Laser fluorescence spectrometry

Recent research has included the areas of laser fluorescence spectrometry, mass spectrometry, tandem accelerator mass spectrometry and improvements in neutron activation analysis (Brauer and Strebin, 1979 Elmore et al., 1980 Goles et al., 1981 Bate and Stokely, 1982 Brauer et al., 1982 Stoffels, 1982). Neutron activation continues to be the method used for most low level analyses. 

Yuzefovsky et al. [241] used Cis resin to preconcentrate cobalt from seawater prior to determination at the ppt level by laser-excited atomic fluorescence spectrometry with graphite electrothermal atomiser. 

Laser-excited atomic fluorescence spectrometry has been used to determine down to 1 ng/1 of lead in seawater [359]. 

Cobalt Co(III) adsorbed on C18 bonded silica Laser excited atomic fluorescence spectrometry - [241]... 

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. 

Earlier methods for the determination of uranium in soils employed spectrophotometry of the chromophore produced with arsenic(III) at 655 nm [237 ] and neutron activation analysis [238]. More recently, laser fluorescence [239] and in situ laser ablation-inductively coupled plasma atomic emission spectrometry [240] have been employed to determine uranium in soil. D Silva et al. [241] compared the use of hydrogen chloride gas for the remote dissolution of uranium in soil with microwave digestion. 

Gholap D, Izmer A, Samber B, van Elteren J, Selih V, Evens R, Schamphelaere K, Janssen C, Balcaen L, Lindemann I, Vincze L, Vanhaecke F (2010) Comparison of laser ablation-induc-tively coupled plasma-mass spectrometry and micro-X-ray fluorescence spectrometry for elemental imaging. Anal Chim Acta 664 19-26. doi 10.1016/j.aca.2010.01.052... 

Atomic fluorescence spectrometry may be the most sensitive of the four techniques — particularly with laser assistance it has rarely been used with solid or slurry sampling and largely for determinations of metals in biological fluids, urine [105-107] and blood [106-110], Typical examples of solid sampling with this technique include the determination of Li in lithium oxalate [111], Ti in electrothermal atomizers [112], Pb and T1 in nickel-based alloys [113], and Co in high-purity tin [114],... 

Whatever the analytical method and the determinand may be, the greatest care should be devoted to the proper selection and use of internal standards, careful preparation of blanks and adequate calibration to avoid serious mistakes. Today the Antarctic investigator has access to a multitude of analytical techniques, the scope, detection power and robustness of which were simply unthinkable only two decades ago. For chemical elements they encompass Atomic Absorption Spectrometry (AAS) [with Flame (F) and Electrothermal Atomization (ETA) and Hydride or Cold Vapor (HG or CV) generation]. Atomic Emission Spectrometry (AES) [with Inductively Coupled Plasma (ICP), Spark (S), Flame (F) and Glow Discharge/Hollow Cathode (HC/GD) emission sources], Atomic Fluorescence Spectrometry (AFS) [with HC/GD, Electrodeless Discharge (ED) and Laser Excitation (LE) sources and with the possibility of resorting to the important Isotope... 

Laser-excited atomic fluorescence spectrometry allowed for the determination of Pb in Vostok deep ice cores with a precision of 20% (63, 64). Values of 2-40 pg g were measured for ages spanning the 155,000-26,000 years BP. The technique permitted sample volumes as low as 20 pi to be dealt with without any preliminary treatment, thus greatly facilitating contamination control. 

C. F. Boutron, M. A. Bolshov, V. G. Koloshnikov, C. C. Patterson, N. 1. Barkov, Direct determination of lead in Vostok Antarctic ancient ice by laser excited atomic fluorescence spectrometry. Atm. Environ., 24A (1990), 1797-1800. 

Laser Excited Atomic Fluorescence Spectrometry (LEAFS) (40, 41, 46-48), Thermal Ionisation Mass Spectrometry (TIMS) (6, 42, 43, 45, 49-53), Electrothermal Atomization Atomic Absorption Spectrometry (ETA-AAS) (24, 28, 54, 55), Differential Pulse Anodic Stripping Voltammetry (DPASV) (27, 49, 56, 57),... 

Laser Excited Atomic Fluorescence Spectrometry (LEAFS) Bi, Cd, Pb (40, 41, 46-48)... 

M. A. Bolshov, C. F. Boutron, F. M. Ducroz, U. Gorlach, O. M. Kompanetz, S. M. Rudniev, B, Hutch, Direct ultratrace determination of cadmium in Antarctic and Greenland snow and ice by laser atomic fluorescence spectrometry. Anal. Chim. Acta, 251 (1991), 169-175. 

M. A. Bolshov, S. N. Rudniev, J. P. Candelone, C. F. Boutron, S. Hong, Ultratrace determination of Bi in Greenland snow by laser atomic fluorescence spectrometry, Spectrochim. Acta, 49B (1994), 1445-1452. 

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. 

Sources for atomic spectrometry include flames, arcs, sparks, low-pressure discharges, lasers as well as dc, high-frequency and microwave plasma discharges at reduced and atmospheric pressure (Fig. 5) [28], They can be characterized as listed in Table 2. Flames are in thermal equilibrium. Their temperatures, however, at the highest are 2800 K. As this is far below the norm temperature of most elemental lines, flames only have limited importance for atomic emission spectrometry, but they are excellent atom reservoirs for atomic absorption and atomic fluorescence spectrometry as well as for laser enhanced ionization work. Arcs and sparks are... 

Tab. 18. Detection limits in laser atomic fluorescence spectrometry.

Bolshov M. A., Zybin A. V. and Smirenkina I. I. (1981) Atomic fluorescence spectrometry with laser sources, Spcctrochim Acta, Part B 36 1143-1152. 

Bolshov M. A., Rudniev S. N., Rudnieva A. A., Boutron C. F. and Hong S. (1997) Determination of heavy metals in polar snow and ice by laser excited atomic fluorescence spectrometry with electrothermal atomization in a graphite cup, Spedrochim Acta, Part B 52 1535-1544. 

Smith B. W., Quentmeier A., Bolshov M. and Niemax K. (1999) Measurement of uranium isotope ratios in solid samples using laser ablation and diode laser-excited atomic fluorescence spectrometry, Spectrochim Acta, Part B 54 943—958. 

In fluorescence spectrometry, the intensity of fluorescence is proportional to the intensity of the radiation source (see Section 16.15). Various continuum UV sources are used to excite fluorescence (see below). But the use of lasers has gained in importance because these monochromatic radiation sources can have high relative intensities. Table 16.5 lists the wavelength and power characteristics of some common laser sources. Only those that lase in the ultraviolet region are generally useful for exciting fluorescence. The nitrogen laser (337.1 nm), which can only be operated in a pulsed mode (rather than continuous wave, or CW, mode), is useful... 

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). 

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