A document by Colette LaMonica Kelly. Click on the document to view its contents.

Rationale: The fundamental understanding of Grignard-type organolanthanides(III) is still in its infancy. Decarboxylation of metal carboxylate ions is a powerful method to obtain organometallic ions which are well suited for gas-phase investigation by using ESI-MS in combination with DFT calculations. Methods： (RCO2)LnCl3- (R = CH3, Ln = La-Lu except Pm; Ln = La, R = CH3CH2, CH2CH, CHC, C6H5 and C6H11) ions were produced via ESI of LnCl3 and RCO2H/RCO2Na in methanol. Collision-induced dissociation (CID) was employed to examine whether RLnCl3- can be obtained via decarboxylation of (RCO2)LnCl3-. With the aid of DFT calculations, the influences of Ln and R on the formation of RLnCl3- can be uncovered. Results: When R was fixed as methyl, CID of (CH3CO2)LnCl3- (Ln = La-Lu except Pm) all gave (CH3)LnCl3- and LnCl3·- with a variation in the relative intensity ratio of (CH3)LnCl3-/LnCl3·-. The trend is following as (CH3)EuCl3-/EuCl3·- < (CH3)YbCl3-/YbCl3·- ≈ (CH3)SmCl3-/SmCl3·- < other (CH3)LnCl3-/LnCl3·-, which generally complies with the trend of Ln(III)/Ln(II) reduction potentials. When Ln was fixed as La and R groups were varied as CH3CH2, CH2CH, CHC, C6H5 and C6H11, the fragmentation behaviors of these (RCO2)LaCl3- are diverse. Except for (C6H11CO2)LaCl3-, the rest four (RCO2)LaCl3- ions all underwent decarboxylation to give RLaCl3-. The relative intensities of RLaCl3- compared to (RCO2)LaCl3- decrease as follow: CHC > CH2CH > C6H5 > CH3 > CH3CH2 >> C6H11 (not visible). Conclusion： A series of Grignard-type organolanthanide(III) ions RLnCl3- (R = CH3, Ln = La-Lu except Pm; Ln = La, R = CH3CH2, CH2CH, CHC and C6H5) were generated from (RCO2)LnCl3- via CO2 loss while (C6H5)LaCl3- not. The experimental and theoretical results suggest that the reduction potentials of Ln(III)/Ln(II) couples as well as the bulkiness and hybridization of hydrocarbyl groups play crucial roles in promoting or limiting the formation of RLnCl3- via decarboxylation.

RATIONALE Boron isotopes are a powerful tool for pH reconstruction in marine carbonates and as tracer for fluid-mineral interaction in geochemistry. Micro-analytical approaches based on laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) often suffer from effects induced by the sample matrix. In this study, we investigated matrix-independent analyses of B isotopic ratios and applied this technique to cold-water corals. METHODS We employed a customized 193 nm femtosecond laser ablation system (Solstice, Spectra-Physics) coupled to a MC-ICP-MS (Nu Plasma II, Nu Instruments) equipped with electron multipliers for in situ measurements of B isotope ratios (11B/10B) at the micron-scale. We analyzed various reference materials of silicate and carbonate matrices using non-matrix match calibration without employing any correction mode. This approach was then applied to investigates defined increments in coral samples from a Chilean fjord. RESULTS We obtained accurate B isotope ratios with a precision of ± 0.9‰ (2 SD) for various reference materials including silicate glasses (GOR132-G, StHs6/80-G, ATHO-G, and NIST SRM 612), clay (IAEA-B-8) and carbonate (JCp-1) using the silicate glass NIST SRM 610 as calibration standard, which shows that neither laser-induced nor ICP-related matrix effects are detectable. The application to cold-water corals (Desmophyllum dianthus) reveal little intra-skeleton variations in δ11B with average values between 23.27 and 26.09‰. CONCLUSIONS Our instrumental set-up provides accurate and precise B isotopic ratios independently of the sample matrix at the micron-scale. This approach opens a wide field of application in geochemistry, including pH reconstruction in biogenic carbonates and deciphering processes related to fluid-mineral interaction.

Rationale. Femtoamp and picoamp electrospray ionization characteristics of a non-polar solvent were explored. The direct ESI-MS analysis of chloroform extract solution enabled rapid analysis of perfluorinated sulfonic acid (PFS) analytes in drinking water. Methods. Neat chloroform solvent and extracts were directly used in a typical wire-in ESI setup using micrometer emitter tips. Ionization currents were measured with femtoamp sensitivity while ramping the spray voltage from 0 to -5000 V. Methanol was used to illustrate the characteristics of spraying chloroform. The effect of spray voltage and inlet temperature was studied. A liquid-liquid extraction workflow was developed to analyze PFOS in drinking water using an ion trap mass spectrometer. Results. The ionization onset of chloroform solution was 41 ± 17 fA at 300 V. The ionization current gradually increased with voltage while remaining below 100 pA when using voltage up to -5000 V. PFOS ion signal was significantly enhanced to improve the detection limit to 25 ppt in chloroform. Coupled with a liquid-liquid extraction workflow, detection limits of 0.38-5.1 ppt, and a quantitation range of 5-400 ppt were achieved for perfluorinated sulfonic compounds in 1 mL drinking water samples. Conclusions. Femtoamp and picoamp modes expand the solvent compatibility range of electrospray ionization and can enable quantitative analysis in ppt concentrations.

Rationale: Position-Specific (PS) δ13C values of propane has proven its ability to provide valuable information on evolution history of natural gases. Two major approaches to measure PS δ13C values of propane are quantitative NMR (qNMR) and GC-Py(rolysis)-GC-IRMS. The qNMR has verified measurement accuracy, however, required large sample size and long experimental time limit its applications. The GC-Py-GC-IRMS is more versatile method with small sample size, but its accuracy has not been demonstrated. Methods: We measured PS δ13C values of propane from nine natural gases, using the both methods and evaluated the accuracy of GC-Py-GC-IRMS method. Results: The results show that large carbon isotope fractionations occurred for the both terminal and central carbons within propane during pyrolysis. The isotope fractionations during the pyrolysis are reproducible at optimum conditions, but vary between the two GC-Py-GC-IRMS systems tested, affected by experimental conditions (e.g., pyrolysis temperature, flow rate, and reactor conditions). Conclusions: Therefore, it is necessary to evaluate and calibrate each GC-Py-GC-IRMS system using propane gases whose PS δ13C values are accurately determined. This study also highlights a need of PS isotope standards for propane and other molecules.