| 1. |
- Chekalin, Nikolai, et al.
(författare)
-
Laser-induced fluorescence in graphite furnaces under low pressure conditions as a powerful technique for studies of atomization mechanisms : investigation of Ag
- 1994
-
Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Elsevier. - 0584-8547 .- 1873-3565. ; 49:12-14, s. 1411-1435
-
Tidskriftsartikel (refereegranskat)abstract
- A new method for accurate studies of atomization processes of various elements in graphite furnaces has been developed. It utilizes the highly sensitive Laser-Induced Fluorescence spectrometry technique for detection of atoms in Graphite Furnaces under Low Pressure conditions (LIF-GF-LP). The high sensitivity of the LIF technique enables the study of atomization processes at low pressures under true analytical conditions (i.e. for low analyte mass) with a minimum of influences from diffusion processes. This first work is concerned with an investigation of the atomization mechanisms of Ag. It was found that the LIF-GF signal area was linear with pressure for virtually all pressures. The LIF-GF signal shape (versus time as well as versus 1/T) was found to vary with both pressure and concentration. The signals were, in general, found to have a shorter duration and higher appearance and peak temperatures, the higher the pressure. Activation energies could be evaluated from the LIF-GF-LP curves very accurately by the Smets method. Excellent agreements with the predicted linear relationship were obtained for a major part of the signal curve (> 50%) under many sample and furnace conditions. Studies of the activation energy dependence on pressure, analyte mass and heating rate gave valuable information about the atomization mechanisms of Ag in graphite furnaces. The findings support a picture that Ag atomizes as individual adatoms under low pressure and low analyte mass conditions. Under atmospheric conditions, repeated desorption and adsorption processes delay the appearance of the signal in time as well as being responsible for formation of 2-D and 3-D microstructures on the surface.
|
|
| 2. |
- Enger, Jonas, et al.
(författare)
-
Direct detection of antimony in environmental and biological samples at trace concentrations by laser-induced fluorescence in graphite furnace with an intensified charge coupled device
- 1995
-
Ingår i: Journal of Analytical Atomic Spectrometry. - : Royal Society of Chemistry. - 0267-9477 .- 1364-5544. ; 10:8, s. 539-549
-
Tidskriftsartikel (refereegranskat)abstract
- The technique of laser-induced fluorescence in graphite furnace (LIF-GF) with intensified charge coupled device (ICCD) detection was used for the detection of Sb at pg ml-1 concentrations in various biological and environmental samples. The ICCD detector permits the simultaneous multichannel detection of large fluorescence wavelength regions, which gives the user the possibility to control and correct for various background signals (which is important when complex environmental and biological samples are to be analysed). The detection limit for Sb in a pure water solution was found to be 5 fg. Antimony was directly detected in pure aqueous solutions down to fg ml-1 concentrations. A variety of aqueous and solid environmental and biological samples were investigated with respect to their Sb content. Good agreement between the measured and certified Sb contents (at pg ml-1 - ng ml-1 levels) was obtained for various certified reference materials, viz., marine sediments (MESS-1 and BCSS-1) and riverine water (SLRS-2). Measurements of the Sb content in non-certified natural drinking water, estuarine water reference material (SLEW-1), serum reference material (Seronorm), and whole blood of healthy Swedish people were also performed. After a thorough investigation and elimination of various sources of contamination (regarding sampling and sample storage), typical levels of Sb in human whole blood at or below several tens of pg ml-1 were obtained. These levels are significantly lower than previously established values of the normal Sb content in human blood. The detection limit for Sb in human whole blood was close to that of pure water.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
- Marunkov, Alexander, et al.
(författare)
-
Detection of trace amounts of Ni by laser-induced fluorescence in graphite furnace with intensified charge coupled device
- 1994
-
Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Elsevier. - 0584-8547 .- 1873-3565. ; 49:12-14, s. 1385-1410
-
Tidskriftsartikel (refereegranskat)abstract
- A laser-induced fluorescence in graphite furnace (LIF-GF) set-up has been equipped with an intensified CCD detector (ICCD) that enables simultaneous multichannel detection of large wavelength regions. The main advantages of such a system in comparison with conventional photomultiplier detection are: simultaneous detection of several fluorescence wavelengths for easy characterization of excitation and fluorescence spectra and for an increase of the absolute sensitivity and spectral selectivity; simultaneous monitoring of background signals, such as those due to matrix interferences, blackbody radiation and scattered laser light; decrease of the susceptibility to radio-frequency pick-ups emitted from the pump laser due to the delayed read-out procedure; time-resolved studies of fluorescence spectra for improved elemental selectivity or for studies of atomization processes, and a possibility to perform two-dimensional imaging of height distributions of atomization and, in combination with an imaging spectrometer. diffusion processes in the furnace. The first work on LIF-GF with ICCD detection has been performed on Ni. The most sensitive and versatile excitation and detection wavelengths have been identified. Detection limits in water solutions by the LIF-GF technique have been improved by two orders of magnitude and are found to be 0.015 pg with ICCD and 0.01 pg using a photomultiplier at the most sensitive excitation and detection wavelengths. Nickel in ng/ml concentrations has been detected in aqueous standard reference samples with sodium concentrations ranging from μg/ml to % (riverine water and estuarine water) with good accuracy and precision. The Ni contents of standard riverine and estuarine water were determined to 1.00 +/- 0.11 and 0.75 +/- 0.07 ng/m
|
|
