Brice Bouyssiere

Gas chromatography with inductively coupled plasma mass spectrometric detection in speciation analysis

Abstract The state-of-the-art of gas chromatography coupled with inductively coupled plasma mass spectrometry (GC-ICP MS) is comprehensively reviewed. Particular attention is given to the recent advances in ICP MS detection including: GC-ICP interface designs; low power plasmas; and alternative mass analyzers (time-of-flight, double-focussing single collector, double-focussing and collision cell single-focussing multicollectors). On the level of sample preparation for speciation analysis by GC-ICP MS, new derivatization reagents and advances in extraction techniques, such as capillary purge-and-trap, solid phase microextraction and stirbar solid phase extraction are discussed. The increasing role of organometallic species labeled with stable isotopes for the detection of sources of errors during sample preparation and for isotope dilution quantification is highlighted. Applications of GC-ICP MS to the analysis of real-world samples are summarized with a focus on the areas which particularly benefit from the high ICP MS detection sensitivity and tolerance to sample matrix.

Speciation analysis of nickel in the latex of a hyperaccumulating tree Sebertia acuminata by HPLC and CZE with ICP MS and electrospray MS-MS detection

Speciation of nickel was investigated in a hyperaccumulator tree, Sebertia acuminata, by liquid chromatography (LC) with parallel ICP MS and electrospray MS-MS detection. The latex of the tree was leached with water. Two separation mechanisms, size-exclusion (SEC) and capillary zone electrophoresis (CZE), were investigated for the separation of Ni-complexes. A preparative scale SEC allowed the isolation of six stable nickel species. A nickel complex with Mr 360 was identified by ES MS. The collision induced fragmentation (CID) of the m/z 360 ion suggested the presence of three carboxylic and one amino groups, and allowed the identification of a Ni-complex with nicotianamine. A modification of the SEC column with Ni2+ ions allowed the isolation of a fraction containing nickel citrate. Quantification of the species showed that in the water extract of the latex 99.4% of the nickel is complexed by citrate and 0.3% by nicotianamine.

Impact of oil on bacterial community structure in bioturbated sediments

Oil spills threaten coastlines where biological processes supply essential ecosystem services. Therefore, it is crucial to understand how oil influences the microbial communities in sediments that play key roles in ecosystem functioning. Ecosystems such as sediments are characterized by intensive bioturbation due to burrowing macrofauna that may modify the microbial metabolisms. It is thus essential to consider the bioturbation when determining the impact of oil on microbial communities. In this study, an experimental laboratory device maintaining pristine collected mudflat sediments in microcosms closer to true environmental conditions – with tidal cycles and natural seawater – was used to simulate an oil spill under bioturbation conditions. Different conditions were applied to the microcosms including an addition of: standardized oil (Blend Arabian Light crude oil, 25.6 mg.g−1 wet sediment), the common burrowing organism Hediste (Nereis) diversicolor and both the oil and H. diversicolor. The addition of H. diversicolor and its associated bioturbation did not affect the removal of petroleum hydrocarbons. After 270 days, 60% of hydrocarbons had been removed in all microcosms irrespective of the H. diversicolor addition. However, 16S-rRNA gene and 16S-cDNA T-RFLP and RT-PCR-amplicon libraries analysis showed an effect of the condition on the bacterial community structure, composition, and dynamics, supported by PerMANOVA analysis. The 16S-cDNA libraries from microcosms where H. diversicolor was added (oiled and un-oiled) showed a marked dominance of sequences related to Gammaproteobacteria. However, in the oiled-library sequences associated to Deltaproteobacteria and Bacteroidetes were also highly represented. The 16S-cDNA libraries from oiled-microcosms (with and without H. diversicolor addition) revealed two distinct microbial communities characterized by different phylotypes associated to known hydrocarbonoclastic bacteria and dominated by Gammaproteobacteria and Deltaproteobacteria. In the oiled-microcosms, the addition of H. diversicolor reduced the phylotype-richness, sequences associated to Actinobacteria, Firmicutes and Plantomycetes were not detected. These observations highlight the influence of the bioturbation on the bacterial community structure without affecting the biodegradation capacities.

Element speciation analysis of petroleum and related materials

Challenges to identification, characterisation and determination of element species in crude and residual oils, oil fractions, natural gas and gas condensates, and related products are presented. The principal elements of concern include vanadium, nickel, sulfur, mercury and arsenic. The state-of-the-art of analytical methods available for element speciation in petroleum-related matrices is discussed with particular attention given to chromatography with plasma source atomic spectrometric detection. Methods for fractionation of metal species prior to chromatography are critically reviewed. Analysis for metal species by gas (GC) and liquid chromatography (LC) using different separation mechanisms (size-exclusion, adsorption, ion-exchange, reversed and normal-phase) and element selective detection are discussed. The potential and limitations of LC-ICP AES, LC-ICP MS, GC-MIP AES and GC-ICP MS are highlighted in the context of techniques allowing a direct insight into the metal coordination in petroleum-related samples, such as X-ray absorption spectroscopy (XAS), electron paramagnetic resonance (EPR) and molecular mass spectrometry (using laser desorption, electrospray and chemical ionization).

