Direct Injection Nebulizer Research Articles

Simultaneous total and speciation analysis of rhenium by capillary electrophoresis-inductively coupled plasma mass spectrometry

As one of the most concerned radionuclides, 99technetium (Tc) usually exists as pertechnetate (TcO4−) and low-valence Tc(IV) in the environment. The speciation analysis of 99Tc plays a crucial role in understanding its toxicity, bioavailability and mobility, and developing effective remediation strategies. However, conventional hyphenated techniques for 99Tc speciation analysis usually require a large sample volume and tedious operation process. In this work, a simple but highly effective system, coupling capillary electrophoresis to inductively coupled plasma mass spectrometry (CE-ICP-MS), was developed to analyze total rhenium (TRe), Re(IV), and Re(VII), known as the analogues of technetium. It is worth noting that by the use of a sprayer with a direct-injection nebulizer as the interface, the CE and ICP-MS were efficiently coupled as an entity that shares the advantages of both modules. In comparison to conventional techniques, the proposed CE-ICP-MS dominates in terms of less sample consumption and higher sample introduction efficiency, thus results in improved sensitivity, reduced radioactive waste, and more significantly, alleviated radiological exposure to operators. Under the optimized conditions, LODs of 0.02 μg L−1 and 0.01 μg L−1 were obtained for TRe and Re(VII), respectively, with relative standard deviations (RSDs) better than 3.0%. In addition, the accuracy and practicability of this hyphenated system were validated by analyzing simulated Hanford site groundwater samples with satisfactory recovery and separation of TRe, Re(IV), and Re(VII). The proposed method retains the great potential for the speciation analysis of 99Tc in various samples.

Piloted Liquid Spray Flames: A Numerical and Experimental Study

ABSTRACT Liquid-fuel spray flames are the primary mode of energy conversion in many high-power-density practical combustion devices. As compared to gaseous fuels, the phase change in liquid-fuel spray flames complicates the environment for laser-based combustion diagnostics and formulating predictive computational models. In this work, we present in-situ, non-intrusive measurement strategies and predictive models for combustion and carbon monoxide (CO) formation in piloted liquid-methanol spray flames. Resolving CO is essential to understand the incomplete oxidation of liquid hydrocarbon fuels and subsequent soot formation. A modified, flat-flame McKenna burner fitted with a direct-injection high-efficiency nebulizer (DIHEN) is used to produce piloted liquid-methanol spray flames. Hydroxyl (OH) planar laser-induced fluorescence (PLIF) is used for characterizing the reaction zones and temperature profiles of liquid-spray flames and two-dimensional (2D) images of CO are obtained via two-photon laser-induced fluorescence (TPLIF) using ultrashort, femtosecond-duration (fs) laser pulses. A three-dimensional (3D) computational model comprised of compressible continuous gas phase using unsteady Reynolds-averaged Navier-Stokes (URANS) in conjunction with two-way coupled Eulerian-Lagrangian spray modeling approach and partially-stirred reactor combustion model has been adapted to the modified McKenna burner. The computational model predicts the general trends of OH, temperature and CO profiles well at certain heights above the burner surface. Limitations of experimental measurements and strategies for improved model predictions pertaining to distributions of droplet sizes, pilot flame temperature, and the coflow temperature are discussed.

μ-dDIHEN: a new micro-flow liquid sample introduction system for direct injection nebulization in ICP-MS

The μ-dDIHEN feeds low and stable flow rates to the ICP-MS, allowing for analyses of small sample volumes (<100 μL) in various applications.

