A new concept for the bioeffects-related analysis of xenoestrogens: Hyphenation of receptor assays with LC-MS

The wide variety of known and unknown endocrine disruptors demands highly efficient methods for detecting the relevant endocrine disrupting pollutants. Bioeffects-related analysis is expected to solve this problem, combining biomolecular recognition processes with chemical analysis, which therefore reduces costs of instrumental chemical analysis to relevant samples. The hyphenation of both steps provides information on potential bioeffects, structure and concentration of the substances of interest. In this work the hyphenation of an enzyme-linked receptor assay (ELRA) with liquid chromatography-tandem mass spectrometry (LC-MSMS) for the analysis of estrogens and xenoestrogens is proposed. Both test systems have been validated with standards and spiked real water samples. The ELRA achieved a detection limit of 0.1 μg/L for 17β-estradiol (without preconcentration). With the LC-MSMS method, steroids could be detected down to 1 ng/L (with preconcentration). Two concepts for a tighter hyphenation of biomolecular interaction and chemical analysis are discussed: the on-line coupling of receptor-affinity chromatography (RAC) to LC-MSMS and the direct measurement of receptor-ligand complexes by LC-MSMS. Received: 30 October 1998 / Revised: 18 December 1998 / Accepted: 26 December 1998     

Sequential injection: a new concept for chemical sensors,process analysis and laboratory assays

Established flow-injection techniques allow advanced solution handling for laboratory purposes, but chemical sensing and continuous monitoring of chemical processes require dramatically simplified flow schemes and instrumentation with the potential for miniaturization and an inherent ruggedness. Considerations based on the random walk model have led to the concept of sensor injection and sequential injection analysis. This new approach to automated analysis is designed to fill a gap in present flow-injection methodology.     

A new high-throughput LC-MS method for the analysis of complex fructan mixtures

In this paper, a new liquid chromatography-mass spectrometry (LC-MS) method for the analysis of complex fructan mixtures is presented. In this method, columns with a trifunctional C18 alkyl stationary phase (T3) were used and their performance compared with that of a porous graphitized carbon (PGC) column. The separation of fructan isomers with the T3 phase improved clearly in comparison with the PGC phase, and retention times were lower and more stable. When the T3-based method was applied on a wheat grain extract, multiple fructan isomers could be discerned, even for fructans with a degree of polymerization of 10. This indicates that wheat grain fructans do not, or not only, have a simple linear structure. The presented method paves the way for elucidation of fructan structures in complex mixtures that contain many structural isomers.     

HyperLab: A new concept in gamma-ray spectrum analysis

HyperLab is a new Ge gamma-ray analysis code for MS Windows, developed using object-oriented design. The novel feature of the program is the extensive use of relational database technology, which allows the efficient storage and handling of any digital data encountered in gamma-ray spectroscopy. While preserving the main concept of the predecessors (HYPERMET and its derivatives) for semi-automatic analysis of multichannel pulse-height spectra, the substantially reshaped basic routines vastly improved the stability and reliability of peak fitting. New features include the fitting of peaks with high energy tail, as well as library-directed Graphical Isotope Identification. Procedures for efficiency, nonlinearity, etc. calibrations are now highly automated. By exploiting all the benefits of MS Windows technology (point-and-click simplicity in task executions, intelligent mouse pointer, etc.) HyperLab is a versatile and user-friendly tool which the discriminating spectroscopist will find of great value.     

Colorimetric and electrochemical phosphodiesterase inhibition assays for yessotoxin detection: development and comparison with LC-MS/MS

This work describes the development and applicability of two functional assays for the detection of yessotoxin (YTX), a polycyclic ether marine toxin produced by dinoflagellates. The assays are based on the interaction between this toxin and the phosphodiesterase (PDE) enzyme and the subsequent measurement of the enzyme activity by colorimetric and electrochemical methods. Firstly, several enzyme substrates were tested in order to select those able to be detected by colorimetry or electrochemistry after enzymatic hydrolysis. The substrates that provided the highest absorbance values and density currents were p-nitrophenyl phenylphosphonate and α-naphthyl phosphate, respectively. After optimisation of the experimental parameters, limits of detection of 0.8 and 0.6 μM were attained by colorimetry and electrochemistry, respectively. An inhibitory effect of YTX on the PDE activity was observed. The assays have been applied to the analysis of YTX production by Protoceratium reticulatum cultures, and results were compared with liquid chromatography–tandem mass spectrometry analysis.     

Hyphenation of Curie-point-pyrolysis high-resolution gas chromatography with several spectroscopic methods for the analysis of cured epoxy resins

The coupling of Curie-point pyrolysis (Py) with gas chromatography (GC) and mass spectrometry (MS) or Fourier transform infrared spectroscopy (FTIR) has been widely reported. The approach reported in this paper combines chromatographic separation with eluent monitoring by use of three different spectroscopic detectors (MS, FTIR and Atomic Emission Detector [AED]). The features of these detectors, with different selectivities, are shown for the analysis of cured epoxy resins. Besides characterisation of major resin constituents by identification of the pyrolysis products, the usefulness of the AED is also revealed by the detection of minor compounds (such as coupling agents) in cured epoxy resins.     

