Abundant production of dimethylsulfoniopropionate as a cryoprotectant by freshwater phytoplanktonic dinoflagellates in ice-covered Lake Baikal.

Phytoplanktonic dinoflagellates form colonies between vertical ice crystals during the ice-melting season in Lake Baikal, but how the plankton survive the freezing conditions is not known. Here we show that the phytoplankton produces large amounts of dimethylsulfoniopropionate (DMSP), which is best-known as a marine compound. Lake-water DMSP concentrations in the spring season are comparable with those in the oceans, and colony water in ice exhibits extremely high concentrations. DMSP concentration of surface water correlates with plankton density and reaches a maximum in mid-April, with temperature-dependent fluctuations. DMSP is released from plankton cells into water in warm days. DMSP is a characteristic osmolyte of marine algae; our results demonstrate that freshwater plankton, Gymnodinium baicalense, has DMSP-producing ability, and efficiently uses the limited sulfur resource (only 1/500 of sea sulfate) to survive in freshwater ice. Plankton in Lake Baikal do not need an osmolyte, and our results clearly indicate that DMSP plays a cryoprotective role. DMSP, although a characteristic marine compound, could also be an important zwitterion for algae of other boreal lakes, alpine snow, and glaciers.

Radioactive isotope separation with 3D-printed flow-based device.

Radioactive isotope (RI) metals are a new type of tracer for positron emission tomography generated from the target metal by proton irradiation using a cyclotron. The generated metal RIs need to be separated from the target metal rapidly and effectively. In the present study, we developed a 3D-printed flow device to separate metal RIs from target metals. The separation was performed with selective formation of ethylenediaminetetraacetic acid (EDTA) complex based on the difference in formation constants. The RI metal selectively formed a EDTA complex, thus changing its ionic charge in solution. The solution was then introduced into a cation exchange column for selective adsorption of the target metal. The solution with added chelator and controlled pH was introduced into the developed system and automatically separated metal RI from target metals within 14 min. The separation method was applied to separate RI 67Ga from target metal Zn using a mixture of 107 pg L-1 67Ga in 250 mg L-1 Zn2+. The recoveries of 67Ga and Zn were 97% and 100%, respectively. Furthermore, an ultraviolet (UV) radiation reactor was integrated into the system to decompose the EDTA complex and recover the Ga3+ ion. Ga3+ recovery by UV radiation was effective, 87%. The developed system was also successfully applied to the separation of Zr and Y. Therefore, the method and system can be applied to separate other metal RIs from target metals.

Electrodialytic Universal Synthesis of Highly Pure and Mixed Ionic Liquids.

Ionic liquids (ILs) have attracted significant attention from researchers in various fields as a result of their unique properties. As new and important applications are identified for these materials, there is also a drive to develop methods for accessing a wider range of ILs. However, despite this demand, only a few techniques have so far been reported and, more importantly, general but efficient processes for IL synthesis have been lacking. Thus, it would be beneficial to devise a cost-effective, environmentally friendly means of producing a wide variety of pure ILs. The present work demonstrates a general purpose electrodialysis approach to the formation of highly pure ILs, based on the formation of nine different ILs from various combinations of cations and anions. In each case, the IL is obtained with a purity of greater than 99%. This method offers the advantages of avoiding the use of hazardous organic solvents and eliminating tedious and costly purification processes. Unlike conventional methods, this membrane-based technology also prevents the generation of side products. Mixed ILs have many potential applications, and the present technique readily generates various mixed ILs based on a simple adjustment of the applied current.

Highly Efficient Separation of Ultratrace Radioactive Copper Using a Flow Electrolysis Cell.