CO Imaging in piloted liquid-spray flames using femtosecond two-photon LIF

Abstract Liquid-spray flames are encountered in many practical combustion devices such as gasoline direct injection and diesel engines, gas turbine combustors as well as industrial furnaces. As opposed to gaseous fuels, additional phase-change steps present in liquid sprays not only complicate the overall combustion process, but also make in-situ, laser-based combustion diagnostics challenging. In particular, the formation of carbon monoxide (CO) due to incomplete fuel-air mixing and partial oxidation becomes a major challenge. In this study, we apply femtosecond, two-photon laser-induced fluorescence (fs-TPLIF) to measure CO concentration in piloted liquid-spray flames, taking into account possible signal interferences in the 230.1-nm, B1Σ+←X1Σ+ excitation scheme. A modified, flat-flame McKenna burner fitted with a direct-injection high-efficiency nebulizer (DIHEN) was used to produce piloted liquid-methanol spray flames. Although single-laser-shot OH-PLIF images show the presence of strong turbulent interactions in the core region, shot-averaged OH-PLIF images indicate that near the nozzle-exit region, the primary reaction takes place in an annular region around the droplet cloud, in general. A detailed spectroscopic study reveals that the signal interference at 460 nm originating from the second-order scattering of the excitation laser, which becomes approximately an order of magnitude stronger than CO fluorescence spectral lines near the nozzle exit region. The specific spectral filtering scheme introduced in our recent work is proved to be capable of suppressing interferences primarily originating from C2 Swan-band emissions. Two-dimensional CO maps along with OH-PLIF flame structure data provide key insights into the CO formation in piloted liquid-spray flames, while providing critical validation datasets for advanced computational models.

A fully automated direct injection nebulizer (d-DIHEN) for MC-ICP-MS isotope analysis: application to boron isotope ratio measurements

This work presents a fully automated setup for using direct injection nebulization as an introduction system for solution measurements by MC-ICP-MS, here applied to boron isotopes in pure boric acid solutions and natural samples.

Direct injection nebulizer with replaceable capillary for micro samples analysis by inductively coupled plasma-optical emission spectrometry

The analytical performance of a low cost direct injection high efficiency nebulizer (DIHEN) with replaceable capillary is evaluated and compared with a high efficiency nebulizer HEN-cyclonic spray chamber arrangement for sample introduction at lower solution uptake rates in inductively coupled plasma optical emission spectrometry (ICP-OES). The system allows the use of a replaceable capillary and optimization of the aerosol generation. The study was performed in terms of the main analytical figure of merits (i.e., sensitivity, limits of detection and signal stability) for plain water solutions and matrix effects caused by nitric acid and sodium in ICP-OES. In general, the DIHEN with replaceable capillary offers better sensitivities than the HEN-Cyclonic system and for some elements, improved detection limits (DL) in the range of 1.1–3.8 ng · mL−1 for Ba, Mg, Zn 206.2–200 nm and Zn 213.8–856 nm were obtained. Strontium’s DL was comparable with both systems and those for Cd and Mn were slightly worse. Short-term precision for this unit is not as good as the HEN-Cyclonic system, but being less than 2%, it can still be considered acceptable. It was more susceptible to changes in matrix composition, being ca. 18% the acid depressive effect and 7% due to sodium with the DIHEN compared to the conventional nebulizer-spray chamber arrangement (13 and 3% acid and sodium depressive effect, respectively). The utility of the developed unit is explored analyzing three certified materials (bovine liver, rice and wheat flours) and the experimental results are within the certified values. The ability of the DIHEN with replaceable capillary to analyze real micro samples (samples reconstituted in 150 µL deionized water) was demonstrated by the determination of Ca, Cd, Cu, Mg, Mn, Sr, and Zn in individual scorpion venoms samples. One of the main advantages over other arrangements is that it can be easily constructed in the laboratory.

Determination of As, Cd, Pb, and Hg in urine using inductively coupled plasma mass spectrometry with the direct injection high efficiency nebulizer

