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Analytical and Bioanalytical Chemistry (v.379, #4)

12th Conference on Solid State Analysis by Gernot Friedbacher (pp. 545-546).

Microstructure and composition of annealed Al/Ti-metallization layers by M. Hofmann; T. Gemming; K. Wetzig (pp. 547-553).

Al/Ti multilayers with columnar grains were deposited by electron-beam evaporation on piezoelectric LiNbO₃ substrates. After annealing in air and under vacuum conditions dissolution of the Ti interlayer was observed for all samples. The original Ti interlayer dissolved completely and globular Al₃Ti grains were formed within an Al matrix. All samples had an oxidized adhesive Ti bottom layer and a 10 nm thin Al layer below this adhesive Ti bottom layer, which remains intact after the applied heat treatment. This resistance against dissolution by interdiffusion could be caused by the oxidation. These changes in the microstructure and in the chemical composition were investigated by conventional and analytical TEM.

Keywords: Al/Ti multilayers; Phase formation at annealing; TEM; EFTEM; Surface-acoustic-wave devices

Niobium nitride films formed by rapid thermal processing (RTP): a study of depth profiles and interface reactions by complementary analytical techniques by A. Berendes; O. Brunkahl; C. Angelkort; W. Bock; F. Hofer; P. Warbichler; B. O. Kolbesen (pp. 554-567).

The nitridation of niobium films approximately 250 and 650 nm thick by rapid thermal processing (RTP) at 800 °C in molecular nitrogen or ammonia was investigated. The niobium films were deposited by electron beam evaporation on silicon substrates covered by a 100 or 300 nm thick thermally grown SiO₂ layer. In these investigations the reactivity of ammonia and molecular nitrogen was compared with regard to nitride formation and reaction with the SiO₂ substrate layer. The phases formed were characterized by X-ray diffraction (XRD). Depth profiles of the elements in the films were recorded by use of secondary neutral mass spectrometry (SNMS). Microstructure and spatial distribution of the elements were imaged by transmission electron microscopy (TEM) and energy-filtered TEM (EFTEM). Electron energy loss spectra (EELS) were taken at selected positions to discriminate between different nitride, oxynitride, and oxide phases. The results provide clear evidence of the expected higher reactivity of ammonia in nitride formation and reaction with the SiO₂ substrate layer. Outdiffusion of oxygen into the niobium film and indiffusion of nitrogen from the surface of the film result in the formation of oxynitride in a zone adjacent to the Nb/SiO₂ interface. SNMS profiles of nitrogen reveal a distinct tail which is attributed to enhanced diffusion of nitrogen along grain boundaries.

Keywords: Niobium nitride; Oxynitride; Nitridation; Rapid thermal processing (RTP); Interface reaction (Nb/SiO₂); SNMS depth profile; TEM/EELS

Comparison of the annealing behavior of thin Ta films deposited onto Si and SiO₂ substrates by R. Hübner; M. Hecker; N. Mattern; V. Hoffmann; K. Wetzig; H.-J. Engelmann; E. Zschech (pp. 568-575).

Structural changes at annealing temperatures (T _an) of 500–1,100°C were investigated for thin Ta films which were sputter-deposited onto pure Si substrates and onto thermally oxidized Si. In the as-deposited state, the Ta layers predominantly consist of metastable tetragonal β-Ta, whereby the [001] texture is independent of the substrate material. At lower annealing temperatures, the microstructural evolution is essentially the same for both Ta films. Incorporation of O atoms causes an increase of the intrinsic compressive stress, and diffusion of C atoms into the Ta layer leads to the formation of Ta₂C. Additionally, a partial transformation of the original β-Ta phase into a second phase with tetragonal unit cell (denoted as β′-Ta) occurs. For the Ta/Si system, the formation of a Ta–Si intermixing layer is initiated at T _an=550°C, and nucleation of crystalline TaSi₂ occurs at T _an=620°C. The formation of a second Ta silicide was not detected up to T _an=900°C. In the case of the Ta film deposited onto the SiO₂ substrate, the metastable β-Ta and the β′-Ta transform completely into the thermodynamically stable cubic α-Ta at T _an=750°C. A marked reaction with the substrate indicated by the formation of Ta₂O₅ and Ta₅Si₃ occurs at T _an=1,000°C.

