Ultrasonic Mist Generation Assist Argon-Nitrogen Mix Gas Effect on Radioactive Strontium Quantification by Online Solid-Phase Extraction with Inductively Coupled Plasma Mass Spectrometry

Pannexins in the musculoskeletal system: new targets for development and disease progression

During cell differentiation, growth, and development, cells can respond to extracellular stimuli through communication channels. Pannexin (Panx) family and connexin (Cx) family are two important types of channel-forming proteins. Panx family contains three members (Panx1-3) and is expressed widely in bone, cartilage and muscle. Although there is no sequence homology between Panx family and Cx family, they exhibit similar configurations and functions. Similar to Cxs, the key roles of Panxs in the maintenance of physiological functions of the musculoskeletal system and disease progression were gradually revealed later. Here, we seek to elucidate the structure of Panxs and their roles in regulating processes such as osteogenesis, chondrogenesis, and muscle growth. We also focus on the comparison between Cx and Panx. As a new key target, Panxs expression imbalance and dysfunction in muscle and the therapeutic potentials of Panxs in joint diseases are also discussed.

Sensitivity enhancement in inductively coupled plasma mass spectrometry using nebulization methods via nitrogen mixed gas effect

We demonstrate the sensitivity enhancement in inductively coupled plasma mass spectrometry (ICP-MS) by combining ultrasonic nebulization via the nitrogen mixed gas effect. We showed the effect of nitrogen gas concentration (0-5%) in the nebulizer gas on the signal sensitivity for 63 elements using commercially available (concentric and ultrasonic) nebulizers. In addition, the limit of detection (ng L^-1) was calculated in each case. Finally, we compared the sensitivity (i.e., the slope of the calibration curve), background noise intensity, and three-dimensional intensity distribution in the plasma to elucidate the effects of the concurrent use of mixed gas plasmas and nebulization methods.

Online solid-phase extraction-inductively coupled plasma-quadrupole mass spectrometric quantification of 90Sr using 88Sr/86Sr isotope dilution method

Due to the lack of a correlation with the natural Strontium (Sr) isotopes, it is difficult to apply the isotope dilution (ID) method to an artificial radioactive mononuclide Strontium-90 (⁹⁰Sr), in inductively coupled plasma-quadrupole mass spectrometry (ICP-QMS). Meanwhile, online solid-phase extraction (SPE)-ICP-QMS (SPE-ICP-QMS) serves as an automatic sequential analytical technique for measuring the ultra-trace amounts of radionuclides; however, apparent assay values obtained using this method are often negatively affected by differences in the sample matrix composition between standard and actual samples. In this study, the pg L^-1 level of ⁹⁰Sr was successfully measured by combining online SPE-ICP-QMS and the ID method with ⁸⁸Sr/⁸⁶Sr ratios in one sample injection, without the radioactive standard. Although naturally occurring abundant isobaric ⁹⁰Zr significantly influences ⁹⁰Sr quantification during mass spectrometry, consecutive separations between automated SPE and dynamic reaction cell (DRC) oxidation enable ⁹⁰Sr quantification, even in the presence of isobaric ⁹⁰Zr (acceptable down to 5.7 × 10^-9 of ⁹⁰Sr/Zr in sample solution), using this method. Through this method, both radioactive ⁹⁰Sr and naturally occurring Sr were simultaneously quantified using ⁸⁸Sr-to-⁸⁶Sr and ⁸⁸Sr-to-⁹⁰Sr ratios without radioactive ⁹⁰Sr standard solutions. This simultaneous quantification of stable Sr and ⁹⁰Sr was achieved within 15 min with good recovery rates. The limit of detection of ⁹⁰Sr was 1.1 pg L^-1 (equivalent to radioactivity 5.6 Bq L^-1) for a 10 mL injection. Finally, water collected from an actual contaminated water storage tank at the Fukushima Daiichi Nuclear Power Plant (Fukushima, Japan) was analyzed using the proposed method, and the obtained results agreed well with those obtained using conventional analytical methods.