Preparing compounds containing the radioisotope 64Cu for use in positron emission tomography cancer diagnostics is an ongoing area of research. In this study, a highly efficient separation method to recover 64Cu generated by irradiating the target 64Ni with a proton beam was developed by employing a flow electrolysis cell (FE). This system consists of (1) applying a reduction potential for the selective adsorption of 64Cu from the target solution when dissolved in HCl and (2) recovering the 64Cu deposited onto the carbon working electrode by desorbing it from the FE during elution with 10 mmol/L HNO3, which applies an oxidation potential. The 64Cu was selectively eluted at approximately 30 min under a flow rate of 0.5 mL/min from the injection to recovery. The newly developed flow electrolysis system can separate the femtomolar level of ultratrace radioisotopes from the larger amount of target metals as an alternative to conventional column chromatography.

Electrodialytic Enrichment and Matrix Conversion for the Determination of Trace Metals in Ultra-Pure Water.

The presence of trace contaminants in ultra-pure water (UPW) used in fabrication process can greatly affect the yield and quality of industrial products. In the present study, the electrodialytic enrichment of metal cations as a means of continuously monitoring the UPW quality was studied. A newly designed electrodialytic enrichment device (EED) was used to quantitatively transfer metal ions from samples to dilute nitric acid, which was then directly introduced into an inductively coupled plasma-mass spectrometry (ICP-MS) instrument. This process could be performed without contamination of the sample, and the enrichment factor was solely dependent on the flow rate ratio of the sample and acceptor solutions. The transference of analytes into the acidic solution improved the responsivity of the ICP-MS analysis, especially at low concentrations of less than 1 µg/L. Blank solutions to support the analysis of UPW could be produced using the EED effluent, from which metal ions were quantitatively removed. In addition, calibration curves with concentration ranges of several nanograms per liter were obtained by preparing standards using a dynamic gravimetric method while employing a single bottle and continuous mass monitoring to avoid any contamination from the volumetric flasks. The sensitivities associated with the ICP-MS analysis of a number of trace metal ions were improved by one or two orders of magnitude. The data show that the present EED is able to continuously produce enriched analyte solutions to allow the ongoing monitoring of UPW quality.

Rapid Flow-Based System for Separation of Radioactive Metals by Selective Complex Formation.

Short-lived radioactive metals are important tracers in clinical diagnosis. Radioactive metals for clinical use are produced from suitable target metals in cyclotrons. The trace amount of radioactive metal produced is contained in a relatively large amount of target metal. A rapid and effective method is required to isolate the radioactive metal. In the present study, selective complex formation followed by cation-exchange adsorption was performed in a continuous flow-based system. Ethylenediamine-N,N,N',N'-tetraacetic acid (EDTA) was selected as the ligand after simulation of the separation of radioactive Ga from the target (Zn). Selectively, the Ga-EDTA complex passed through the cation trap, while Zn2+ was trapped. This separation principle is opposite to that of typical solid-phase extraction, which captures the target ion. The proposed separation was performed in a flow-based system with a parallel, open-channel ion trap. The performance was optimized by altering the channel dimensions, channel-filling mesh, and flow rate. Finally, the target radioactive metal, Ga, was selectively and effectively (>99%) separated from a mixture of 50 fg Ga/L and 100 mg Zn/L. The concentration of Zn remaining in the Ga solution was 2.3 µg/L. The complexed Ga was converted to free Ga3+ by a simple UV irradiation method. The proposed method effectively and rapidly separates trace amounts of radioactive metals contained in larger amounts of target metals using a simple flow system that can be operated on site.

Indirect Potentiometric pH Detection of Weak Acids with Absolute Quantitation by a Theoretical Approach.

A fast response potentiometric flow-through pH sensor was applied for organic acid determination. The analyte response with the pH sensor was obtained by eluent pH modification following ion exclusion chromatography with HClO4 as an eluent. The response characteristics depend on the adjusted baseline pH. The baseline pH adjustment was successfully done with an ammonia permeation device without solution mixing, which may cause analyte dilution, dispersion, and mixing noise. After pH adjustment, the pH response was universal to the equivalent of introduced analyte acids because the pH response was obtained by the titration of the permeant ammonia by the analytes. The average of limit of detections (S/N = 3) was 0.06 mM for seven target organic acids. Furthermore, the pH response follows the theoretical pH calculation with the concentrations of the eluent, pH modifier, and analyte. Thus, the analyte concentration in the sample can be theoretically calculated from the pH response without calibration by the analyte standard. Predicted concentrations of injected standards were within 5% of the actual standard concentration. Additionally, analysis of real samples was performed and compared with the conventional post-column reaction with a bromothymol blue (BTB) method. The results obtained with the present system (absolute quantification with theoretical calculation) and conventional BTB method agreed within 10% of errors.

