Finnigan MAT Research Articles

In situ analysis of trace elements in quartz by using laser ablation inductively coupled plasma mass spectrometry

There are several benefits which would result from the development of an in situ analytical technique for ultra trace elemental analysis of quartz, including rapid screening of possible high-purity quartz resources, by eliminating the need to remove solid and liquid inclusions by expensive dressing techniques prior to chemical analysis of structural impurities. Information on the petrogenetic history of the quartz can also be obtained from the distribution of trace elements. The main purpose of this paper is to describe an analytical method for estimating the concentrations of structural bounded trace elements in quartz. A double focusing sector field inductively coupled plasma mass spectrometry (ICP-MS, Finnigan MAT model ELEMENT), with the CD-1 Guard Electrode and a 266-nm UV laser ablation system was used in the development of the method for in situ analysis of quartz. The following elements are included in the analytical protocol: Al, Ba, Be, Cr, Fe, Ge, K, Li, Mg, Mn, Pb, Rb, Sr, Th, Ti, U. Analyses were carried out in low mass resolution ( m/Δ m=300), except for Mg, Ti, Cr, Fe (medium mass resolution, MR, m/Δ m≈3500) and K (high mass resolution, HR, m/Δ m>8000). The isotope 29Si was used as an internal standard at low resolution, and 30Si at medium and high resolution. External calibration was done by using the international reference materials: NIST 612, NIST 614, NIST 616, NIST 1830 from the National Institute of Standards and Technology (NIST), BCS 313/1 from the Bureau of Analysed Samples (BAS), the rhyolite RGM-1 reference sample from the United States Geological Survey (USGS), Reston and the certified reference material “pure Substance No. 1” silicon dioxide SiO 2 from the Federal Institute for Material Research and Testing, Berlin, Germany (BAM). Because of the absence of an SiO 2 blank, the BAM no. 1 SiO 2 was used for the estimation of detection limits. Detection limits for most of the elements are between 0.2 and 0.01 μg g −1. Analysis time and laser spot size were adjusted so that the raster did not exceed 300×300 μm on a 200-μm-thick section. New data for the international reference materials BCS 313/1 (BAS) and NIST 1830 and the standards BR-K1 and BR-FR2 are reported. To improve the lower limit of quantification and analytical uncertainty at low concentrations, it is important to have calibration curves with well defined intercepts. This can be achieved by the use of certified standards, with trace element concentrations lower than the BAM no.1 SiO 2 or a sample blank.

Determination of domoic acid in shellfish by liquid chromatography with electrospray ionization and multiple tandem mass spectrometry

Amnesic shellfish poisoning is a potentially lethal human toxic syndrome which is caused by domoic acid (DA) that originates in marine phytoplankton belonging to the Pseudonitzschia genus. A new sensitive liquid chromatographic–mass spectrometry (LC–MS) method has been developed for the determination of DA in various marine biological samples. The characteristic fragmentation pathways for DA were established using multiple stage MS on selected daughter ions, which were sequentially trapped and fragmented. Chromatography was performed using a gradient of acetonitrile–water (5:95 to 40:60), containing trifluoroacetic acid (0.05%), over 25 min at 0.2 ml/min with a C 18 column (Luna-2, 150×2.0 mm, 5 μm). Using electrospray ionisation, multiple tandem MS experiments were performed with an ion-trap mass spectrometer (Finnigan MAT LCQ). The protonated DA molecule was the precursor ion, m/z 312, and the relative collision energies were optimised for multiple MS (MS n , n=2–4) studies. LC–MS 3 using the ions, m/z 266 and 220, from the loss of two HCOOH molecules, produced the best sensitivity data. Calibration data for various MS modes were: MS (0.05–10 μg DA/ml, r 2=0.9973); MS 2 (0.025–10 μg DA/ml, r 2=0.9997); MS 3 (0.025–10 μg DA/ml, 0.9994). The detection limits (3:1 signal:noise) were better than 0.02 μg DA/ml for LC–MS, 0.014 μg DA/ml for LC–MS 2 and 0.008 μg DA/ml for LC–MS 3. This method was applied to determine DA in scallop ( Pecten maximus) tissues, which subsequently led to the closure of several shellfish harvesting sites on the west coast of Ireland.

