V.G. Koloshnikov

Changes in cadmium concentrations in Antarctic ice and snow during the past 155,000 years

Changes in Cd concentrations in Antarctic ice and snow during the last full climatic cycle (the past 155,000 yrs) have been investigated by analysing various sections of the Dome C and Vostok deep Antarctic ice cores and several blocks of recent Antarctic snow. Each sample was mechanically decontaminated using ultraclean procedures and then analysed for Cd by the new ultrasensitive laser excited atomic fluorescence technique. Cd concentrations are found to have been highly variable in ancient Antarctic ice and therefore in the past pristine south polar atmosphere during the last climatic cycle, the highest values being observed during the cold terminal stages of the last and next to last ice ages. Concentrations measured in recent Antarctic snows are comparable with those in Antarctic Holocene ice several thousand years old, which suggests that the anthropogenic influence is probably still negligible for this heavy metal in the south polar atmosphere. For some of the samples, measured Cd concentrations can be simply accounted for by rock and soil dust and volcanic emissions, while for others there is a significant excess over the contributions from these two sources.

Automated laser excited atomic fluorescence spectrometer for determination of trace concentrations of elements

Abstract A new version of a computer-controlled laser excited atomic fluorescence spectrometer LAFAS-1 is described. The laser part of the spectrometer consists of a dye laser pumped by an excimer laser. Electrothermal atomization in an argon atmosphere and under vacuum conditions may be employed. The spectrometer was tested by acidified standard solutions prepared in the Grenoble clean laboratory. These standards were based on ultrapure water. A limit of detection for Pb of 0.18 pg/ml was achieved. For a 20 μl aliquot volume this value gives an absolute limit of detection of 4fg. A Pb content of 0.28 pg/ml in the Grenoble ultrapure water was measured by LAFAS-1 with a confidence interval of 0.05 pg/ml. This value is in excellent agreement with that obtained previously by isotope dilution mass spectrometry: 0.27 pg/ml.

The use of a dye laser for the detection of sub-picogram amounts of lead and iron by atomic fluorescence spectrometry

Abstract The frequency-doubled radiation of a dye laser excited by the second harmonic radiation of a YAG:Nd 3+ laser has been used as light source in graphite-tube atomic fluorescence analysis. Detection limits and linear ranges of the analytical curves for two elements, Pb and Fe, were studied. Direct-line fluorescence at 373.5 mn for Fe and at 405.8 nm for Pb was observed. The limits of detection, obtained using linear extrapolation to the background level, were 25 pg/ml for Fe and 2.5 pg/ml for Pb. This corresponds to an absolute detection limit of 0.75 pg for Fe and 0.075 pg for Pb. In the case of Pb, saturation was reached at an intensity of the exciting radiation of about 20 kW/cm 2 , but in the case of Fe, linearity was maintained up to 300 kW/cm 2 .

Laser excited fluorescence analysis with electrothermal sample atomization in vacuum

Abstract Electrothermal sample atomization in a vacuum for the laser excited atomic fluorescence method has been studied. A calibration curve for aqueous standards and synthetic standards, based on super-pure tin matrix was constructed. Limits of detection for aqueous solutions and pure tin were 0.2 and 0.5 ng g , respectively. The cobalt content in tin, vegetation samples and quartz glass was measured. For all investigated matrices and aqueous solutions the analytical signals for the samples with equal cobalt content coincided within the limits of experimental precision. It means that vacuum atomization decreases matrix interferences as a result of collisionless expansion of the atomized sample components.

Direct determination of lead in vostok antarctic ancient ice by laser excited atomic fluorescence spectrometry

Concentrations of lead (Pb) have been directly measured by laser excited atomic fluorescence spectrometry down to pg g^(−1) level in six sections of the 2083 m Vostok deep Antarctic ice core which had previously been mechanically decontaminated. Very small volumes of samples (20μl) were used, and there was no need for any preliminary chemical treatment or preconcentration step. The results are in very good agreement with those previously obtained for these core sections by isotope dilution mass spectrometry.

Detection of extremely low lead concentrations by laser atomic fluorescence spectrometry

Abstract The possibilities of the detection of extremely low atomic concentrations by laser atomic fluorescence were examined using Pb as an example. A detection limit of 250 atoms cm 3 or 30 atoms in the analytical volume was achieved in the experiments with saturated lead vapour in an evacuated quartz cell. A detection limit of 0.05 pg ml was achieved in the experiments with aqueous solutions as reference using a graphite atomizer.

Some characteristics of laser excited atomic fluorescence in a three-level scheme

Abstract Atomic fluorescence of Pb excited by the intense radiation of a tunable dye laser has been theoretically and experimentally studied. The accumulation of atoms at the metastable level has been shown to be significant. The existence of an optimal (for maximum analytical sensitivity) time duration of the laser pulse was shown theoretically. It was established experimentally that about 40% of the total number of Pb atoms are transferred on to the metastable level within a 5-ns, 10-kW/cm 2 laser pulse. This result agrees well with the calculations based on the three-level approximation for Pb atomic fluorescence.

Detection of trace amounts of toxic metals in environmental samples by laser-excited atomic fluorescence spectrometry. Invited lecture

Results for the direct determination of trace amounts of Pb and Cd in Antarctic and Greenland ancient ice and recent snow by laser-excited atomic fluorescence spectrometry (LEAFS) are presented. The whole procedure starting from field sampling, mechanical decontamination of the samples in an ultra-clean laboratory and final analysis of the decontaminated samples is described. The measured concentrations varied in the ranges 0.1–3 pg ml–1 for Cd and 0.3–30 pg ml–1 for Pb. The results for direct analysis by LEAFS agree favourable with those obtained by isotope dilution mass spectrometry and electrothermal atomic absorption spectrometry, which require time-consuming pre-treatment and pre-concentration stages.

Analytical applications of a LEAFS-ETA method

Abstract The results of some real sample analyses by laser excited atomic fluorescence spectrometry with electrothermal atomization are presented. Atomization in an argon atmosphere and under vacuum conditions were employed. A strong matrix interference for the real sample analysis under argon was observed. Some methods of reducing the matrix effect are discussed. The limits of detection for the LEAFS version under vacuum are worse than those in an argon atmosphere, but in the analysis of pure tin, plant samples, quartz glass, lead and copper alloys, no matrix interference was observed.