Keywords: Ta films; Diffusion barriers; X-ray diffraction; Glow discharge optical emission spectroscopy; Transmission electron microscopy

Analytical investigations of tunnel magnetoresistance layers by Jürgen Thomas; Rainer Reiche; Hartmut Vinzelberg (pp. 576-581).

The basic elements of tunnel magnetoresists are two magnetic layers separated by an insulating barrier layer. The uniformity of this only 1–2 nm thick barrier layer up to dot edges and the chemical composition of the layers are properties important for the efficiency of tunnel magnetoresistance devices. These key-properties have been investigated by analytical TEM methods like high resolution TEM imaging and energy-filtered imaging. With regard to the chemical composition the TEM results have been confirmed by XPS investigations. The subsequent oxidation of the barrier is one of the most critical steps of the deposition procedure of the layer stacks. An undersized oxygen dose leads to an incomplete oxidation of the barrier layer with uncontrollable tunnel behaviour. An overdose of oxygen leads to oxygen diffusion in the layers beneath the barrier and uncontrollable magnetic hardness of the lower magnetic electrode.

Keywords: Tunnel magnetoresistance (TMR); Analytical TEM; XPS; Quality of the tunnel barrier

Direct observation of reconstruction induced changes of surface stress for Sb on Si(111) by P. Kury; P. Zahl; M. Horn-von Hoegen (pp. 582-587).

With the combination of high resolution low energy electron diffraction and a bending sample technique we have simultaneously studied surface stress and surface structure during adsorption and desorption of antimony on the Si(111) surface. During desorption, several surface reconstructions with significantly different effects on the stress signal evolve. The surface stress of all observed structures has been obtained.

Keywords: Stress; Si(111); Antimony; SSIOD; SPA-LEED

Characterizing single crystal surfaces using high resolution electron diffraction by D. Thien; F.-J. Meyer zu Heringdorf; P. Kury; M. Horn-von Hoegen (pp. 588-593).

Characterization and controlled manipulation of surfaces is a crucial factor in modern processing of the technologically relevant Si(100) surface. Using spot profile analyzing low energy electron diffraction, the morphological changes from a single stepped vicinal Si(100) surface to a single-domain (2×1) reconstructed surface have been investigated in situ during Si deposition. The temperature range for formation of this kinetically-stabilized single-domain surface was found to be 400–500 °C. This single-domain surface could be preserved for further characterization and experiments after quenching to room temperature.

Keywords: Si(100); Electron diffraction; Epitaxy; Reconstruction; SPA-LEED

Surface acoustic waves for the characterization of BN-coated fibres observed by Brillouin light scattering by T. Wittkowski; K. Jung; B. Hillebrands; S. Stöckel; K. Weise; G. Marx (pp. 594-598).

The observation of acoustic phonons located at the surface of uncoated fibres or guided in thin films deposited on fibres by Brillouin light scattering spectroscopy (BLS) is reported. The BLS technique is non-destructive and non-intrusive and is well applicable to non-planar sample geometries. Investigations were carried out on bundles of commercially available carbon fibres, in which a single fibre was 5 μm in diameter. With regard to the detected surface acoustic excitations, each fibre can be considered as an infinite halfspace owing to the large ratio of fibre diameter to wavelength. The shear modulus, which is highly relevant for the intended technical application, was determined by measurement of the Rayleigh mode phase velocity of the uncoated fibres. These fibre bundles were coated with boron nitride (BN) in a continuously driven thermal chemical vapour deposition (CVD) process using trimethyl borate and ammonia as precursors. In comparison to carbon, BN is expected to improve the mechanical properties of fibre-reinforced composites such as fracture toughness at high temperatures. The measured velocity dispersion of the Rayleigh mode of this film-on-substrate system permitted the comparison of the shear stiffness of the carbon fibre and of the BN film material. The results evidence the desired effect of a distinct stiffness reduction of the coated fibre relative to the uncoated fibre in the near-surface region. Additional information can be obtained on the homogeneity of the deposition across the whole fibre bundle.

Keywords: Brillouin light scattering; Carbon fibres; Boron nitride; Surface acoustic waves; Elastic constants

Quantitative SIMS depth profiling of diffusion barrier gate-oxynitride structures in TFT-LCDs by Sabine Dreer; Peter Wilhartitz; Kurt Piplits; Karl Mayerhofer; Johann Foisner; Herbert Hutter (pp. 599-604).

