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Analytical and Bioanalytical Chemistry (v.382, #8)
Liquid chromatography–electron capture–atmospheric pressure chemical ionization-mass spectrometry
by Uwe Karst (pp. 1744-1746).
Integrating functional components into capillary electrophoresis systems using liquid-core waveguides
by Shi-Li Wang; Zhao-Lun Fang (pp. 1747-1750).
Progress in plasmonic engineering of surface-enhanced Raman-scattering substrates toward ultra-trace analysis by Gary A. Baker; David S. Moore (pp. 1751-1770).
This review describes advances made toward the application of surface-enhanced Raman scattering (SERS) in sensitive analysis and diagnostics. In the early sections of this review we briefly introduce the fundamentals of SERS including a discussion of SERS at the single-molecule level. Applications relevant to trace analysis, environmental monitoring, and homeland security and defense, for example high explosives and contaminant detection, are emphasized. Because the key to wider application of SERS analysis lies in the development of highly enhancing substrates, in the second half of the review we focus our attention on the extensive progress made in designing innovative soluble, supported, and ordered SERS-active nano-architectures to harness the potential of this technique toward solving current and emerging analytical tasks. No attempt or claim is made to review the field exhaustively in its entirety nor to cover all applications, but only to describe several significant milestones and progress made in these important areas and to provide some perspective on where the field is quickly moving.
Keywords: Surface-enhanced Raman scattering; Surface plasmon resonance; Nanoparticles; Nanoshells; Nanostructures; Nanophotonics; Plasmonics; Single-molecule detection
Single-molecule fluorescence detection in microfluidic channels—the Holy Grail in μTAS? by Petra S. Dittrich; Andreas Manz (pp. 1771-1782).
Both single-molecule detection (SMD) methods and miniaturization technologies have developed very rapidly over the last ten years. By merging these two techniques, it may be possible to achieve the optimal requirements for the analysis and manipulation of samples on a single molecule scale. While miniaturized structures and channels provide the interface required to handle small particles and molecules, SMD permits the discovery, localization, counting and identification of compounds. Widespread applications, across various bioscience/analytical science fields, such as DNA-analysis, cytometry and drug screening, are envisaged. In this review, the unique benefits of single fluorescent molecule detection in microfluidic channels are presented. Recent and possible future applications are discussed.
Keywords: Fluorescence spectroscopy; Single-molecule detection; Microfluidics; Cytometry; Lab-on-a-chip
Present and future applications of carbon nanotubes to analytical science by Miguel Valcárcel; Bartolomé M. Simonet; Soledad Cárdenas; Beatriz Suárez (pp. 1783-1790).
This article reviews the impact of carbon nanotubes on analytical science, and the main current and future applications of carbon nanotubes in this field. Given that it is necessary to solubilize carbon nanotubes for many applications, we consider the procedures developed to achieve this. The use of carbon nanotubes in analytical chemistry as a target analyte and as an analytical tool is also discussed. Chromatographic and electrophoretic methods used to separate and characterize carbon nanotubes are presented. The use of carbon nanotubes as an analytical tool in filters and membranes, as sorbent material for solid phase extraction, in electrochemical (bio)sensors, and in separation methods is discussed. It is clear that while nanotubes are being tested for use in many different fields, their truly enormous potential has yet to be realized in analytical chemistry.
Keywords: Carbon nanotubes; Separation and purification techniques; Analytical uses
Analysis of ALD-processed thin films by ion-beam techniques by Matti Putkonen; Timo Sajavaara; Lauri Niinistö; Juhani Keinonen (pp. 1791-1799).
This review introduces the possibilities of ion-beam techniques for the analysis of thin films and thin-film structures processed by atomic layer deposition (ALD). The characteristic features of ALD are also presented. The analytical techniques discussed include RBS, NRA and ERDA with its variants, viz. the TOF-ERDA and HI-ERDA. The thin film examples are taken from flat-panel display technology (TFEL structures) and the semiconductor industry (high-k insulators).
Keywords: Ion-beam techniques; Atomic layer deposition; Thin films; Electroluminescent displays; High-k insulators
Traceability of environmental chemical analyses: can theory match practice? by P. Quevauviller (pp. 1800-1807).
According to the ISO definition, the traceability concept basically implies that measurement data are linked to stated references through an unbroken chain of comparisons, all with stated uncertainties. This concept may be quite clear in theory, but we may wonder how it may be applicable to complex chemical measurements such as environmental chemical analyses in practice. This paper discusses this issue, giving some examples of drawbacks that are being faced in different environmental sectors (water, sediment, soil, biota and particulate atmospheric samples).
Isotope dilution ICP-MS with laser-assisted sample introduction for direct determination of sulfur in petroleum products by Sergei F. Boulyga; Jens Heilmann; Klaus G. Heumann (pp. 1808-1814).
