Systematic studies on the determination of Hg-labelled proteins using laser ablation-ICPMS and isotope dilution analysis

A method was developed for the precise and accurate determination of ovalbumin labelled with p-hydroxy-mercuribenzoic acid (pHMB) using polyacrylamide gel electrophoresis with ns-laser ablation-inductively coupled plasma mass spectrometry. Following systematic optimisation of the ablation process in terms of detection sensitivity, two different quantification strategies were applied: external calibration using standards of the derivatized protein after 13C+ normalization and, as a proof of concept, label-specific isotope dilution analysis (IDA) using pHMB enriched in the isotope 199Hg. Due to the inhomogeneous distribution of the protein within the gel bands, it could be demonstrated that the IDA approach was superior in terms of precision and accuracy. Furthermore, it permits a reliable quantification, if more complex separation protocols are applied, as typically occurring analyte loss and degradation can be compensated for as soon as complete mixture of spike and sample is achieved. The estimated limit of detection was 160fmol in the case of ovalbumin. In contrast to earlier studies using metals naturally present in proteins, no loss of mercury was observed during separation under denaturing conditions and other sample preparation steps. Using label-specific IDA, the measured isotope ratios in the gel corresponded to recoveries between 95% and 103

Systematic studies on the determination of Hg-labelled proteins using laser ablation-ICPMS and isotope dilution analysis

ISSN:1618-2650ISSN:1618-264

Physical-chemical properties and metal budget of Au-transporting hydrothermal fluids in orogenic deposits

We use a set of analytical techniques for fluid inclusion analysis to determine the bulk properties of the ore fluids from five orogenic gold deposits. The most common ore fluid is a low salinity (0.4-6.5 wt% NaCl) two- to three-phase aqueous-carbonic fluid. Its Th(total) range is 200-400 \ub0C, and total homogenization occurs by bubble or liquid disappearance. A less common aqueous fluid of similar bulk salinity and Th(total) is also documented. Microchemical data show that the ore fluid in the five deposits is chemically uniform and made of Na, subordinateK and B and minor to trace amounts of Cu, As, Li, Sr, Rb, Ba, Cs, Sb and Au (range 0.5-5 \u3bcg/g). Thermodynamic modelling carried out for one of the studied deposits indicates that the ore fluid was in equilibrium with vein minerals at the time of gold deposition, and that its vapour phase was distinctly enriched in Au, B, As and Sb. The proposed mechanism of gold precipitation is a combination of fluid decompression and boiling. Combining these results with 3D geometrical reconstructions of one of the studied deposits (Sigma), we estimate that a minimum ore fluid volume of c. 0.1-1.0 km3 is sufficient to generate a world-class orogenic deposit

Laser ablation Mn/Ca ratios of single foraminiferal shells from the Gulf of Lions

Foraminiferal trace element concentrations were determined using two laser ablation ICP-MS systems. Prior to laser ablation, all samples were gently cleaned in methanol (x1) and UHQ water (x4). Between each rinse, the samples were placed in a sonic bath for several seconds to thoroughly clean the tests. Benthic foraminifera from 745m (station D), 980m (station C), 1488m (station B), and 1987m (station A) were measured at Utrecht University using a deep UV (193 nm) ArF excimer laser (Lambda Physik) with GeoLas 200Q optics. Ablation was performed at a pulse repetition rate of 10 Hz and an energy density of 1.4 J/cm², with a crater size of 80 μm. Ablated particles were measured by a quadrupole ICP-MS (Micromass Platform) equipped with a collision and reaction cell. Such a collision and reaction cell improves carbonate analyses by eliminating interferences on mass 44. Scanned masses included 24Mg, 26Mg, 27Al, 42Ca, 43Ca, 55Mn, 88Sr, 137Ba, 138Ba, and 208Pb. Benthic foraminifera from stations F (350 m) and E (552 m) were analyzed at ETH Zurich (due to laboratory renovations at Utrecht University). The laser type and ablation parameters were identical to those detailed above. The ablated particles were measured using a quadrupole ICP-MS (ELAN 6100 DRC, PerkinElmer). In both cases, calibration was performed using an international standard (NIST610) with Ca as an internal standard (Jochum et al., 2011). The same masses as measured in Utrecht were monitored, in addition to 7Li, 23Na, 47Ti, 60Ni, 61Ni, and 89Y. Interlaboratory compatibility was monitored using a matrix-matched calcite standard. For Mn, reported here, this standard showed a precision better than 3%over all analyses, at ETH and UU, and with an offset of less than 5%from an offline-determined (solution ICP-AES) concentration analyzing discrete subsamples. The matrix-matched standard is routinely included in the analyses and has been monitored since 2010 at Utrecht University. Analytical error (equivalent to 1 sigma), based on repeated measurement of an external standard, was < 5% for reported elements. Each laser ablation measurement was screened for contamination by monitoring Al and Pb. On encountering surface contamination, the data integration interval was adjusted to exclude any Al or Pb enrichment. Cross-plots between Al and Pb versus Mn showed that they are unrelated, confirming the accuracy of the integrations