Natural dimethyl sulfide gradients would lead marine predators to higher prey biomass.

Finding prey is essential to survival, with marine predators hypothesised to track chemicals such as dimethyl sulfide (DMS) while foraging. Many predators are attracted to artificially released DMS, and laboratory experiments have shown that zooplankton grazing on phytoplankton accelerates DMS release. However, whether natural DMS concentrations are useful for predators and correlated to areas of high prey biomass remains a fundamental knowledge gap. Here, we used concurrent hydroacoustic surveys and in situ DMS measurements to present evidence that zooplankton biomass is spatially correlated to natural DMS concentration in air and seawater. Using agent simulations, we also show that following gradients of DMS would lead zooplankton predators to areas of higher prey biomass than swimming randomly. Further understanding of the conditions and scales over which these gradients occur, and how they are used by predators, is essential to predicting the impact of future changes in the ocean on predator foraging success.

Measurement Device for Ambient Carbonyl Sulfide by Means of Catalytic Reduction Followed by Wet Scrubbing/Fluorescence Detection.

A portable chemical analysis system for monitoring ambient carbonyl sulfide (COS) was investigated for the first time. COS is paid attention to from the perspectives of photosynthesis tracer, breath diagnosis marker, and new process-use in the manufacture of semiconductors. Recently, the threshold level value of COS was settled at 5 ppm in volume ratio (ppmv) for workplace safety management. In this work, COS was converted to H2S by a small column packed with alumina catalyzer at 65 °C. Then, the H2S produced was collected in a small channel scrubber to react with fluorescein mercuric acetate (FMA), and the resulting fluorescence quenching was monitored using an LED/photodiode-based miniature detector. The miniature channel scrubber was re-examined to determine its robustness and easy fabrication, and conditions of the catalyzer were optimized. When the FMA concentration used was 1 µM, the limit of detection and dynamic range, which were both proportional to the FMA concentration, were 0.07 and 25 ppbv, respectively. Ambient COS in the background level and even contaminated COS in the nitrogen gas cylinder could be detected. If necessary, H2S was removed selectively by reproducible adsorbent columns. COS concentrations of engine exhaust were measured by the proposed method and by cryo-trap-gas chromatography-flame photometric detection, and the results obtained (0.5-5.9 ppbv) by the two methods agreed well (R 2 = 0.945, n = 19). COS in ambient air and exhaust gases was successfully measured without any batchwise pretreatment.

Electrodialytic Handling of Radioactive Metal Ions for Preparation of Tracer Reagents.

Radioactive metals are applied in biochemistry, medical diagnosis such as positron emission tomography (PET), and cancer therapy. However, the activity of radioisotopes exponentially decreases with time; therefore, rapid and reliable probe preparation methods are strongly recommended. In the present study, electrodialytic radioactive metal ion handling is studied for counter ion conversion and in-line probe synthesis. Presently, counter ion conversion and probe synthesis are achieved by evaporative dryness and solution mixing, respectively. Evaporative dryness is time-consuming and is a possible process that can lead to loss of radioactive metal ions. Mixing of solutions for synthesis makes dilution and undesirable effects of counter ion on the synthesis. An optimized electrodialytic flow device can transfer a radioisotope, 64Cu2+, with high recovery from HCl matrices to HNO3 (∼100%). Matrices can also be transferred into acetic acid and citric acid, even though the concentration of the metal ion is at the picomolar level. The ion transfer can also be achieved with simultaneous counter ion conversion, complex synthesis, and enrichment. When the ligand was dissolved in an acceptor solution, the transferred metal ions from the donor were well mixed and formed a complex with the ligand in-line. The efficiency of the synthesis was ∼100% for 1.0 pM 64Cu. A relatively larger donor-to-acceptor flow rate can enrich the metal ion in the acceptor solution continuously. The flow rate ratio of 10 (donor/acceptor) can achieve 10 times enrichment. The present electrodialytic ion handling method can treat ultra-trace radioisotopes in a closed system. With this method, rapid, effective, and safe radioisotope treatments were achieved.

