Yoshitaka Takagai

Synthesis and evaluation of different thio-modified cellulose resins for the removal of mercury (II) ion from highly acidic aqueous solutions

Seven different types of thio- and/or amine-modified cellulose resin materials were synthesized and their mercury (II) ion adsorption properties determined. All seven resins showed good mercury (II) adsorption capability in the more neutral pH regions. However, the o-benzenedithiol- and o-aminothiophenol-modified cellulosic resins were found to be very effective in removing mercury (II) ions from strongly acidic media. For example, 93.5-100% mercury (II) ion recoveries from very acid aqueous solutions (nitric acid concentration ranged from 0.1 to 2.0 mol/L) were obtained using the o-benzenedithiol-modified resin while recoveries ranged from ca. 50% to 60% for the o-aminothiophenol-modified resin. An adsorption capacity of 23 mg (as Hg atoms) per gram of resin was observed for the o-benzenedithiol-modified cellulose in the presence of 1.0 mol/L nitric acid. This same resin shows very good selectivity for mercury (II) as only ruthenium (II) also somewhat adsorbed onto it out of 14 other metal ions studied (Ag(+), Al(3+), As(3+), Co(2+), Cd(2+), Cr(3+), Cu(2+), Fe(3+), Mn(2+), Ni(2+), Pt(2+), Pb(2+), Ru(2+), and Zn(2+)).

Cloud Point Extraction with Surfactant Derivatization as an Enrichment Step Prior to Gas Chromatographic or Gas Chromatography−Mass Spectrometric Analysis

Cloud point extraction (CPE) using Triton X-114 was successfully applied as an extractive preconcentration step prior to gas chromatographic-mass spectrometric analysis. No liquid chromatographic or back-extraction steps were required to remove the target analyte(s) from the surfactant-rich extractant phase. Instead a post-extraction derivatization step is employed in which the surfactant of the surfactant-rich phase is reacted with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) prior to injection into the gas chromatograph. Such derivatization of the Triton X-114 surfactant following CPE was found to provide improved chromatographic performance yielding a reasonable elution time window that is free of derivatized surfactant signals, reproducible analyte retention times, and quantitative results. Mixtures of polycyclic aromatic hydrocarbons (PAHs), herbicides, and profens were utilized to demonstrate the feasibility and performance of this approach. The retention times of six PAHs (acenaphthene, acenaphthylene, anthracene, biphenyl, dibenzofuran, and fluorene) were found to be very reproducible with relative standard deviations (RSDs) in the range of 0.5-0.8%. Quantitative gas chromatography-mass spectrometry (GC/MS) analysis of a herbicide test mixture (composed of alachlor, atrazine, butachlor, hexachlorocyclopentadiene, metolachlor, and simazine) following their CPE from spiked water samples yielded detection limits in the range of 6.6-97 ng/L (except for that of hexachlorocyclopentadiene which was 482 ng/L). The enrichment factors achieved for these herbicides ranged from 17 to 33. The recovery of the herbicides from spiked water samples ranged from 90 to 100% except for simazine and atrazine which were 50% and 74%, respectively. The BSFTA derivatization step can serve not only to derivatize the surfactant but also appropriate nonvolatile (or less volatile) analytes. An ibuprofen and flurbiprofen test mix was utilized to demonstrate this feature. The proposed protocol offers an attractive alternative means by which surfactant-mediated extractions can be utilized as an enrichment step prior to gas chromatographic or gas chromatographic-mass spectrometric analysis of analytes which should serve to expand the scope of CPE in gas chromatographic (GC) analysis.