The application of the large-bore direct injection high efficiency nebulizer (LB-DIHEN) for the determination of arsenic (As), cadmium (Cd), lead (Pb), and mercury (Hg) in urine by inductively coupled plasma mass spectrometry (ICP-MS) is described. The LB-DIHEN is compared with the standard method using a concentric pneumatic nebulizer and cyclonic spray chamber. In addition to the toxicological significance of As, Cd, Pb, and Hg, these elements represent a cross-section of analytical issues including spectral interferences (e.g., 40Ar 35Cl + on 75As + and 98Mo 16O + on 114Cd +) and memory effects (Hg). In this study, the low sample consumption of the LB-DIHEN is used to reduce the volume of urine needed for analysis, and to reduce the volume of final diluted sample required for analysis. Eliminating the spray chamber and reducing the dead volume of the nebulizer reduces memory effects, especially for analytes such as Hg. The Dynamic Reaction Cell (DRC) is used in this study to attenuate the background level of ArCl + in spite of the increase in the solvent load and, in turn, the urine matrix (chloride) delivered to the plasma by the LB-DIHEN. This is the first report on coupling the LB-DIHEN to a standard autosampler for unattended sample analysis. The robustness of direct injection nebulization for routine analysis and the issues associated with automation of the sample introduction process are discussed. Although the figures of merit (sensitivity, limit of detection, and precision) determined for both nebulizers are slightly poorer for the LB-DIHEN than for the concentric pneumatic nebulizer, there is not a clinically significant difference between the results for both sample introduction systems. The accuracy of results is assessed using archived urine materials that are circulated by several different proficiency testing (PT) programs and external quality assessment schemes (EQAS). Results obtained using the LB-DIHEN were within the acceptable range established by a consensus pool generated using different methods, none of which are likely to be using direct injection nebulization. Internal quality control sample results obtained using the LB-DIHEN were compared to those obtained using the conventional nebulizer. Reported results were similar for both nebulizers. Thus, these results show that the LB-DIHEN is certainly feasible for the analysis of urine specimens.

Comparison of aerosol properties and ICP-MS analytical performance of the Vulkan direct injection nebuliser and the Direct Injection High Efficiency Nebuliser

Monodisperse polymer particles consisting of DVB and styrene-copoly-DVB were successfully synthesized by photoinitiated precipitation polymerization with 2,2'-azobis(2-methylpropionitrile) (AIBN) as initiator. A focused 150 W xenon short arc lamp was used to radiate the sample mixtures. The size of the particles ranged from 1.5 to 4 m and could be varied by changing the monomer concentration between 2 and 10% (v/v) and by means of the time of polymerization. By using photoinitiation instead of thermal initiation, it was possible to avoid coagulum and arrive at spherical particles with an exceptionally high monodispersity for particles of this size range (polydispersity index < 1.02) and with monomer loadings well above 5%.

Noise characteristics and analytical precision of inductively coupled plasma mass spectrometry using a Vulkan direct injection nebuliser for sample introduction

Noise and precision of ion count rate measurements were characterised for ICP-MS using a Vulkan direct injection nebuliser (Vulkan DIN) for sample introduction. For comparison, experiments were also carried out using a direct injection high efficiency nebuliser (DIHEN). The Vulkan DIN gave considerably higher relative white noise compared with the DIHEN, −40.3 compared with −45.8 dB, and measurements of aerosol characteristics showed that this was a result of broader size distribution and larger mean size of droplets for the Vulkan DIN. At a liquid flow rate of 85 μL min−1, the aerosol volume fraction constituted by droplets with a diameter smaller than 10 μm was only 5% for the Vulkan DIN compared to 38% for the DIHEN, and the Sauter mean diameter was 30.2 and 11.1 μm, respectively. Compared with the DIHEN, interference noise from a peristaltic pump was very small with the Vulkan DIN because at the liquid flow rate giving maximum sensitivity, the analyte signal intensity was not much affected by changes in liquid flow rate. Although this had a positive effect on precision, it indicated that the plasma is cooled by large droplets that do not positively contribute to the analyte signal intensity. For analytical precision data it was evident that with the Vulkan DIN, precision was limited by the high white noise in the frequency range 0.4–500 Hz, but for the DIHEN there were relatively large contributions from 1/f and/or interference noise to the observed precision. When using integration times of 1000 ms or longer, the DIHEN did, however, appear to give slightly better precision for most of the isotopes tested. For comparison, precision data was also generated when using a conventional spray chamber sample introduction system and it was found that, with a 3000 ms integration time, both direct injection nebulisers gave better precision for most isotopes. Although analytical precision is impressive, the results in this paper also show that both direct injection nebulisers produce aerosols that are far from ideal for the types of ICPs currently used in commercial instruments.