Determination of oxoanions and water-soluble species of arsenic, selenium, antimony, vanadium, and chromium eluted in water from airborne fine particles (PM2.5): effect of acid and transition metal content of particles on heavy metal elution.

Heavy metals in particulate matter (PM) are of great concern, and their effects on the environment and human health depend on their solubilities and species present. In this study, the solubility of As, Se, Sb, V and Cr and their species eluted in water was investigated. As, Se, Sb, and V were present mostly in fine particles, and they were predominantly water-soluble in fine particles (<2.5 µm, PM2.5) but insoluble in coarse particles (>2.5 µm). Solubility of Cr was poor even in fine particles. It was found that for fine particles, solubilities of the heavy metals were related to the nitrate and sulfate contents. This suggests that the higher the acidity of the particles, the higher the solubility of the heavy metals. Oxoanions of the five kinds of heavy metals in water extracts of fine particles were determined by inductively coupled plasma mass spectrometry preceded by ion chromatography. The results suggested the presence of atmospheric oxidation during the aerosol transportation. Also, the As(iii)/As(v) (arsenite/arsenate) ratios for the fine particle extracts were related to the transition metal concentrations, which indicated that Fe, Cu, etc. in fine particles affected the As redox equilibrium. It was suggested that the heavy metals exist as complexes with iron hydroxide and dissolved organic matter in addition to the free oxoanions. These investigations were performed for PM samples collected in winter and summer in Kumamoto, west Japan, where the site is strongly exposed to westerly winds from continental East Asia. The obtained results improve our understanding of the behavior of the heavy metals in airborne PM after depositing on a wet environment and biota.

The atypical E2F transcription factor DEL1 modulates growth-defense tradeoffs of host plants during root-knot nematode infection.

In plants, growth-defense tradeoffs are essential for optimizing plant performance and adaptation under stress conditions, such as pathogen attack. Root-knot nematodes (RKNs) cause severe economic losses in many crops worldwide, although little is known about the mechanisms that control plant growth and defense responses during nematode attack. Upon investigation of Arabidopsis thaliana infected with RKN (Meloidogyne incognita), we observed that the atypical transcription factor DP-E2F-like 1 (DEL1) repressed salicylic acid (SA) accumulation in RKN-induced galls. The DEL1-deficient Arabidopsis mutant (del1-1) exhibited excessive SA accumulation in galls and is more resistant to RKN infection. In addition, excessive lignification was observed in galls of del1-1. On the other hand, the root growth of del1-1 is reduced after RKN infection. Taken together, these findings suggest that DEL1 plays an important role in the balance between plant growth and defense responses to RKN infection by controlling SA accumulation and lignification.

Miniaturized crossflow ion transfer device for post-column enrichment in ion chromatography.

The sensitivity of an ion chromatography system was improved using electrodialytic post-column enrichment. Even though post-column reactions, such as suppression, have been used to enhance the sensitivity, there are only a few methods available to increase the concentration and improve the sensitivity. Post-column in-line enrichment was achieved with a miniaturized crossflow ion transfer device (ITD) prepared in our laboratory. In the crossflow ITD, separated ionic solutes in the suppressed eluent were transferred into the acceptor solution (in-line purified ultrapure water), which had a flow rate less than that of the eluent. Because of highly efficient ion transfer, the analytes were enriched in the acceptor solution and the enrichment factor was depending on flow rate ratio of acceptor to eluent. Furthermore, the crossflow ITD minimized peak dispersion in the channel. The limit of detection improved by 5.0 ± 0.3 times when the flow rate ratio was 10.