Sequential inductively coupled plasma quadrupole mass-spectrometric quantification of radioactive strontium-90 incorporating cascade separation steps for radioactive contamination rapid survey

Radioactive strontium-90 scattered by a nuclear power plant accident was specifically quantified by conventional inductively coupled plasma quadrupole mass-spectrometry (ICP-QMS) preceded by on-line chelate column separation (based on lab-on-valve) and oxygen reaction (designated the cascade step). The proposed system overcomes the isobaric interference of 90Zr, whose soil concentration exceeds that of 90Sr by more than six orders of magnitude. In addition, the system requires no ultimate mass spectrometry or radioactive 90Sr standards. The radioactive 90Sr standard was replaced with the stable isotope 88Sr as a pseudo-standard. The modified ICP-QMS system yielded a precise, reproducible sharp 90Sr peak in the ICP-MS profile. The elution time of 90Sr was highly reproducible (RSD = 0.5%). After implementing the cascade-step, the detection limit (DL) was 2.3 Bq L−1 (equivalent to 0.46 ppq as 90Sr). Analysis of microwave-digested soil yielded a DL of 3.9 Bq kg−1 (equivalent to 0.77 ppq as 90Sr). The 90Sr from environmental contaminated soil samples collected from areas at a distance of 10 and 20 km from the Fukushima Daiichi nuclear power plant ranged from 52 Bq kg−1 to 73 Bq kg−1, with no statistical difference between the proposed and general methods at 95% confidence level. The proposed method offers an attractive alternative use for ICP-other ionization mass spectrometry as an enrichment or purification step, thereby expanding the scope of ICP-mass-spectrometric analysis.

Sequential Injection Analysis System Exploiting On-line Solid-phase Extraction for the Determination of Strontium and Nickel by Microwave Plasma Atomic Emission Spectrometry

A sequential flow-based analysis system with on-line solid-phase extraction (SPE) columns coupled to microwave plasma atomic emission spectrometry (MP-AES) was developed for strontium and nickel determination. Crown ether chromatographic resin and dimethylglyoxime polymethacrylate resin were used for strontium and nickel retention under acidic and basic conditions, respectively; eluted with a nitric acid solution in both cases followed by MP-AES detection. The calculated detection limits were 0.25 μg L-1 for strontium and 3.56 μg L-1 for nickel.

β-Cyclodextrin as a Metal-anionic Porphyrin Complexation Accelerator in Aqueous Media

The rate of the complexation reaction between anionic porphyrins and 11 metal ions was found to be accelerated by the presence of β-cyclodextrin (β-CD) in aqueous media at room temperature without the need for additional heating or sonication. The porphyrin complexation reaction with metal ions under aqueous conditions can be difficult due to the strong hydration energy between the metal ions and water. In this study, the specific role of β-CD as an accelerator was determined and found to enhance the typically slow reaction of the porphyrin with metal ions. A significant acceleration effect was exhibited when the model anionic porphyrin, 5,10,15,20-tetraphenyl-21H,23H-porphine-tetrasulfonic acid, and Pb(II) ions were combined in the presence of β-CD. Other than for Hg ion, the addition of β-CD decreased the metalation reaction time from 30 to 2 min. The order in the degree of acceleration was Pb >> Zn, Cd > Cu > Fe, Pd > Sn >> Ag, Co, Mn. Using Pb(II) as the model ion, it was determined that the complexation rate constant was enhanced by a factor of 2.4, while the dissociation rate constant was diminished by a factor of 135 in the presence of added β-CD relative to that in its absence. Overall, the complex was much more stable (formation equilibrium constant 324-fold greater in the β-CD medium. The formation of a ternary complex (cf. bicapped complex; (β-CD)2-porphyrin-metal ion) was demonstrated through the use of nuclear magnetic-resonance spectroscopy and mass spectrometry. This acceleration effect is expected to be applicable systems in which porphyrin ligands are employed for determining of metal ions in chemical analysis and separation science.

Gas chromatography-mass spectrometric determination of ivermectin following trimethylsilylation with application to residue analysis in biological meat tissue samples

