Microwave-induced Plasma Mass Spectrometry Research Articles

Solid-phase microextraction followed by gas chromatography for the speciation of organotin compounds in honey and wine samples: A comparison of atomic emission and mass spectrometry detectors

An environmentally friendly method for the determination of seven organotin compounds in honey and wine samples, using headspace solid-phase microextraction (HS-SPME) and gas chromatography (GC), was developed. The analytes were derivatized in situ with sodium tetraethylborate, and the derivatization and preconcentration steps were optimized. A 100μm polydimethylsiloxane fiber was the most suitable for preconcentrating the derivatized analytes from the headspace of an aqueous solution containing the sample. When microwave-induced plasma atomic emission (MIP-AED) and mass spectrometry (MS) detection were compared, higher sensitivity was attained for all compounds with MS, although MIP-AED showed more specific chromatograms. Using MS, detection limits ranged roughly from 0.3 to 4.3pg(Sn)/g, depending on the compound for honey samples, and from 0.1 to 2pg(Sn)/mL for wine samples. The optimized method was successfully applied to different samples, and the compounds studied were detected in some wines at 0.05–5ng(Sn)/mL levels.

Dissolution effect and cytotoxicity of diamond-like carbon coatings on orthodontic archwires

Nickel-titanium (NiTi) has been used for implants in orthodontics due to the unique properties such as shape memory effect and superelasticity. However, NiTi alloys are eroded in the oral cavity because they are immersed by saliva with enzymolysis. Their reactions lead corrosion and nickel release into the body. The higher concentrations of Ni release may generate harmful reactions. Ni release causes allergenic, toxic and carcinogenic reactions. It is well known that diamond-like carbon (DLC) films have excellent properties, such as extreme hardness, low friction coefficients, high wear resistance. In addition, DLC film has many other superior properties as a protective coating for biomedical applications such as biocompatibility and chemical inertness. Therefore, DLC film has received enormous attention as a biocompatible coating. In this study, DLC film coated NiTi orthodontic archwires to protect Ni release into the oral cavity. Each wire was immersed in physiological saline at the temperature 37 degrees C for 6 months. The release concentration of Ni ions was detected using microwave induced plasma mass spectrometry (MIP-MS) with the resolution of ppb level. The toxic effect of Ni release was studied the cell growth using squamous carcinoma cells. These cells were seeded in 24 well culture plates and materials were immersed in each well directly. The concentration of Ni ions in the solutions had been reduced one-sixth by DLC films when compared with non-coated wire. This study indicated that DLC films have the protective effect of the diffusion and the non-cytotoxicity in corrosive environment.

Determination of Trace Levels of Rare Earth Elements in Organs of Mice by Microwave-Induced Plasma Mass Spectrometry

Determination of Trace Levels of Rare Earth Elements in Organs of Mice by Microwave-Induced Plasma Mass Spectrometry

Crystal structure of alanyl‐tRNA synthetase editing‐domain homolog (PH0574) from a hyperthermophile, Pyrococcus horikoshii OT3 at 1.45 Å resolution

Crystal structure of alanyl‐tRNA synthetase editing‐domain homolog (PH0574) from a hyperthermophile, <i>Pyrococcus horikoshii</i> OT3 at 1.45 Å resolution

Determination of selenium in biological samples by slurry sampling-electrothermal vaporization-in situ fusion-isotope dilution-microwave-induced nitrogen plasma mass spectrometry