Semi-continuous Monitoring of Cr(VI) and Cr(III) during a Soil Extraction Process by Means of an Ion Transfer Device and Graphite Furnace Atomic Absorption Spectroscopy.

Electrodialytic separation of Cr(VI) and Cr(III) followed by graphite furnace atomic absorption spectrometry for monitoring of soil extraction was studied. The sensitivity was improved by in-line purification of the solutions and bi-polar pulse cleaning. The detection limit for both Cr(VI) and Cr(III) was 0.01 µg L-1. The system was successfully used to monitor the concentration change during soil extraction with dual solution line filtration. The results demonstrate the difference in concentration changes with the different sources of Cr(VI).

Identification of Naturally Occurring Polyamines as Root-Knot Nematode Attractants.

Root-knot nematodes (RKNs; genus Meloidogyne) are a class of plant parasites that infect the roots of many plant species. It is believed that RKNs target certain signaling molecules derived from plants to locate their hosts; however, currently, no plant compound has been unambiguously identified as a universal RKN attractant. To address this question, we screened a chemical library of synthetic compounds for Meloidogyne incognita attractants. The breakdown product of aminopropylamino-anthraquinone, 1,3-diaminopropane, as well as its related compounds, putrescine and cadaverine, were found to attract M. incognita. After examining various polyamines, M. incognita were found to be attracted specifically by natural compounds that possess three to five methylene groups between two terminal amino groups. Using cryo-TOF-SIMS/SEM, cadaverine was indeed detected in soybean root cortex cells and the surrounding rhizosphere, establishing a chemical gradient. In addition to cadaverine, putrescine and 1,3-diaminopropane were also detected in root exudate by HPLC-MS/MS. Furthermore, exogenously applied cadaverine is sufficient to enhance M. incognita infection of Arabidopsis seedlings. These results suggest that M. incognita is likely attracted by polyamines to locate the appropriate host plants, and the naturally occurring polyamines have potential applications in agriculture in developing protection strategies for crops from RKN infection.

High Sensitivity Monitoring Device for Onboard Measurement of Dimethyl Sulfide and Dimethylsulfoniopropionate in Seawater and an Oceanic Atmosphere.

An automated device has been developed to measure aqueous dimethyl sulfide (DMSaq), its precursor dimethylsulfoniopropionate (DMSP), and atmospheric gaseous dimethyl sulfide (DMSg). In addition to having a role in the oceanic atmosphere, DMS and DMSP have recently gained substantial interest within the biosciences and are suspected as chemoattractants for predators searching for prey. To provide the spatial resolution relevant for biogeochemical functions, fast and on-site analysis of these compounds is an important technique. The system described measures the dimethyl sulfur compounds by sequential vaporization of DMSaq and DMSP to their gas phase, which is then analyzed by chemiluminescence detection (SVG-CL). The device has five analysis modes (full, DMS, water, gas, and DMSP mode) that can be selected by the user depending on the required analyte or desired sampling rate. Seawater analyses were performed by the developed SVG-CL system and, simultaneously, by an ion molecule reaction-mass spectrometer and a gas chromatograph-flame photometric detector to verify quantitative analysis results. Results obtained by the new method/device agreed well with those by the other methods. Detection limits of the SVG-CL system are 0.02 ppbv and 0.04 nM for DMSg and DMSaq/DMSP, respectively, which are much better than those of the mass spectrometer. The SVG-CL system can be easily installed and operated on a boat. Spatial variability in DMS and DMSP off the coast of Japan were obtained, showing significant changes in the concentrations of the components at the brackish/saline water interface and at the channel between the closed and open seas.

Universal HPLC Detector for Hydrophilic Organic Compounds by Means of Total Organic Carbon Detection.

