A new interface for combining capillary electrophoresis with inductively coupled plasma-mass spectrometry

This paper describes the development and design of a new, efficient, simple and robust interface for coupling capillary electrophoresis (CE) with inductively coupled plasma-mass spectrometry. The interface is based on a modified microconcentric nebulizer which permits a low flow rate of about 6 μL/min in the free aspiration mode. This interface construction provides an electrical connection for stable electrophoretic separations and adapts the flow rate of the electro-osmotic flow inside the CE capillary to the flow rate of the nebulizer for efficient transport of the analytes into the plasma. By optimization of the fluid mechanical properties the interface prevents the nebulizer from causing any laminar flow in the CE capillary and thus the high resolution power of CE can be preserved. Furthermore, this new device permits independent optimization of the nebulization from the CE whereby exact positioning of the CE capillary is not necessary, thus enabling fast exchange. A low dead volume spraychamber has been constructed which circumvents any band broadening of the sharp CE signals. Peak widths down to 3.5 s comparable to CE with UV detection are possible. Received: 5 February 1999 / Revised: 21 April 1999 / Accepted: 23 April 1999     

A new interface for combining capillary electrophoresis with inductively coupled plasma-mass spectrometry

This paper describes the development and design of a new, efficient, simple and robust interface for coupling capillary electrophoresis (CE) with inductively coupled plasma-mass spectrometry. The interface is based on a modified microconcentric nebulizer which permits a low flow rate of about 6 μL/min in the free aspiration mode. This interface construction provides an electrical connection for stable electrophoretic separations and adapts the flow rate of the electro-osmotic flow inside the CE capillary to the flow rate of the nebulizer for efficient transport of the analytes into the plasma. By optimization of the fluid mechanical properties the interface prevents the nebulizer from causing any laminar flow in the CE capillary and thus the high resolution power of CE can be preserved. Furthermore, this new device permits independent optimization of the nebulization from the CE whereby exact positioning of the CE capillary is not necessary, thus enabling fast exchange. A low dead volume spraychamber has been constructed which circumvents any band broadening of the sharp CE signals. Peak widths down to 3.5 s comparable to CE with UV detection are possible. Received: 5 February 1999 / Revised: 21 April 1999 / Accepted: 23 April 1999     

Quantitative description of element concentrations in longitudinal river profiles by multiway PLS models

Partial least squares (PLS) models were used to examine the relationships between the distributions of elements in different compartments of a river. These relationships, if existing, enabled predictions to be made of the element concentrations in one compartment by knowing the concentrations in another compartment. The subjects of the study were the element concentrations measured in the water and the sediment of the river Saale as well as in the water and the suspended matter of the river Elbe. Special emphasis was placed on a comparison between two-way and three-way PLS.     

Characterization and quantification of metallothionein isoforms by capillary electrophoresis–inductively coupled plasma–isotope-dilution mass spectrometry

In a new approach to the characterization and quantification of metallothionein isoforms an on-line isotope-dilution method in combination with the coupling of capillary electrophoresis (CE) to an inductively coupled plasma-sector field mass spectrometer (ICP-SFMS) is reported. Metallothionein (MT) isoforms are separated by CE and the elements Cu, Zn, Cd, and S are detected simultaneously by use of ICP-SFMS in the medium resolution mode. On-line isotope dilution is performed by continuous introduction of an isotopically enriched, species-unspecific spike solution after the separation step. MT from rabbit liver and a further purified MT-1 isoform were quantified by determination of sulfur, and the stoichiometric compositions of the metalloprotein complexes are characterized by determination of their sulfur-to-metal ratios.     

Atomic structure of highly strained BiFeO3 thin films

We determine the atomic structure of the pseudotetragonal T phase and the pseudorhombohedral R phase in highly strained multiferroic BiFeO(3) thin films by using a combination of atomic-resolution scanning transmission electron microscopy and electron energy-loss spectroscopy. The coordination of the Fe atoms and their displacement relative to the O and Bi positions are assessed by direct imaging. These observations allow us to interpret the electronic structure data derived from electron energy-loss spectroscopy and provide evidence for the giant spontaneous polarization in strained BiFeO(3) thin films.     

Quasiclassical Wavefunctions

A convergent quasiclassical formula for the wavefunctions of a closed quantum or wave system is obtained. This is expressed entirely in terms of classical orbits. The result is at the same level as earlier results expressing the spectrum as a finite resurgent sum over composite periodic orbits.     

Hyphenated techniques for the characterization and quantification of metallothionein isoforms

Recent developments in the coupling of highly selective separation techniques such as capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC) to element-specific and molecule-specific detectors, such as inductively-coupled plasma mass spectrometry (ICP-MS) and electrospray ionization-tandem mass spectrometry (ESI-MS/MS) for the characterization and quantification of metallothioneins (MTs) are critically reviewed and discussed. This review gives an update based on the literature over the last five years. The coupling of CE to ICP-MS is especially highlighted. As a result of progress in new interface technologies for CE-ICP-MS, research topics presented in the literature are changing from "the characterization of interfaces by metallothioneins" to the "characterization of metallothioneins by CE-ICP-MS". New applications of CE-ICP-MS to the analysis of MTs in real samples are summarized. The potential of the on-line isotope dilution technique for the quantification of MTs and for the determination of the stoichiometric composition of metalloprotein complexes is discussed. Furthermore, a selection of relevant papers dealing with HPLC-ICP-MS for MT analysis are summarized and compared to those dealing with CE-ICP-MS. In particular, the use of size-exclusion (SE)-HPLC as a preliminary separation step for metallothioneins in real samples prior to further chromatographic or electrophoretic separations is considered. Additionally, the application of electrospray ionisation-tandem mass spectrometry (ESI-MS/MS) for the identification of metallothionein isoforms following electrophoretic or chromatographic separation is discussed.