Gate oxynitride structures of TFT-LCDs were investigated by SIMS, and successful solutions are demonstrated to overcome difficulties arising due to the charging effects of the multilayer systems, the matrix effect of the method, and the small pattern sizes of the samples. Because of the excellent reproducibility achieved by applying exponential relative sensitivity functions for quantitative analysis, minor differences in the barrier gate-oxynitride composition deposited on molybdenum capped aluminium-neodymium metallisation electrodes were determined between the centre and the edge of the TFT-LCD substrates. No differences were found for molybdenum-tungsten metallisations. Furthermore, at the edge of the glass substrates, aluminium, neodymium, and molybdenum SIMS depth profiles show an exponential trend. With TEM micrographs an inhomogeneous thickness of the molybdenum capping is revealed as the source of this effect, which influences the electrical behaviour of the device.The production process was improved after these results and the aging behaviour of TFT-LCDs was investigated in order to explain the change in control voltage occurring during the lifetime of the displays. SIMS and TEM show an enrichment of neodymium at the interface to the molybdenum layer, confirming good diffusion protection of the molybdenum barrier during accelerated aging. The reason for the shift of the control voltage was finally located by semi-quantitative depth profiling of the sodium diffusion originating from the glass substrate. Molybdenum-tungsten was a much better buffer for the highly-mobile charge carriers than aluminium-neodymium. Best results were achieved with PVD silicon oxynitride as diffusion barrier and gate insulator deposited on aluminium-neodymium metallisation layers.

Keywords: SIMS; Quantification; Diffusion; Gate oxynitride

Characterization of the distribution of the sintering activator boron in powder metallurgical steels with SIMS by Dragan Krecar; Vassilka Vassileva; Herbert Danninger; Herbert Hutter (pp. 605-609).

Powder metallurgy is a well-established method for manufacturing ferrous precision parts. A very important step is sintering, which can be strongly enhanced by the formation of a liquid phase during the sintering process. Boron activates this process by forming such a liquid phase at about 1200 °C. In this work, the sintering of Fe–B was performed under the protective atmospheres of hydrogen, argon or nitrogen. Using different grain sizes of the added ferroboron leads to different formations of pores and to the formation of secondary pores. The effect of boron was investigated by means of Secondary Ion Mass Spectrometry (SIMS) supported by Scanning Electron Microscopy (SEM) and Light Microscopy (LM). To verify the influence of the process parameters on the mechanical properties, the microstructure (pore shape) was examined and impact energy measurements were performed.The concentrations of B in different samples were varied from 0.03–0.6 weight percent (wt%). Higher boron concentrations are detectable by EPMA, whereas the distributions of boron in the samples with interesting overall concentration in the low wt% range are only detectable by means of SIMS.This work shows that the distribution of boron strongly depends on its concentration and the sintering atmosphere used. At low concentration (up to 0.1 wt%) there are boride precipitations; at higher concentration there is a eutectic iron–boron grain boundary network. There is a decrease of the impact energy observed that correlates with the amount of eutectic phase.

Keywords: SIMS; Sintering; Activator; Boron; PM

Phosphorus as sintering activator in powder metallurgical steels: characterization of the distribution and its technological impact by Dragan Krecar; Vassilka Vassileva; Herbert Danninger; Herbert Hutter (pp. 610-618).

Powder metallurgy is a highly developed method of manufacturing reliable ferrous parts. The main processing steps in a powder metallurgical line are pressing and sintering. Sintering can be strongly enhanced by the formation of a liquid phase during the sintering process when using phosphorus as sintering activator. In this work the distribution (effect) of phosphorus was investigated by means of secondary ion mass spectrometry (SIMS) supported by Auger electron spectroscopy (AES) and electron probe micro analysis (EPMA). To verify the influence of the process conditions (phosphorus content, sintering atmosphere, time) on the mechanical properties, additional measurements of the microstructure (pore shape) and of impact energy were performed. Analysis of fracture surfaces was performed by means of scanning electron microscopy (SEM). The concentration of phosphorus differs in the samples from 0 to 1% (w/w). Samples with higher phosphorus concentrations (1% (w/w) and above) are also measurable by EPMA, whereas the distributions of P at technically relevant concentrations and the distribution of possible impurities are only detectable (visible) by means of SIMS. The influence of the sintering time on the phosphorus distribution will be demonstrated. In addition the grain boundary segregation of P was measured by AES at the surface of in-situ broken samples. It will be shown that the distribution of phosphorus depends also on the concentration of carbon in the samples.