A new concept of automated radiochemical analysis based on substoichiometric separation

Tracer methods, such as radioisotope dilution, radiometric analysis, concentration dependent distribution, saturation analysis etc., are compared on a basis of radioactivity-mass balance relationships, and their automation is proposed. The requirements of a chemical separation, which is an integral part of these methods, are discussed. It is shown that automation, in addition to its obvious advantages, enables entirely new procedures to be developed, based on chemical separations which do not give reproducible results when performed normally. Simple commercially available apparatus has been used to verify these concepts by determination of traces of mercury. As little as 0.005 ppm of Hg can be determined, the detection limit being about a tenth of this. In the range 2.4-0.03 ppm, 20 samples/hr can be analysed, for lower amounts the sampling rate is 10 samples/hr.     

Flow injection analyses: Part I. A new concept of fast continuous flow analysis

The concept of a new continuous flow analyser system is described. Based on instant discrete sampling by injection into a carrier stream, the system allows continuous flow analysis to be performed in a fast, much simplified way. As the continuous flowing stream is characterized by a turbulent rather than a laminar flow, the discrete instant sampling creates geometrically well-defined segments of sample solution within the flowing stream. Because of the absence of lag phase, an unprecedented sampling rate for continuous flow analysis of well over 200 samples per hour can be achieved; and even manual injection of the samples allows a very high degree of accuracy and precision to be obtained ( ? ± 1%). Uses of the system in various analytical procedures are described and discussed. A potentiometric sensor (the air-gap electrode used in a flow-through unit) and a spectrophotometric arrangement with a flow-through cell have been used as detector units.     

A new concept for the quasi non-destructive microsampling of historical glasses

A mobile and easily practicable microsampling technique for historical glasses and its application is presented. About 100 μg of material is scraped off the object with a fine grinding file. The analysis of main, minor and trace elements in the digested sample is performed by IC, GFAAS and FIA with photometric detection. The procedure has been verified by measurements of standard glasses. Investigations of baroque ruby glasses showed the suitability of the microsampling technique for archaeometrical application. Received: 6 January 1997 / Revised: 17 March 1997 / Accepted: 25 March 1997     

A new concept for the quasi non-destructive microsampling of historical glasses

A mobile and easily practicable microsampling technique for historical glasses and its application is presented. About 100 μg of material is scraped off the object with a fine grinding file. The analysis of main, minor and trace elements in the digested sample is performed by IC, GFAAS and FIA with photometric detection. The procedure has been verified by measurements of standard glasses. Investigations of baroque ruby glasses showed the suitability of the microsampling technique for archaeometrical application. Received: 6 January 1997 / Revised: 17 March 1997 / Accepted: 25 March 1997     

Hyphenation of optimized microfluidic sample preparation with nano liquid chromatography for faster and greener alkaloid analysis

A glass liquid–liquid extraction (LLE) microchip with three parallel 3.5 cm long and 100 μm wide interconnecting channels was optimized in terms of more environmentally friendly (greener) solvents and extraction efficiency. In addition, the optimized chip was successfully hyphenated with nano-liquid chromatography with ultraviolet and mass spectrometric detection (nanoLC–UV–MS) for on-line analysis. In this system, sample pretreatment, separation and detection are integrated, which significantly shortens the analysis time, saves labor and drastically reduces solvent consumption. Strychnine was used as model analyte to determine the extraction efficiency of the optimized 3-phase chip. Influence of organic solvent, pH of feed phase, type of alkaloid, and flow rates were investigated. The results demonstrated that the 3-phase chip nanoLC–UV/MS hyphenation combines rapid (∼25 s) and efficient (extraction efficiency >90%) sample prep, with automated alkaloid analyses. The method was applied to real samples including Strychnos nux-vomica seeds, Cephaelis ipecacuanha roots, Atropa belladonna leaves, and Vinca minor leaves.     

A new concept for corrosion inhibition of magnesium: Suppression of iron re-deposition

In our recent work (Höche et al. 2016) we proposed that non-faradaic dissolution of Fe impurities and/or iron containing phases with subsequent re-deposition of thin film of pure (“in statu nascendi”) iron enlarges cathodically active sites at the surface of corroding magnesium. The effect drastically accelerates corrosion of impurity containing Mg. In the present work we assume that if Fe re-deposition is prevented, the area of cathodic sites can be drastically decreased and hence corrosion of Mg can be suppressed. In this proof of concept work we use strong Fe^3 + complexing agents in order to remove dissolved iron cations from corrosion sites and prevent iron re-deposition. All used iron complexing agents efficiently lowered the corrosion rate of Mg. Direct correlation of complex stability with its inhibiting efficiency was established. It was shown that cyanide, salicylate, oxalate, methylsalicylate and thiocyanate efficiently reduce hydrogen evolution and suppress critical dark area formation.     

