Microconcentric Nebulizer Research Articles

Speciation of lead compounds in fish by capillary electrophoresis-inductively coupled plasma mass spectrometry

A capillary electrophoresis-inductively coupled plasma mass spectrometric (CE-ICP-MS) method for lead speciation application is described. Sample containing ionic lead compounds were subjected to electrophoretic separation before injection into the micro-concentric nebulizer (CEI-100). The species studied include inorganic lead (PbII), trimethyl lead (TML) and triethyl lead (TEL). The separation has been achieved on a 70 cm length × 75 μm id fused silica capillary. The electrophoretic buffer used is 15 mmol l−1 Tris (pH 8.25) containing 10 mmol l−1 SDS (sodium dodecyl sulfate), 0.2 mmol l−1 EDTA and 2% v/v methanol, while the applied voltage is set at +26 kV. The lead species in biological tissues are extracted into 1% m/v EDTA solution taken in a closed centrifuge tube and kept on a water bath, using microwaves at 70 °C for 10 min. The extraction efficiencies of individual lead species added to the sample at 2 μg Pb g−1 level are between 97% and 102%. The detection limits of the species studied are in the range 0.2–0.6 ng Pb ml−1. The procedure has been applied for the speciation analysis of two reference materials namely dogfish liver tissue (NRCC DOLT-3) and oyster tissue (NIST SRM 1566a) and two real-world samples.

Comparison of Laser Ablation and Dried Solution Aerosol as Sampling Systems in Inductively Coupled Plasma Mass Spectrometry

This paper describes a study designed to determine the possibility of using a dried aerosol solution for calibration in laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The relative sensitivities of tested materials mobilized by laser ablation and by aqueous nebulization were established, and the experimentally determined relative sensitivity factors (RSFs) were used in conjunction with aqueous calibration for the analysis of solid steel samples. To such a purpose a set of CRM carbon steel samples (SS-451/1 to SS-460/1) were sampled into an ICP-MS instrument by solution nebulization using a microconcentric nebulizer with membrane desolvating (D-MCN) and by laser ablation (LA). Both systems were applied with the same ICP-MS operating parameters and the analyte signals were compared. The RSF (desolvated aerosol response/ablated solid response) values were close to 1 for the analytes Cr, Ni, Co, V, and W, about 1.3 for Mo, and 1.7 for As, P, and Mn. Complementary tests were carried out using CRM SS-455/1 as a solid standard for one-point calibration, applying LAMTRACE software for data reduction and quantification. The analytical results are in good agreement with the certified values in all cases, showing that the applicability of dried aerosol solutions is a good alternative calibration system for laser ablation sampling.

Ultratrace and isotope ratios analyses of some radionuclides by ICP-MS

AbstractExtensive work is under way using High Resolution-ICP-MS for90Sr,234U,235U,238U,239Pu,240Pu, and241Am detection. Sample preparation procedures based on liquid-liquid extraction and ion exchange chromatography were developed. Sr, U, Pu, and Am were separated from their matrix and concentrated to improve the power of detection in the mass spectrometer. A microconcentric nebulizer with a desolvation introduction system (Ardius) is used. Instrumental limits of detection using Sr and U standard solutions are 0.01 ppt and 0.006 ppt for Sr and U, respectively. A study is presented on the mass interferences for the specified radionuclides. In the environmental samples investigated the90Sr/86Sr isotope ratio is 6.02×10-9and for240Pu/239Pu the isotope ratio is 0.17.

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.

Reduction of UH+ formation for 236U/238U isotope ratio measurements at ultratrace level in double focusing sector field ICP-MS using D2O as solvent

