Frédéric Chartier

Comparison between infrared and ultraviolet laser ablation at atmospheric pressure—implications for solid sampling inductively coupled plasma spectrometry

The efficiency of laser solid sampling was investigated as a function of several experimental parameters under experimental conditions similar to those used for laser ablation (LA) inductively coupled plasma spectrometry. This was done by studying the amount of material removed as a function of melting temperature of the (metallic) matrix material, laser wavelength and laser energy, and by studying the plasma ignition in air and argon buffer gases as a function of laser wavelength. It was found that direct LA is the major process responsible for the removal of material in the case of a UV laser, as opposed to with an IR laser, where shielding of the laser radiation by the absorbing plasma limits direct LA and increases the temperature of the plasma. The consequences of this difference between IR and UV laser radiation are considerable and lead to a superior performance of UV laser sampling in every analytical aspect: reproducibility, matrix effects, quantification, spatial resolution and sensitivity.

Determination of erbium in nuclear fuels by isotope dilution thermal ionization mass spectrometry and glow discharge mass spectrometry

A thermal ionization mass spectrometer (TIMS) and a laboratory-built glow discharge mass spectrometer (GDMS) have been employed for the determination of the isotopic composition of erbium and its concentration, with respect to uranium, in nuclear fuel samples before irradiation. First, the GDMS results on erbium isotopic composition in erbium metal and erbium oxide samples have been compared with those obtained from TIMS measurements. Then, the isotopic composition of uranium and erbium has been measured by TIMS after dissolution of inactive erbium-doped molybdenum-uranium fuel samples. The atomic 166 Er: 238 U ratio has also been determined with the double spike isotope dilution method. A 167 Er: 233 U spike solution has been prepared and calibrated for this determination. However, to avoid matrix effects in TIMS analyses, it has first been necessary to perform chemical separations to isolate U and Er from the high quantities of molybdenum and iron present in the liquid samples. The glow discharge mass spectrometer has been used for the analyses of the same samples. For the evaluation of this technique, the isotopic compositions of U and Er have been measured directly on the solid samples and the atomic 166 Er: 238 U ratio has been determined by a calibration procedure with home-made standards. Results are compared in terms of accuracy and precision with the analyses performed by TIMS, used as the reference technique.

Introduction of organic/hydro-organic matrices in inductively coupled plasma optical emission spectrometry and mass spectrometry: A tutorial review. Part II. Practical considerations

Inductively coupled plasma optical emission spectrometry (ICP-OES) and mass spectrometry (ICP-MS) are increasingly used to carry out analyses in organic/hydro-organic matrices. The introduction of such matrices into ICP sources is particularly challenging and can be the cause of numerous drawbacks. This tutorial review, divided in two parts, explores the rich literature related to the introduction of organic/hydro-organic matrices in ICP sources. Part I provided theoretical considerations associated with the physico-chemical properties of such matrices, in an attempt to understand the induced phenomena. Part II of this tutorial review is dedicated to more practical considerations on instrumentation, instrumental and operating parameters, as well as analytical strategies for elemental quantification in such matrices. Two important issues are addressed in this part: the first concerns the instrumentation and optimization of instrumental and operating parameters, pointing out (i) the description, benefits and drawbacks of different kinds of nebulization and desolvation devices and the impact of more specific instrumental parameters such as the injector characteristics and the material used for the cone; and, (ii) the optimization of operating parameters, for both ICP-OES and ICP-MS. Even if it is at the margin of this tutorial review, Electrothermal Vaporization and Laser Ablation will also be shortly described. The second issue is devoted to the analytical strategies for elemental quantification in such matrices, with particular insight into the isotope dilution technique, particularly used in speciation analysis by ICP-coupled separation techniques.

Comparison of the Performance of a Laboratory-built High Resolution Glow Discharge Mass Spectrometry With That of a Quadrupole Inductively Coupled Plasma (Glow Discharge) Mass Spectrometer for Boron and Gadolinium Isotopic Analysis

A double focusing glow discharge mass spectrometer (HR GDMS system) was developed from a spark source mass spectrometer to allow isotopic measurements directly on solid samples. The effects on signals of the discharge cell geometry, including anode–cathode distance and aperture diameter of the anode, are discussed. A comparison was made, after optimization of operating parameters, between this system and a quadrupole mass spectrometer with an inductively coupled plasma and a glow discharge as ion sources [quadrupole ICP-(GD)MS system]. The comparison included spectral characteristics, isobaric interferences and stability measurements. HR GDMS was applied to B isotope ratio measurements in Zr samples; these measurements cannot be performed with quadrupole GDMS because of an isobaric interference between10B+ and Ar4+. The two GDMS systems were also used for Gd isotopic determinations; however, for large samples (greater than 55 mm in diameter), only HR GDMS offers the possibility of isotopic analysis, owing to the design of the quadrupole GDMS sample holder. ICP-MS was employed to obtain isotopic measurements of these two elements on the same samples after dissolution. The accuracy and precision of the results are discussed and compared with those obtained by thermal ionization mass spectrometry (TIMS), used as a reference technique.

