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41.
N. Omenetto 《Applied physics. B, Lasers and optics》1988,46(3):209-220
Several laser-based methods, namely laser induced fluorescence, laser enhanced ionisation and thermal lensing spectrophotometry are discussed with respect to their capabilities of approaching the extremely high detection sensitivity which is nowadays required in many fields of application, notably in high purity materials, in biomedicine and in the nuclear industry. The discussion is restricted to atomisers operated at atmospheric pressure, i.e., combustion flames, plasmas and graphite furnaces. It is shown that the analytical limit of detection can be in the range of femtograms and that double-resonance excitation possesses significant advantages over single-resonance excitation, both in terms of signal-to-noise ratio and spectral selectivity. In addition, the combination of the fluorescence and ionisation techniques represents a remarkable diagnostic tool. In the nuclear field, the suitability of the technique of thermal lensing for the direct determination and chemical speciation of very low levels of uranium in water is discussed. 相似文献
42.
H. Beissler G. A. Petrucci K. Bächmann U. Panne P. Cavalli N. Omenetto 《Fresenius' Journal of Analytical Chemistry》1996,355(3-4):345-347
A method is described for measuring the gold content of integral and size-segregated samples of atmospheric particulate matter. After acid digestion and a liquid/ liquid extraction, the sample are analysed by Two-Colour Laser Induced Fluorescence in a graphite furnace. An absolute instrumental detection limit of 1 fg is achieved. Assuming a sampled volume of 1 m3, this corresponds to an atmospheric concentration of 50 fg m–3. Due to blank limited noise, the above limits increase to 20 fg and 1 pg m–3, respectively. Results of the analysis of filter samples as well as of size-segregated impactor samples are presented. 相似文献
43.
44.
N. Omenetto N.N. Hatch L.M. Fraser J.D. Winefordner 《Spectrochimica Acta Part B: Atomic Spectroscopy》1973,28(2):65-78
A pulsed, tunable dye laser, pumped with a nitrogen laser is used to excite the atomic fluorescence of Sc, V, Hf, Nb, Os, Zr, W, Rh and Ru. Except in the case of Rh, the nitrous oxide-acetylene flame has been used. The results obtained for Zr and W are due to scattering of the laser radiation from unvaporized particles in the flame. Since, for most elements, several fluorescence lines of comparable intensity have been observed after the primary excitation process, the usefulness of observing non-resonance fluorescence is stressed, particularly with regard to the possibility of minimizing spectral interferences. The experimental results demonstrate that the limits of detection obtained with the dye laser source are comparable or better than the best atomic absorption limits only when the same primary absorption line used for the atomic absorption measurements can be used for exciting the fluorescence. 相似文献
45.
Beissler H Petrucci GA Bächmann K Panne U Cavalli P Omenetto N 《Analytical and bioanalytical chemistry》1996,355(3-4):345-347
A method is described for measuring the gold content of integral and size-segregated samples of atmospheric particulate matter. After acid digestion and a liquid/ liquid extraction, the sample are analysed by Two-Colour Laser Induced Fluorescence in a graphite furnace. An absolute instrumental detection limit of 1 fg is achieved. Assuming a sampled volume of 1 m(3), this corresponds to an atmospheric concentration of 50 fg m(-3). Due to blank limited noise, the above limits increase to 20 fg and 1 pg m(-3), respectively. Results of the analysis of filter samples as well as of size-segregated impactor samples are presented. 相似文献
46.