Most quantifications are achieved by comparison of the signals obtained with the sample to those from a standard. Thus, the purity and stability of the standard are key in chemical analysis. Furthermore, if an analyte standard cannot be obtained, quantification cannot be achieved, even if the chemical structures are identified by a qualification method (e.g., high-resolution mass spectrometry). Herein, we describe a universal and analyte standard-free detector for aqueous-eluent-based high-performance liquid chromatography. This universal carbon detector (UCD) was developed based on total organic carbon detection. Separated analytes were oxidized in-line and converted to carbon dioxide (CO2). Generated CO2 was transferred into the gas phase and collected into ultrapure water, which was followed by conductivity detection. The system can be applied as a HPLC detector that does not use an organic solvent as an eluent. The system can be calibrated with a primary standard of sodium bicarbonate for organic compounds. The universality and quantification were evaluated with organic compounds, including organic acids, sugars, and amino acids. Furthermore, the system was successfully applied to evaluation of the purity of formaldehyde in formalin solution, and determination of sugars in juices. The results show the universal carbon detector has good universality and can quantify many kinds of organic compounds with a single standard such as sodium bicarbonate.

Ultra-sensitive Trace-Water Optical Sensor with In situ- synthesized Metal-Organic Framework in Glass Paper.

Monitoring of trace water in industrial gases is strongly recommended because contaminants cause serious problems during use, especially in the semiconductor industry. An ultra-sensitive trace-water sensor was developed with an in situ-synthesized metal-organic framework as the sensing material. The sample gas is passed through the sensing membrane and efficiently and rapidly collected by the sensing material in the newly designed gas collection/detection cell. The sensing membrane, glass paper impregnated with copper 1,3,5-benzenetricarboxylate (Cu-BTC), is also newly developed. The amount and density of the sensing material in the sensing membrane must be well balanced to achieve rapid and sensitive responses. In the present study, Cu-BTC was synthesized in situ in glass paper. The developed system gave high sensing performances with a limit of detection (signal/noise ratio = 3) of 9 parts per billion by volume (ppbv) H2O and a 90% response time of 86 s for 200 ppbv H2O. The reproducibility of the responses within and between lots had relative standard deviations for 500 ppbv H2O of 0.8% (n = 10) and 1.5% (n = 3), respectively. The long-term (2 weeks) stability was 7.3% for 400 ppbv H2O and one-year continuous monitoring test showed the sensitivity change of <∼3% before and after the study. Furthermore, the system response was in good agreement with the response achieved in cavity ring-down spectroscopy. These performances are sufficient for monitoring trace water in industrial gases. The integrated system with light and gas transparent structure for gas collection/absorbance detection can also be used for other target gases, using specific metal-organic frameworks.

Electrodialytic extraction of anionic pharmaceutical compounds from a single drop of whole blood using a supported liquid membrane.

A method to introduce target analytes to a chromatograph from a single drop of whole blood was investigated for minimally invasive monitoring of anionic pharmaceuticals. In this work, salicylate and loxoprofen were examined as organic anions. A micro ion extractor (MIE) has been developed for extraction of inorganic trace anions from whole blood, but this device is not suitable for extraction of pharmaceuticals. In the present study, we improved and optimized the MIE device for organic anion extraction. Various supported liquid membranes were evaluated for use as the ion transfer membrane, with each membrane placed between a droplet sample (donor) and an acceptor solution. A supported liquid membrane of porous polypropylene impregnated with 1-butanol was selected. In addition, the methods for electric field creation and electrode contact were examined to improve the characteristics of the MIE device. The current and extraction time were also optimized. With the optimized method, salicylate and loxoprofen were successfully extracted from a single drop of whole blood. Changes in the concentrations of these pharmaceuticals in blood over time were monitored after administration. As only 25µL of whole blood was required for analysis, repeat measurements could be conducted to monitor changes in the concentrations. This MIE will be useful for monitoring pharmaceutical concentrations in blood.