Extraction of CO2 from air samples for isotopic analysis and limits to ultra high precision delta18O determination in CO2 gas.

The determination of delta18O values in CO2 at a precision level of +/-0.02 per thousand (delta-notation) has always been a challenging, if not impossible, analytical task. Here, we demonstrate that beyond the usually assumed major cause of uncertainty - water contamination - there are other, hitherto underestimated sources of contamination and processes which can alter the oxygen isotope composition of CO2. Active surfaces in the preparation line with which CO2 comes into contact, as well as traces of air in the sample, can alter the apparent delta18O value both temporarily and permanently. We investigated the effects of different surface materials including electropolished stainless steel, Duran glass, gold and quartz, the latter both untreated and silanized. CO2 frozen with liquid nitrogen showed a transient alteration of the 18O/16O ratio on all surfaces tested. The time to recover from the alteration as well as the size of the alteration varied with surface type. Quartz that had been ultrasonically cleaned for several hours with high purity water (0.05 microS) exhibited the smallest effect on the measured oxygen isotopic composition of CO2 before and after freezing. However, quartz proved to be mechanically unstable with time when subjected to repeated large temperature changes during operation. After several days of operation the gas released from the freezing step contained progressively increasing trace amounts of O2 probably originating from inclusions within the quartz, which precludes the use of quartz for cryogenically trapping CO2. Stainless steel or gold proved to be suitable materials after proper pre-treatment. To ensure a high trapping efficiency of CO2 from a flow of gas, a cold trap design was chosen comprising a thin wall 1/4" outer tube and a 1/8" inner tube, made respectively from electropolished stainless steel and gold. Due to a considerable 18O specific isotope effect during the release of CO2 from the cold surface, the thawing time had to be as long as 20 min for high precision delta18O measurements. The presence of traces of air in almost all CO2 gases that we analyzed was another major source of error. Nitrogen and oxygen in the ion source of our mass spectrometer (MAT 252, Finnigan MAT, Bremen, Germany) give rise to the production of NO2 at the hot tungsten filament. NO2+ is isobaric with C16O18O+ (m/z 46) and interferes with the delta18O measurement. Trace amounts of air are present in CO2 extracted cryogenically from air at -196 degrees C. This air, trapped at the cold surface, cannot be pumped away quantitatively. The amount of air present depends on the surface structure and, hence, the alteration of the measured delta18O value varies with the surface conditions. For automated high precision measurement of the isotopic composition of CO2 of air samples stored in glass flasks an extraction interface ('BGC-AirTrap') was developed which allows 18 analyses (including standards) per day to be made. For our reference CO2-in-air, stored in high pressure cylinders, the long term (>9 months) single sample precision was 0.012 per thousand for delta13C and 0.019 per thousand for delta18O.

Rapid determination of 230Th and 231Pa in seawater by desolvated micro-nebulization Inductively Coupled Plasma magnetic sector mass spectrometry

Difficulties in determining the 230Th and 231Pa concentration of seawater have hindered rapid progress in the application of these unique natural tracers of particle scavenging and ocean circulation. In response, we have developed an ICP/MS analytical procedure combining a degree of sensitivity, precision and sample throughput that can facilitate the systematic measurement of basin-scale changes in 230Th and 231Pa seawater concentration, and provide important constraints on circulation and mixing rates in the deep ocean. Seawater samples are spiked with 229Th and 233Pa and equilibrated before pre-concentration using conventional methods of Fe oxyhydroxide co-precipitation and anion exchange. Isotopic ratios are measured using a Finnigan MAT Element magnetic sector Inductively Coupled Plasma mass spectrometer (ICP/MS) equipped with a desolvating micronebulizer. Measurements are done on 10–20 l seawater samples with an internal precision of ∼2% and a reproducibility of ∼5% (95% confidence intervals (CI)) in deep water. After correction for procedural blank, 232Th tailing, and 232Th1H interference, the detection limits are ∼3 fg for 230Th and ∼0.4 fg for 231Pa. Applied to 20 l volumes, these detection limits correspond to concentrations of 0.15 fg/kg for 230Th and 0.02 fg/kg for 231Pa, which are 5–15 times lower than typical concentrations in surface water. The capability of this method is illustrated by two seawater profiles from the Equatorial Atlantic region that show systematic variations in 230Th and 231Pa concentration consistent with patterns of deep water circulation.