Cobalt Speciation Study in the Cobalt-Cysteine System by Electrospray Ionization Mass Spectrometry and Anion-Exchange Chromatography Inductively Coupled Plasma Atomic Emission Spectrometry.

This paper describes the ability of the combination of electrospray ionization mass spectrometry (ESI-MS) and anion-exchange chromatography coupled with inductively coupled plasma atomic emission spectrometry (AEC-ICP-AES) for cobalt speciation study in the binary cobalt–cysteine system. ESI-MS, allowing the identification and the characterization of the analytes, is used as a technique complementary to AEC-ICP-AES, providing elemental information on the separated species. The methods have been developed through the study of samples containing Co2+ and 1-fold to 5-fold molar ratios of cysteine over a pH range 2.5 to 11. In each case, cobalt–cysteine complexes were characterized by ESI-MS in negative ion mode. AEC-ICP-AES allowed further separation and detection of the cobalt species previously characterized. The strong influence of pH and ligand-to-metal ratios on the nature and stoichiometry of the species is demonstrated. For the first time, a direct experimental speciation diagram of cobalt species has been established owing to these analytical techniques. This work is a promising basis for the speciation analysis of cobalt, since a good knowledge of cobalt speciation is of prime importance to better understanding its fate in biological and environmental media.

Multi-elemental Gd, Eu, Sm, Nd isotope ratio measurements by liquid chromatography coupled to MC-ICPMS with variable Faraday cup configurations during elution

The high-precision isotopic characterization of actinides and fission products in nuclear samples is fundamental for various applications such as the management of spent nuclear fuel or the validation of neutronic calculation codes. However multi-elemental isotope ratio measurements by mass spectrometric techniques are hampered by the presence of both spectral and non-spectral interferences as complex sample matrices are encountered in such topics, but also due to the lack of high precision mass spectrometers able to cover the entire mass spectrum. This work describes a new LC-MC-ICPMS approach allowing simultaneous high-precision and multi-elemental isotope ratio measurements of four fission products of interest for nuclear issues (Nd, Sm, Eu, Gd) within a single elution run. Variable motorized Faraday cup configurations were successively used during a specifically designed elution procedure in order to take into account the non-natural Nd, Sm, Eu, Gd isotopic compositions encountered in irradiated nuclear samples. This new method, involving the relevant isotopic reference standard injection timings for on-line mass bias corrections, was validated by the analysis of a simulated fission product fraction from a 235U-irradiated target. Reproducibilities better than 2‰ (k=2), comparable to those obtained by off-line measurements and the classic sample-standard bracketing mass bias correction approach, were obtained for all isotope ratios, except those involving isotopes with a transient signal peak apex lower than 100mV, for which the reproducibilities were comprised between 2‰ and 6‰.

Simple separation and characterization of lanthanide–polyaminocarboxylic acid complexes by HILIC ESI-MS

The separation and characterization of lanthanide (Ln) complexes bearing ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA), species of concern in advanced nuclear fuel treatment processes, were investigated by hydrophilic interaction liquid chromatography (HILIC) coupled with electrospray ionization mass spectrometry (ESI-MS). Selectivity properties of stationary phases with different polar functions (cross-linked diol, cyano, zwitterionic and amide) towards the Ln (Er, Eu, Gd, Nd)–EDTA/DTPA complexes were assessed. Only amide bonded stationary phases allowed simple separation of the complexes in isocratic mode, while the other stationary phases did not provide sufficient selectivity, leading to the co-elution of the complexes whatever the mobile phase composition. The chromatographic properties of two amide-based columns with different surface characteristics (XBridge and TSK Gel) were probed with a set of lanthanide complexes under identical conditions. The column giving the best performances was selected for further retention mechanism study. The effect of several parameters, such as the acetonitrile (ACN) content (40–80%) and ammonium acetate concentration (5–20 mmol L−1) was studied on the retention of the lanthanide complexes. The results showed that electrostatic interactions did not significantly affect their elution, while the adsorption mechanism was found to be predominant for ACN percentages higher than 55%. In the final step, faster HPLC conditions were applied by using an amide column packed with sub-2 μm particles (Acquity). More efficient separation of the lanthanide complexes, and decreases in analysis time, solvent consumption and generated effluent volumes, were obtained. Such an approach could lead to the development of greener analytical methods than conventional chromatographic separations, which is of prime concern for the study of radioactive samples.

