Christophe Pécheyran

Simultaneous use of strontium:calcium and barium:calcium ratios in otoliths as markers of habitat: Application to the European eel (Anguilla anguilla) in the Adour basin, South West France

Sr:Ca and Ba:Ca ratios in water from the Adour estuary show a clear relationship with the salinity of the surrounding water for salinities <20, while ratios are almost constant above this level of salinity. A positive relationship was observed for the Sr:Ca ratio, whereas it was inverse for the Ba:Ca ratio. These two elemental ratios were measured in the otoliths of the European eels (Anguilla anguilla L.) using femtosecond laser ablation linked to an ICP-MS (fs-LA-ICP-MS). There was a direct relationship between the elemental ratios recorded in eel otoliths and those found in water from fresh and marine areas, suggesting that Sr:Ca and Ba:Ca ratios in eel otoliths can be used as markers of habitat in this estuary. Continuous profiling allowed the determination of three behaviour patterns in terms of habitat: freshwater, estuary and migratory individuals. Finally, the above results support the simultaneous use of both ratios for a better understanding of the migratory contingents and also as a relevant method to avoid a misidentification of environmental migratory history due to the presence of vaterite crystal in the otolith matrix.

Simultaneous Determination of Volatile Metal (Pb, Hg, Sn, In, Ga) and Nonmetal Species (Se, P, As) in Different Atmospheres by Cryofocusing and Detection by ICPMS

A sensitive method for multielemental speciation analysis of volatile metal and metalloid compounds in air has been developed. The analytes are sampled simultaneously in the field by cryofocusing on a small glass wool-packed column at -175 °C. Detection is performed in the laboratory by low-temperature GC hyphenated with ICPMS. Oxygen addition in the carrier gas was used to reduce interferences originating from the presence of volatile carbon-containing species in the samples. Plasma stability during analysis was monitored continuously by internal standardization (Xe). This system provides routine absolute detection limits of 0.06-0.07 pg (as Pb) for tetraalkyllead species (Me(4)Pb, Et(4)Pb), 0.2 pg (as Sn) for tetraalkyltin species (Me(4)Sn, Et(4)Sn), 0.8 pg (as Hg) for mercury species (Hg(0), Me(2)Hg, Et(2)Hg), and 2.5 pg (as Se) for selenium species (Me(2)Se). This instrumentation makes it possible to collect small air sample volumes and has been successfully applied to the determination of volatile metal and metalloid species in the atmosphere in urban and rural locations. Qualitative application in the semiconductor industry is also reported with regard to the detection of arsenic (ASH(3), tert-butylarsine), phosphorus (PH(3), tert-butylphosphine), alkylindium, and gallium species.

Approach to Measure Isotopic Ratios in Species Using Multicollector-ICPMS Coupled with Chromatography

A new approach was demonstrated for the isotope ratio measurement in different elemental species of Hg using transient signal obtained by chromatography coupled with multicollector-inductively coupled plasma mass spectrometry (MC-ICPMS). The method based on the slope of linear regression by transient intensities of different isotopes shows improved accuracy and reproducibility (0.2-0.5 per thousand as 2 standard deviation (SD)). Internal precision (RSD) of the method is very close to the theoretical value given by the counting statistic and is better by a factor of 6 in comparison with previous conventional methods of calculation. We demonstrated that internal RSD (uncertainty) depends on regression coefficients of the linear function (R(2)). The typical internal precision of isotopic ratio measurements (0.003-0.02%) was achieved for delta(202)Hg when injecting as low as 90 pg of Hg species. With the new methodology, it is possible to (i) measure the isotopic composition when a sample and a bracketing standard have significantly different concentrations, (ii) measure the isotopic composition of different species in samples versus single species in a bracketing standard, and (iii) measure the isotopic ratios for low abundant isotopes. We demonstrated application of this method for different environmental samples and processes.

Isotopic precision for a lead species (PbEt4) using capillary gas chromatography coupled to inductively coupled plasma-multicollector mass spectrometry

Precision and accuracy of lead isotope ratios of a volatile lead species (PbEt4) were determined by coupling a capillary GC to a magnetic sector multicollector ICP-MS. PbEt4 was prepared by ethylation of a certified lead isotope solution (NIST SRM 981). Coupling was achieved by a transfer line, which allowed simultaneous introduction of a thallium standard solution to correct for mass discrimination. Seven isotopes (202Hg, 203Tl, 204Pb, 205Tl, 206Pb, 207Pb, 208Pb) were monitored simultaneously with a transient resolution of 50 ms. Pb isotope ratios for the PbEt4 peaks were calculated using transient peak integrals of each isotope signal. Absolute detection limits were 20 (204Pb), 0.7 (206Pb), 1 (207Pb) and 0.3 pg (208Pb). Precision was assessed for five replicate injections of PbEt4 in iso-octane, corresponding to a total amount of 300 pg of Pb. Precision of isotope ratios for 206Pb, 207Pb and 208Pb were better than 0.07% (RSD), with ratios including 204Pb being one order of magnitude worse. Accuracy using mass bias correction via 203Tl/205Tl ranged from 0.18% for 208Pb/206Pb to 0.9% for 208Pb/204Pb.