Metal-triggered structural transformations, aggregation, and fibrillation of human alpha-synuclein. A possible molecular NK between Parkinson's disease and heavy metal exposure.

Parkinson's disease involves the aggregation of alpha-synuclein to form fibrils, which are the major constituent of intracellular protein inclusions (Lewy bodies and Lewy neurites) in dopaminergic neurons of the substantia nigra. Occupational exposure to specific metals, especially manganese, copper, lead, iron, mercury, zinc, aluminum, appears to be a risk factor for Parkinson's disease based on epidemiological studies. Elevated levels of several of these metals have also been reported in the substantia nigra of Parkinson's disease subjects. We examined the effect of various metals on the kinetics of fibrillation of recombinant alpha-synuclein and in inducing conformational changes, as monitored by biophysical techniques. Several di- and trivalent metal ions caused significant accelerations in the rate of alpha-synuclein fibril formation. Aluminum was the most effective, along with copper(II), iron(III), cobalt(III), and manganese(II). The effectiveness correlated with increasing ion charge density. A correlation was noted between efficiency in stimulating fibrillation and inducing a conformational change, ascribed to formation of a partially folded intermediate. The potential for ligand bridging by polyvalent metal ions is proposed to be an important factor in the metal-induced conformational changes of alpha-synuclein. The results indicate that low concentrations of some metals can directly induce alpha-synuclein fibril formation.

Hypochlorous acid oxygenates the cysteine switch domain of pro-matrilysin (MMP-7). A mechanism for matrix metalloproteinase activation and atherosclerotic plaque rupture by myeloperoxidase.

Myeloperoxidase uses hydrogen peroxide (H2O2) to generate hypochlorous acid (HOCl), a potent cytotoxic oxidant. We demonstrate that HOCl regulates the activity of matrix metalloproteinase-7 (MMP-7, matrilysin) in vitro, suggesting that this oxidant activates MMPs in the artery wall. Indeed, both MMP-7 and myeloperoxidase were colocalized to lipid-laden macrophages in human atherosclerotic lesions. A highly conserved domain called the cysteine switch has been proposed to regulate MMP activity. When we exposed a synthetic peptide that mimicked the cysteine switch to HOCl, HPLC analysis showed that the thiol residue reacted rapidly, generating a near-quantitative yield of products. Tandem mass spectrometric analysis identified the products as sulfinic acid, sulfonic acid, and a dimer containing a disulfide bridge. In contrast, the peptide reacted slowly with H2O2, and the only product was the disulfide. Moreover, HOCl markedly activated pro-MMP-7, an MMP expressed at high levels in lipid-laden macrophages in vivo. Tandem mass spectrometric analysis of trypsin digests revealed that the thiol residue of the enzyme's cysteine switch domain had been converted to sulfinic acid. Thiol oxidation was associated with autolytic cleavage of pro-MMP-7, strongly suggesting that oxygenation activates the latent enzyme. In contrast, H2O2 failed to oxidize the thiol residue of the protein or activate the enzyme. Thus, HOCl activates pro-MMP-7 by converting the thiol residue of the cysteine switch to sulfinic acid. This activation mechanism is distinct from the well-studied proteolytic cleavage of MMP pro-enzymes. Our observations raise the possibility that HOCl generated by myeloperoxidase contributes to MMP activation, and therefore to plaque rupture, in the artery wall. HOCl and other oxidants might regulate MMP activity by the same mechanism in a variety of inflammatory conditions.

Selective and rapid liquid chromatography–mass spectrometry method for the quantification of rofecoxib in pharmacokinetic studies with humans

An easy, rapid and selective method for the determination of rofecoxib in human plasma is presented. The analytical technique is based on reversed-phase high-performance liquid chromatography coupled to atmospheric pressure chemical ionisation mass spectrometry (Finnigan Mat LCQ ion trap). The retention time of rofecoxib was 1.2 min. The method has been validated over a linear range from 1 to 500 μg/l using celecoxib as internal standard. After validation, the method was used to study the pharmacokinetic profile of rofecoxib in 12 healthy volunteers after administration of a single oral dose (12.5 mg). The presented method was sufficient to cover more than 95% of the area under the curve. The pharmacokinetic characteristics (mean±SD) were t max: 2.4±1.0 h, c max: 147±34 μg/l, AUC ∞: 2038±581 μg h/l and t 1/2: 11.3±2.1 h.