The main factors affecting the accurate and precise determination of 236U using ICP-MS are instrumental background, the isobaric interference of 235UH+ molecular ion on 236U+ analyte ions, and the presence of 238U+ and 235U+ peak tails. An optimized analytical method for attenuating the influence of these factors on uranium isotope ratio measurements at ultratrace level of environmental samples has been developed. In order to reduce 235UH+ formation, D2O (heavy water) is used as a solvent for the dissolution and dilution of uranium samples. Abundance sensitivity was improved by use of medium mass resolution (m/Δm = 4450) in comparison with low mass resolution in double-focusing sector field ICP-MS (ICP-SFMS). For solution introduction the performances of several different sample introduction systems (Meinhard, Aridus and ultrasonic nebulizer) were studied. It has been shown, that for all nebulization systems, a diminution in UH+/U+ is observed in D2O as compared with H2O as solvent. Optimum results were obtained in ICP-SFMS for a desolvating microconcentric nebulizer system (Aridus) with a minimum hydride formation rate of 9 × 10−7 and a limit for 236U/238U isotopic ratio measurements of 3 – 5 × 10−7. A comparison was performed of three commercially available sector field ICP-MS devices, with good agreement found between single collector and multiple collector ICP-MS (MC-ICP-MS).

Characterization of microconcentric nebulizer uptake rates for capillary electrophoresis inductively coupled plasma mass spectrometry

There is demonstrated interest in combining capillary electrophoresis (CE) with inductively coupled plasma mass spectrometry (ICP-MS) for speciation determinations. When self-aspirating nebulizers are used for this application, it is important to offset the suction effect to avoid degradation of the separation. In this study, sample uptake rates for three microconcentric nebulizers of the same model, in combination with a cyclonic spray chamber, were characterized and compared for future utilization in CE–ICP-MS interfaces. The specific model studied was a MicroMist with a nominal uptake rate of 100 μl/min at 1 l/min argon gas flow rate per the manufacturer's specifications. Sample uptake rates at various nebulizer gas flows were measured by aspirating water from a weighed container and calculating the uptake rate in microliter per minute. The nebulizers studied provided good reproducibility from day to day, but a comparison of the different nebulizers reflected a significant difference in performance. A characteristic observed during the study was that uptake rates decreased with increasing nebulizer gas flow. This can be used for sample introduction for CE–ICP-MS. Interestingly, very different performance was observed when comparing the three different nebulizers of the same model. Uptake rates showed strong dependence on argon gas flow rates and the dimensions of the sample uptake tubing.

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.

High-speed digital photographic study of an inductively coupled plasma during laser ablation: comparison of dried solution aerosols from a microconcentric nebulizer and solid particles from laser ablation

High-speed photographs and videos of an ICP are used to examine the fates of solid particles produced by laser ablation (LA) in an inductively coupled plasma (ICP). The trajectories, lifetimes, and emission behavior of particles traversing the plasma are studied under a variety of conditions. Desolvated particles from a nebulized yttrium solution and particles ablated from a Y2O3 pellet are mixed and introduced simultaneously into an ICP. High-resolution digital photographs and video sequences are captured using shutter speeds of approximately 65 µs. The plasma behavior of particles generated by a quadrupled Nd:YAG laser (266 nm) and an ArF excimer laser (193 nm) are compared, and either argon or helium is used as the transport gas through the ablation cell. No red emission clouds from YO are visible in the ICP when a 20 µL min−1 nebulizer is used to spray a 2000 ppm aqueous Y solution, suggesting that the wet droplets from this nebulizer desolvate almost completely before entering the ICP. These desolvated particles from the nebulized solution atomize and ionize like the small dry particulates from laser ablation. However, many large ablated particulates are observed to fly through the plasma intact, possibly contributing to signal noise, deposition on the sampler and skimmer cones, and elemental fractionation.

Spatially-resolved analysis of solids by laser ablation-inductively coupled plasma-mass spectrometry: trace elemental quantification without matrix-matched solid standards

A two-point calibration method for laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is assessed. Desolvated particles from a Teflon microconcentric nebulizer and particles ablated from a localized position on a solid sample are mixed and introduced simultaneously into an ICP magnetic sector mass spectrometer. Analyte signals from the solution are compared with those from the ablated solid for calibration. Matrix-matched or pelletized solid standards and prior knowledge of sample composition are not required for calibration. The transport of sample particulates from the ablation cell is measured online with a piezoelectric microbalance to provide signal normalization. The relative accuracy of the quantitative analysis of NIST SRM 612 glass and NIST SRM 1264a steel is 3% to 12%, respectively, except for the elements Pb and Bi in steel. These two elements are distributed heterogeneously and are probably subject to fractionation. The use of helium instead of argon as transport gas reduced fractionation but did not eliminate it. The analyte concentrations were approximately 15–51 ppm in NIST SRM 612 glass and 9–2500 ppm in NIST SRM 1264a steel.