A part per trillion isotope ratio analysis of 90Sr/88Sr using energy-filtered thermal ionization mass spectrometry

Strontium-90 is a major radioactive nuclide released by nuclear accidents and discharge waste. Input of such radioactive nuclide into earth surface environment causes potential threat of long-term internal exposure when taken up by organism. Rapid and precise measurement of ⁹⁰Sr in variety of environmental sample is important to understand the distribution and dynamics of ⁹⁰Sr in the local environment after the accident and to assess the effect of radioactive nuclide inputs on bodies. However, previous ⁹⁰Sr measurement techniques have drawbacks such as long measurement times for radiometry and high detection limits for mass spectrometry. Here we present a technique to accurately measure a significantly small amount of ⁹⁰Sr in natural environmental samples using an energy-filtered thermal ionization mass spectrometry. Our technique achieved a ⁹⁰Sr detection limit of 0.23 ag, which corresponds to a ⁹⁰Sr activity of 1.2 µBq. The detection limit was lowered by two orders of magnitude compared with the previous mass spectrometric ⁹⁰Sr analyses. The ability of our technique will expand the applicability of mass spectrometric ⁹⁰Sr survey not only to the rapid ⁹⁰Sr survey upon nuclear accidents but also to study a long-term environmental diffusion of radioactive materials using size-limited environmental and biological samples.

Effect of operating variables on the separation of radiostrontium from aqueous matrices with ion-selective solid-phase extraction systems

Radiostrontium (r-Sr: ⁹⁰Sr) is one of the primary fission products in nuclear power plants and generates liquid radioactive waste when intermixed to the aqueous matrix. Therefore, separation or preconcentration of r-Sr from the aqueous matrices is necessary for environmental monitoring or nuclear forensics. The solid-phase extraction (SPE) approach is prevalently used for r-Sr isolation and to design matrix-specific methods, while generalized SPE-assisted operating protocols are not proposed by far. In the current work, four different SPEs, namely AnaLig Sr-01, Eichrom Sr, Triskem TK100, and Eichrom DGA, were evaluated for selective separation of Sr from aqueous matrices. Operating variables, e.g., solution acidity, washing solvent, eluent-type or volume, loading or elution flow-rate, were varied to optimize the SPEs performance. The objective was to ascertain the operating variables for maximum Sr-separation yield from aqueous environmental samples with the SPEs mentioned above. In addition, the Sr-separation efficiency of SPEs was evaluated by calculating the separation factor (SF_Sr/M) between Sr and interfering elements to r-Sr (M = Ca, Mg, Ba, or Y), and the Sr-retention capacity of the SPEs was determined. Finally, the optimized operating variables for the evaluated SPEs were used to construct protocols for r-Sr separation from aqueous matrices. Real ⁹⁰Sr contaminated aqueous samples from the Chernobyl nuclear power plant cooling pond were treated by those protocols, and the results are validated comparing with the IAEA-recommended classical protocol. All the SPEs were able to isolate Sr at varying extents from matrices at the optimum conditions, even at much higher contents of interfering elements. Eichrom Sr or AnaLig Sr-01 showed better Sr-retention capability among the SPEs, while Triskem TK100 showed superiority over other SPEs regarding Sr-selectivity.

Online Solid-Phase Extraction-Inductively Coupled Plasma-Quadrupole Mass Spectrometry with Oxygen Dynamic Reaction for Quantification of Technetium-99

Quantification of pg/L levels (i.e., 0.6 mBq/L) of radioactive technetium-99 (⁹⁹Tc) was achieved within 15 min in the presence of isobaric and polyatomic interference sources such as ruthenium-99 (⁹⁹Ru) and molybdenum hydride (⁹⁸Mo¹H) at 3-11 orders of magnitude higher concentrations. Online solid-phase extraction-inductively coupled plasma-quadrupole mass spectrometry (ICP-QMS) with oxygen (O₂) dynamic reaction cell (online SPE-ICP-MS-DRC) was shown to be a thorough automatic analytical system, circumventing the need for human handling. At three stepwise separations (SPE-DRC-Q mass filters), we showed that interference materials allowed the coexistence of abundance ratios of 1.5 × 10^-13 and 1.1 × 10^-5 for ⁹⁹Tc/Mo and ⁹⁹Tc/Ru, respectively. A classical mathematical correction using the natural isotope ratio of ⁹⁹Ru/¹⁰²Ru was used to calculate the residues of ⁹⁹Ru. Using this optimized system, a detection limit (DL; 3σ) of ⁹⁹Tc was 9.3 pg/L (= 5.9 mBq/L) for a 50 mL injection and sequential measurements were undertaken at a cycle of 24 min/sample. For the measurement of a lower concentration of ⁹⁹Tc, an AG1-X8 anion-exchange column was used to study 20 L of seawater. Its DL was approximately 1000 times greater than that of previous methods (70.0 fg/L). Thus, this method withstands coexistences of 5.8 × 10^-18 and 3.5 × 10^-9 for ⁹⁹Tc/Mo and ⁹⁹Tc/Ru, respectively. Spike and recovery tests were conducted for environmental samples; the resulting values showed good agreement with the spike applied.

