Analytical investigation of plasma-treated carbon fibres.

As-grown and heat-treated vapour grown carbon fibres (VGCF) in the as-prepared state, washed in HCl/H(2)O, and treated in O(2) plasma for different periods have been investigated by means of XPS and scanning electron microscopy (SEM). The surface energy of the carbon fibres before and after plasma treatment was determined from the wetting contact angle. Washing introduced hydroxyl, carbonyl and carboxyl groups onto the fibre surfaces and oxygen plasma treatment increases the total atomic concentration of oxygen up to 17%. This is in good agreement with the value of the polar component of the surface energy. Plasma treatment also enhanced the fibre surface porosity (by etching).

Unexpected surface chemistry in capillaries for electrophoresis.

Good and reproducible capillary quality is needed to develop robust methods and to facilitate method transfer in CE. Physical surface defects no longer play a major role in variability of fused-silica capillaries. Nevertheless, problems are frequently being reported when buffers in the pH range between 4 and 7 are used. Thus the surface chemistry has been studied by X-ray photoelectron spectroscopy. Silicon-carbon bindings have been found on inner capillary surfaces for electrophoresis. This binding type is not completely removed by pre-conditioning with 1 M NaOH for 30 min. This corresponds to the result, that capillaries provide more stable migration times, especially in the pH range 4-7, when they are pre-conditioned for longer than 1 h. The origin of this Si-C bond is still not quite clear. They could be caused by graphite which is used during the fabrication of the raw cylinders prior to capillary drawing. Further investigations are intended in order to understand if there are any differences in surface carbon content from batch to batch and if this can influence experimental results in CE. A better understanding of the surface chemistry should not only improve robustness in CE, but also help to facilitate and accelerate capillary pre-conditioning and rinsing procedures to remove strongly adsorbed analytes or matrices.

The nature of oxygen in sporopollenin from the pollen of Typha angustifolia L.

Native and peracetylated sporopollenin from the pollen of Typha angustifolia L. was investigated using several spectroscopic methods, inducing Fourier transform infrared spectroscopy (FTIR), solid-state 13C-nuclear magnetic resonance spectroscopy (13C-NMR) and X-ray photoelectron spectrometry (XPS). Interpretation of the experimental data shows that the greater part of oxygen found in sporopollenin originates from hydroxyl groups and must be derived from aliphatics and not from aromatics. This result indicates that not only aromatics and long unbranched aliphatics but also poly-hydroxyl aliphatic components are involved in the complex structure of the polymer. Furthermore, it is most probable that the monomers of the sporopollenin skeleton are linked by ether- and not by ester-linkage. Two possible approaches are suggested for the characterisation of sporopollenin structure.

Structural and elemental investigations of isolated aquatic humic substances using X-ray photoelectron spectroscopy.

Structural and elemental investigations of aquatic humic substances (HS) by means of X-ray photoelectron spectroscopy (XPS) are described. For that purpose small amounts (10-50 microg) of dissolved reference HS, which were characterized within the German research program DFG-ROSIG, were dried as thin films on small pieces of a high-purity silicon wafer. The photoelectrons from such HS layers exhibited characteristic signals of carbon C1s, nitrogen N1s, oxygen O1s and sulfur S2s, which could be fitted by Gaussian curves and used for the quantification of various moieties of HS: carbon (C-C, C-O, C=O, O=C-O), oxygen (C-O, C=O), nitrogen (C-N, C-N+) and sulfur. Moreover, by adding up the element signals of the HS samples their elemental composition of C, O, N and S was assessed. A comparison of the data based on solution state NMR and conventional elementary analysis revealed a satisfactory accuracy with those obtained by XPS.

Quantitative Auger electron spectrometric depth profile analysis of binary alloy reference materials.

Using AES/sputtering, the binary alloy systems Ag/Cu, Ni/Cr and Pb/Sb ranging from 0 to 100% have been studied experimentally with respect to the shape of the calibration curve. The signal intensities are modified by the composition of the matrix. A formal description of the calibration line by a two-parameter approach is derived, including the matrix effect factors. This approach fits well all the experimental data. The significance of the individual matrix effects in these systems is indicated.

Comparative investigation on copper oxides by depth profiling using XPS, RBS and GDOES.

Depth profiling has been performed by using X-ray photoelectron spectrometry (XPS) in combination with Ar-ion sputtering, Rutherford backscattering spectrometry (RBS) and glow discharge optical emission spectrometry (GDOES). The data obtained by XPS have been subjected to factor analysis in order to determine the compositional layering of the copper oxides. This leads to two or three relevant components within the oxide layers consisting of Cu(2)O or CuO dependent on the sample preparation. GDOES measurements show sputtering profiles which are seriously influenced by a varying sputter rate. To ensure the results obtained so far, RBS measurements of the oxide layers have been carried out in order to discover artefacts of the other methods used and to demonstrate the excellent suitability of RBS for quantitative analysis of these layers. Chemical analysis consisting of (1) carrier-gas fusion analysis (CGFA) and (2) selective dissolution of Cu(2)O/CuO allows the determination of the total amount of oxygen and copper, respectively, and can serve as a cornerstone of quantitative analysis.