Determination of selenium in certified reference biological materials by slurry sampling electrothermal vaporization (ETV)-isotope dilution (ID)-microwave-induced nitrogen plasma mass spectrometry (MIP-MS) was performed. Several parameters such as the heating conditions were studied in order to obtain optimal conditions. A special heating stage called the in situ fusion stage was applied just before the pyrolysis stage in the electrothermal vaporization process in order to fuse the biological sample and to achieve selenium isotope-equilibration between selenium in the sample and the 78Se spike solution. The slurry sample containing an appropriate amount of biological sample, 78Se spike solution, and sodium hydroxide as an alkaline flux was injected into the electrothermal vaporization unit. The slurry sample was in situ fused, pyrolyzed, and then vaporized. The ion counts at m/ z=78 and 80, the spike and reference isotopes, respectively, could be measured accurately without interference caused by argon since nitrogen plasma was used. The analytical utility of the proposed slurry sampling-electrothermal vaporization-in situ fusion-microwave-induced nitrogen plasma mass spectrometry was evaluated by determining the selenium concentration in certified reference biological materials, and the analytical results obtained were in good agreement with the certified values. The limit of detection for selenium was 90 ng g −1. The relative standard deviation of the determination of selenium was 8–15% with a high sample throughput (less than 30 min per sample including a slurry preparation.)

Plasma-source mass spectrometry for speciation analysis: state-of-the-art

Current and emerging capabilities of plasma-source mass spectrometry (PS-MS) as it is employed for elemental speciation analysis are reviewed. Fundamental concepts and their advantageous aspects, experimental conditions, and analytical performance are described and illustrated by recent examples from the literature. Novel instrumentation, techniques, and strategies for inductively-coupled plasma mass spectrometry (ICP-MS), microwave-induced plasma (MIP) mass spectrometry, glow-discharge (GD) mass spectrometry, and electrospray ionization (ESI), among others, are described. The use of ionization sources that provide tunable ionization, others that can be modulated between different sets of operating conditions, and others used in parallel is also examined.

High-performance liquid chromatography–ultrasonic nebulizer high-power nitrogen microwave-induced plasma mass spectrometry, real-time on-line coupling for selenium speciation analysis

The coupling of a high-power nitrogen (N 2) microwave-induced plasma (MIP) mass spectrometry – (MS) (1.3 kW) with high-performance liquid chromatography, connected with concentric nebulizer (CN), ultrasonic nebulizer (USN) and a hydride generation (HG) systems, for the optimization and determination of selenium compounds, has been carried out. The MIP-MS system fulfils the ideal requirement being an on-line real-time chromatographic detector for Se speciation analysis. Interchanging of MIP-MS system fabricated nebulizer (concentric) with an ultrasonic nebulizer increases about 3.4–12 (peak height) and 6.5–10 (peak area) times ion signals for the selenium compounds. The detection limits for selenate, selenite, trimethylselenonium ion (TmSe), selenomethionine (Semet) and selenoethionine (Seet) (in Milli-Q-water) obtained with the optimized HPLC–USN-N 2MIP-MS system are 0.11, 0.14, 0.09, 0.14 and 0.10 μg L −1, respectively, about 12–48 times lower than the HPLC–CN-MIP-MS and 1.5–4.4 (peak height) times lower compared to the HPLC–CN-inductively coupled plasma (ICP)–MS coupling. Considering peak area, the repeatability (R.S.D. for three successive analyses) and intermediate precision (R.S.D. for three successive analyses performed on three different days), achieved for five Se compounds are 0.8–5.6, and 1.1–5.9%, comparable with the HPLC–CN-ICP-MS, HPLC–HG-MIP-MS and HPLC–CN-MIP-MS systems. The combined HPLC–USN-N 2MIP-MS has been adequately applied for the determination of Se compounds in certified National Institute for Environmental studies human urine CRM No. 18. The results reasonably agree with the HPLC–CN-ICP-MS values. This encouraging combination may be an alternative ion source of mass spectrometry for coming generation in regard to the selenium speciation analysis.

Isotope dilution analysis of selenite and selenate in natural water using microwave-induced nitrogen plasma mass spectrometry.

Isotope dilution analysis of the sub-microg l(-1) levels of selenite and selenate in natural water samples by microwave-induced nitrogen plasma mass spectrometry (MIP-MS) was performed. An appropriate amount of a spike solution containing 78Se-selenite and 78Se-selenate was added to the natural water sample to be analyzed. Both analytes in the water were then concentrated simultaneously by passing the sample through a column that was filled with an anionic exchange resin. After the concentration process, all of the selenite and some of the selenate on the resin were eluted by 0.03 M nitric acid. The residual selenate was eluted by 0.13 M nitric acid. The eluted sample solutions were injected into MIP-MS, and isotope dilution analyses were carried out. Selenite and selenate concentrations as low as 0.01 microg l(-1) in the natural water sample were successfully determined by the proposed method.