Using septum‐capped vials with continuous‐flow isotope ratio mass spectrometric analysis of atmospheric CO2 for Keeling plot applications

AbstractRecent advances in continuous‐flow isotope ratio mass spectrometry have made possible automated analysis of δ13C and δ18O in CO2 in air from 10‐mL septum‐capped vials. With the potential to collect, transport, and analyze a large number of air samples using these small inexpensive vials, the opportunity exists for routine and statistically robust sampling of CO2 for Keeling plot applications.With the above‐mentioned objectives in mind, we measured the precision of carbon and oxygen stable isotope ratios in the CO2 of air within septum‐capped vials using a Finnigan MAT Deltaplus XL continuous‐flow isotope ratio mass spectrometer (CF‐IRMS) interfaced to a GasBench II. The standard deviation of 45 δ13CPDB and δ18OVSMOW measurements from five vials filled with identical tank air was 0.08‰ and 0.14‰, respectively. This translated into a measurement precision (standard error; SE) of 0.01‰ δ13CPDB and 0.02‰ δ18OVSMOW. This precision was similar to that obtained with the tank air introduced directly into the GasBench II by bypassing the vials/autosampler (also with a SE = 0.01‰ for both δ13CPDB and δ18OVSMOW), suggesting minimal vial‐related effects with no storage time at ambient pressure and CO2 concentration. Further, puncturing the butyl rubber septa during filling just prior to analysis did not affect the precision (SE = 0.01‰ for both δ13CPDB and δ18OVSMOW, n = 45).After nine days of storage in vials with unpunctured septa, neither δ13CPDB nor δ18OVSMOW changed significantly, although the precision decreased to ∼0.04‰ for both δ13CPDB and δ18OVSMOW. A greater decrease in precision was observed for vials with punctured septa (from 0.01‰ to 0.10‰ SE for both δ13CPDB and δ18OVSMOW). Further, whereas vials with punctured septa showed no change in δ18OVSMOW, δ13CPDB decreased by 0.07‰/day (r2 = 0.96). In practice, such storage‐related effects could be accounted for based on concurrent changes in reference standards.These results suggest that air may be collected and stored in 10‐mL septum‐capped vials and analyzed in an automated fashion with the Gas Bench II/Deltaplus with sufficient precision for Keeling plot applications. Further, a relatively high sample throughput of about 4 vials per hour or about 100 vials or 2000 injections per day offers the potential for high precision with large sample sizes. Higher throughput should permit experimental advances that were not possible before. Copyright © 2001 John Wiley & Sons, Ltd.

L'excursion isotopique du carbone organique (delta 13 C org ) dans les paleoenvironnements continentaux de l'intervalle Paleocene/Eocene de Varangeville (Haute-Normandie)