Capillary electrophoresis‐inductively coupled plasma‐mass spectrometry: A report on technical principles and problem solutions, potential, and limitations of this technology as well as on examples of application

This paper summarizes some basic principles of capillary electrophoresis (CE), inductively coupled plasma-mass spectrometry (ICP-MS), and coupling of both devices. Especially the interfacing is described in detail. A special focus is drawn to various interface developments reported in literature and technical problems, i.e., requirements to the interface setup and respective solutions. Nowadays, typically sheath flow-based interfaces are used. The sheath flow fulfills two requirements of hyphenation, (i) the closing of the electrical circuit of CE and (ii) the feeding of the used nebulizer with an adequate flow rate. In the beginning of CE-ICP-MS coupling predominantly home-made interface-nebulizer constructions were developed and tested for various speciation problems. Now increasingly such laboratory-constructed interfaces are left. Mostly commercial nebulizers are employed being combined with commercially available tee or cross fittings to connect the CE capillary to the electrode, the additional sheath flow, and the nebulizer. Due to the low sample amounts and low flow rates from CE, such nebulizers are typically low-flow nebulizers like, e.g., the microconcentric nebulizer (MCN) and the direct injection nebulizer (DIN). However, there are also reports on couplings using standard Meinhard systems. Still the control and reduction of a siphoning sucting flow and sufficient detection limits are the major problems in hyphenating CE to ICP-MS. Different solutions are reported on these problems and summarized here. Finally numerous applications are reported. Mostly, applications are performed on speciation of selenium, arsenic, metallothionein isoforms, mercury, or cobalt.

Sample introduction systems for reversed phase LC-ICP-MS of selenium using large amounts of methanol—comparison of systems based on membrane desolvation, a spray chamber and direct injection

Three sample introduction systems were compared for their efficiency in introducing a variety of biologically relevant selenium species in organic solutions with the purpose of mimicking the effluent from a chromatographic system. The sample introduction systems consisted of a microconcentric nebuliser (MCN) in combination with a membrane desolvator (MD), a MCN in combination with a cyclonic spray chamber (CS) and a direct injection nebuliser (DIN), respectively. Thirteen selenium standards diluted in 50% methanol were introduced in each system at a flow rate of 50 μl min−1. Except for the selenite and methaneseleninic acid standards that were lost in the MCN-MD system, similar normalized response factors were achieved for the standards regardless of the sample introduction system. When trimethylselenonium and selenate standards were continuously infused in a linear methanol gradient from 10 to 90%, the signal was almost unaffected when the MCN-MD was used as interface. The signals from the MCN-CS introduction system were almost unaffected in methanol concentrations between 10 and 40%, after which they slowly declined. The signal from the DIN showed a plateau in signal intensity at methanol concentrations between 35 and 70%. Detection limits in flow injection analysis, expressed as the concentration that would result in a signal equivalent to three times the peak to peak noise of the baseline, were estimated to be 200, 150 and 100 ng Se L−1 for the MCN-CS, MCN-MD and DIN, respectively. The independence of the signal from the methanol concentration in the eluent allowed quantification of human selenoprotein P isoforms by gradient microbore reversed phase chromatography (μRPC) on the basis of an internal trimethylselenonium standard. The MCN-MD system was applied for μRPC analysis of 77Se enriched yeast samples and more than 30 selenium containing compounds were separated using a linear gradient from 5% to 95% methanol, some of the selenium species eluting in 85% methanol.

Radial ICP characteristics for ICP-AES using direct injection or microconcentric nebulisation