Comparison of direct injection nebulizer and desolvating microconcentric nebulizer for analysis of chlorine-, bromine- and iodine-containing compounds by reversed phase HPLC with ICP-MS detection

With the purpose of finding ways to combine micro-bore reversed phase HPLC with ICP-MS detection for analysis of drug substances containing chlorine, bromine and iodine, the suitability of a direct injection nebulizer and an Aridus desolvating microconcentric nebulizer was compared. Using the direct injection nebulizer at flow rates of 25 and 50 µl min−1, the influence of 0–50% methanol and 0–25% acetonitrile on the sensitivity was studied. For chlorine and bromine, the relative sensitivity decreased with increasing amounts of organic solvent. For iodine, the relative sensitivity reached a maximum at low concentrations of organic solvent and then declined with increasing amounts of organic solvent. The response of the direct injection nebulizer was independent of the chemical structure of the analyte. For the desolvating microconcentric nebulizer, the response was dependent on the analyte structure. Many chlorine-, bromine-, and iodine-containing compounds were partially lost in the desolvating unit. For those chlorine- and iodine-containing compounds that were not lost, the sensitivity was independent of methanol concentration in the solvent when a 0–100% methanol gradient was applied.

Glass nebulizer interface for capillary electrophoresis–Fourier transform infrared spectrometry

A capillary electrophoresis system has been successfully interfaced to a Fourier transform infrared spectrometer. The design of the interface is a custom-designed glass microconcentric nebulizer. Typical deposit characteristics include reproducible circular deposits of uniform thickness that lack any splatter as found in earlier designs. Interface performance is demonstrated in that there is no loss of electrical current during operation and spectra of analytes can be readily produced. Furthermore, it has been shown that the interface maintains the plug flow characteristic of capillary electrophoresis.

Determination of monophosphate nucleotides by capillary electrophoresis inductively coupled plasma mass spectrometry.

A preliminary study of a modified microconcentric nebulizer (CEI-100, CETAC) as the sample introduction device of capillary electrophoresis inductively coupled plasma mass spectrometry (CE-ICP-MS) for the determination of monophosphate nucleotides is described. The monophosphate nucleotides studied include adenosine 5'-monophosphate (AMP), guanosine 5'-monophosphate (GMP), uridine 5'-monophosphate (UMP) and inosine 5'-monophosphate (IMP). The species studied were well separated using a 70 cm length x 75 microm id fused silica capillary while the applied voltage was set at -22 kV and a 20 mmol l(-1) ammonium citrate/citric acid buffer (pH 4.0) containing 0.1% m/v cationic polymer (hexadimethrine bromide, Polybrene) was used as the electrophoretic buffer. The electroosmotic flow was reversed by flushing the fused silica capillary with 0.2% m/v Polybrene to accelerate separation. The detection limit of various species studied was in the range of 0.036-0.054 microg P ml(-1), which corresponded to the absolute detection limit of 1.1-1.6 pg P based on the injection volume of 30 nl. We determined the concentrations of nucleotides in two IG-enriched monosodium glutamates purchased from the local market. The recovery was in the range of 100-112% for various species, and the concentrations of IMP and GMP in these samples were in the range of 0.15-0.18% m/m.

Determination of pu isotopes in seawater by an on-line sequential injection technique with sector field inductively coupled plasma mass spectrometry.

