Operational modes for transient isotachophoretic preconcentration-capillary zone electrophoresis and detectable concentration of rare earth ions.

Operational modes for transient isotachophoretic preconcentration capillary zone electrophoresis (tr-ITP-CZE) were studied by using 5 microM and 0.5 microM rare earth mixtures as analytes in comparison with field-enhanced sample stacking. After examination of several operational modes for tr-ITP, it was found that tr-ITP effectively occured even if both the leading electrolyte and the terminating electrolyte were injected after the sample plug. This was explained as the result of a field-enhanced stacking for both sample components and the leading and terminating ions. The observed theoretical plate numbers were 4-20 times higher than those obtained by normal stacking; and the estimated low limit of detectable concentration of rare-earth elements (REE) was ca. 0.1 microM which was 2.5 times lower compared to normal stacking. For the 0.5 microM sample, a concentration factor of 20 000 could be achieved after only tr-ITP.     

Isotachophoretic separation behavior of rare-earth EDTA chelates and analysis of minor rare-earth elements in an iron ore by bidirectional isotachophoresis-particle-induced X-ray emission.

Mobilities of 16 anions of rare-earth-EDTA 1:1 chelate (RE-EDTAs) were isotachophoretically measured by using two leading electrolytes (pH 3.6 and 6.0) in order to assess their separation behavior. The leading electrolyte was 20 mM hydrochloric acid. The pH of the solution was adjusted to 3.6 by adding beta-alanine and to 6.0 by adding histidine. The obtained mobilities were very close to each other in the range 20.1x10(-5)-21.9x10(-5) cm2 V(-1) s(-1) with the minimum mobilities for Pr-EDTA and Nd-EDTA for pH 3.6 and 6.0, respectively, and pH dependence was hardly observed. On the basis of the above knowledge. minor rare-earth elements in a standard iron ore sample were determined as RE-EDTAs by bidirectional isotachophoresis-particle-induced X-ray emission (PIXE), where the Fe(II) matrix digested by alkali fusion was separated as Fe(II)Phen3(2+) (phen = 1,10-phenanthroline). Since 5% of the total iron was still detected as Fe(III)EDTA- and might disturb PIXE analysis of RE-EDTA-, itaconic acid was used as the spacer for Fe(III)EDTA- and RE-EDTA-. The fractions of RE-EDTA- were successfully analyzed off-line by a multielemental analytical method, PIXE [analytical result (3.62% (w/w) as RE2O3]; the nominal value was 3.37% (w/w) as RExOy.     

Synthesis of rumphellaone A via epoxy nitrile cyclization

The first enantioselective total synthesis of rumphellaone A, a cytotoxic 4,5-seco-caryophyllane isolated from the gorgonian coral Rumphella antipathies, has been achieved from a known olefinic alcohol by a 16-step sequence involving Stork's epoxy nitrile cyclization as the key step to concomitantly install a cyclobutane ring and three contiguous stereogenic centers contained in the molecule.     

Electrokinetic supercharging preconcentration prior to CGE analysis of DNA: Sensitivity depends on buffer viscosity and electrode configuration

Aiming to high sensitivity DNA analysis by CGE, electrokinetic supercharging (EKS) approach was adopted in this article. EKS is known as an online preconcentration technique that combines electrokinetic sample injection (EKI) with transient ITP (tITP). Herein, two factors of buffer viscosity and electrode configuration were studied to further improve EKS performance. An ultralow‐viscosity Tris‐Boric acid‐EDTA (TBE) buffer solution, consisted of 2% low‐molecular‐weight hydroxypropyl methyl cellulose (HPMC) and 6% mannitol and with pH 8.0 adjusted by boric acid, was applied. The boric acid would make a complex with mannitol and generates borate polyanion, which acts as the leading ion for tITP process. The new electrode configuration, a Pt ring around capillary, was modified on Agilent CE system to lead large amount sample introduction during EKS. The standard DNA sample of φX174/HaeIII digest was used to evaluate the qualitative and quantitative abilities of the proposed strategy. The 170 000‐fold highly diluted sample at concentration of 3.0 ng/mL was enriched by EKS and detected by normal UV detection method. The obtained LOD of the weakest peak of 72 bp fragment was around 7.7 pg/mL, apparently improved more than 10 000‐fold in comparison with conventional CGE with UV detection.     

