ABSTRACT
The direct determination of element signatures in polar ice core samples from Greenland by laser ablation with subsequent inductively coupled plasma mass spectrometry analysis has been investigated. A cryogenic sample chamber enables the element determination in ice directly from the solid (frozen) state. A procedure was developed to analyse up to 38 elements (traces: Mg, Al, Fe, Zn, Cd, Pb and rare earth elements; minor constituents: Na) in ice samples from Greenland with a previously unachievable spatial resolution of 4 mm along the core axis. This resolution is helpful to detect seasonal variations of element concentration in thin annual layers of deep ice. We report operating conditions and analytical performance of the experimental set up, the improvement of signal stability by (17)OH internal standardisation and application of a desolvation unit. Calibration of the system was performed with frozen multielement standard solutions along a special preparation procedure. Detection limits for the tracers Na, Mg (sea salt), Al (mineral dust) and Zn (anthropogenic source) are 0.1-1 microg kg(-1). Best detection limits in the range of 0.001-0.01 microg kg(-1 )were reached for Co, Pb and all rare earth elements. To validate the method, frozen standard reference materials were measured. The recovery is about +/-10%. Greenland ice core samples from different ages were analysed with the new technique. The results obtained by laser ablation were compared with values from solution analysis, available published data and the particle content. Most elements have shown good correlation with the particle content in the Greenland samples; however, differences could be seen between the values obtained by laser ablation and solution bulk analysis after a tri-acid digestion. The influence of particles is discussed. The high spatially resolved 2D mapping of element concentrations shows strong inhomogeneities along the core axis most probably due to seasonal variations of element deposition.
ABSTRACT
A new method for the detection of trace elements in polar ice cores using laser ablation with subsequent inductively coupled plasma mass spectrometry analysis is described. To enable direct analysis of frozen ice samples a special laser ablation chamber was constructed. Direct analysis reduces the risk of contamination. The defined removal of material from the ice surface by means of a laser beam leads to higher spatial resolution (300-1000 microm) in comparison to investigations with molten ice samples. This is helpful for the detection of element signatures in annual layers of ice cores. The method was applied to the successful determination of traces for the elements Mg, Al, Fe, Zn, Cd, Pb, some rare-earth elements (REE) and minor constituents such as Ca and Na in ice cores. These selected elements serve as tracer elements for certain sources and their element signatures detected in polar ice cores can give hints to climate changes in the past. We report results from measurements of frozen ice samples, the achievable signal intensities, standard deviations and calibration graphs as well as the first signal progression of 205Pb in an 8,000-year-old ice core sample from Greenland. In addition, the first picture of a crater on an ice surface burnt by an IR laser made by cryogenic scanning electron microscopy is presented.
ABSTRACT
Laser ablation inductively coupled plasma mass spectrometry (laser ablation-ICP-MS) has been applied to the spatially resolved determination of the elements Mg, Ca, Cu, Ni, Ba, Al, Pb, Sr and Mn in green leaves of oak trees. Instrument operating parameters such as the laser wavelength and the pulse energy have been optimized to provide the sensitivity and reproducibility required for the analysis. The method provides spatial resolution down to 300 microm with the use of the 355 nm wavelength (3rd harmonic of the 1,064 nm Nd:YAG laser wavelength) and the pulse energy of 50 mJ. Plant standards and cellulose, doped with multi element solution standards, dried and pressed to pellets were used as calibration samples. To compensate for signal fluctuations caused by the variation of the ablated sample mass 13C was used as a "natural" internal standard. The accuracy of the calibration was verified with selected samples analyzed by ICP-MS (high pressure digestion, 170 degrees C, 10(7) Pa, HNO3, 2 h) and by laser ablation-ICP-MS. Recovery rates between 93% (Cu) and 108% (Mn) were obtained. Leaves taken from oak trees (Quercus robur) were analyzed.
Subject(s)
Plant Leaves/chemistry , Rosales/chemistry , Trace Elements/analysis , Trees , Calibration , Lasers , Mass Spectrometry/methodsABSTRACT
An element-specific detection method, based on atomic absorption spectrometry (AAS) using solar blind photocells instead of a dispersion system, is described for the determination of Hg-, As-, and Se-species. Spectrometric investigations of AAS background lamps for As and Se measured with a CsI-cathode photocell shows its quality as narrow band detector. Species determination can be carried out subsequently to prior separation by HPLC or GC. The LODs for alkylated Hg species were below 1 ng/L, and for methylated As species below 1 microg/L. The relative standard deviation was < 10%. With the components described the production of cheap and automated dedicated speciation spectrometers is possible.
ABSTRACT
The autocorrelation function of the concentration of elements in growth rings has been used to study their migration from ring to ring. The correlation time which can be calculated by the autocorrelation function gives an indication of the transport of elements. However, a large correlation time might only be taken as a necessary criterion for the migration but not for a sufficient one. Laser sampling-ICP-MS has been used for the determination of the contents of elements in the rings of an 150 years old oak - the autocorrelation functions of selected elements have been calculated. Large correlation times have been only obtained for Ca, Fe and Cr. It may be concluded that Mg, Zn, Cu, Sr, Pb, Ni, Ba, Al and Mn hardly migrate radially in the trunk of an oak.
ABSTRACT
Particulates of platinum group elements (Pt, Rh, Pd, Ir) emitted in automotive catalyst exhaust were measured down to the pg/m(3) level. Samples were taken from a standard type three-way catalyst equipped gasoline engine, running on a computer controlled dynamometer. Particulates in catalyzed car exhaust were sampled fractionated according to size by using the cascade impactor with separate targets mounted underneath each nozzle. The targets, small flat discs made of pure graphite, were subsequently analyzed by ETV-ICP-MS without any preparatory steps.