Determination of selenoethionine by flow injection-hydride generation-atomic absorption spectrometry/high-performance liquid chromatography-hydride generation-high power nitrogen microwave-induced plasma mass spectrometry

A simple direct flow injection hydride generation atomic absorption spectrometric method was developed using sodium tetrahydroborate and hydrochloric acid for the determination of selenoethonine (Seet) that excluded any chemical pretreatment prior to hydride generation. The detection limit (3 σ of blank) of the method was 0.25 ng ml −1 selenium (standard solutions in Milli-Q water). The reproducibility (R.S.D. of three analyses performed on three different days) and the repeatability (R.S.D. of seven successive analyses) of the method were 9.2% for 5.05 ng ml −1 and 2.8–9.5% for 20.0–1.00 ng ml −1 of standard selenium (Milli-Q water), respectively. The calibration graph was linear up to 20.0 ng ml −1. This HG method is very promising and was successfully applied for the on-line estimation of Seet (spiked) in human urine with using high-performance liquid chromatography-hydride generation-high power nitrogen microwave-induced plasma mass spectrometry (HPLC-HG-N 2-MIP-MS). The separation was performed on a GS-220 gel-permeating column with a 25 mM tetramethylammonium hydroxide+25 mM malonic acid buffer (pH 7.5), which showed 26–30% signal suppression due to less volatile hydride formation from Seet among the mobile phases examined. The recovery of Seet that was prepared in the above mobile phase is about 74% as that of the Seet prepared in Milli-Q water. In the PRP-X100 anion-exchange column with the 15 mM phosphate (pH 7.0) mobile phase, Seet eluted out after 600 s keeping a broad peak with enlarging the baseline signal. The concentration of selenite found in the human urine was 3.6±0.2 μg l −1 and that agreed well with the high-performance liquid chromatography inductively coupled plasma mass spectrometry (HPLC-ICP-MS) value (3.8±0.2 μg l −1).

A multimicrospray nebulizer for microwave-induced plasma mass spectrometry

We have developed a nebulizer, called a multimicrospray nebulizer (MMSN), that efficiently introduces analytes for plasma mass spectrometry and plasma emission spectrometry. In this nebulizer, both the sample solution and the nebulizer gas are divided into several streams to produce a multispray. That is, the MMSN is a nebulizer that contains several micronebulization units, each unit including an orifice for passing the nebulizer gas and a capillary for introducing a sample solution. The microspray from each micronebulization unit can be operated at a microliter per minute sample uptake rate to achieve high nebulization efficiency. The multimicrospray nebulizer is capable of introducing more analyte to the plasma compared with a single-orifice micronebulizer, which has a very low sample uptake rate. In this work, an MMSN with three orifices was found to be suitable for microwave-induced plasma mass spectrometry (MIP-MS). The sample uptake rate can be varied within a range of 5-250 microL/min. Therefore, the nebulizer is unique in its ability to deal with various sample volumes and provide high nebulization efficiency. The sensitivity for all elements obtained with the MMSN was higher than that obtained with a conventional concentric nebulizer (CCN), which is difficult to achieve with other types of microintroduction nebulizers. For most elements, the MIP-MS sensitivity was improved about 2-fold at a sample uptake rate of 150 microL/min, a much lower rate than that for the CCN (usually 0.5-1.5 mL/min). The sensitivity for arsenic was improved by a factor of 5. The relative standard deviation was found to be less than 2.0%.