A gas chromatography-mass spectrometric (GC-MS) method utilizing electron impact ionization has been developed for the quantitation of the antiparasitic agent, ivermectin (IVM). The approach is based upon the pre-column derivatization of IVM by reaction with N,O-bis(trimethylsilyl)tri-fluoroacetamide (BSTFA) in the presence of 1-methylimidazole as catalyst and carbon tetrachloride as solvent to form the trimethylsilyl (TMS) derivative of IVM (IVM-TMS) prior to injection into the GC-MS system. The derivatization reaction is complete within 5.0 min at room temperature and allows the GC-MS determination of IVM. A limit of detection for IVM of 0.67 ng g−1 was achieved (via monitoring the peak with m/z = 185 in the selective ion mode and benzophenone-d10 as the internal standard). The method was utilized with success for the determination of IVM in spiked horse meat samples yielding recoveries very similar to that obtained using a reference liquid chromatography-mass spectrometric method (LC-MS). In addition, this GC-MS method can be employed to determine not only IVM but also other related macrolide veterinary drugs such as eprinomectin and moxidectin which are often administered along with IVM. Detection limits of 3.72 and 5.44 ng g−1 were obtained for eprinomectin and moxidectin, respectively.

On-line pseudo-stationary magnetic solid-phase extraction using magnetic cation exchange microparticles and its application to the determination of strontium

An on-line magnetic solid-phase extraction (MSPE) system using a micrometer-sized cation exchanger was developed for strontium determination by microwave plasma atomic emission spectrometry (MP-AES). Micro-magnetic silica-based particles chemically immobilizing diethyl sulfone functional groups were pseudo-stationarily placed inside a knotted tube reaction flow-coil under the influence of an external magnetic field from two sandwiched magnets. In this study, the effect on the analytical impact was investigated using Sr as a model analytical target. The adsorption of Sr was carried out under acidic conditions, and its elution was performed with a nitric acid solution followed by MP-AES detection. The calculated detection limit was 0.59 μg L−1 with a 10-times sensitivity enhancement factor.

Unique aluminosilicate-based natural nanoparticles in the volcanogenic Goshiki-numa pond

We report here the occurrence of uniquely shaped nanoparticles newly discovered in natural ponds. Nanoparticles originate from the Goshiki-numa pond community in Japan, where volcanic activity facilitated the formation of four specific ponds. We built a steric three-dimensional image of nanoparticles by integrating 120 transmission-electron-microscope image fragments obtained from various angle ranges. The thick-walled, cylindrically shaped particle has an outer diameter that measures approximately 40xa0nm and a length that measures 70xa0nm. A 10-nm-thick wall surrounds a 30xa0nm hole located in the particle centre. Particles are composed of an aluminium silicate-based material with an Al2O3:SiO2 ratio of 2:1. They also exhibit an amorphous X-ray diffraction pattern. Although the water solubility characteristics and the infrared spectrum of these newly discovered particles resembles imogolite, these two materials do not have identical structural characteristics.

HPLC-spectrophotometric detection of trace heavy metals via ‘cascade’ separation and concentration

A cascade pre-concentration and separation system involving continuous solid-phase extraction and one-drop solvent concentration was developed to enable high-performance liquid chromatography (HPLC) determination of trace levels of Ni(II), Co(II), Cu(II), Se(IV) and Cr(VI) ions in aqueous solution via complexation with sodium diethyldithiocarbamate. The metal complexes were almost completely adsorbed on the solid phase (octadecylsilyl packed column). Ethyl acetate (eluent) containing the metal complexes was then placed in a centrifuge tube, to which a microvolume of dimethyl sulfoxide (DMSO) was added. Successful pre-concentration of the metal complexes into the DMSO phase was accomplished by removing the ethyl acetate using a compact evaporator in a water bath (40°C); 1000-fold concentration was achieved within 45 min. A portion of the residual DMSO phase was then subjected to HPLC analysis. The proposed method has high reproducibility and high sensitivity with detection limits (3σ) for Ni(II), Co(II), Cu(II), Se(IV) and Cr(VI) ions of 0.08, 0.11, 0.12, 0.44 and 0.20 µg/L, respectively. Relative standard deviations (RSDs) (n = 5) at Ni(II) 5.87 µg/L, Co(II) 5.89 µg/L, Cu(II) 6.35 µg/L, Se(IV) 7.90 µg/L and Cr(VI) 5.20 µg/L (1.0 × 10−7 mol/L each) were 4.0%, 4.6%, 4.6%, 7.2% and 3.4%, respectively.