Development of a tip enhanced near-field laser ablation system for the sub-micrometric analysis of solid samples

A near-field laser ablation system was developed for the analysis of inorganic solid samples in the nanometer resolution range. The instrument is based on the coupling of a nanosecond Nd:YAG laser with an atomic force microscope. The technique uses a tip enhancement effect obtained by the interaction of laser radiation with the conductive tip of the AFM maintained at a few nanometers above the sample surface. By applying this technique to conducting gold and semiconducting silicon samples, a lateral resolution of 100 nm was demonstrated. With a single laser pulse, craters of about 100 nm in diameter and a few nanometers in depth were obtained. A multi-parametric study was carried out in order to understand the effect of different experimental parameters (laser fluence, tip-to-sample distance, sample and tip nature) on the near-field laser ablation efficiency, crater dimensions and amount of ablated material. Numerical simulations of the localized heating with a home-made 3-D code presented a good explanation for the nanometer-sized crater diameters obtained in our experiments.

A new procedure for high precision isotope ratio determinations of U, Cu and Zn at nanogram levels in cultured human cells: What are the limiting factors?

The monitoring of isotopic fractionations in in vitro cultured human cell samples is a very promising and under-exploited tool to help identify the metabolic processes leading to disease-induced isotopic fractionations or decipher metabolic pathways of toxic metals in these samples. One of the limitations is that the analytes are often present at small amounts, ranging from tens to hundreds of ng, thus making challenging low-uncertainty isotope ratio determinations. Here we present a new procedure for U, Cu and Zn purification and isotope ratio determinations in cultured human neuron-like cells exposed to natural U. A thorough study of the influence of the limiting factors impacting the uncertainty of δ238U, δ66Zn and δ65Cu is also carried out. These factors include the signal intensity, which determines the within-day measurement reproducibility, the procedural blank correction and the matrix effects, which determine the accuracy of the mass bias correction models. Given the small Cu and U amounts in the cell samples, 15-30 and 20ng respectively, a highly efficient sample introduction system was employed in order to improve the analyte transport to the plasma and, hence, the signal intensity. With this device, the procedural blanks became the main uncertainty source of δ238U and δ65Cu values, accounting over 65% of the overall uncertainty. The matrix effects gave rise to inaccuracies in the mass bias correction models for samples finally dissolved in the minimal volumes required for the analysis, 100-150µL, leading to biases for U and Cu. We will show how these biases can be cancelled out by dissolving the samples in volumes of at least 300µL for Cu and 450µL for U. Using our procedure, expanded uncertainties (k = 2) of around 0.35‰ for δ238U and 0.15‰ for δ66Zn and δ65Cu could be obtained. The analytical approach presented in this work is also applicable to other biological microsamples and can be extended to other elements and applications.

Accurate measurements of 129I concentration by isotope dilution using MC-ICPMS for half-life determination

Abstract Determining the 129I concentration, a long-lived radionuclide present in spent nuclear fuel, is a major issue for nuclear waste disposal purpose. 129I also has to be measured in numerous environmental, nuclear and biological samples. To be able to accurately determine the 129I concentration, an analytical method based on the use of a multicollector-inductively coupled plasma mass spectrometer (MC-ICPMS) combined with an isotope dilution technique using an 127I spike, was developed. First, the influence of different media (HNO3, NaOH and TMAH) on natural 127I signal intensity and stability and on memory effects was studied. Then an analytical procedure was developed by taking into account the correction of blanks and interferences. Tellurium was chosen for instrumental mass bias correction, as no certified standards with suitable 127I/129I ratio are available. Finally, the results, reproducibility and uncertainties obtained for the 129I concentration determined by isotope dilution with a 127I spike are presented and discussed. The final expanded relative uncertainty obtained for the iodine-129 concentration was lower than 0.7% (k = 1). This precise 129I determination in association with further activity measurements of this nuclide on the same sample will render it possible to determine a new value of the 129I half-life with a reduced uncertainty (0.76%, k = 1).