Abstract The late Palaeocene carbon isotope excursion (C.I.E.) is often regarded as the best means of correlating marine and continental deposits. The few isotopic studies carried out in continental environments were based on pedogenic carbonate [Koch et al., 1992], or on organic matter. Sinha [1997] took up this subject starting from the outcrops on the coast of the English Channel at Varangeville, where marine sequences biostratigraphically constrain the isotopic excursion. His work documents a negative delta 13 C org excursion value approximately -27 per mil PDB. The present work points out that it is necessary to study more complete sections than those studied by Sinha. A section named Phare d'Ailly has been sampled in detail (figs. 1, 2, 3). In this section, for which detailed analysis of sedimentology, palaeontology and organic matter facies establish the continental nature of the palaeoenvironment, isotopic analysis of organic matter reveals a very negative delta 13 C org excursion value approximately -30 per mil PDB. The P/E interval synthesized in figure 2 shows three main groups, the stratigraphy of which is strongly constrained between the calcareous nannofossil Zones NP8 and NP11. The marine Thanetian facies belong to Zones NP8 and NP9. Above, the "Sparnacian" (Mont Bernon Group) is divided into 5 units referred to as SP. Unit SP2 is attributed to the Peckichara disermas Charozone, equivalent to Zone NP9. For unit SP4, an indirect correlation with Zone NP10 may be deduced. The upper part of the Varangeville Formation is known for its nannofossil association attributed to Zone NP11. We may conclude from these observations that the sparnacian sediments are synchronous with NP9-10 Zones and that they are effectively located in the time interval of the delta 13 C excursion. The SP1 and SP2 sediments were analysed for carbonate content, grain size distribution, clay mineralogy and total organic content (T.O.C.), using standard laboratory methods (fig. 3). An optical specification of the organic matter has been obtained from semiquantitative analysis of the organic matter facies. The survey of macro- and microfossils has supplied complementary supports for isotopic analysis (seed, wood and charcoal). The isotopic measurements were carried out on the bulk sediment and on complementary supports with a mass spectrometer in continuous flow delta + (Finnigan Mat). The measurement precision is better than 0.1 per mil and the reproducibility is about 0.15 per mil. Washing residues provide Gasteropoda, Bivalvia, Ostracoda, Characea, as well as fruits and seeds, microcodiums and otolith. All the palaeontological data illustrate a continental biota of a pure lacustrine environment, quiet and shallow, in a hot and humid climate. The organic matter facies analysis confirms the absence of any marine influence and documents a palaeoenvironment of lakes and ponds having an anoxic floor. Thus the carbon of the organic matter is considered to be continental and their isotopic variations linked to those of the atmospheric carbon.

Liquid chromatographic–mass spectrometric determination of celecoxib in plasma using single-ion monitoring and its use in clinical pharmacokinetics

Celecoxib is a cyclooxygenase-2 specific inhibitor, that has been recently and intensively prescribed as an anti-inflammatory drug in rheumatic osteoarthiritis. A robust, highly reliable and reproducible liquid chromatographic–mass spectrometric assay is developed for the determination of celecoxib in human plasma using sulindac as an internal standard. The run cycle-time is <4 min. The assay method involved extraction of the analytes from plasma samples at pH 5 with ethyl acetate and evaporation of the organic layer. The reconstituted solution of the residue was injected onto a Shim Pack GLC-CN, C 18 column and chromatographed with a mobile phase comprised of acetonitrile–1% acetic acid solution (4:1) at a flow-rate of 1 ml/min. The mass spectrometer (LCQ Finnigan Mat) was programmed in the positive single-ion monitoring mode to permit the detection and quantitation of the molecular ions of celecoxib and sulindac at m/ z 382 and 357, respectively. The peak area ratio of celecoxib/sulindac and concentration are linear ( r 2>0.994) over the concentration range 50–1000 ng/ml with a lowest detection limit of 20 ng/ml of celecoxib. Within- and between-day precision are within 1.58–4.0% relative standard deviation and the accuracy is 99.4–107.3% deviation of the nominal concentrations. The relative recoveries of celecoxib from human plasma ranged from 102.4 to 103.3% indicating the suitability of the method for the extraction of celecoxib and I.S. from plasma samples. The validated LC–MS method has been utilized to establish various pharmacokinetic parameters of celecoxib following a single oral dose administration of celecoxib capsules in two selected volunteers.

High accuracy analysis of low level sulfur in diesel fuel by isotope dilution high resolution ICP-MS, using silicon for mass bias correction of natural isotope ratios