Field determination of volatile selenium species at ultra trace levels in environmental waters by on-line purging, cryofocusing and detection by atomic fluorescence spectroscopy

The field determination of selenium species was obtained after stripping 1 l of water, removal of the water vapour by a water trap, and cryofocusing in a small packed chromatographic column hyphenated to a non dispersive atomic fluorescence detector. Water trap and purging conditions were carefully studied. Under routine operating conditions, absolute detection limits of 4 and 4.5 pg of Se for Me2Se and Me2Se2 were obtained, respectively. Under routine conditions, linearity extended up to 1 ng as Se for the different species studied. The selectivity of the system is discussed in the presence of carbon-containing species. This system was applied to the determination of volatile selenium species in the Gironde estuarine environment (France). Me2Se was found to be the main volatile selenium species in concentrations ranging from 0.8 to 6.3 pmol l–1. Seasonal variations have been observed and commented upon. Correlation with water temperature and salinity is also discussed.

Elemental fractionation effects in high repetition rate IR femtosecond laser ablation ICP-MS analysis of glasses

An IR-femtosecond laser ablation ICPMS coupling was used to investigate the influence of the high repetition rate on elemental fractionation effects for the analysis of silicate glass SRM NIST 610. First, elemental fractionation inherent to the ICP was minimised by working on wet plasma conditions which had greater tolerance to mass loading and demonstrated a higher robustness compared to dry plasma conditions. Because of the use of a narrow laser beam producing small craters (17 µm in diameter), a special arrangement of pulses was used to perform resulting craters of 100 µm diameter. The ablation strategy developed in this work consisted in a series of concentric circle trajectories ablated at high repetition rates by moving the laser beam rapidly thanks to a scanning beam device. Two scanner speeds (0.25 mm s−1 and 1.5 mm s−1), five laser repetition rates (from 0.1 kHz to 10 kHz) and three fluence values (5 J cm−2, 14 J cm−2, and 25 J cm−2) were investigated in detail. For this purpose, critical elemental ratios (namely 238U/232Th, 208Pb/238U, and 66Zn/65Cu) of aerosols produced by fs-LA of silicate glass were studied to evaluate the impact of the different laser parameters on elemental fractionation. No heating zones or preferential evaporation of elements were found depending on the repetition rate employed. However, particle-size-fractionation was measured during the ablation of the sample surface, and this effect was reduced by using a high repetition rate as well as a high scanner speed which allow the dilution of the large particles coming from the surface layer with finer particles coming to deeper levels. Additionally, the ablation rate induced by the selected ablation strategy had a low influence on fractionation effects due to the high robustness of the ICP plasma and, on the other hand, fractionation indices were not particularly affected by the laser repetition rate although they could be improved by the use of high fluence values. Finally, it could be stressed that no differences on the structure of the aerosol particles collected on membrane filters were found depending on the ablation parameters.

Solid-spiking isotope dilution laser ablation ICP-MS for the direct and simultaneous determination of trace elements in soils and sediments

The direct and simultaneous determination of Cu, Zn, Sn and Pb in soil and sediment samples by femtosecond laser ablation inductively coupled plasma isotope dilution mass spectrometry (fs-LA-ICP-IDMS) has been accomplished in this work with the development of a solid-spiking sample preparation procedure. The total analysis time, in comparison with previous approaches, has been significantly reduced by developing a solid-spiking procedure based on the synthesis of a unique isotopically-enriched solid spike and the preparation of isotope-diluted blend pellets for each sample. The laser repetition rate and the ablation mode were carefully selected (10 kHz and the 2D scanning sampling mode, respectively) in order to reduce the effect of possible local inhomogeneities of the powdered samples on the precision of isotope ratio measurements. Special attention was focused on the heterogeneous distribution of trace elements in the isotopically-enriched solid spike and the isotope-diluted blend samples in order to assure that the measured isotope ratios remained constant (precisions lower than 10% RSD; n = 8). The proposed methodology was tested for the analysis of two soil (CRM 142R, GBW-07405) and two sediment (PACS-2, IAEA-405) reference materials. The concentrations obtained by solid-spiking fs-LA-ICP-IDMS were in agreement not only with the certified values but also with those obtained by ICP-IDMS after the microwave-assisted digestion of the solid samples, demonstrating therefore the validity of the proposed solid-spiking procedure for a rapid and accurate analysis of solid samples.

