Werner Faubel

Combined use of molecular biology taxonomy, Raman spectrometry, and ESEM imaging to study natural biofilms grown on filter materials at waterworks

DNA-based population analysis was applied in combination with Raman spectrometry and Environmental Scanning Electron Microscopy for the characterisation of natural biofilms from sand and activated carbon filters operated for a long term at a municipal waterworks. Whereas the molecular biology polymerase chain reaction combined with denaturing gradient gel electrophoresis approach provides a deeper insight into the bacterial biofilm diversities, Raman spectrometry analyses the chemical composition of the extracellular polymer substances (EPS), microorganisms embedded in EPS as well as other substances inside biofilm (inorganic compounds and humic substances). Microscopy images the spatial distribution of biofilms on the two different filter materials. In addition, bacterial bulk water populations were compared with biofilm consortia using the molecular fingerprint technique mentioned. Population analysis demonstrated the presence of more diverse bacterial species embedded in a matrix of EPS (polysaccharides, peptides, and nucleic acids) on the sand filter materials. In contrast to this, activated carbon granules were colonised by reduced numbers of bacterial species in biofilms. Besides alpha-, beta-, and gamma-Proteobacteria, a noticeable specific colonisation with Actinobacteria was found on activated carbon particles. Here, the reduced biofilm formation came along with a decreased EPS synthesis. The taxonomy profiles of the different biofilms revealed up to 60% similarity on the same filter materials and 32% similarity of different materials. Similarity of adherent communities from filter materials and bulk water populations from the filter effluent varied between 36% and 58% in sand filters and 6-40% in granular activated carbon filters. The biofilm investigation protocols are most crucial to subsequent acquisition of knowledge on biofilm dynamics and bacterial contributions to transformation or adsorption processes in waterworks facilities.

Optimization of Instrumental Parameters of a Near-Field Thermal-Lens Detector for Capillary Electrophoresis

The optical scheme of a near-field dual-beam mode-mismatched thermal-lens detector for capillary electrophoresis with a crossed-beam configuration employing a multimode HeCd laser (325 nm) as an excitation source was optimized. It is shown that a multimode laser can be successfully used as an excitation source in thermal lensing with minimal deviations in thermal responses from Gaussian excitation sources. An equation for diffraction thermal-lens theory for near-field measurements is deduced, and the experimental results agree with the deduced equation. The temperature rise in the capillary was estimated, and the exponential decrease of the signal with time for static conditions and low flow velocities was explained. The optimum configuration of the detector from the viewpoint of the maximum sensitivity and beam sizes was found. The detector provides a significant improvement in the detection limits for model compounds absorbing at 325 nm (nitrophenols) compared to the results obtained with a commercial absorbance detector operating at the same wavelength.

Protrusions in a painting by Max Beckmann examined with confocal μ-XRF

Max Beckmanns “Pierrette und Clown” (Pierrette and Clown), 1925, is undoubtedly one of the major works in the collection of the Kunsthalle Mannheim, Germany. In this painting, damages can be seen, described as protrusions. These are blisters and crater-like holes, filled with metallic soap aggregates. Painting samples and cross-sections of the ground layer have been examined by environmental scanning electron microscopy (ESEM) and by confocal synchrotron radiation micro-X-ray fluorescence (CSRμXRF) in order to get compositional and spatial distribution information about the components and their behaviour. The analyzed samples of the unpainted ground layer consist of lithopone (ZnS·BaSO4), as several bulges resembling small blisters, presumably protrusions in the nascent state. Direct CSRμXRF measurements on closed blisters showed that these blisters have a high concentration of zinc in the centre with surrounding layers of barium and strontium. Relatively small amounts of lead have been recorded. In order to determine the composition of the organic compounds (e.g.fatty acids) and of the inorganic pigments (lead white, zinc white, lithopone), Raman spectroscopy has been successfully applied to flakes of an opened protrusion. The obtained Raman spectra could be assigned to derivatives of fatty acids and lithopones. These results allow conclusions to be made about the chemical behaviour by measuring the identical sample spot of the protrusion with CSRμXRF as well as Raman spectroscopy.

Indirect thermal lens detection for capillary electrophoresis

Thermal lens detection with a 325.0nm He-Cd excitation laser is used for thermooptical indirect detection in combination with the capillary electrophoretic separation of organic anions. The optimization of indirect thermooptical detection is discussed. With Mordant Yellow 7 (an azo dye) chosen as a probe ion limits of detection for 1-heptane-, 1-pentane-, 1-butane-, 1-propanesulfonic, and acetic acid at a level of nx10(-7)M were achieved with a separation electrolyte containing 50muM of the probe ion and 5mM Tris pH 9.90. A further increase in the detection sensitivity (twofold decrease in the limit of detection ) was obtained with a separation electrolyte containing a volume fraction of 20% acetonitrile.