質量分析法による環境試料中のヨウ素-129定量法の開発

Iodine-129 is an important radionuclide for environmental assessment, because it has a long halflife.A new analytical technique using Microwave Induced Plasma Mass Spectrometry (MIP-MS) was applied to the determination of iodine-129 in environmental samples. In environmental samples, a large amount of matrix elements is present. Therefore, the matrix elements were eliminated by ashing at 1000°C, and iodine was trapped by activated charcoal and finally extracted by tetramethylammonium hydroxide.A soil sample was analyzed by neutron activation analysis as well as MIP-MS method. Excellent agreement resulted.

Determination of selenium at sub-μg/g-levels in biological materials by MIP-MS

Determination of Se in biological materials was attempted by microwave-induced plasma mass spectrometry (MIP-MS). (1) Serum samples were available after 10 times dilution with 0.5% nitric acid solution containing 0.1% Triton X-100. When oxygen gas was inserted into the plasma gas (nitrogen) in order to improve the combustion, the sensitivity was reduced to 45%. The detection limit of this method was 0.5 ng/mL. (2) Standard reference materials on commercial base were used to evaluate the accuracy of the Se determination by MIP-MS after microwave digestion. In samples like bovine liver and human hair with Se concentrations of more than 0.7 μg/g, the standard curve method after internal standard (IS) correction was acceptable. This procedure was unsuitable for samples with low Se concentrations such as milk powder (certified value of Se 0.11 μg/g), or plant leaf samples. (3) Instead of IS correction, the peak height of the spectrum was used for calculations from the matrix matched calibration curve. The results of all materials were close to the certified values, even at 25 ng/g. The detection limit of the MIP-MS with microwave digestion and IS correction was 0.05 ng/mL in standard solutions. The detection limit of the peak height method was 0.1 ng/mL and was estimated to be < 20 ng/g in plant materials.

Determination of tungsten in bulk drug substance and intermediates by ICP-AES and ICP-MS

A quick and sensitive method has been developed and validated for the determination of tungsten in bulk drug substance and intermediates using either Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) or Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Sample preparation is by direct dissolution with a 80:20 (v/v) concentrated nitric acid:deionized water mixture and avoids labor intensive and potentially hazardous digestion techniques. Excellent agreement was found between ICP-AES and ICP-MS results and between Merck results and Microwave Induced Plasma Mass Spectrometry (MIP-MS) results provided by an independent raw material vendor.

Determination of Selenium Concentrations in Human Blood Plasma by Microwave-Induced Plasma Mass Spectrometry

Microwave-induced plasma mass spectrometry (MIP-MS) was used to determine the selenium concentrations in human blood plasma. Blood plasma from volunteers, the standard reference materials of human blood serum and bovine serum, were used to investigate the suitability of the digestion method and the matrix effects due to coexisting elements, and to confirm the accuracy of the obtained values. Two sample-preparation procedures, microwave digestion and simple dilution with 0.1% Triton X-100 solution, were examined. In the latter method, oxygen gas was mixed into plasma nitrogen gas at a gas flow of 30 ml/min to prevent any instability of the measurement caused by carbide formed from organic components. The selenium concentrations were calculated from the ion counts at m/z=80 using a calibration curve with an internal standard correction. Both sample-preparation procedures were suitable for human blood plasma. The concentrations of several other elements, such as magnesium, iron, copper, zinc, and rubidium in blood plasma and in serum sam-ples, could be measured simultaneously with selenium, indicating that MIP-MS was useful for a simple and rapid determination of elements in blood plasma.

Isotope dilution analysis of Se in human blood serum by using high-power nitrogen microwave-induced plasma mass spectrometry coupled with a hydride generation technique.

