Atomic fluorescence applications

Sekatskii S K and Ketokhov V S 1996 Single fluorescence centres on the tips of crystal needles first observation and prospects for application in scanning one-atom fluorescence microscopy Appl. Phys. B 63 525-30... 

Instead of employing the high temperature of a flame to bring about the production of atoms from the sample, it is possible in some cases to make use of either (a) non-flame methods involving the use of electrically heated graphite tubes or rods, or (b) vapour techniques. Procedures (a) and (b) both find applications in atomic absorption spectroscopy and in atomic fluorescence spectroscopy. 

As indicated in Fig. 21.3, for both atomic absorption spectroscopy and atomic fluorescence spectroscopy a resonance line source is required, and the most important of these is the hollow cathode lamp which is shown diagrammatically in Fig. 21.8. For any given determination the hollow cathode lamp used has an emitting cathode of the same element as that being studied in the flame. The cathode is in the form of a cylinder, and the electrodes are enclosed in a borosilicate or quartz envelope which contains an inert gas (neon or argon) at a pressure of approximately 5 torr. The application of a high potential across the electrodes causes a discharge which creates ions of the noble gas. These ions are accelerated to the cathode and, on collision, excite the cathode element to emission. Multi-element lamps are available in which the cathodes are made from alloys, but in these lamps the resonance line intensities of individual elements are somewhat reduced. 

The scope of this review Is limited to electrothermal atomic absorption spectrometry, with emphasis upon Its clinical applications. This article Is Intended to supplement the recent treatises on the basic technique which have been written by Aggett and Sprott ( ) > Ingle ( ), Klrkbrlght (34), Price (63), and Woodrlff (83). This resume does not consider various related topics, such as (a) atomic fluorescence or emission spectrometry (b) non-flame atomization devices which employ direct current... 

Klrkbrlght, G. F. "The Application of Non-Flame Atom Cells In Atomic Absorption and Atomic Fluorescence Spectroscopy. 

Hedeishi and McLaughlin [457] have reported the application of the Zeeman effect for the determination of mercury. Atomic absorption and atomic fluorescence techniques using closed system reduction-aeration have been applied widely to determine mercury concentrations in natural samples [458-472]. 

There are many fluorescent indicators for detection of [Mg +] [319] and fluori-nated NMR reporters have been proposed. The simplest is fluorocitrate [313], which shows a change in chemical shift upon binding Mg +. However, it is critical that the reporter molecule be used as the + isomer only, which has relatively little toxicity [320], Levy et al. [8,321] developed the o-aminophenol-A/,A/,0-triacetic acid (APTRA) structure both for fluorescent application and by incorporation of fluorine atoms for F NMR, which have been used in the perfused rat heart [322]. 

T. Stoichev, R. C. Rodriguez-Martin-Doimeadios, D. Amouroux, N. Molenat and O. F. X. Donard, Application of cryofocusing hydride generation and atomic fluorescence detection for dissolved mercury species determination in natural water samples, J. Environ. Monit., 4, 2002, 517-521. 

New boxed applications include an arsenic biosensor (Chapter 0). microcantilevers to measure attograms of mass (Chapter 2), molecular wire (Chapter 14), a fluorescence resonance energy transfer biosensor (Chapter 19), cavity ring-down spectroscopy for ulcer diagnosis (Chapter 20), and environmental mercury analysis by atomic fluorescence (Chapter 21). 

HPLC units have been interfaced with a wide range of detection techniques (e.g. spectrophotometry, fluorimetry, refractive index measurement, voltammetry and conductance) but most of them only provide elution rate information. As with other forms of chromatography, for component identification, the retention parameters have to be compared with the behaviour of known chemical species. For organo-metallic species element-specific detectors (such as spectrometers which measure atomic absorption, atomic emission and atomic fluorescence) have proved quite useful. The state-of-the-art HPLC detection system is an inductively coupled plasma/MS unit. HPLC applications (in speciation studies) include determination of metal alkyls and aryls in oils, separation of soluble species of higher molecular weight, and separation of As111, Asv, mono-, di- and trimethyl arsonic acids. There are also procedures for separating mixtures of oxyanions of N, S or P. 

The use of GC-MIP-AES is advantageous because it avoids the predecomposition step required in the AAS detection mode. The first applications of the MIP-AES detector for Hg speciation and detection were reported in the 1970s [27-29]. Despite the overall good detection ability of the detectors, however, most of the above methods require large sample volumes, tedious solvent extraction procedures, and usually lead to the final determination of only the Me-Hg species. The description of the feasibility of quantitative in situ aqueous ethylation of Hg2-1- and Me-Hg followed by on-line preconcentration and detection by atomic fluorescences pectro-metry (AFS) or AAS certainly produces a wealth of information since it allows all Hg species to be detected in the same chromatographic run. Also on-line speciation of Hg and Me-Hg by chromatography-AFS hydride generation (HG) was used [30]. 