Nicoló Omenetto Giuseppe A. Petrucci Paolo Cavalli James D. Winefordner 《Fresenius' Journal of Analytical Chemistry》1996,355(7-8):878-882
The absolute limit of detection usually expresses the minimum amount of analyte detectable, while the relative limit of detection refers to the minimum concentration of analyte detectable. These concepts and their differences are obviously familiar to all analytical spectroscopists. Nevertheless, the two definitions are used liberally in the literature. For example, it is not uncommon to refer to exceptional sub-femtograms detection limits for a technique used to analyse ultratrace levels of an element in water and to a modest part per million detection limit of another technique used to characterise the microdistribution of an element in a sample mass of about one microgram. In this paper, an attempt is made to point out that the terms ultratrace analysis and microanalysis must refer to two conceptually different approaches and that there are cases in which one definition is more appropriate than the other. It is argued that, while there is no objection in reporting both detection limits when a single technique is evaluated, one has to be careful in choosing the most appropriate definition when different analytical techniques are compared. 相似文献
47.
Renato Seeber Gian Antonio Mazzocchin Ulderico Mazzi Edoardo Roncari Fiorenzo Refosco 《Transition Metal Chemistry》1984,9(8):315-318
Summary The anodic and cathodic behaviour of the complexesmer-[ReCl(CO)3(PMe2Ph)2],fac[ReCl(CO)3(PMe2Ph)2],mer-[ReCl(CO)3(PPh3)2], and [ReCl(CO)2(PMe2Ph)3] in acetonitrile solvent were studied using platinum and mercury electrodes. Cyclic voltammetry and controlled potential coulometry were the main electroanalytical techniques employed. The nature of the electrolysis products and of the electrode oxidation and reduction processes were investigated. In particular, [ReCl(CO)(MeCN)2(PMe2Ph)3][ClO4]2, [ReCl3(CO)2(PMe2Ph)2], and a not completely defined rhenium(-I) complex were electrochemically synthesized and characterized by means of i.r. and1H n.m.r. spectroscopy, and by elemental analysis. 相似文献
48.
The application of laser-based techniques to the study of different problems related to atmospheric chemistry is well established. Among the various laser spectroscopic methods, the focus here is directed towards selected applications of the laser photofragmentation and fluorescence techniques, which are used to investigate the complex chemistry of tropospheric sulphur species, with particular emphasis on the oxidation of dimethyl sulphide (DMS) and the consequent formation of sulphuric acid, and to the possibility of detecting with very high sensitivity and selectivity a particular element (e.g., gold) in size-segregated aerosol particles in view of its possible release as a tracer in the atmosphere. The atomic fluorescence technique is also applied to the real time detection of lead in a miniature air-acetylene flame, in which monodisperse aerosol particle are introduced. 相似文献
49.
Omenetto N Petrucci GA Cavalli P Winefordner JD 《Analytical and bioanalytical chemistry》1996,355(7-8):878-882
The absolute limit of detection usually expresses the minimum amount of analyte detectable, while the relative limit of detection refers to the minimum concentration of analyte detectable. These concepts and their differences are obviously familiar to all analytical spectroscopists. Nevertheless, the two definitions are used liberally in the literature. For example, it is not uncommon to refer to exceptional sub-femtograms detection limits for a technique used to analyse ultratrace levels of an element in water and to a modest part per million detection limit of another technique used to characterise the microdistribution of an element in a sample mass of about one microgram. In this paper, an attempt is made to point out that the terms "ultratrace analysis" and "microanalysis" must refer to two conceptually different approaches and that there are cases in which one definition is more appropriate than the other. It is argued that, while there is no objection in reporting both detection limits when a single technique is evaluated, one has to be careful in choosing the most appropriate definition when different analytical techniques are compared. 相似文献
50.
Summary 2,6-Dimethyl-4H-pyran-4-thione (DMTP) acts as a sulphur donor towards PtII and PdII halides yielding adducts of general formula [M(DMTP)2X2] (M=Pd or Pt; X=Cl, Br or I). When complex syntheses are performed in benzene, the solvated species [M(DMTP)2X2]·C6H6 (M=Pd or Pt; X=Cl or Br) are obtained. The compounds have been characterized by i.r. and n.m.r. (1H and13C) spectroscopy and by thermogravimetric data. The adduct geometry and the influence of benzene are discussed. 相似文献