Johannes T. van Elteren

Validation of bismuth film electrode for determination of cobalt and cadmium in soil extracts using ICP-MS.

A study is presented on the use of the bismuth film electrode (BiFE) operated in the anodic stripping and the cathodic adsorptive stripping voltammetry (ASV, CAdSV) modes, for the determination of two trace heavy metals (Cd and Co, respectively), in soil extract samples. Two types of BiFE were examined in this study: the in situ prepared BiFE, which was employed in ASV determination of Cd, and the ex situ prepared BiFE, which was used in CAdSV of Co with dimethylglyoxime (DMG) as complexing agent. A series of unpretreated soil extracts with varying Cd and Co concentrations were analyzed, and the results obtained compared to those determined using inductively coupled plasma-mass spectrometry (ICP-MS). The results revealed the suitability of stripping analysis at the BiFE for determination of mugl(-1) levels of heavy metals in soil extracts. The promising results obtained here, coupled with the non-toxic nature of bismuth (in comparison to commonly used mercury electrodes employed in stripping analysis), offer great promise in centralized and decentralized analysis of trace heavy metals in complex environmental matrices.

Determination of arsenic compounds in reference materials by HPLC-(UV)-HG-AFS

Arsenic compounds were determined in six reference materials of biological origin. None of them has yet been certified for arsenic compounds but some are in the process of certification; for most of these reference materials indicative literature values are available. Eight commonly used arsenic standards were used for quantification using a recently developed hyphenated speciation system comprising high performance liquid chromatography (HPLC) and atomic fluorescence spectrometry (AFS), interfaced via a UV-photoreactor and a hydride generation (HG) unit. Absolute detection limits were ca. 0.2 and 0.4 ng As for separation on anion and cation exchange columns, respectively. Our results agree well with indicative literature values which were generated by different authors using various separation and detection methods. The HPLC-(UV)-HG-AFS system validated in this way is suitable for quantification of eight arsenic compounds. Moreover, the system is capable of separation of at least six more compounds in the mentioned reference materials, of which two could be attributed to arsenosugars (OH and phosphodiester form) but due to the lack of standards, quantification was not possible. For accurate and extensive speciation analysis the availability of certified reference materials and standards for arsenic compounds should be promoted.

Comparison of laser ablation-inductively coupled plasma-mass spectrometry and micro-X-ray fluorescence spectrometry for elemental imaging in Daphnia magna

Visualization of elemental distributions in thin sections of biological tissue is gaining importance in many disciplines of biological and medical research. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and scanning micro-X-ray fluorescence spectrometry (micro-XRF) are two widely used microanalytical techniques for elemental mapping. This article compares the capabilities of the two techniques for imaging the distribution of selected elements in the model organism Daphnia magna in terms of detection power and spatial resolution. Sections with a thickness of 10 and 20 microm of the fresh water crustacean Daphnia magna were subjected to LA-ICP-MS and micro-XRF analysis. The elemental distributions obtained for Ca, P, S and Zn allow element-to-tissue correlation. LA-ICP-MS and micro-XRF offer similar limits of detection for the elements Ca and P and thus, allow a cross-validation of the imaging results. LA-ICP-MS was particularly sensitive for determining Zn (LOD 20 microg g(-1), 15 microm spot size) in Daphnia magna, while the detection power of micro-XRF was insufficient in this context. However, LA-ICP-MS was inadequate for the measurement of the S distributions, which could be better visualized with micro-XRF (LOD 160 microg g(-1), 5 s live time). Both techniques are thus complementary in providing an exhaustive chemical profiling of tissue samples.

Preliminary study on the determination of selenium compounds in some selenium-accumulating mushrooms

Using various chromatographic techniques (size exclusion, anion exchange, and cation exchange) combined with several detectors (neutron activation analysis and atomic fluorescence spectrometry), an attempt was made to characterize selenium compounds in some edible, selenium-accumulating mushrooms (Albatrellus pes-caprae and Boletus edulis).The mushrooms contained mostly low-molecular-weight (6 kDa) selenium compounds. After proteolysis, only a small fraction of the extractable selenium could be identified as selenite (3.0–9.2%, Albatrellus pes-caprae), selenocystine (minor, Albatrellus pes-caprae; 7.5%, Boletus edulis), or selenomethionine (1.0%, Boletus edulis), leaving the form of the bulk still to be elucidated.