Keywords: SIMS; AES; PM; Sintering; Activator; Phosphorus

Hardness and phase analysis of IN 718 deformed at high strain rate by L. Renhof; S. Guder; E. Werner (pp. 619-621).

Specimens of the nickel base alloy IN 718 deformed at high strain rate (~10 s⁻¹), as realized in a screw press, have higher strength than parts forged conventionally in a hydraulic press. Microstructure analyses in light and transmission electron microscopes reveal the precipitation of very small Ni₃Nb particles (γ″-phase) to be the reason for the increased hardness. Several processing routes are discussed and analyzed in relation to the TTT-diagram of IN 718.

Keywords: IN 718; Ni₃Nb-precipitation; γ″-phase; Electron microscopy

Ion-beam analysis of CuInSe₂ solar cells deposited on polyimide foil by D. Spemann; M. Lorenz; T. Butz; K. Otte (pp. 622-627).

CuInSe₂ (CIS) solar cells deposited on polyimide foil by the Solarion company in a web-coater-based process using sputter and evaporation techniques were investigated in the ion beam laboratory LIPSION of the University of Leipzig by means of Rutherford backscattering spectrometry (RBS) and particle-induced X-ray emission (PIXE) using high-energy broad ion beams and microbeams. From these measurements the composition of the absorber and the lateral homogeneity and film thicknesses of the individual layers could be determined on the basis of some reasonable assumptions. For the first time, quantitative depth profiling of the individual elements was performed by microPIXE measurements on a beveled section prepared by ion-beam etching of a CIS solar cell. Within the CIS absorber layer no significant concentration–depth gradients were found for Cu, In, and Se, in contrast with results from secondary neutral mass spectrometry (SNMS) depth profiling, which was applied to the same samples for comparison. Furthermore, both PIXE and SNMS showed the presence of a remarkable amount of Cd from the CdS buffer layer in the underlying absorber.

Keywords: CIS thin films; Flexible solar cells; Beveled section; Elemental depth profiling

Statistical evaluation of potash-lime-silica glass weathering by M. Melcher; M. Schreiner (pp. 628-639).

Two potash-lime-silica model glasses with compositions similar to those of medieval stained glass were exposed at 26 test sites all over Europe and in North America for 3–6 years. The objectives of this large-scale field exposure programme were: (a) a qualitative analysis of the weathering products formed on the surface of the samples in the (environmental) scanning electron microscope in combination with energy dispersive X-ray microanalysis (ESEM/EDX or SEM/EDX, respectively); (b) a statistical evaluation of the weathering phenomena by applying a multiple linear regression (MLR) analysis to find correlations between the degree of weathering, which was measured in terms of surface coverage with reaction products, and environmental parameters such as the concentration (c) of the acidifying gases SO₂, NO₂ and O₃, the temperature (T) and the relative humidity (RH); and (c) the calculation of a time-dependence function of the weathering process of these glasses. Mainly sulfates of calcium and potassium such as gypsum (CaSO₄·2 H₂O), arcanite (K₂SO₄) and syngenite (CaSO₄·K₂SO₄·H₂O) could be identified in the SEM and ESEM. Carbonates, nitrates and many particles deposited on the glass surface were found as well. MLR calculations exhibit significant dependencies of the degree of weathering on T, RH, c(NO_x), c(SO₂) and c(O₃). Applying a time-dependence function of the general form y=a·t b (t=time) results in a value of approximately 0.42 for the exponent b, which comes close to values expected from various studies in the literature.

Keywords: Potash-lime-silica (PLS) glass; Scanning electron microscopy (SEM); Environmental scanning electron microscopy (ESEM); Leaching; Multiple linear regression (MLR); Glass corrosion; Glass weathering

Qualitative and quantitative determination of micro-inclusions by automated SEM/EDX analysis by Markus Nuspl; Wolfhard Wegscheider; Johann Angeli; Wilhelm Posch; Michael Mayr (pp. 640-645).