To establish a method for sensitive, accurate, and precise determination of Se in real samples, isotope dilution analysis using high-power nitrogen microwave-induced plasma mass spectrometry (N2 MIP-IDMS) was conducted. In this study, freeze-dried human blood serum (Standard Reference Material, NIES No. 4) provided by NIES (National Institute for Environmental Studies) was used as a real sample. The measured isotopes of Se were 78Se and 80Se which are the major isotopes of Se. The appropriate amount of a Se spike solution was theoretically calculated by using an error multiplication factor (F) and was confirmed experimentally for the isotope dilution analysis. The mass discrimination effect was corrected for by using a standard Se solution for the measurement of Se isotope ratios in the spiked sample. However, the sensitivity for the detection of Se was not so good and the precision of the determination was not improved (2-3%) by N2 MIP-IDMS with use of the conventional nebulizer. Therefore, a hydride generation system was connected to N2 MIP-IDMS as a sample introduction system (HG-N2 MIP-IDMS) in order to establish a more sensitive detection and a more precise determination of Se. A detection limit (3 sigma) of 10 pg mL-1 could be achieved, and the RSD was less than 1% at the concentration level of 5.0-10.0 ng mL-1 by HG-N2 MIP-IDMS. The analytical results were found to be in a good agreement with those obtained by the standard addition method using conventional Ar ICPMS.

Substoichiometric isotope dilution mass spectrometry as a new analytical method

A novel analytical method, the substoichiometric isotope dilution mass spectrometry (SIDMS) has been proposed. This method consists of the substoichiometric separation of the element in question and the subsequent intensity measurement of a stable isotope of the element with a mass spectrometer. In SIDMS, the correction of the mass discrimination of isotope measurement is not necessary and the use of expensive enriched stable isotopes may be avoided. The validity and the usefulness of SIDMS are demonstrated by the substoichiometric extraction of iron(III) with 4-isopropyltropolone and 3,5-dichlorophenol following microwave-induced plasma mass spectrometry.

An application of nitrogen microwave-induced plasma mass spectrometry to isotope dilution analysis of selenium in marine organisms.

Nitrogen microwave-induced plasma mass spectrometry was studied for its applicability to the isotope dilution analysis of selenium in biological samples. Spectroscopic interference by calcium, which is present in high concentrations in biological samples, was investigated. No detectable background spectrum was observed for the major selenium isotopes of 78Se and 80Se. No detectable interferences by sodium, potassium, calcium and phosphorus on the isotope ratio 80Se/78Se were observed up to concentration of 200 mg/ml. The method was applied to the analysis of selenium in biological reference materials of marine organisms. The results showed good agreement between the certified and found values.

Isotope Dilution Analysis of Selenium in Biological Materials by Nitrogen Microwave-Induced Plasma Mass Spectrometry

Nitrogen microwave-induced plasma mass spectrometry was applied to isotope dilution analysis of selenium in biological matrices. The precision of isotope ratio ( 80 Se/ 78 Se) measurements of a 100 ng/mL standard solution was 0.5% under practical analysis conditions and could be after lowered by increasing the integration time. spectroscopic interference at m/z=80 arising from SO 3 + was observed, but the extent was not so much as to cause a serious problem at the sulfur level normally found in biological materials. Isotopic ratios in digested clinical specimens pod well with those in the standard solution, indicating no other spectroscopic interferences on selenium isotopes in real samples. The proposed method was successfully applied to the analysis of selenium in biological reference materials. The results showed good agreement with the certified values

Evaluation of a Direct-Injection Nebulizer (DIN) for Liquid Sample Introduction in Helium Microwave-Induced Plasma Mass Spectrometry (MIP-MS)

A direct-injection nebulizer (DIN) has been evaluated for liquid sample introduction in helium microwave-induced plasma mass spectrometry (MIP-MS). A short-term stability test with the direct-injection nebulizer was found to give less than 0.5% RSD for twenty minutes. Isotope abundances for K, Ca, Cr, and Se were determined with less than 10% error on all isotopes. All elements have linear dynamic ranges of two to three orders of magnitude. Detection limits are low to sub-ppb for all elements. Ion lens tuning plays an important role in multielement determinations. Oxide, hydroxide, and doubly charged ions are determined for Cr, As, Sr, Cs, Ba, and Pb. The effect of 10% methanol and high-dissolved salts is investigated.

特集 夢の金属へのアプローチ“基礎研究と高性能化” 溶液法によるマイクロ波誘導プラズマ質量分析

特集 夢の金属へのアプローチ“基礎研究と高性能化” 溶液法によるマイクロ波誘導プラズマ質量分析