Evaluation of Ni/Mn multilayer samples with glancing-incidence and take-off X-ray fluorescence analysis

A Glancing-Incidence and Take-off X-Ray Fluorescence (GIT-XRF) apparatus with which both incident angle of primary X-ray and take-off angle of fluorescent X-rays can be controlled has been newly developed for characterizing surfaces and interfaces. Using this apparatus, Ni/Mn multilayer samples were evaluated obtaining Take-off-Angle-Dependent X-Ray Fluorescence (TAD-XRF) curves at arbitrary incident angles of primary X-ray. In particular, we could obtain information on the near surface by measuring TAD-XRF curves at the incident angle less than the critical angle of total reflection for primary X-rays.     

Refraction effect of scattered X-ray fluorescence at surface

The angular distribution of X-ray fluorescence shows anisotropic radiation. We proved that the origin of the anisotropic radiation is X-ray refraction by using a scattered X-ray fluorescence model. Utilizing the refraction effect of X-ray fluorescence, we can obtain much information: for example, surface density, chemical condition, surface roughness, and particle diameter of element, as a new tool of studying surfaces and interfaces. We introduce a new X-ray dispersive system utilizing X-ray refraction.     

Use of ESCA for a convenient and semi-quantitative state analysis of copper-nickel alloy surfaces

Summary A semi-quantitative technique by means of ESCA was applied to the surface state analysis of copper-nickel alloys. With area integrated intensity of peaks at the L₃M_{4, 5}M_{4, 5} region of copper and 2 p 3/2 region of nickel, cuprous state and nickel oxide state on alloys could be semi-quantitatively determined. As to oxygen states on alloy surfaces, interstitial (Cu₂O and NiO states), non-stoichiometric (represents -OH) and molecular states (adsorbed) were estimated. Further, the surface composition of alloys after heating under high vacuum was discussed.

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Einsatz von ESCA für die einfache halbquantitative Zustandsanalyse von Oberflächen von Kupfer-Nickel-Legierungen

Zusammenfassung Das ESCA-Verfahren wurde für die Untersuchung des Oberflächenzustandes von KupferNickel-Legierungen eingesetzt. Mit Hilfe der flächenintegrierten Peakintensitäten (L₃ M_{4, 5} M_{4, 5} für Kupfer, 2 p 3/2 für Nickel) konnten Kupfer(II) und Nickeloxid auf den Legierungen halbquantitativ bestimmt werden. Sauerstoff wurde im interstitiellen (Cu₂O, NiO) nichtstöchiometrischen (-OH) und molekularen (adsorbierten) Zustand gefunden. Weiterhin wurde die Oberflächenzusammensetzung der Legierungen nach Erhitzen im Hochvakuum diskutiert.

     

Study of a novel sample injection method (floating electrokinetic supercharging) for high-performance microchip electrophoresis of DNA fragments

Aiming to achieve high-performance analysis of DNA fragments using microchip electrophoresis, we developed a novel sample injection method, which was given the name of floating electrokinetic supercharging (FEKS). In the method, electrokinetic injection (EKI) and ITP preconcentration of samples was performed in a separation channel, connecting two reservoir ports (P3 and P4) on a cross-geometry microchip. At these two stages, side channels, crossing the separation channel, and their ports (P1 and P2) were electrically floated. After the ITP-stacked zones passed the cross-part, they were eluted for detection by using leading ions from P1 and P2 that enabled electrophoresis mode changing rapidly from ITP to zone electrophoresis (ZE). Possible sample leakage at the cross-part toward P1 and P2 was studied in detail on the basis of computer simulation using a CFD-ACE+ software and real experiments, through which it was validated that the analyte recovery to the separation channel was almost complete. The FEKS method successfully contributed to higher resolution and shorter analysis time of DNA fragments on the cross-microchip owing to more rapid switching from ITP status to ZE separation in comparison with our previous EKS procedure realized on a single-channel microchip. Without any degradation of resolution, the achieved LODs were on average ten times better than using conventional pinched injection.