Laser-induced fluorescence with an OPO system. Part II: direct determination of lead content in seawater by electrothermal atomization-laser-excited atomic fluorescence (ETA-LEAF).

Fluorescence was induced by coupling a laser with an optical parametric oscillator (OPO) to develop an analytical method for the direct determination of lead content, at ultra-trace level, in seawater by electrothermal atomization-laser-excited atomic fluorescence (ETA-LEAF). The optimization of atomization conditions, laser pulse energy, and mainly temporal parameters allowed us to reach a 3 fg detection limit (0.3 ng L(-1)) despite the low repetition rate of the device. The expected error on predicted concentrations of lead, at trace levels, in seawater was below 15%.

Molecular and atomic ultra trace analysis by laser induced fluorescence with OPO system and ICCD camera.

This paper presents a synthesis of some analytical potentialities of an equipment designed for both laser induced molecular and atomic fluorescence in the field of ultra-trace analysis (ng l(-1)). Excitation of fluorescence was performed with a pulsed Nd:Yag laser coupled to an optical parametric oscillator (OPO). Fluorescence spectra were recorded with a spectrograph and an intensified charge-coupled device (ICCD). The high energy and the tunability of the excitation combined with the sensitivity of the ICCD and the time-resolution provide better limit of detection (LOD) and selectivity. By molecular fluorescence, some major organic contaminants in the environment were studied, i.e. polycyclic aromatic hydrocarbons (PAHs) (benzo[a]pyrene and hydroxypyrene) and a pesticide (carbaryl). The LODs achieved by direct analysis were far below the restricted European values for tap water. Analysis was performed in water containing humic acids using time resolution to avoid the matrix fluorescence. By electro thermal atomisation-laser excited atomic fluorescence (ETA-LEAF), we detected traces of aluminium and lead in seawater. Some general considerations about the signal to noise ratio optimisation are reported. LODs reached the femtogram level.

Laser-induced fluorescence with an OPO system. Part I. Optimisation of the analytical system by use of experimental design methodology. Application to the direct quantification of traces of benzo[ a]pyrene.

This study deals with the optimisation and application of a method for direct analysis of trace pollutants in water by laser-induced fluorescence. The arrangement used consisted of an Nd:YAG Laser coupled with an optical parametric oscillator (LYOPO) and connected to a spectrophotometer and a high-sensitivity camera. Optimisation was achieved by developing an experimental design methodology to maximise the signal-to-noise ratio and reduce the limit of detection. The technique was then applied to the detection of benzo[ a]pyrene in water. The experimental results were evidence of its high sensitivity and time-resolution potential. The detection limit for benzo[ a]pyrene was 0.7 ng L(-1) in drinking water and 4 ng L(-1) in raw water containing 1 mg L(-1) humic acids.

Estimation of the sulfate content of hydrothermal vent bacterial polysaccharides by Fourier transform infrared spectroscopy.

Deep-sea hydrothermal vents are characterized by unusual chemical and physical parameters, including high pressure and temperature. In this extreme environment, unusual microorganisms of biotechnological importance survive. Polymer-producing bacteria have been specifically studied for several years with the aim of demonstrating their ability to produce unusual polysaccharides in terms of physical, chemical, and biological properties. Because sulfates play an important role in the biological properties of polysaccharides, it is very important to determine their content with accuracy. Fourier transform infrared spectroscopy (FT-IR) was used for sulfate analysis and the results were compared with those of other analytical techniques. We found a good correlation between FT-IR and other analytical techniques for sulfate concentrations ranging from 2.4 to 20%. The data indicated that this technique could be used to determine the chemical composition of the polymers along with a semiquantitative estimation of the sulfate content.