With the help of an automated SEM/EDX analysis system non-metallic micro-inclusions in steel can be detected on a metallographically prepared surface area. The system makes it possible to determine position, size, shape and composition of each particle. Usually more than 1000 inclusions are found on one scan area. Therefore a new offline evaluation method has been developed to classify the large amount of inclusions and calculate specific size and shape data. A summary sheet is created to show the area contents and the mean values of all important properties for each class. Size and XY distributions as well as binary and ternary phase diagrams are drawn to depict the results. The strengths of this analytical technique are demonstrated by evaluation of an LC (low-carbon) steel. Alumina, common spinel, sulfide and oxisulfide inclusions could be identified as dominant inclusion types in LC steel.

Keywords: Automated SEM/EDX analysis; Non-metallic inclusion; Micro-inclusion; LC steel

Characterization of the adsorption of ω-(thiophene-3-yl alkyl) phosphonic acid on metal oxides with AR-XPS by Barbara Adolphi; Evelin Jähne; Gernot Busch; Xuediao Cai (pp. 646-652).

The aim of the work discussed in this paper was to characterize adsorbed self-assembled monolayers on different metal oxide substrates with angle-resolved XPS measurements. The substrates used were silicon wafers (100) coated with 300 nm Al, Ta, or Ti. They were coated with acids by immersing them in an ethanol solution. The orientation of long-chain organic acids adsorbed on metal oxides has been successfully identified by angle-resolved XPS. On Al, Ta, and Ti substrates, C₁₁ chains are orientated in the right manner, i.e. with the phosphonic group at the bottom and the thiophene group on top. The orientations of the C₂ and C₆ chains are not clear. The thickness of the layers could be obtained by using Tougaard nanostructure analysis, and it shows monolayers. A model of the chemical bonds between the phosphonic group and the metal could be developed from the chemical shift. For titanium, all three P–O bonds bind to the metal substrate, whereas only the P–O(H) bond binds to the metal on aluminium and tantalum.

Keywords: XPS; Chemical shift; Self assembled monolayer; Phosphonic acid

Low-temperature investigation of the growth mechanism of alkylsiloxane self-assembled monolayers by A. Glaser; J. Foisner; G. Friedbacher; H. Hoffmann (pp. 653-657).

The growth behavior of self-assembled monolayer films strongly depends on parameters such as solvent, water concentration in the solvent, substrate type, and deposition method. A further parameter, the temperature, is of particular importance. It has been found that growth kinetics, size, and shape of the structures obtained strongly depend on the deposition temperature. Thus, exact adjustment and control of the solution temperature is of crucial importance for investigation of deposition mechanisms. The development of a temperature control unit has been the basis for a series of experiments on deposition of octadecyltrichlorosilane (OTS) on silicon wafers to study the influence of temperature on growth kinetics and film structure. Characterization of the films was performed with ellipsometry and atomic-force microscopy. It has been found that octadecylsiloxane (ODS) island sizes decrease with increasing temperature. Furthermore, a characteristic temperature exists above which increasingly disordered deposition occurs. At low temperatures (5–10 °C) smaller dot-like features are observed besides larger fractally shaped islands characteristic for self-assembly growth of ODS films. Our results indicate that these small dot-like features originate from ordered aggregates in the adsorption solution and that they are the precursors of the formation of larger islands. However, they can only be observed at low temperatures, because at room temperature they coalesce quickly to form larger units, due to the high surface mobility.

Keywords: Self-assembly; Alkylchlorosilane; Silicon; Atomic force microscopy; Low temperature

A radiofrequency glow-discharge-time-of-flight mass spectrometer for direct analysis of glasses by Jorge Pisonero; José Manuel Costa; Rosario Pereiro; Nerea Bordel; Alfredo Sanz-Medel (pp. 658-667).