A novel isotope dilution mass spectrometry method using ICP-MS is presented for establishing high accuracy reference values for sulfur in fossil fuels. The European Community plans to reduce the permitted content of sulfur in fossil fuels. In the case of diesel fuel the 1993 limit of 2000 µg g−1 is to be reduced to 50 µg g−1 by the year 2003. The new approach will readily meet the needs set by these new legal limits. Samples were prepared by closed vessel microwave digestion to ensure retention of the volatile sulfur compounds in solution and spike equilibration. The natural and spiked isotopic ratios of 32S/34S were then measured using a Finnigan MAT Element magnetic sector ICP-MS operating in medium resolution (R = 3000) mode to avoid the spectral interference of O2 on the sulfur isotopes. The natural isotopic composition of sulfur varies in nature and so must be measured in each sample. Here, we demonstrate a novel method in which silicon is used to correct for the effects of mass bias. The isotopic composition of silicon is well characterised and has minimal natural variation. The combined uncertainty of natural ratio measurements in sulfur solutions and sample digests is about 0.4%. The new ICP-IDMS method shows excellent agreement with the certified values for NIST SRM (SRM2724b) of 427 ± 7 µg g−1 compared to reference values of 428 ± 4 µg g−1. There is also good agreement with industry standard methods of analyses for low sulfur diesel. The combined uncertainty of the new method is 1–2% at <50 µg g−1. Samples taken from UK retail outlets sold as low sulfur diesel (<50 µg g−1) differ from the target sulfur content by up to 15 µg g−1. This deviation is comparable to the range in results for recognised routine methods and highlights how improved reference values at these concentrations will aid both the producer and legislator.

LC-MS ANALYSIS OF SELECTED SULFUR-CONTAINING NON-STEROID ANTI-INFLAMMATORY AGENTS: APPLICATIONS TO PHARMACEUTICAL PRODUCTS

A rapid, specific, sensitive, and reproducible high performance liquid chromatography-mass spectrometric assay has been developed for the quantitation of five sulfur-containing non-steroid anti-inflammatory drugs (NSAIDs), namely, celecoxib (Cel), piroxicam (Per), rofecoxib (Rof), sulindac (Sul), and tenoxicam (Ten), in available tablets and capsules. The examined compounds were extracted from the dosage forms with methanol and chromatographed on a Shim-Pack column using a mobile phase of acetonitrile and 1% acetic acid solution in a ratio 4:1 (Cel, Per, Sul, Ten) or acetonitrile and 20 mM ammonium acetate buffer solution (4:1) (Rof). The analytes were determined by an ion-trap mass spectrometer (Finnigan Mat) using APCI as an ionization process. The eluted compounds were detected either in the positive single ion monitoring mode at m/z 382.0, 332.0, 357.0, 338.4 (Cel, Per, Sul, Ten), or in the negative single ion monitoring mode at m/z 313.2 (Rof). Linear correlations of the peak area and concentration were confirmed for all compounds over the concentration ranges 0.25–1.0 μg /mL (Cel), 0.5–1.5 μg/mL (Per), 0.25–1.0 μg/mL (Sul), 1.0–2.0 μg/mL (Ten), and 0.1–1.0 μg/mL (Rof). The high specificity of the method was elucidated by analyzing mixtures of piroxicam/tenoxicam and celecoxib/sulindac. The developed method was successfully applied to determine the examined drugs in marketed pharmaceutical products.

Quadrupole ion trap mass spectrometry: a view at the turn of the century

A personal account of the quadrupole ion trap researches carried out in my laboratory and in collaboration with other laboratories. This account commences with the announcement, in 1983, of the first commercially available ion trap detector, manufactured by Finnigan MAT, and continues to the present day. Much of the ion trap mass spectrometry research that took place during the period following this announcement until 1994 has been discussed in detail in three volumes entitled Practical Aspects of Ion Trap Mass Spectrometry that were published in 1995. Except for those researches that impinged directly on our work during this period, no discussion of the contents of these three volumes is repeated here. The ion trap literature from 1994 to the present has been reviewed selectively so as to convey to the reader the dynamic nature of ion trap mass spectrometry and the wide variety of its application.

Separation and identification of volatile components in the fermentation broth of Trichoderma atroviride by solid-phase extraction and gas chromatography-mass spectrometry.

A preseparated fermentation broth of Trichoderma atroviride strain 11 is analyzed by gas chromatography followed by mass-spectral detection using a Finnigan MAT GCQ apparatus. After preseparation in a C18 and a silica gel column, nineteen pyrone and dioxolane derivatives and two aliphatic esters are obtained, respectively. Among these, the four dioxolane derivatives have not been identified previously. The main component is found to be 5,5'-dimethyl-2H-pyran-2-on. The relative standard deviation for the determination of the retention time and the peak area (measured in ion counts) is 0.1% and 4.5%, respectively.