Radial analyte signal intensities, fundamental plasma parameters, and non-spectral interference effects were characterized for inductively coupled plasma atomic emission spectrometry (ICP-AES) using a direct injection nebuliser (Vulkan DIN) or a microconcentric nebuliser (MCN) coupled to a cyclonic spray chamber for sample introduction. Radial analyte signal intensity profiles for atomic and ionic lines with energy sum (Esum) between 1.85 and 15.41 eV were used. When using the MCN system, for all lines the signal intensity profiles were parabolic with maxima at the axial centre of the plasma. For the Vulkan DIN, the shapes of the profiles were dependent on their Esum showing minimum intensities at the axial centre of the plasma for lines with high Esum values. The ionisation temperature, electron number density and magnesium ion-atom line intensity ratio determined indicated that ionisation and excitation capabilities were deteriorated at the centre of the plasma when using the Vulkan DIN compared with the MCN. This was found to be not simply a result of high aerosol load when using the Vulkan DIN, but because of poor plasma–aerosol interaction, possibly caused by the confined distribution of aerosol in the plasma and high nebuliser gas velocity. Indeed, for the Vulkan DIN, electron number density and ionisation temperature increased with liquid flow rate, which could be explained by plasma shrinkage, or the thermal pinch effect, which increased the aerosol–plasma interaction at increased liquid flow rates. As a consequence, when increasing the liquid flow rate in the range 20–90 μL min−1: (i) analyte sensitivity increased linearly; (ii) the plasma became unstable; (iii) the magnitude of matrix effects remained almost unaffected. These results are partly in contrast to observations made with other types of direct injection nebulisers and ICP instruments.

Quantitative determination of selenium metabolites in human urine by LC-DRC-ICP-MS

Two selenium metabolites, Se-methylseleno-N-acetylgalactosamine (SeGal-N-Ac) and Se-methylselenogalactosamine (SeGal-NH2), were quantified in human urine by LC-DRC-ICP-MS. Urine samples were analysed after 1 + 1 dilution in a reversed phase chromatographic system using an eluent consisting of 200 mM ammonium acetate and 5% methanol with a pH of 9.25 and quantified by standard addition. Samples were collected from 8 volunteers before and after 5 days ingestion of 100 μg Se day−1 in form of selenized yeast. The average concentration of (SeGal-NH2) before and after selenium intake was 1.4 and 1.9 μg Se L−1, respectively, while the average concentration of Se-Gal-N-Ac increased from 2.6 to 11.6 μg Se L−1 before and after selenium consumption. Detection limits calculated on basis of three times the standard deviation on peak areas of 2 μg Se L−1 solutions were 0.1 μg Se L−1 for SeGal-NH2 and 0.2 μg Se L−1 for SeGal-N-Ac based on peak areas and monitoring 80Se. The precision expressed as the relative standard deviation (n = 6) at the 2 μg Se L−1 level was 3.1 and 1.7% for SeGal-NH2 and SeGal-N-Ac, respectively, while the corresponding values were 1.0 and 0.7% at the 10 μg Se L−1 level. Linearity in urine matrix was examined in the range 0.5–100 μg Se L−1 and correlation coefficients better than 0.999 were obtained. As the cationic compound SeGal-NH3+ may be confounded with the trimethylselenonium ion (TMSe+), urine samples were also analysed in a cation exchange chromatographic system in which SeGal-NH3+ was separated from the trimethylselenonium ion. None of the samples contained TMSe+ in detectable amounts. Three sample introduction systems were compared—a microconcentric nebuliser in combination with a cyclonic spray chamber (MCN), a direct injection nebuliser (DIN) and an ultrasonic nebuliser (USN). The MCN was most suitable for this purpose.

Determination of B in body fluids by isotope dilution inductively coupled mass spectrometry with direct injection nebulization

The determination of B in small volumes of undigested blood plasma and urine by isotope dilution and high efficiency direct injection nebulization (DIN) inductively coupled plasma mass spectrometry (ICP-MS) is proposed. The C interference over 11B was removed by precipitating the samples proteins. Samples aliquots of 1 ml were spiked with an enriched 10B solution and shaken during 1 h to attain the isotopic equilibrium. Thereafter, the sample proteins were denaturated with nitric acid and the supernatant was analyzed. This procedure was effective to reduce C concentrations in approximately 94%. Sample volumes of 50 μl were introduced into the ICP by the direct injection nebulizer producing transient signals lasting 30 s for B isotopes measurements. Precision of 10B/ 11B measurements was characterized by relative standard deviation (RSD) lower than 1%. The instrumental mass discrimination factor was lower than 5%. Total B concentrations from 100 to 135 μg L −1 in plasma and 0.499 to 3.021 mg L −1 in urine samples were found. Reproducibility of triplicate samples was characterized by RSD<2.0% for plasma and lower than 1.3% for urine samples. Limit of detection (3 σ) of 0.6 ng ml −1 was calculated from synthetic blood plasma blank. Results of the denatured supernatant and digested plasma and urine samples were comparable at the 95% confidence level.