A radiofrequency (rf) glow-discharge (GD) ion source coupled to a commercial on-axis time-of-flight mass spectrometer (TOFMS) has been developed for the direct analysis of non-conducting samples. Different instrumental configurations of the rf-GD source, including the optional use of a sampler cone and the possibility of allowing electrical floating of the discharge, were evaluated first with a conducting sample. Higher ion signals were obtained when the GD was electrically floating and no sampler cone was used. A homogeneous glass was then analyzed using two different rf-GD configurations—with a sampler cone and discarding the use of the sampler cone. The atomic mass spectra obtained with the TOFMS using both configurations were compared. Analyte signals were systematically higher for the latest mode which avoids the sampler cone. The analytical capability of the proposed rf-GD–TOFMS system for the analysis of thick glasses, up to 6 mm, has been investigated in terms of sensitivity, isotopic ratio accuracy, and mass-resolving power. Different homogeneous glasses (including glasses as thick as 6 mm) have been analyzed and major and minor elements were detected. Isotope ratio accuracies of about ±1% and mass resolving powers of about 700 were observed.

Keywords: Radiofrequency glow discharge ; Time-of-flight mass spectrometry; Direct solid analysis; Elemental analysis; Glass

Rapid molecular typing of Tuber melanosporum, T. brumale and T. indicum from tree seedlings and canned truffles by J. P. Douet; M. Castroviejo; D. Mabru; G. Chevalier; C. Dupré; F. Bergougnoux; J. M. Ricard; B. Médina (pp. 668-673).

We have developed new DNA extraction and purification procedures for investigation of mycorrhized seedlings and canned truffles. Use of these procedures on approximately 100 mg initial material enabled good sample representation. For mycorrhized seedlings, Taq polymerase inhibitors were discarded irrespective of tree species. In routine analysis we systematically used consensus primers ITS1/ITS4 to check the absence of Taq polymerase inhibitors and the presence of fungus DNA. Positive response with ITS validates other positive or negative PCR results. Absence of amplification with ITS prevents validation of other results. For canned truffles, DNA harvested from ascocarps sterilized for one and a half hours at 115°C was amplified with specific primers. We have developed consensus primers, named R12/F12, to check for the presence of amplifiable fungus DNA and the absence of Taq polymerase inhibitors. Here also, positive response with consensus R12/F12 validates other positive or negative PCR results. We have developed one primer pair specific for T. brumale and another specific for T. melanosporum. We can then characterize these two taxa, which enables the use of “truffle or truffled” French designations. We can also characterize T. indicum, the Asiatic black truffle that might fraudulently be sold as T. melanosporum and T. brumale. These three specific primer pairs were used independently of DNA extraction from tree seedlings or canned truffles. Our process is specific, sensitive, convenient, and quick.

Keywords: Tuber ; Tuber melanosporum ; T. brumale ; T. indicum ; Black truffles; Chinese truffles; Process control; PCR

Micro-Raman analysis of coloured lithographs by K. Castro; P. Vandenabeele; M. D. Rodríguez-Laso; L. Moens; J. M. Madariaga (pp. 674-683).

Raman micro-spectroscopy was chosen for analysis and identification of the pigments present in four nineteenth-century hand-coloured lithographs, as this technique has several advantages over others for this purpose. The possibility of performing completely non-destructive analysis without any sampling is probably one of its most favourable qualities for art analysis. Raman spectroscopy can also be used to determine some pigments that cannot be detected using FTIR, such as vermilion, carbon blacks, cadmium pigments, etc. Among others, Prussian blue, ultramarine blue, carbon black, chrome yellow, yellow ochre, red lead, red iron oxide, burnt Sienna, indigo blue, chrome orange, phthalocyanine green, and some other organic pigments, were determined in the specimens. The results obtained have led to doubts about the age of the lithographs.

Keywords: Raman; Microscopy; Lithographs; Pigments; Becquet freres; Forgery

Study of traffic pollution by metals in Seville (Spain) by physical and chemical speciation methods by A. J. Fernández-Espinosa; M. Ternero-Rodríguez (pp. 684-699).