Investigation of ionene adsorption on quartz surfaces by thermal-lens spectrometry

Thermal-lens spectrometry was used for the investigation of the adsorption of ionene to quartz surfaces. The thermooptical analysis of the surface makes it possible to distinguish the modified surface from a clean quartz surface and to provide sensitive direct concentration measurements of the light absorbing co-adsorbed substance. The co-adsorption of chromate ions and 2,10-ionene from aqueous solutions to quartz surfaces was investigated and the desorption procedure proposed.

Photothermal trace detection in capillary electrophoresis for biomedical diagnostics and toxic materials (invited)

Two applications of a near-field thermal lens capillary electrophoresis detector in the deep ultraviolet region (pump beam 257 nm wavelength) will be presented: (1) Capillary electrophoretic determination of the pharmaceuticals Tramadol, Verapamil, and Papaverin. Direct separation techniques were used for the different classes of substances with characteristic absorbance spectra. The combination of capillary electrophoresis and the highly sensitive detection with thermal lens spectroscopy permits the analysis of nanoliter volume samples common in biomedical diagnostics without any preconcentration step. (2) The determination of (nonfluorescent) nitro aromatic explosives in contaminated soil. These compounds are detected with the laboratory built thermal lens detector after their separation by micellar electrokinetic chromatography. Its shown that this type of detection makes it possible to obtain limits of detection 1–2 orders of magnitude lower than those obtained with classical absorption spectrometric ...

Photoacoustic FT-IR Spectroscopy of Natural Copper Patina

Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS) has proved to be a useful tool for nondestructive testing of copper corrosion layer (patina) formed in the atmosphere. The samples cut from a piece of the roof of the Stockholm City Hall were examined without any additional pretreatment. The components of the patina—brochantite Cu4(OH)6SO4, antlerite Cu3(OH)4SO4, and basic cupric carbonate Cu2CO3(OH)6 · H2O—as well as some other minerals were identified. The photothermal beam deflection (PBD) method was used for independent photoacoustic characterization of the samples. The depth profiling capability of FT-IR/PAS was used to determine the degree of photoacoustic saturation of the spectral bands and to evaluate the depth distribution of the main patina components. The technique thus compares favorably with more common approaches of patina examination which are more expensive and require special sample preparation.

Quantitative analysis of corroded copper patina by step scan and rapid scan photoacoustic Fourier transform infrared spectroscopy

Atmospheric corrosion enhanced by increasing air pollution causes increasing damage at valuable metallic monuments worthy of protection, e.g., the roof of the Stockholm City Hall. To explore the potential use of Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) in quantitative corrosion product analysis, the determination of the chemical composition of copper patina samples formed under atmospheric conditions was studied. As an experimental technique, we used a FTIR spectrometer in combination with sample-gas-microphone PAS using helium as the transfer gas at room temperature. The main components of the different samples—brochantite Cu4SO4(OH)6 and antlerite Cu3SO4(OH)4—were identified by their characteristic vibrational absorption bands. A quantitative analysis of these two components has been performed with rapid- and step-scan FTIR/PAS by using artificially corroded copper samples with differing ratios of composition. From these data, calibration curves were obtained allowing a nondestru...

Determination of light-absorbing layers at inner capillary surface by cw excitation crossed-beam thermal-lens spectrometry

A thermal-lens spectrometric unit suitable for selective quantitative measurements of light-absorbing layers adsorbed onto the inner surface of a quartz glass capillary is described. The quantitative description of the thermal-lens signal generated in a quartz glass capillary with a light-absorbing layer at the inner surface of capillary is developed, which is based on the description for the thermal-lens experiment in the layered solids presented elsewhere. The accuracy of calculations is demonstrated by the comparison of predicted results with the experimental data and those predicted by the conventional theory. The data achieved prove the accuracy of calculations both for the time dependent thermal-lens signal and for the lock-in amplifier signal under variation of the spectrometer configuration for capillaries having an adsorbed layer. The proposed technique is used for the investigation of chromate/2,10-ionene and 4-aminoazobenzene adsorption at capillary walls. The estimates of the minimum light absorption detectable at capillary walls are at a level of 1 x 10(-5) abs. units; the linear range of the thermal-lens signal from the inner surface layer no less than three orders of magnitude is predicted.

Photothermal Deflection Determination of Iron(II) with Ferrozine with Sorption Preconcentration on Silufol Plates

Photothermal deflection spectroscopy was applied to the selective detection of iron(II) chelate with ferrozine by its sorption preconcentration on Silufol plates. The linearity range was 1 × 10−11–6 × 10−8 mol cm−2 of chelate at the plate surface, which corresponded to 1 × 10−9–4 × 10−6 M of chelate in solution. The limits of detection and quantification are 8 × 10−12 and 2.5 × 10−11 mol cm−2 at the plate from 15 μL of test solution (0.5 nM and 1.5 nM in solution, respectively), and the absolute detection limit is 8 fmol in the whole spot applied to a plate. Characteristics and features of photothermal deflection detection are discussed.