Development of a new method for the separation of vanadium species and chloride interference removal using modified silica capillaries-DIN-ICP-MS

A new on-line method for the separation of vanadium (IV) and vanadium (V) as well as for the removal of ClO + mass spectral interference on vanadium determination by quadrupole-ICP-MS has been developed. The sample introduction system consists of a modified fused silica capillary coupled to a direct injection nebuliser (DIN), between the solvent delivery system and the ICP. Fused silica capillaries were treated with different anion and cation exchanger reagents and were tested for the retention of Cl − and the separation of vanadium ions at μg l −1 levels. A suitable strong anion exchanger functional group (3-aminopropyltrimethoxy silane) was selected. Chlorine anions were retained in this anionic capillary and the separation between V(IV) and V(V) was possible in the pH range 2–4. The selections of instrumental ICP-MS conditions for the minimisation of the ClO+ interference were carefully considered. Factors affecting the chromatographic separation such as sample pH, sample flow rate, effect of methanol in the mobile phase and length of the capillary for the separation were optimised. The proposed methodology provides a simple and rapid method for vanadium speciation. A relative detection limit of 12 l −1 (i.e. absolute detection limits of 120 pg) for V(IV) based on peak height measurements was obtained. The relative standard deviation for V(IV) was 2.4% for a 10 μl injection ( n=6).

Selenium speciation in human urine samples by LC- and CE-ICP-MS—separation and identification of selenosugars

Human urine samples were analysed by a reversed-phase chromatographic system and an ion-pair chromatographic system. The chromatographic system was connected to the ICP-MS either by a microconcentric nebulizer (MCN) in combination with a cyclonic spraychamber or by a modified direct injection nebulizer (MDIN). The sensitivity of the latter was better than the sensitivity of the MCN, which on the other hand was more robust for the analysis of samples with high concentrations of dissolved solids. Urine sample composition did not seem to change when urine was exposed to evaporation under nitrogen at ambient temperature and methanol extraction. A pre-concentration factor of 10 was achieved with this procedure. On occasions when a pre-concentration factor of 100 was obtained by lyophilsation and methanol extraction, at least 10 selenium compounds were separated in the urine sample. Urine samples were collected from two healthy volunteers who had been supplied with 1000 µg and 2000 µg of selenium, respectively, in the form of selenized yeast. When samples were spiked with 8 different standards, only two standards co-eluted with compounds in urine in both chromatographic systems: the major urinary metabolite Se-methyl-N-acetylgalactosamine and Se-methyl-N-acetylglucosamine. The presence of Se-methyl-N-acetylglucosamine in urine was verified by co-migration with the standard in capillary electrophoresis after fractionation by preparative reversed-phase chromatography. Se-methyl-N-acetylglucosamine is only a minor metabolite as its concentration was less than 2% of the concentration of Se-methyl-N-acetylgalactosamine. The presence of this metabolite in urine has, to our knowledge, not been suggested before. Trimethylselenonium, selenomethionine, Se-methylselenocysteine, Se-methylselenomethionine and selenocystamine were not detected in these samples.

Investigation of trialkoxysilane hydrolysis kinetics using liquid chromatography with inductively coupled plasma atomic emission spectrometric detection and non-linear regression modeling

A novel approach is demonstrated for measuring rates of the consecutive acid–base catalyzed hydrolysis reactions of (3-glycidoxypropyl)trimethoxysilane (GPTMS) and (3-aminopropyl)triethoxysilane (APTES) in dilute aqueous solution using liquid chromatography with inductively coupled plasma atomic emission spectrometric (ICP-AES) detection. The hydrolysis reactions are monitored by sampling kinetic solutions in a timewise manner and performing liquid chromatographic separations of the parent silane and organosilicon hydrolysis products. The column effluent is fed into the ICP through a direct injection nebulizer for online monitoring of silicon atomic emission at 251.611 nm, producing a series of silicon chromatograms for each kinetic run. Reversed phase separations are effected using acetonitrile–water gradients and are complete in 6 min or less. The systematic changes in peak areas provide information from which the rate constants of the consecutive hydrolysis reactions ( k 1, k 2, and k 3) are obtained by non-linear regression modeling. Using a quenching scheme, hydrolysis half-lives as brief as 3 min for the parent silane can be monitored. For each compound, a series of rate constants are obtained over a range of pH and buffer concentration, permitting estimation of the catalytic constants k H 3O + and k OH − for the consecutive acid–base catalyzed hydrolysis reactions by multiple regression analysis.