Isotope Dilution-Total Evaporation-Thermal Ionization Mass Spectrometric Direct Determination of Radioactive Strontium-90 in Microdrop Samples

Thermal ionization mass spectrometry (TIMS) was used to directly quantify an ultratrace of radioactive ⁹⁰Sr in microliter droplet samples. No chemical separation was required in removing isobaric interferences on M = 90 such as ⁹⁰Zr and organic molecules in the mass spectrum because the difference in evaporation and ionization (emission) temperature among organic molecules, Zr and Sr, allows us to control the emission manner and significantly suppress the isobaric interferences. Direct quantification was achieved by improving the intercalibration of Faraday cups and ion counting in an isotope dilution (ID) method. Furthermore, the use of a total evaporation method (TE) enhanced the detection efficiency by the complete collection of the ⁹⁰Sr ion beam from the samples and minimized the complexity of the fractionation effect in the isotope ratio calculation. In this study, 1 fg of ⁹⁰Sr (equal to activity of 5 millibecquerel (mBq)) in a very low-volume sample with 10⁸ times greater isobaric interference from ⁹⁰Zr was successfully measured using the proposed ID-TE-TIMS method. The limit of detection was 0.029 fg (equal to 0.15 mBq) without any preconcentration. To demonstrate the wide usability of this method, low-volume samples of tears, eyelashes, saliva, environmental standards, and water samples (i.e., seawater and ground water) were analyzed within 1 h. The relationship of the measured values between this ID-TE-TIMS method and a radiometric analysis was shown to have good linearity.

Development of Online Dilution System for Quantification of 90Sr Using Automatic Solid-phase Extraction Inductively Coupled Plasma Mass Spectrometry

In this paper, we propose an online dilution system for the rapid quantification of radioactive strontium-90 (⁹⁰Sr) with inductively coupled plasma mass spectrometry coupled solid-phase extraction and O₂ dynamic reaction (cascade ICP-MS). The proposed system automatically provides a higher dilution ratio, which is at most 3.3 ± 0.2-times the ratio obtained by the previous method, without increasing the analysis time (<15 min). A detection limit of 2.7 Bq/kg wet (0.54 pg/kg wet) was achieved. The recovery test results were consistent with two different spiked values.

Separation and Preconcentration of Trace Uranium(VI) by Solid Phase Extraction with 2,3-Dihydroxynaphthalene and Cetyltrimethylammonium Bromide on Molten Naphthalene and Its LED Fluorimetric Determination in Water Samples

A simple and rapid solid phase extraction (SPE) procedure has been developed for the extraction and determination of uranium in water samples. The method is based upon the adsorption of uranium(VI)-2,3-dihydroxynaphthalene complex on microcrystalline naphthalene at the pH range 10 - 12 in the presence of a counter cation cetyltrimethylammonium ion. The solid mass consisting of uranium-2,3-dihydroxynaphthalene-CTA complex and naphthalene is ignited in the furnace at a temperature of 700°C for 1 h and then digested in dil. HNO3 solution. Uranium is then determined by LED fluorimetry using fluorescence enhancing pyrophosphate buffer. The effects of different variables like pH of the solution, reagent concentrations, counter cations, stirring time, interfering ions etc. have been investigated thoroughly for the quantitative recovery of uranium. The accuracy of the developed method has been ascertained by standard addition method as well as conventional pellet fluorimetry method involving co-precipitation of uranium using aluminum phosphate as a carrier.