Hyphenation of infrared spectroscopy to liquid chromatography for qualitative and quantitative polymer analysis: degradation of poly(bisphenol A)carbonate

Hyphenation of infrared spectroscopy (IR) to liquid chromatography (LC) has been applied to study chemical changes in poly(bisphenol A)carbonate (PC) as a result of degradation. Especially coupling of LC to FTIR through solvent elimination is a sensitive approach to identify changes in functionality observed in the LC chromatograms as has been demonstrated by coupling of liquid chromatography under critical conditions (LCCC) to IR. Furthermore, an example is shown in which two-dimensional liquid chromatography, i.e. LCCCxSEC, was coupled to IR by means of a flow cell. This resulted in data sets containing most probably valuable data, but extracting relevant information from these large data sets is not straightforward at all. Therefore, multivariate data analysis (MVDA) of SEC-FTIR data was used to extract relevant data from large data sets. This approach revealed chemical differences due to degradation that could not be detected by other means. Spectral features could be identified that allowed to quantitatively predict the degradation of poly(bisphenol A)carbonate as a function of degradation conditions.     

O-alkenyl hydroxylamines: a new concept for cyclofunctionalization

[reaction: see text] Treatment of O-homoallylhydroxylamines with palladium(II) and copper(II) in the presence of a base, methanol, and carbon monoxide results in the formation of isooxazolidines. An electron-withdrawing group on the hydroxylamine nitrogen is essential. When carbamate groups are used the products are formed exclusively as their cis isomers.     

Secondary doping: A new concept in conducting polymers

Phenomenologically, a primary dopant for a conducting polymer is a substance which drastically changes the electronic, optical, magnetic, and/or structural properties of the polymer and is accompanied by a large increase in conductivity. Phenomenologically, a secondary dopant is an apparently “inert” substance which, when applied to a primary-doped polymer, induces still further changes in the above properties including a further increase in conductivity. The concept of secondary doping will be illustrated using polyaniline and its derivatives.     

A new data management concept for AES and SAM

The problem of interchangeability of surface analytical data is gaining increasing importance in multi-method surface analysis. There are various surface analytical instruments in different laboratories on several automation levels. For these instruments, which are controlled by computer systems working with company-specific software under various operating systems, a standardised data format is necessary to allow an exchange of data. Therefore, we are developing a software package for the transfer, archiving and editing of surface analytical data called MAXMIND (management and exchange of method independent data), which is based on public domain software products. It allows the storage of all available and necessary information on experimental conditions and all parameters specific for a number of analytical techniques such as AES, SAM, XPS, SIMS, STM and AFM. Additionally, all data concerning the sample-preparation and the state of the instrument are included in order to allow a well-founded evaluation of the data and improved reproducibility of the experiment. This concept is demonstrated in detail for the two Auger techniques AES (Auger Electron Spectroscopy) and SAM (Scanning Auger Microscopy).Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday     

A new two-chip concept for continuous measurements on PMMA-microchips

A new concept for continuous measurements on microchips is presented. A PMMA (polymethylmethacrylate) based capillary electrophoresis chip with integrated conductivity detection is combined with a second chip, which undertakes the task of fluid handling and electrical connections. The combination of electrokinetic and hydrodynamic flows allows long-term continuous stable analyses with good reproducibilities of migration time and peak heights of analytes. The two-chip system is characterized in terms of stability and reproducibility of separation and detection of small ions. Relative standard deviations of <1% and 3% respectively for retention times and peak heights during long-term measurements can be achieved. The new system combines simple handling and automated analysis without the need for refilling, cleaning or removal of the separation chip after one or several measurements.     

Hyphenation of quadrupole MS to GC and comprehensive two-dimensional GC for the analysis of suspected allergens: review and improvement

This survey reviews papers that have been previously published on the quantitative analysis of suspected allergens. The routine gas chromatography (GC)-mass spectrometry (MS) method allows their evaluation in most fragrances, but the application of an automated data treatment sometimes leads to over- or underestimations when target compounds are coeluted or shifted because of the presence of other fragrance ingredients. In such cases, an appropriate retreatment of data generated by the routine analysis is proposed to better estimate these shifted or coeluted peaks. A second and more sophisticated approach, based on comprehensive bidimensional GC hyphenated to quadrupole MS, overcomes coelution problems. However, its use is still time consuming because of the lack of a commercial program. In this work, a software prototype is tested to reprocess the data. It dramatically shortens the data treatment and offers good quantitative results.     

Interpretation of the real plate number concept: A fundamental analysis

The real plate number concept is interpreted in terms of the fundamental properties of a chromatograph. It is shown that the linear relationship between the total peak width at half height, (b_0.5)T, t, and k is only an approximation of the more general linear relationship between (b_0.5)²T, t and (1 + k)². In the case where the relationship between (b_0.5)T, t and k approaches linearity, it is concluded, firstly, that b₀ = a, i. e., b₀ is a column property and independent of extra-column phenomena and, secondly, that n_real=n_theor. When the relationship becomes non-linear, b₀ is determined partly by extra-column phenomena, but not in terms of a useful relationship. It is concluded that it is unnecessary to introduce the parameters a, b₀ and n_real, since they all have counterparts in the established theory of chromatography. These counterparts prove to be equally useful in the practical analysis of chromatographic systems.