Isotope Studies of Hydrogen and Oxygen in Ground Ice - Experiences with the Equilibration Technique

Equilibration technique suitable for a large amount ofsamples is described for hydrogen and oxygen isotope analyses of ground ice, especially ice wedges, including the sampling strategy and the analytical procedure as well as the calibration of the Finnigan MAT Delta-S mass spectrometer in June, 1999. Since for future analyses of ice wedges, a higher sampling resolution with limited sample volume is required, the limit of the equliibration technique for small water samples size of between 0.05 and 5 ml was checked. For water samples smaller than 1ml, corresponding to a molar ratio [H2O]/[H2] of smaller than 0.994, a balance correction has to be applied. The experimental errors due to partial evaporation during evacuation, the balance calcultion of the isotope equilibration process, the linearity as well as memory effects of the mass spectrometer for smaples with large differences in δ18O and δD are tackled in this paper. In the polar regions of Northern Siberia without Late Pleistocene and Holocene glaciation, ground ice is used as an archive for paleoclimate studies. First results of stable isotope measurements on ice wedges clearly show a shift towards heavier isotopes and thus warmer winter temperatures as well as a change in the source of the precipitation between Late Pleistocene and Holocene. These results indicate the high potential of ground ice for paleoclimate studies.

Determination of linsidomine in human plasma by tandem LC–MS with ESI

A sensitive method for the determination of linsidomine in plasma was developed, using high-performance liquid chromatographic (HPLC) separation with tandem mass spectrometric detection. Linsidomine was derivatised with propyl chloroformate and extracted with tert-butyl methyl ether/1,2-dichloroethane (55:45, v/v), back-extracted into HCl (0.01 M) followed by alkalinisation and back-extraction into ether; the final ether extract evaporated, reconstituted in mobile phase and then separated on a Phenomenex® Luna C18 (2) 5 μ 2.1×150 mm column with a mobile phase consisting of methanol–water–formic acid (98/100%) (400:600:0.05, v/v/v) at a flow-rate of 0.4 ml min −1. Detection was achieved by a Finnigan MAT mass spectrometer (LCQ) at unit resolution in the selected reaction monitoring (SRM) mode monitoring the transition of the protonated molecular ion m/ z 257.0 to the product ion m/ z 86.0. The mean recovery for linsidomine was 51% with a lower limit of quantification of 0.70 ng/ml using 1 ml plasma for extraction. This LC–MS/MS method for the determination of linsidomine in human plasma allows for better specificity and a higher sample throughput than the traditional LC–UV methods. It also demonstrates the profound effect that the composition of acidic modifiers and matrix constituents can have on the electrospray ionisation (ESI) of the analyte.

Determination of Rh, Pd and Pt in environmental silica containing matrices: capabilities and limitations of ICP-SFMS

Quantification of three platinum group elements most relevant to environmental monitoring, i.e. Pt, Rh and Pd, was performed in road dust, exploiting the high mass resolution capabilities of ICP-SFMS (ELEMENT, Finnigan MAT, Bremen, Germany). Sample preparation involved complete microwave assisted acid digestion of the silicate matrix with HNO3–HCl–HF mixtures. A USN6000AT+ ultrasonic nebulizer (Cetac Technologies, Omaha, NE, USA) incorporating a membrane desolvation unit was used as the introduction system. For Pt the Hf oxide interference could be eliminated effectively by membrane desolvation alone. For Rh and Pd, interferences, which could not be eliminated by mass resolution, were evaluated carefully by standard addition of the concomitant ions. It could be shown that no mathematical correction of the result was necessary for Rh, provided that membrane desolvation was employed. Pd in turn could not be measured interference free with this instrumental set-up. A mathematical correction procedure was developed for Sr. Concentrations of 63 ng g−1 Pt, 9 ng g−1 Rh and 17 ng g−1 Pd were found in the road dust samples. The limits of detection were 0.4 ng g−1 for Pt, 0.1 ng g−1 for Rh and 0.5 for Pd. The overall method precision determined for six samples ranged from 6% (Pt) to 13% (Pd).

