Laser excited atomic fluorescence spectrometry LEAF

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)... 

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). 

Principles and Characteristics The analytical capabilities of the conventional fluorescence (CF) technique (c/r. Chp. 1.4.2) are enhanced by the use of lasers as excitation sources. These allow precise activation of fluorophores with finely tuned laser-induced emission. The laser provides a very selective means of populating excited states and the study of the spectra of radiation emitted as these states decay is generally known as laser-induced fluorescence (LIF, either atomic or molecular fluorescence) [105] or laser-excited atomic fluorescence spectrometry (LEAFS). In LIF an absorption spectrum is obtained by measuring the excitation spectrum for creating fluorescing excited state... 

Graphite Furnace Laser-excited Atomic Fluorescence Spectrometry (GF-LEAFS)... 

LEAFS laser-excited atomic fluorescence spectrometry... 

Laser Fluorescence Noise Sources. Finally, let us examine a technique with very complex noise characteristics, laser excited flame atomic fluorescence spectrometry (LEAFS). In this technique, not only are we dealing with a radiation source as well as an atomic vapor cell, as In atomic absorption, but the source Is pulsed with pulse widths of nanoseconds to microseconds, so that we must deal with very large Incident source photon fluxes which may result in optical saturation, and very small average signals from the atomic vapor cell at the detection limit [22]. Detection schemes involve gated amplifiers, which are synchronized to the laser pulse incident on the flame and which average the analyte fluorescence pulses [23]. 

In laser vaporisation experiments, generating a plume , the laser s frequency may be synchronised with the resonance line of the element (analyte) to be analysed. The basic principles are (i) absorption of the radiation by the analyte (LAAS laser atomic absorption spectrometry) (ii) fluorescence (LIE, laser-induced fluorescence LEAFS) or (Hi) production of ionisation products (ions and electrons). LIF is an analytical method of high precision that is suitable for the measurement of diatomic species in the plume. Excitation spectroscopy or laser-excited fluorescence is not concerned with the spectral composition of the fluorescence but with how the overall intensity of emission varies with the wavelength of excitation. 

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