Precise and accurate determination of boron isotope ratios by multiple collector ICP-MS: origin of boron in the Ngawha geothermal system, New Zealand

A new technique has been developed for the measurement of boron isotope ratios in fluids using a double focusing multiple collector inductively coupled plasma (ICP) mass spectrometer. Sample introduction using a direct injection nebuliser was found to eliminate memory problems that are common where spray chambers are involved. The 4–9% mass bias can be corrected for by bracketing sample measurements with standards. As matrices were found to affect the mass bias all samples must be purified and that sample and standard solutions must be similar. A new purification technique was developed that yields adequately purified samples. Using this technique, it is possible to make rapid measurements (4 min) from samples containing 250 ng B to a precision of ±0.2‰. This analytical technique has been applied to the Ngawha geothermal system in New Zealand in an attempt to determine the source of B in geothermal fluids where the B concentrations can exceed 100 mmol/l. The δ11B values range between −3.1‰ and −3.9‰ indicating that no seawater sources are involved and that the elevated B concentrations can only be accounted for by low water/rock ratios with the B being derived from basement greywacke/argillite. The similarity of B isotope ratios for hydrothermal fluids that have been diluted and cooled with groundwaters indicates that isotope fractionation due to adsorption is unlikely to occur in cool geothermal fluids (<40 °C).

Anodic stripping voltammetry combined on-line with inductively coupled plasma-MS via a direct-injection high-efficiency nebulizer.

A direct-injection high-efficiency nebulizer (DIHEN) is used to couple a thin-layer electrochemical flow cell on-line with an ICP-mass spectrometer to perform anodic stripping voltammetry (ASV) at a thin mercury film followed by subsequent ICPMS measurements for the stripped metal analytes. The resultant hyphenated technique (ASV-DIHEN-ICPMS) is capable of analyzing select heavy metals present at ultratrace levels (down to low-ppt to sub-ppt levels) that are lower than the detection limits obtained by conventional ICPMS. In addition to its good analytical performance, the technique offers other attractive features such as the ability to eliminate detrimental matrix effects that can compromise ICPMS analyses and the possibility of probing electrode reactions involving trace amounts metal species with ICPMS. For conducting ASV on-line with ICPMS, the DIHEN was found to be more advantageous than the microconcentric nebulizer in terms of minimizing memory effects and potential artifacts caused by the erosion of the Hg film into the flowing solution stream. Compared to a direct injection nebulizer (DIN), the DIHEN was easier to operate. Moreover, its simpler design and the lack of back pressure from the DIHEN capillary made it more compatible with coupling to the thin-layer electrochemical cell than a DIN system.

Boron isotope dilution in cellular fractions of coffee leaves Evaluated by Inductively Coupled Plasma Mass Spectrometry with direct injection nebulization (DIN-ICP-MS)

Enriched 10B (94.14 atom %) was supplied to coffee plantlets for three months. Then boron isotope ratios were determined in the leaf cell compartments, cell wall, nuclei and chloroplast, after a sub-cellular fractionation procedure. The isotopic measurements were performed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) provided with a direct injection nebulizer (DIN), introducing a sample volume of 50 mL. Isotopic ratios from 1.002 to 1.326 were determined with precision characterized by RSD lower than 1.5% for the enriched cell fractions with B concentrations ranging from 3.3 to 10.8 mg g-1. The detection limit (3s) was 0.5 ng B mL-1. The average enrichments in 10B atom % found in the cell walls, nuclei and chloroplasts were 46.7, 44.5 and 48.8, respectively.