New applications for laser ablation high resolution ICPMS (LA-HR-ICP-MS): Quantitative measurements of gallium diffusion across human root dentin

Laser-ablation high-resolution inductively coupled plasma mass spectrometry (LA-HR-ICP-MS) has been used for in situ determination of gallium concentration in treated human teeth. Gallium salts have an inhibitory effect on osteoclastic activity. Established as a therapeutic agent in regulating serum calcium and bone resorption, gallium has recently been proposed as a treatment for external root resorption. This study examines the diffusion of gallium introduced as the nitrate, through root dentin from the prepared root canal toward the root surface. Root canals from extracted human teeth were biomechanically prepared, sealed apically, and closed off coronally with polyethylene tubing. A 1.0 M solution of gallium nitrate, chelated by 1.0 M citrate buffer (pH 7.4), was introduced into canals, and roots were then suspended in test tubes of distilled water. The gallium-treated teeth were analyzed for 43Ca, 69Ga, and 71Ga isotopes. Elemental data were obtained by ablation with Nd∶YAG laser operating in the UV region (266 nm) by Merchantek and isotopic analysis with a Sector Field ICP-MS by Finnigan MAT. A 50 ppm glass standard (NIST-612) was also analyzed for the same isotopes. Quantification was performed by assuming a uniform nominal calcium concentration value of 27 g per 100 g of dry dentin across the root and using the 43Ca signal for internal calibration. The precision (RSD%) of measurements for 43Ca for the NIST-612 glass standard was found to be within 3.2% to 4.6% and for the tooth samples within 15.4% to 19.1%. The precision of determination for 69Ga for the NIST-612 glass standard was between 3.1% and 5.7%. The analysis revealed a significant uptake of gallium by the root dentin, ranging from ≈20000 ppm for the upper portion of the root to ≈8000 ppm for the areas in the lower sections. The analysis also revealed that a significant concentration gradient was established for gallium nitrate across the root dentin. The results from this study suggest that, in an effort to inhibit root resorption, therapeutic concentrations of gallium can be achieved throughout the root dentin when the prepared root canal is treated with 1.0 M gallium nitrate.

Electrospray Mass Spectrometric Study on Complexation of Transitional Metal Ions with Oligobipyridine Ligand

Positive-ion mode electrospray mass spectrometry (ES-MS) was used to investigate the reaction of oligobipyridine ligand L (L = 5,5'-bis[2-(2,2'-bipyridin-6-yl)ethyl]-2,2'-bipyridine) with M(ClO4)2 in various mole ratios [M = Fe(II), Co(II), Ni(II) and Cu(II)]. The results indicate that the oligobipyridine L coordinated to the transitional metal ions to form mononuclear complexes. The ES mass spectra of isolated complex [FeL3](PF6)2 were measured under various electrospray conditions to examine the influence of the spray voltage, capillary temperature, capillary voltage, and tube lens offset on the fragmentation of the complex in electrospray ionization process. The results show that the fragmentation was mainly controlled by the capillary temperature, capillary voltage, and tube lens offset potential for Finnigan MAT LCQ system. The present study confirmed that the ES-MS is a powerful technique for determining the species existing in solution and for investigation of the reaction between oligobipyridine and transitional metal ions.

On-line nitrate-delta(15)N extracted from groundwater determined by continuous-flow elemental analyzer/isotope ratio mass spectrometry.

Nitrate-delta(15)N from groundwater samples is determined on an inorganic nitrate derivative using automated, continuous-flow elemental analyzer/isotope ratio mass spectrometry (EA/IRMS). Nitrate is extracted and concentrated based on a recently published ion-exchange resin method. Freeze-dried AgNO(3) (0.5-1.5 mg) is packed in silver-foil cups and combusted within the reactor of an NC2500 elemental analyzer (CE Instruments, Milan, Italy) using its existing reaction scheme for nitrogen and carbon analysis. delta(15)N is determined using a Finnigan MAT DELTA(plus) isotope ratio mass spectrometer (Bremen, Germany). Results are drift-corrected to a AgNO(3) working standard that has been calibrated against known AgNO(3). Despite high concentrations of carbonate, the precision for all runs is better than 0.10 per thousand. The combination of this extraction procedure with commercially available delta(15)N analysis instrumentation offers a precise on-line alternative to existing methods, with considerable reduction in labor and analysis time.