As noted earlier, USNs have been employed for sample insertion into atomic spectrometers suoh as flame atomio absorption spectrometry (FAAS) [9,10], electrothermal atomic absorption speotrometry (ETAAS) [11], atomic fluorescence spectrometry (AFS) [12,13], induotively ooupled plasma-atomic emission spectrometry (ICP-AES) [14,15], inductively coupled plasma-mass spectrometry (ICP-MS) [16,17] and microwave induced plasma-atomic emission spectrometry (MIP-AES) [18,19]. Most of the applications of ultrasonic nebulization (USNn) involve plasma-based detectors, the high sensitivity, selectivity, precision, resolution and throughput have fostered their implementation in routine laboratories despite their high cost [4]. 

The association of a spectrometer with a liquid chromatograph is usually to aid in structure elucidation or the confirmation of substance identity. The association of an atomic absorption spectrometer with the liquid chromatograph, however, is usually to detect specific metal and semi-metallic compounds at high sensitivity. The AAS is highly element-specific, more so than the electrochemical detector however, a flame atomic absorption spectrometer is not as sensitive. If an atomic emission spectrometer or an atomic fluorescence spectrometer is employed, then multi-element detection is possible as already discussed. Such devices, used as a LC detector, are normally very expensive. It follows that most LC/AAS combinations involve the use of a flame atomic absorption spectrometer or an atomic spectrometer fitted with a graphite furnace. In addition in most applications, the spectrometer is set to monitor one element only, throughout the total chromatographic separation. 

Piy2) from NaK photodissociation found to vary markedly with the application of an external magnetic field Photodissociation of Nal, Til, HgBr, and PbBr using polarized 193 nm radiation. Polarization of the atomic fluorescence observed for T1 and HgBr but not for Na and Pb. Polarization of the Hg fluorescence observed to be weak Evidence of emission from transition states of Nal in the photolysis of Nal at 222 nm... 

Kingsley, G. R., Clinical chemistry. Anal. Chem. 43, 15R-41R (1971). Kirkbright, G. F., The application of non-flame atom cells in atomic absorption and atomic fluorescence spectroscopy. Analyst London) 96, 609-623 (1971). Kirkbright, G. F., Saw, C. G., and West, T. S., Determination of trace amounts of tellurium by inorganic spectrofluorimetry at liquid nitrogen temperature. Analyst London) 94, 457-460 (1969). 

Inorganic extractables/leachables would include metals and other trace elements such as silica, sodium, potassium, aluminum, calcium, and zinc associated with glass packaging systems. Analytical techniques for the trace analysis of these elements are well established and include inductively coupled plasma—atomic emission spectroscopy (ICP-AES), ICP-MS, graphite furnace atomic absorption spectroscopy (GFAAS), electron microprobe, and X-ray fluorescence. Applications of these techniques have been reviewed by Jenke. " An example of an extractables study for certain glass containers is presented by Borchert et al. ". ... 

When the extracted analytes provide no response on passing through a flow-cell located in a detector connected on-line to the continuous extractor via a dynamic manifold, the extractor outlet can also be connected to a manifold where the extract is merged with a stream of an appropriate reagent to derivatize the analytes as they are extracted, thereby enabling their subsequent on-line determination. This approach has been used to extract selenium from sand and sludge [57], and selenium, arsenic and mercury from coal. In the latter application, on-line derivatization with sodium tetrahydroborate (for selenium and arsenic) and tin chloride (for mercury) allowed the analytes to be determined in a direct manner using the atomic fluorescence technique [46]. 

When using two lasers and applying two-photon spectroscopy, only those atoms that do not have a velocity component in the observation direction will undergo LEI. Then the absorption signals become very narrow (Doppler-free spectroscopy). This enhances the selectivity and the power of detection, however, it also makes isotope detection possible. Uranium isotopic ratios can thus be detected, similarly to with atomic fluorescence [673] or diode laser AAS. Thus for dedicated applications a real alternative to isotope ratio measurements with mass spectrometry is available. 

J. D. (1979) Atomic fluorescence spectrometry basic principles and applications, Prog Anal Spectrosc 2 1-183. 

The application of microtron photon activation analysis with radiochemical separation in environmental and biological samples was described by Randa et al. (2001), and both flame and plasma emission spectroscopic methods are also widely used. A more recently developed technique is that of laser-excited atomic fluorescence spectrometry (LEAFS) (Cheam et al. 1998). 

Many other methods have been applied - or continue to be applicable - to elemental determinations, but have not been individually covered in this chapter due not only to page constraints but also to their less dominant roles in elemental determinations and current less widespread usage. Methods include thermochemical or thermal analysis, infra-red spectrometry (IR), near-infra-red analysis (NIR), NMR, EPR, kinetic methods of analysis, Mbssbauer spectrometry, gravimetry, volumetry (titrimetry), gas-ometry, fluorescence spectrometry (molecular) (including fluorometry, fluorimetry, spectrophotofluorometry, phosphorimetry, chemiluminescence), atomic fluorescence spectrometry (AFS) (including ICP atomic fluorescence, ICP-AFS, and flame atomic fluorescence). The chapter by Watkinson... 

Caupeil, J.E., Hendrikse, P.W., and Bongers, J.S. (1976) Non-dispersive atomic-fluorescence spectrometry for the determination of mercury and its application to fish samples. Anal. Chim. Acta, 81, 53-60. 

La.scrs. with their high intensities and narrow band-widths. would appear to be the ideal. source for atomic fluorescence measurements. Their high cost and oper-titional complexities, however, have discouraged their widespread application to routine atomic fluorescence methods. 

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