E Lounejeva

Raman spectroscopy of natural silica in Chicxulub impactite, Mexico

A series of natural silica impactite samples from Chicxulub (Mexico) was investigated by Raman microprobe (RMP) analysis. The data yield evidence for high-pressure shock metamorphism in the rock. The impactite contains three polymorphs of silica: the original α-quartz, and two high-pressure varieties – coesite and disordered quartz representing various degrees of crystallinity. We found systematic changes in frequencies and half-widths of the Raman bands, caused by increasing irregularities of bond-lengths and bond-angles and a general breaking-up of the structure as a result of impact events. Therefore, RMP is an adequate tool for measuring the crystallinity of disordered quartz. The half-width Γ and the frequency ω of the symmetric SiOSi stretching vibrational band (A1 mode) of the SiO4 tetrahedra are the most amenable parameters for estimating the degree of crystallinity. In well-crystallized quartz, Γ=5 cm−1 and ω=464 cm−1, while in highly disordered quartz this line shifts up to ω=455 cm−1 and broadens up to Γ=30 cm−1. The Raman lineshapes appear to depend strongly on the degree of lattice disorder subsequent to impact events. To cite this article: M. Ostroumov et al., C. R. Geoscience 334 (2002) 21–26

Pharmacokinetics and hematotoxicity of a novel copper-based anticancer agent: casiopeina III-Ea, after a single intravenous dose in rats.

Casiopeina III‐Ea is a mixed chelate copper (II) complex that has shown cytotoxic and antitumor activity in vitro and in vivo. The aim of this study was to investigate the pharmacokinetics of total copper derived from casiopeina III‐Ea administered by intravenous bolus injection to Wistar rats. Other objective was to evaluate the hematotoxicity produced by this compound in those animals. Wistar rats received a single intravenous dose of 4 mg/kg of casiopeina III‐Ea. Blood samples were taken and pharmacokinetics evaluated. Furthermore, erythrocyte copper levels were determined to identify a potential target and Zn levels were analyzed to determine a possible change. For the evaluation of hematotoxicity, both blood and urine samples were collected for hematological and biochemical analyses; moreover, Fe determination was performed. Blood copper and zinc levels, red blood cell copper levels as well as copper, zinc, and iron amounts excreted into urine were analyzed by ICP‐MS. The blood concentration–time profile of copper derived from casiopeina III‐Ea was fitted to a two‐compartment model with a zero‐order input. Cumulative amounts of Cu, Zn, and Fe excreted into rat urine after administration of casiopeina III‐Ea were different with respect to control. Hematological and biochemical data indicated a hemolytic toxicity. Pharmacokinetic analysis of total copper derived from casiopeina III‐Ea provided a general knowledge about distribution and elimination process of this compound. Additionally, the systemic exposure of the copper derived from casiopeina III‐Ea accounts for the hematotoxicity of this complex at test dose.

Assessment of sample preparation methods for the analysis of trace elements in airborne particulate matter

The determination of trace element composition of airborne particles usually requires dissolution in acidic media followed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analysis. Analytical methods are usually validated on NIST SRM 1648 and 1648a, but without any further discussion regarding their application to real atmospheric samples. Here, we present an assessment of 5 digestion methods (over a hot plate and using a microwave system) for SRM 1648a and atmospheric particles based on the analysis of 30 elements by ICP-MS. Recoveries of NIST-certified elements for SRM 1648a confirm that a digestion method using HNO3–HF on a hot-plate yields acceptable recoveries for most of the NIST-certified elements (with the exception of Cr). By conducting the elemental analysis in triplicate samples of particles collected on PTFE filters, we determined that the analytical method is reproducible within 9% for real PM samples. Heterogeneity of the reference material and atmospheric samples, as well as differences in chemical composition and particle size between both, suggests that uncertainties related to the dissolution of trace elements using acidic mixtures are not well characterized.

Direct analysis of lanthanides by ICPMS in calcium-rich water samples using a modular high-efficiency sample introduction system–membrane desolvator

Lanthanoids (also known as rare-earth elements – REE) are well-known tracers of water–rock interaction processes due to their behavior being coherent with their atomic radii, and the capability of Ce and Eu to reflect redox conditions. However, analysis of REE in natural waters is hampered by their relatively low concentration (sub-pg g−1), and the concentration of dissolved solids ranging in the hundreds of μg g−1, imposing important matrix effects to the analysis. Because of this, different analytical techniques have been developed to analyze them by Q-ICPMS and SF-ICPMS, which usually involve matrix removal and analyte pre-concentration. Analysis of REE in karstic waters, those naturally saturated in CaCO3, presents an additional challenge due to the presence of high Ba concentrations (several ng g−1) which can bias the analysis due to the formation of BaO+ and BaOH+ ions during ionization, interfering with the mass range of 148–155 m/z+, including both Eu isotopes, and significantly hampering the direct analysis of such samples. Here, using a modular high-efficiency sample introduction system and desolvator we eliminate the formation of BaO+, and significantly reduce BaOH+, allowing us to analyze small samples (1–2 ml) with Ba/Eu ratios as high as 8 × 104 (mol/mol), and up to 600 μg g−1 of Ca, without any sample pretreatment. Our methodology was validated by analyzing VIDAC18 and SERMIN1 reference materials, and permits the quantification of all REE with detection limits ranging between 500 and 30 fg g−1 and with RSD ∼ 10% for 1 pg g−1, controlled by counting statistics.

Matrix dependency for oxide production rates by LA-ICP-MS

The production rates of polyatomic oxygen interferents (MO+/M+) during LA-ICP-MS analysis were investigated in a range of silicate materials and metals. The total amount of oxygen in the ICP is significantly lower for laser ablation analysis compared to solution nebulisation analysis resulting in lower oxide production rates. However, these interferents can still be significant for some elements. The contribution of oxygen from the material being ablated was found to influence the oxide production rate (OPR). When using a well degassed system to minimise the entrainment of atmospheric oxygen, the OPR for Al, Si and W was up to 4 times lower when ablating the elements as a metal compared to when ablating oxygen-bearing minerals. There is a relationship between the MO+/M+ production rate and the cation–oxygen dissociation energy for elements measured by solution and by laser ablation ICP-MS. However, for Hf and Th the OPR varied significantly depending on the mineral being ablated under the same analytical conditions (0.007–0.02% for Hf and 0.09–0.2% for Th), whereas UO+/U+ was more consistent (0.058–0.063%). The effects of carrier gas flow rate and resulting differences in aerosol breakdown and ionisation in the ICP were investigated for U and Th oxides in NIST610, NIST612, zircon (ZrSiO4), monazite ([REE,Th]PO4) and uraninite (UO2). Increasing the Ar flow rate had a larger effect on the Th OPR (0.05 to 0.5%) compared to U (0.04 to 0.09%) when ablating the NIST610 glass. The relative differences in the OPR between minerals compared to NIST610 were small for U, with all minerals having the same OPR except for uraninite at high carrier gas flow rates (35% higher). In contrast the OPR for Th was highly variable between all minerals and showed differing responses to changes in the Ar flow. This study highlights the complexities in oxide production for LA-ICP-MS compared to solution analyses, and that the OPR for some elements is strongly dependent on the material being ablated. Also, that there can be a significant contribution to the MO+ production from ionisation of an incompletely atomised sample aerosol in the plasma.