Development of a fast laser ablation-inductively coupled plasma-mass spectrometry cell for sub-μm scanning of layered materials

Performance data are reported for a commercially available laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) setup, equipped with a custom-made cell. The low dispersion ablation cell and the connecting tubing achieve a 99% washout of the aerosol in ∼6 ms, enabling separated pulse responses at frequencies up to 200–300 Hz. In addition, the cell employed supports a post-acquisition methodology for the deconvolution of overlapping ablation positions in scanning mode by an iterative Richardson–Lucy algorithm. This enables correction of the distortion in the scan profile upon traversing layers with dimensions below the physical size of the laser beam. By overlapping the ablation positions of a 1 μm diameter laser beam, a lateral resolution in the order of 0.3 ± 0.1 μm was demonstrated for scanning of μm-sized layers in high capacitance multi-layer ceramic capacitors.

Differential cadmium and zinc distribution in relation to their physiological impact in the leaves of the accumulating Zygophyllum fabago L

Cadmium and zinc share many similar physiochemical properties, but their compartmentation, complexation and impact on other mineral element distribution in plant tissues may drastically differ. In this study, we address the impact of 10 μm Cd or 50 μm Zn treatments on ion distribution in leaves of a metallicolous population of the non-hyperaccumulating species Zygophyllum fabago at tissue and cell level, and the consequences on the plant response through a combined physiological, proteomic and metabolite approach. Micro-proton-induced X-ray emission and laser ablation inductively coupled mass spectrometry analyses indicated hot spots of Cd concentrations in the vicinity of vascular bundles in response to Cd treatment, essentially bound to S-containing compounds as revealed by extended X-ray absorption fine structure and non-protein thiol compounds analyses. A preferential accumulation of Zn occurred in vascular bundle and spongy mesophyll in response to Zn treatment, and was mainly bound to O/N-ligands. Leaf proteomics and physiological status evidenced a protection of photosynthetically active tissues and the maintenance of cell turgor through specific distribution and complexation of toxic ions, reallocation of some essential elements, synthesis of proteins involved in photosynthetic apparatus or C-metabolism, and metabolite synthesis with some specificities regarding the considered heavy metal treatment.

Multi-element quantification of ancient/historic glasses by laser ablation inductively coupled plasma mass spectrometry using sum normalization calibration.

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for quantitative analysis of ancient/historic glasses is subject to calibration issues which have been addressed in this work. Since ancient/historic glasses have widely ranging matrix compositions, a complementary analysis by an alternative method is generally employed to determine at least one major element which can be used as an internal standard. We demonstrate that such a complementary analysis is unnecessary using a so-called sum normalization calibration technique (mathematically formulated) by simultaneous measurement of 54 elements and normalizing them to 100% [w/w] based on their corresponding oxide concentrations. The crux of this approach is that by assuming a random internal standard concentration of a particular major oxide, e.g. SiO2, the normalization algorithm varies the internal standard concentration until the cumulated concentrations of all 54 elemental oxides reach 100% [w/w]. The fact that 54 elements are measured simultaneously predetermines the laser ablation mode to rastering. Nine glass standards, some replicating historic compositions, were used for calibration. The linearity of the calibration graphs (forced through the origin) represented by the relative standard deviations in the slope were between 0.1 and 6.6% using SiO2 as an internal standard. This allows high-accuracy determination of elemental oxides as confirmed by good agreement between found and reported values for major and minor elemental oxides in some synthetic glasses with typical medieval composition (European Science Foundation 151 and 158). Also for trace elemental concentrations of lanthanides in a reference glass (P&H Developments Ltd. DLH7, a base glass composition with nominally 75 microg g(-1) elements added) accurate data were obtained. Interferences from polyatomic species and doubly charged species on the masses of trace elements are possible, depending on the base composition of the glass, with Ba and Sb glasses showing potential interferences on some lanthanides. We showed that they may be reduced to a great extent by using an Octopole Reaction System although the overall sensitivity decreases which may be a problem for some low-level determinations.