Eighty-three samples of atmospheric particles were collected at a representative traffic site in the Mediterranean city of Seville during a period of one year. Urban particles were collected on quartz filters with a high-volume sampler coupled with a cascade impactor which separates particles into six size ranges: >10, 10–4.9, 4.9–2.7, 2.7–1.3, 1.3–0.6, and <0.6 μm. The total metal content, its distribution by size (physical speciation), and the concentrations of different chemical forms (chemical speciation) in particles less than 0.6 μm were determined. The chemical speciation scheme furnished four fractions: soluble and exchangeable metals; carbonates, oxides, and reducible metals; oxidisable and sulfidic metals bound to organic matter; and residual metals. The samples were analysed by ICP–OES for Pb, Ni, Cd, S, Fe, Zn, Cu, Ba, Mn, and V. Gaseous pollutants, traffic intensities, and primary meteorological data provided by the atmospheric and traffic networks were statistically related to the analytical data. Analytical and statistical results from physical and chemical speciation singled out Ba as a valid tracer of vehicular traffic, instead of Pb, in cities with high traffic density. Another important relationship was found between Pb and Cu. Physical speciation of lead showed that the major risk for health was from fine particles less than 2.7 μm, because particles between 2.7 and 0.6 μm were the size fractions of the total suspended particles with the major mass abundance of lead (mainly particles between 2.7 and 1.3 μm) and because particles less than 0.6 μm were the fraction of airborne particles most abundant in the urban air. Chemical speciation results showed that special attention must be taken with Ni and Cd concentrations, because of their high potential bioavailability, mainly a result of the high solubility of the chemical forms of Ni in the finest particles.

Keywords: Heavy metals; Airborne particles; Traffic pollution; Analytical characterisation; Chemical speciation; Size fractionation

Mercury-free sono-electroanalytical detection of lead in human blood by use of bismuth-film-modified boron-doped diamond electrodes by Jaanus Kruusma; Craig E. Banks; Richard G. Compton (pp. 700-706).

We report the electroanalytical determination of lead by anodic stripping voltammetry at in-situ-formed, bismuth-film-modified, boron-doped diamond electrodes. Detection limits in 0.1 mol L^–1 nitric acid solution of 9.6x10⁻⁸ mol L^–1 (0.2 ppb) and 1.1x10⁻⁸ mol L^–1 (2.3 ppb) were obtained after 60 and 300 s deposition times, respectively. An acoustically assisted deposition procedure was also investigated and found to result in improved limits of detection of 2.6×10⁻⁸ mol L^–1 (5.4 ppb) and 8.5×10⁻¹⁰ mol L^–1 (0.18 ppb) for 60 and 300 s accumulation times, respectively. Furthermore, the sensitivity obtained under quiescent and insonated conditions increased from 5.5 (quiescent) to 76.7 A mol^–1 L (insonated) for 60 s accumulation and from 25.8 (quiescent) to 317.6 A mol^–1 L (insonated) for 300 s accumulation. Investigation of the use of ultrasound with diluted blood revealed detection limits of the order of 10⁻⁸ mol L^–1 were achievable with excellent inter- and intra-reproducibility and sensitivity of 411.9 A mol^–1 L . For the first time, electroanalytical detection of lead in diluted blood is shown to be possible by use of insonated in-situ-formed bismuth-film-modified boron-doped diamond electrodes. This method is a rapid, sensitive, and non-toxic means of clinical sensing of lead in whole human blood.

Keywords: Bismuth film; Blood; Anodic stripping voltammetry; Lead; Ultrasound

Effect of Cu(II) on the electrochemically initiated reaction of thiols with N,N-diethyl-p-phenylenediamine: methodology for the indirect voltammetric determination of Cu(II) by Jessica A. Kershaw; Olga Nekrassova; Craig E. Banks; Nathan S. Lawrence; Richard G. Compton (pp. 707-713).

The effect of Cu(II) on the determination of homocysteine via its electrochemically initiated reaction with N,N-diethyl-p-phenylenediamine is examined. The presence of copper inhibited the detection process for homocysteine owing to a complexation reaction occurring. This provided an indirect route for the sensitive and selective determination of Cu(II), which produced a linear response over the range from 2.5 to 500 μM and a limit of detection of 2.5 μM. The detection pathway was examined in the presence of metallic and inorganic ions, with negligible interference observed.

Keywords: N,N-Diethyl-p-phenylenediamine; Homocysteine; Copper; Complexation; Electrochemistry

An improved transmutation method for quantitative determination of the components in multicomponent overlapping chromatograms by Xueguang Shao; Zhengliang Yu; Chaoxiong Ma (pp. 714-719).