Rapid Quantification of Radioactive Strontium-90 in Fresh Foods via Online Solid-Phase Extraction-Inductively Coupled Plasma-Dynamic Reaction Cell-Mass Spectrometry and Its Comparative Evaluation with Conventional Radiometry

This paper describes a rapid quantification method for radioactive strontium (⁹⁰Sr) in fresh foods (perishable foods) and has been comparatively evaluated with the common classical radiometric quantification method. Inductively coupled plasma-dynamic reaction cell-mass spectrometry with online solid-phase extraction (cascade-ICP-MS) rapidly determines ⁹⁰Sr in a pure water-based sample. Despite its advantages, its application to fresh foods (perishable foods) has not yet been reported; however, the analytical potential of this method for fresh foods must be evaluated. In this study, ⁹⁰Sr was determined in 12 fresh foods via improved cascade-ICP-MS (Icas-ICP-MS). Addition and recovery tests were demonstrated using real samples of grape, apple, peach, Japanese pear, rice, buckwheat, soybean, spinach, shiitake mushroom, grass, sea squirt, and flounder. With a decomposed solution of Japanese pear, the measurement value coincided with the amount of spiked ⁹⁰Sr. The reproducibility of the measurements was represented by relative standard deviations of 14.2 and 5.0% for spiked amounts of 20 and 200 Bq/kg, respectively (n = 10), and the recovery rates were 93.7 ± 7.1%. In this case, the limit of detection (LOD) was 2.2 Bq/kg (=0.43 pg/kg). These results were compared with the data obtained using a common classical radiometric quantification method (nitrate precipitation-low background gas flow counter (LBC) method) in the same samples. Both the methods showed equivalent performances with regard to reproducibility, precision, and LODs but different analysis times. Icas-ICP-MS required ∼22 min for analysis, whereas the nitrate precipitation-LBC method required 20 days, confirming that Icas-ICP-MS is the suitable method for analyzing ⁹⁰Sr in fresh foods.

Phosphomethylated Polyethyleneimine-immobilized Chelating Resin: Role of Phosphomethylation Rate on Solid-Phase Extraction of Trace Elements

Chelating resins immobilizing phosphomethylated polyethyleneimine (PM-PEI) with different phosphomethylation (PM) rates were prepared by using different amounts of both phosphonic acid and paraformaldehyde in the phosphomethylation of PEI immobilized on a methacrylate resin as a base resin. The extraction of many elements improved with increasing PM rate; REEs, Be, Fe, Mo, Ti, and V were quantitatively extracted at pH 2. The elution of the elements tended to become difficult with increasing PM rate. When a PM-PEI resin with a PM rate of 0.26 was used, REEs and Be could be eluted using 0.2 mol L^-1 EDTA solution adjusted to a pH of 7 and 3 mol L^-1 nitric acid, respectively, although the elution of Fe, Mo, Ti, and V was insufficient. The PM-PEI resin could be reused at least 10 times to recover REEs and Be without the influence of any other elements. The PM-PEI resin could be applied to a recovery test using artificial seawater spiked with REEs, except for Sc, Tm, Yb, and Lu, and the separation of the REEs in NIST SRM 1515 Apple Leaves.

Simple Radiometric Determination of Strontium-90 in Seawater Using Measurement of Yttrium-90 Decay Time Following Iron-Barium Co-precipitation

A radiometric quantitative methodology of ⁹⁰Sr in seawater was developed using a measurement of the ⁹⁰Y decay time following iron-barium co-precipitation. With calculations of its decay time, the radioactivity of ⁹⁰Sr can be indirectly determined under conditional environmental samples. In addition, to avoid the interference of other radionuclide, the prepared samples were measured using a germanium semi-conductivity detector; then, the deposited radioactivity was subtracted from the actual measurement values of beta-ray counting. In this paper, the seawater samples were collected within 2 km around Fukushima Daiichi Nuclear Power Plants during the term from October 2011 to March 2012. This method showed good linearity between the ⁹⁰Sr concentration and the total beta counting following the proposed method, with a correlation coefficient of 0.99 in seawater sample analysis. No interference that was caused by other radionuclides, such as radioactive cesium, was not observed in the quantification of ⁹⁰Sr. The whole process requires 12 h to quantify ⁹⁰Sr; this time is 1/40 shorter than traditional milking-low background gas-flow counting method. The lower limit of detection (average value n = 60) of the ⁹⁰Sr radioactivity was shown to be 0.03 Bq/L (uncertainty 4.2%).