Impact of salinity on early reproductive physiology of tomato (Solanum lycopersicum) in relation to a heterogeneous distribution of toxic ions in flower organs

The effect of short-term treatments (10 days) by a high salt level (150 mm NaCl) on vegetative and reproductive development was investigated in tomato plants (Solanum lycopersicum L. cv. Ailsa Craig) at two developmental stages. Salinity applied during flowering transition reduced shoot biomass and delayed the appearance of the first inflorescence. Both shoot and root biomasses were reduced when salt was applied during the development of the first inflorescence. At both stages, areas of young leaves decreased and time to first anthesis increased, while total number of flowers in the first inflorescence was not affected. Flower abortion, reduction of pollen number and viability were higher when salinity was applied during inflorescence development. Na+ accumulated in all organs while K+ decreased. Laser ablation inductively coupled plasma mass spectrometry microanalysis revealed that Na+ accumulated in style, ovaries and anther intermediate layers but not in the tapetum nor in the pollen grains when salinity was applied during inflorescence development. K+ was not significantly affected in these structures. Soluble carbohydrates dramatically increased in leaves and decreased in the inflorescence under salt stress conditions. The failure of inflorescence to develop normally under salt stress can be better explained in terms of altered source-sink relationships rather than accumulation of toxic ions.

Speciation of inorganic arsenic in some bottled Slovene mineral waters using HPLC–HGAFS and selective coprecipitation combined with FI-HGAFS

Five bottled mineral waters from the Radenska and the Rogaska springs (Slovenia) were analyzed for their inorganic arsenic species As(III) and As(V) using existing speciation procedures. Both a hyphenated technique (HPLC-HGAFS) and a more conventional technique based on selective coprecipitation of As(III) with dibenzyldithiocarbamate prior to arsenic analysis (FI-HGAFS) were used. The techniques yielded data which were not significantly different on the 5% level, with HPLC-HGAFS to be the least sensitive (DL 1 microgl(-1)) and the selective coprecipitation technique to be suitable for sub pgl(-1) levels (DL 0.05 microgl(-1)). The latter technique showed recoveries of 96.4 +/- 0.4%. In none of the mineral waters As(III) was found whereas the Radenska minerals waters (vrelec Radin vrelec Miral, Kraljevi Vrelec) contained little As(V) (only detectable with the selective coprecipitation technique) and the Rogaska mineral waters (Tempel, Donat Mg) (very) high As(V) concentrations. Rogaska, Donat Mg even had an average As(V) concentration around the permittable level of 50 microgl(-1) for arsenic in minerals waters, viz. 47.8 microg l(-1). Speciation calculations based on pH and Eh and taking into account the ionic strength gave a similar speciation pattern then speciation analysis with additional information about the degree of protonation of As(III) and As(V).

Submicrometer Imaging by Laser Ablation-Inductively Coupled Plasma Mass Spectrometry via Signal and Image Deconvolution Approaches

In this work, pre- and postacquisition procedures for enhancing the lateral resolution of laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) in two- and three-dimensional (2D, 3D) nuclide distribution mapping beyond the laser beam waist are described. 2D images were constructed by projecting a rectangular grid of discrete LA positions, arranged at interspacings smaller than the dimensions of the laser beam waist, onto the sample surface, thus oversampling the region of interest and producing a 2D image convolved in the spatial domain. The pulse response peaks of a low-dispersion LA cell were isolated via signal deconvolution of the transient mass analyzer response. A 3D stack of 2D images was deconvolved by an iterative Richardson-Lucy algorithm with Total Variance regularization, enabling submicrometer image fidelity, demonstrated in the analysis of trace level features in corroded glass. A point spread function (PSF) could be derived from topography maps of single pulse craters from atomic force microscopy. This experimental PSF allows the approach to take into account the laser beam shape, beam aberrations, and the laser-solid interaction, which in turn enhances the spatial resolution of the reconstructed volume.