An on-line sequential injection (SI) system combined with sector field inductively coupled plasma mass spectrometry was developed for the determination of ultratrace level 239Pu and 240Pu in seawater. The potential of this method is the substantial reduction of a sample volume and rapidity in the determination of Pu isotopes. A chemical purification and preconcentration of Pu isotopes were accomplished by the on-line SI system with two microcolumns of solid-phase extraction resins, Sr-Spec and TEVA-Spec. The MCN-6000 microconcentric nebulizer was used as a sample introduction system because of low interference effect and good sample utilization. With this method, it was possible to analyze ultratrace levels of Pu isotopes in only 5 L of surface seawater with an analysis speed of 4 h/sample. The precision of the measurement for the 239Pu and 240Pu was less than 3.4 (n = 7) and 5% (n = 7) for 5 L of seawater. The detection limits for 239Pu and 240Pu were 0.64 (1.5 microBq/mL) and 0.19 fg/mL (1.6 microBq/mL), respectively. The accuracy of this method was verified by using the reference seawater (IAEA-381) as well as by the comparison with the a-spectrometry.

On-line Chloride Interference Removal for Arsenic Determination in Waste Water and Urine by ICP-MS Using a Modified Capillary

The determination of arsenic in environmental samples like waste waters from industrial effluents and in biological samples like urine is very important due to the toxic nature of some of its species at moderate levels of exposure. The objective of this study was to evaluate the capability of modified anionic capillaries to remove chloride for ICP-MS determination of arsenic, which causes spectral interference due to formation of 40 Ar 35 Cl + . Also high chloride content gives non-spectral interferences. The results indicate that arsenic at a concentration higher than 1 µg L m 1 in a matrix with a chloride content up to 600 mg L m 1 can be accurately determined using a 3-aminopropyltrimethoxysilane (APTMS) modified capillary connected to a microconcentric nebuliser (MCN). The interference level of chloride is considerably reduced due to its retention in the capillary. The method has been successfully applied and validated for waste water and by recovery tests for urine (diluted 1 : 15) samples.

Isotopic analysis of uranium and plutonium using ICP-MS and estimation of burn-up of spent uranium in contaminated environmental samples

Environmental monitoring of actinides and evaluation of the contamination source (nuclear weapons tests, nuclear power plant and nuclear reprocessing plant accidents, etc.) requires precise and accurate isotopic analysis of actinides, especially uranium and plutonium. Double-focusing sector-field inductively coupled plasma mass spectrometry (ICP-SFMS) using a low-flow microconcentric nebulizer with membrane desolvation, “Aridus”, was applied for isotopic measurements of uranium and plutonium at the ultratrace level. The detection limit (3σ) for 236U and 239Pu after chemical extraction was 0.2 pg l−1 in aqueous solution and 0.04 pg g−1 in soil, respectively. 235U/238U, 236U/238U and 240Pu/239Pu isotope ratios were measured in soil samples collected within the 30 km zone around the Chernobyl nuclear power plant. The average 240Pu/239Pu isotope ratio in contaminated surface soil was 0.396 ± 0.014. The burn-up grade and the portion of spent uranium in the spent uranium/natural uranium mixture in soil were calculated using the iteration method. A slight variation in the burn-up grade of spent reactor uranium was revealed by analyzing 235U/238U and 236U/238U isotope ratios. A relationship between the 240Pu/239Pu isotope ratio and burn-up of spent uranium was observed.

Micro-scale flow system for on-line multielement preconcentration from saliva digests and determination by inductively coupled plasma optical emission spectrometry

A micro-scale flow system is proposed for on-line preconcentration of Cd, Cu, Mn, Ni and Pb in saliva samples and their determination by inductively coupled plasma optical emission spectrometry (ICP-OES). A small column containing 8 μl of AG50W-X8 resin was inserted into the flow system, assembled with capillary tubes and connected to a micro-concentric nebulizer. The elution of the analytes was performed with 3 mol l −1 HCl at a flow rate of 82 μl min −1. The ICP-OES signal acquisition program permits measurements for 5 s in the concentrated portion of the transient elution peaks. A sample volume of 1 ml was required to obtain enrichment factors of 46, 23, 17, 18 and 44 for Cd, Cu, Mn, Ni and Pb, respectively. The relative standard deviations for a 50-μg l −1 multi-analyte solution were ≤6.5%. The recoveries for Cd, Cu, Mn, Ni and Pb in digested human saliva samples were between 86 and 111%. The sample throughput was 24 h −1.

Development of a procedure for the multi-element determination of trace elements in wine by ICP-MS.