Direct determination of Cu isotope ratios in dried urine spots by means of fs-LA-MC-ICPMS. Potential to diagnose Wilson's disease

This work investigates the potential of a 257 nm femtosecond (fs) laser ablation (LA) device operating at a high repetition rate (10 000 Hz) coupled to a multicollector (MC)-ICPMS to develop a method for the direct determination of Cu ratios in dried urine spots, prepared by deposition of urine (300 μL) onto precut clinical filter paper discs (16 mm diameter). The sampling capabilities offered by the fs LA system, permitting ablation of 150 μm thick coronas in the rim area of the filter, together with the use of admixed Ni as an internal standard, the proper optimization of the MC-ICPMS conditions (e.g., use of pseudo high-resolution mode to avoid interferences) and the use of a data processing approach particularly suitable for short transient signals (linear regression fit) enabled analysis of real urine samples with precision values around 500 ppm (RSD) for urinary Cu contents of a few hundred μg L−1. The methodology developed could prove to be useful for implementing screening protocols to detect Wilsons disease (WD), a well-known disorder related to Cu metabolism. In fact, the use of this analytical methodology permitted us to observe significant differences between (i) untreated WD patients and (ii) WD patients that are under treatment and control samples. This work represents the first time that determination of 65Cu/63Cu ratios has been used in the context of WD research, and serves as a proof of principle, suggesting that Cu isotope analysis could help in developing earlier and more reliable means to diagnose WD.

Direct determination of trace elements in powdered samples by in-cell isotope dilution femtosecond laser ablation ICPMS

A method has been developed for the direct and simultaneous multielement determination of Cu, Zn, Sn, and Pb in soil and sediment samples using femtosecond laser ablation inductively coupled plasma mass spectrometry (fs-LA-ICPMS) in combination with isotope dilution mass spectrometry (IDMS). The in-cell isotope dilution fs-LA-ICPMS method proposed in this work was based on the quasi-simultaneous ablation of the natural abundance sample and the isotopically enriched solid spike, which was performed using a high repetition rate laser and a fast scanning beam device in a combined manner. Both the sample preparation procedure and the total analysis time have been drastically reduced, in comparison with previous approaches, since a unique multielement isotopically enriched solid spike was employed to analyze different powdered samples. Numerous experimental parameters were carefully selected (e.g., carrier gas flow rate, inlet diameter of the ablation cell, sample translation speed, scanner speed, etc.) in order to ensure the complete mixing between the sample and the solid spike aerosols. The proposed in-cell fs-LA-ICP-IDMS method was tested for the analysis of two soil (CRM 142R, GBW-07405) and two sediment (PACS-2, IAEA-405) reference materials, and the analysis of Cu, Zn, Sn, and Pb yielded good agreement of usually not more than 10% deviation from the certified values and precisions of less than 15% relative standard deviation. Furthermore, the concentrations were in agreement not only with the certified values but also with those obtained by ICP-IDMS after the microwave-assisted digestion of the solid samples, demonstrating therefore that in-cell fs-LA-ICP-IDMS opens the possibility for accurate and precise determinations of trace elements in powdered samples reducing the total sample preparation time to less than 5 min. Additionally, scanning electron microscope measurements showed that the aerosol generated by in-cell fs-LA-ICP-IDMS predominantly consisted of linear agglomerates of small particles (in the order of few tens of nanometers) and a few large spherical particles with diameters below 225 nm.

Biosynthesis, purification and analysis of selenomethionyl calmodulin by gel electrophoresis-laser ablation-ICP-MS and capillary HPLC-ICP-MS peptide mapping following in-gel tryptic digestion

A biosynthesis method was developed to produce a standard of a selenium-containing protein. It consisted of the expression of calmodulin in Escherichia coli culture in the presence of selenomethionine, which allowed the replacement of all methionine residues by selenomethionine. The resulting 17 kDa protein containing 8 selenomethionine residues was purified by two-step hydrophobic interaction chromatography. The selenomethionyl calmodulin was subsequently used to develop a method for the characterization of selenium-containing proteins (detected in the polyacrylamide gel by laser ablation-ICP-MS) by means of peptide mapping using capillary HPLC-ICP-MS. The monitoring of the 80Se isotope using an ICP mass spectrometer equipped with a collision cell allowed as little as 0.3 pg as Se (1.3 ng ml−1 in the analysed solution) to be detected in the gel. The band containing the protein of interest was excised, the protein was digested with trypsin and the Se-containing peptides were analyzed by capillary HPLC-ICP-MS. The sensitivity of the method was at least a factor of 5 higher than that of capillary LC-electrospray MS/MS in similar conditions. Some of the selenopeptides detected by capillary LC-ICP MS could nevertheless be identified by retention time matching using a set of peptides generated by trypsin digestion from the concentrated selenomethionyl calmodulin standard.