coupled plasma mass spectrometry neutron activation analysis and spectrophotometry (see Mass SPECTROMETRY Spectroscopy, OPTICAL). Other instrumental methods include polarography, potentiometry, emission spectroscopy, x-ray diffraction, and x-ray fluorescence. 

Until now, little attention has been given to the analysis of ancient copper alloys with LA-ICP-MS. This type of material is usually analyzed with fast or instrumental neutron activation analysis (FNAA or INAA), particle induced X-ray emission (PIXE), X-ray fluorescence (XRF), inductively coupled plasma-atomic emission spectrometry or inductively coupled plasma-atomic absorption spectrometry (ICP-AES or ICP-AAS). Some of these techniques are destructive and involve extensive sample preparation, some measure only surface compositions, and some require access to a cyclotron or a reactor. LA-ICP-MS is riot affected by any of these inconveniences. We propose here an analytical protocol for copper alloys using LA-ICP-MS and present its application to the study of Matisse bronze sculptures. 

It can be seen from the above that the sample stream emerging from the plasma will be rich in free ions and.atoms of the elements from the sample. Thus, the ICP could provide an attractive source for analytical methods other than those based upon straightforward emission. Instruments using the ICP source as a basis for atomic fluorescence have been developed. More importantly, however, the ICP source has been applied to provide a source of ions for mass spectrometry (vide infra). 

Additional methods used were X-Ray fluorescence spectrometry (for total S determination) flame atomic absorption (Hg and As). Organic C was determined using Leco instrument, after decomposition of the carbonate by HC1. C,H,N,S in the kerogen were analysed using microanalysis techniques. 

Part V covers spectroscopic methods of analysis. Basic material on the nature of light and its interaction with matter is presented in Chapter 24. Spectroscopic instruments and their components are described in Chapter 25. The various applications of molecular absorption spectrometric methods are covered in some detail in Chapter 26, while Chapter 27 is concerned with molecular fluorescence spectroscopy. Chapter 28 discusses various atomic spectrometric methods, including atomic mass spectrometry, plasma emission spectrometry, and atomic absorption spectroscopy. 

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