Sensitivity improvement in ICP MS analysis of fuels and light petroleum matrices using a microflow nebulizer and heated spray chamber sample introduction.

Reasons for signal suppression during the analysis of light petroleum matrices by inductively coupled plasma mass spectrometry (ICP MS) were examined. A decrease of the ionization efficiency of the plasma was found to be the principal factor responsible for this loss of sensitivity. Consequently, an interface based on a total consumption micronebulizer and a heated spray chamber was constructed to alleviate this problem. A method based on flow-injection ICP MS using this interface was developed for the direct multielement analysis of undiluted fuels (gasoline, kerosene) and gas condensates offering an increase in sensitivity by at least a factor of 3-4 in comparison with the existing setups.

μFlow-injection–ICP collision cell MS determination of molybdenum, nickel and vanadium in petroleum samples using a modified total consumption micronebulizer

An interface based on a total consumption micronebulizer was developed for the introduction of xylene solutions into ICP MS. The increase in the nebulizer capillary diameter and the elimination of the internal connections reduced the problem of clogging, pressure instability and memory effects. The xylene carrier could be introduced for several hours at a rate of 30 μl min−1. The sample (2.5 μl) was injected into the carrier flow to produce peaks of 5 s at half-height (20 s at the base) which allowed a throughput of ca. 100 h−1 for the simultaneous determination of Mo, Ni and V. Calibration curves with good linearity (R2 > 0.999) over at least three orders of magnitude and detection limits at the sub-ng ml−1 levels were obtained. The method was validated by the analysis of a sample by an independent (ICP AES) method and by the analysis of a NIST CRM 1085c lubricating oil material. The use of a helium-pressurized collision cell was essential to obtain good accuracy for Ni and V but was not required for Mo.

Speciation analysis for mercury in gas condensates by capillary gas chromatography with inductively coupled plasma mass spectrometric detection.

A method allowing species-selective determination of atomic mercury, non-polar dialkylated mercury compounds,polar monoalkylated species and inorganic mercury complexes in natural gas condensates was developed. Inductively coupled plasma mass spectrometry was employed as a detection method for capillary gas chromatography and compared with microwave induced plasma atomic emission detection for the analysis of hydrocarbon-rich matrices. The method was based on two consecutive injections allowing comprehensive speciation analysis. First a sample aliquot was diluted with toluene and analysed for Hg0 and individual dialkylmercury compounds. Then, another aliquot was butylated with a Grignard reagent for the species specific determination of Hg(II) and monoalkylated mercury species. The detection limits were down to 0.08 pg level.

Identification of selenium-containing proteins in selenium-rich yeast aqueous extract by 2D gel electrophoresis, nanoHPLC-ICP MS and nanoHPLC-ESI MS/MS.

An approach based on the consecutive use of nanoHPLC-ICP collision cell MS and nanoHPLC-electrospray MS was proposed for the analysis of water-soluble selenium-containing proteins in selenium-rich yeast after their separation by 2D gel electrophoresis (GE). An ultrasonic probe was employed for fast protein extraction avoiding sample heating and thus reducing the risk of protein degradation. The efficiency of different extraction steps were critically evaluated by total selenium analysis and size-exclusion chromatography (SEC)-ICP MS. Prior to electrophoresis proteins were purified by acetone precipitation. The protein-containing spots from 2D GE were excised and digested with trypsin. The digests obtained were analyzed by nanoHPLC-ICP MS in order to check for the presence of selenium-containing peptides; this allowed the detection of target proteins for further analyses (two out of five spots). The subsequent analyses of the selected digests by nanoHPLC-ES MS/MS allowed the attribution of amino acid sequences to peaks detected by ICP MS revealing the presence of two selenium-containing proteins: SIP 18 and HSP 12.

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.

Direct multi-element analysis of crude oils and gas condensates by double-focusing sector field inductively coupled plasma mass spectrometry (ICP MS)

A double-focusing sector field ICP MS was optimized for the direct simultaneous determination of Ag, Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Sn, Ti, V in organic solutions. Polyatomic interferences originating from the carbon-rich matrix were completely eliminated at a resolution of 4000 allowing the detection limits at the low pg g−1 level to be obtained (typically one order of magnitude lower than using a quadrupole ICP MS). A method for the routine comprehensive trace element analysis of xylene solutions of oil samples using external calibration was developed. It was validated by the analysis of three certified reference materials and applied to the analysis of 2 gas condensate samples and 4 oil samples of different origins.