An inductively coupled plasma mass spectrometric (ICP-MS) procedure has been developed for the determination of trace elements in wine. The procedure consists in simple 1+1 dilution of the wine and semi-quantitative analysis (without external calibration) using In as internal standard. Thirty-one elements at concentrations ranging from 0.1 mg mL(-1) to 0.5 ng mL(-1) can be determined by ICP-MS analysis with and without digestion. It was investigated whether a matrix effect observed for EtOH in the wine matrix can be overcome by application of a micro-concentric nebulizer with a membrane desolvator (MCN 6000). The results obtained for the MCN 6000 are compared with those obtained by use of a conventional Meinhard nebulizer. It is shown that the observed matrix effect can only be compensated by use of an internal standard for the Meinhard nebulizer, but not for the MCN 6000. Results for ICP-MS are compared with those obtained by total reflection X-ray fluorescence spectrometry (TXRF).

Determination of molybdenum isotope fractionation by double‐spike multicollector inductively coupled plasma mass spectrometry

Molybdenum isotopic compositions are precisely determined by MC‐ICP‐MS measurements using a Mo double spike. The double spike is added prior to chemical purification, so that laboratory and instrumental mass fractionations are separated from natural mass‐dependent fractionation. Fractionation is determined on four Mo mass ratios, providing an internal consistency check. The external standard reproducibility is at 0.06 per mil on the 98Mo/95Mo ratio (2 standard deviation)). Using a normal microconcentric nebuliser with a cyclonic spray chamber, the minimum quantity of Mo is ∼1 μg for high‐precision results. A hydrothermal molybdenite shows fractionation of −0.3 per mil on the 98Mo/95Mo ratio relative to our standard (Johnson Matthey, 1000 μg/mL (±0.3%) ICP standard solution, lot 602332B). Fine‐grained sediments show fractionation of 0.1 and −0.3 per mil on the 98Mo/95Mo ratio. The observed Mo isotope fractionation is small but resolvable with the presented high‐resolution technique.

Micro flow system to perform programmable isotope dilution for inductively coupled plasma-mass spectrometry

A flow system using computer controlled devices to implement binary sampling of small volumes of sample and spike solutions was coupled to an inductively coupled plasma-mass spectrometer to perform programmable isotope dilutions. A computer running software in QuickBasic controlled the time-based sampling of sample and spike solution by switching on/off a set of solenoid valves. Mixing was improved by sampling 15 small aliquots of both solutions at a flow-rate of 65 μl min −1 through a capillary tubing connected to a micro-concentric nebulizer (MCN). Each aliquot of 6 μl containing the sample plus spike was introduced during 4 s. Programming the sample to spike volumetric ratios in each aliquot allowed to perform different isotopic dilutions generated from a single enriched solution. The flow system was calibrated measuring the isotopic ratios of 112 Cd/ 114 Cd by binary sampling of natural abundance Cd solutions as sample and enriched 112 Cd (97 at.%) solution as spike. The programmed and the measured ratios in the range from 6 to 25 presented good correlation (0.997). For routine analysis, using an estimate analyte concentration, and the isotope ratio within the defined range, the software calculates the time delays to introduce the sample and spike volumes. The true and found concentrations for solutions containing from 2.0 to 20.0 μg l −1 Cd attained good agreement at the 95% of confidence level. For these solutions the consumption of enriched 112 Cd (97 at.%) ranged from 33 to 168 pg per determination. About 30 isotope dilutions per hour were achieved.

Determination of 241Am in sediments by isotope dilution high resolution inductively coupled plasma mass spectrometry (ID HR ICP-MS)

Trace levels (pg kg −1) of 241Am in sediments were determined by isotope dilution high resolution inductively coupled plasma mass spectrometry (ID HR ICP-MS) using a microconcentric nebulizer. 241Am was isolated from major elements like Ca and Fe by different selective precipitations. In further steps, Am was first separated from other transuranic elements and purified by anion exchange and extraction chromatography prior to the mass spectrometric measurements. The ID HR ICP-MS results are compared with isotope dilution alpha spectrometry.