An improved method is proposed for the quantitative determination of multicomponent overlapping chromatograms based on a known transmutation method. To overcome the main limitation of the transmutation method caused by the oscillation generated in the transmutation process, two techniques—wavelet transform smoothing and the cubic spline interpolation for reducing data points—were adopted, and a new criterion was also developed. By using the proposed algorithm, the oscillation can be suppressed effectively, and quantitative determination of the components in both the simulated and experimental overlapping chromatograms is successfully obtained.

Keywords: Transmutation; Resolution; Overlapping chromatogram; Wavelet transform

Estimation of uncertainty in pK _a values determined by potentiometric titration by Eve Koort; Koit Herodes; Viljar Pihl; Ivo Leito (pp. 720-729).

A procedure is presented for estimation of uncertainty in measurement of the pK _a of a weak acid by potentiometric titration. The procedure is based on the ISO GUM. The core of the procedure is a mathematical model that involves 40 input parameters. A novel approach is used for taking into account the purity of the acid, the impurities are not treated as inert compounds only, their possible acidic dissociation is also taken into account. Application to an example of practical pK _a determination is presented. Altogether 67 different sources of uncertainty are identified and quantified within the example. The relative importance of different uncertainty sources is discussed. The most important source of uncertainty (with the experimental set-up of the example) is the uncertainty of pH measurement followed by the accuracy of the burette and the uncertainty of weighing. The procedure gives uncertainty separately for each point of the titration curve. The uncertainty depends on the amount of titrant added, being lowest in the central part of the titration curve. The possibilities of reducing the uncertainty and interpreting the drift of the pK _a values obtained from the same curve are discussed.

Keywords: Measurement uncertainty; Sources of uncertainty; ISO; Eurachem; Dissociation constants; pK _a ; pH

Fluorescence enhancement method for measuring anionic surfactants with a hydrophobic cyanine dye by Chang-Qing Zhu; Yu-Qin Wu; Hong Zheng; Jin-Long Chen; Shu-Juan Zhuo; Yong-Xin Li (pp. 730-734).

A novel fluorimetric method based on use of a hydrophobic cationic cyanine dye has been developed for determination of the anionic surfactant sodium dodecylbenzenesulfonate (DBS). The method is based on the enhancement effect of DBS on the fluorescence of the hydrophobic cyanine dye 2-[-4′-chloro-7′-(1′′-ethyl-3′′,3′′-dimethylindolin-2′′-ylidene)-3′,5′-(propane-1′′′,3′′′-diyl)-1′,3′,5′-heptatrien-1′-yl]-1-ethyl-3,3-dimethyl-3H-indolium iodide. Under the optimum conditions the extent of fluorescence enhancement is proportional to the concentration of DBS in the range 0.05–5.0 mg L^–1; the detection limit is 0.014mg L^–1. The relative standard deviation for 0.35 mg L^–1 DBS was 1.1% (n=10). The proposed method, which avoided use of toxic solvents and tedious solvent-extraction, and was applied to the determination of DBS in natural water with recoveries between 99.9 and 107%. Preliminary research shows that the fluorescence enhancement is due to the formation of a dye aggregate facilitated by DBS.

Keywords: Fluorimetric method; Sodium dodecylbenzenesulfonate (DBS); Hydrophobic cyanine dye

Identification of steel by X-ray fluorescence analysis with a pyroelectric X-ray generator by Hiroyuki Ida; Jun Kawai (pp. 735-738).

An application of X-ray fluorescence analysis with a pyroelectric X-ray generator is presented. Steel standard samples were identified by X-ray fluorescence analysis with this novel X-ray generator to check its capability for performing qualitative and quantitative analysis as an X-ray source for X-ray fluorescence spectrometers. Cr, Ni, V, Co, and W were detected in steel standard samples. V and Cr can be detected even when the content is below 1%. Although it is difficult to detect minor elements because of the low power of the excitation X-rays, it is possible to identify the analyzed samples on the basis of major elements at the percentage level. The pyroelectric X-ray generator is very suitable for portable X-ray fluorescence spectrometers.

Keywords: X-ray fluorescence analysis; Pyroelectric crystal; X-ray generator; Steel

LC-APCI-MS-MS methodology for determination of glybenclamide in human plasma by Mirian R. L. Moura; Gilberto de Nucci; Susanne Rath; Felix G. R. Reyes (pp. 739-740).

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Analytical and Bioanalytical Chemistry (v.379, #4)

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Analytical and Bioanalytical Chemistry (v.379, #4)