Inductively coupled plasma isotope dilution mass spectrometry (ICP-IDMS) with direct laser-assisted introduction of isotope-diluted samples into the plasma, using a laser ablation system with high ablation rates, was developed for accurate sulfur determinations in different petroleum products such as ‘sulfur-free’ premium gasoline, diesel fuel, and heating oil. Two certified gas oil reference materials were analyzed for method validation. Two different 34S-enriched spike compounds, namely, elementary sulfur dissolved in xylene and dibenzothiophene in hexane, were synthesized and tested for their usefulness in this isotope dilution technique. The isotope-diluted sample was adsorbed on a filter-paper-like material, which was fixed in a special holder for irradiation by the laser beam. Under these conditions no time-dependent spike/analyte fractionation was only observed for the dibenzothiophene spike during the laser ablation process, which means that the measured 34S/32S isotope ratio of the isotope-diluted sample remained constant—a necessary precondition for accurate results with the isotope dilution technique. A comparison of LA-ICP-IDMS results with the certified values of the gas oil reference materials and with results obtained from ICP-IDMS analyses with wet sample digestion demonstrated the accuracy of the new LA-ICP-IDMS method in the concentration range of 9.2 μg g−1 (‘sulfur-free’ premium gasoline) to 10.4 mg g−1 (gas oil reference material BCR 107). The detection limit for sulfur by LA-ICP-IDMS is 0.04 μg g−1 and the analysis time is only about 10 min, which therefore also qualifies this method for accurate determinations of low sulfur contents in petroleum products on a routine level.
Keywords: Isotope dilution mass spectrometry; Laser ablation; Sulfur trace analysis; Petroleum products; Routine method
Fully automated multianalyte determination of different classes of pesticides, at picogram per litre levels in water, by on-line solid-phase extraction–liquid chromatography–electrospray–tandem mass spectrometry by Adamantia A. Kampioti; Ana C. Borba da Cunha; Maria López de Alda; Damià Barceló (pp. 1815-1825).
This paper reports the development of a fully automated method for the multianalyte determination of twenty pesticides belonging to different classes (triazines, phenylureas, organophosphates, anilines, acidic, propanil, and molinate) in natural and treated waters. The method, based on on-line solid-phase extraction–liquid chromatography–electrospray–tandem mass spectrometry, is highly sensitive (limits of detection between 0.004 and 2.8 ng L−1), precise (relative standard deviations between 2.0 and 12.1%), reliable (two selected reaction-monitoring transitions are monitored per compound), rapid (45 min per sample), and simple. The application of this method to the monitoring of the target compounds in a waterworks revealed the presence of the pesticides investigated at concentrations up to 516 and 82 ng L−1 (total pesticide concentration) in river water and ground water, respectively, used as sources, and their gradual removal through the purification process.
Keywords: Pesticides; Water; Analysis; On-line solid-phase extraction; Tandem mass spectrometry; Automation
Sample introduction assisted by compressed air in flame furnace AAS: a simple and sensitive method for the determination of traces of toxic elements by Harald Berndt; Erika Pulvermacher (pp. 1826-1834).
The power of detection of flame AAS for the toxic elements Cd, Hg, Pb and Tl can be improved by 1–2 orders of magnitude by using flame furnace AAS. In flame-furnace AAS, liquid samples are introduced directly into a nickel tube located in the flame, in the simplest case through a ceramic thermospray capillary. Transportation of the samples is achieved by using compressed air only. Comparatively low detection limits are achieved by both beam injection flame furnace (BIFF-AAS) and thermospray flame furnace AAS (TS-FF-AAS). For TS-FF-AAS, a pressure of less than 20 kPa (<80 in. water) is required. The TS-FF-AAS technique is very simple, robust and cheap. The detection limits were 0.2–0.4 μg L−1 (Cd), 40–100 μg L−1 (Hg), 5–9 μg L−1 (Pb) and 4–14 μg L−1 (Tl), respectively, depending on the method, flow rate and sample volume used. Pb and Cd were found at concentrations of 0.1–2 and 0.005–0.3 μg g−1, respectively, in samples of various spices.
Keywords: Flame furnace AAS; Beam injection flame furnace AAS; Thermospray flame furnace AAS; Air-supported sample transport; Air-supported flow system; Toxic trace elements in spices
Determination of cadmium in coal using solid sampling graphite furnace high-resolution continuum source atomic absorption spectrometry by Alessandra Furtado da Silva; Daniel L. G. Borges; Fábio Grandis Lepri; Bernhard Welz; Adilson J. Curtius; Uwe Heitmann (pp. 1835-1841).
This work describes the development of a method to determine cadmium in coal, in which iridium is used as a permanent chemical modifier and calibration is performed against aqueous standards by high-resolution continuum source atomic absorption spectrometry (HR-CS AAS). This new instrumental concept makes the whole spectral environment in the vicinity of the analytical line accessible, providing a lot more data than just the change in absorbance over time available from conventional instruments. The application of Ir (400 μg) as a permanent chemical modifier, thermally deposited on the pyrolytic graphite platform surface, allowed pyrolysis temperatures of 700 °C to be used, which was sufficiently high to significantly reduce the continuous background that occurred before the analyte signal at pyrolysis temperatures <700 °C. Structured background absorption also occurred after the analyte signal when atomization temperatures of >1600 °C were used, which arose from the electron-excitation spectrum (with rotational fine structure) of a diatomic molecule. Under optimized conditions (pyrolysis at 700 °C and atomization at 1500 °C), interference-free determination of cadmium in seven certified coal reference materials and two real samples was achieved by direct solid sampling and calibrating against aqueous standards, resulting in good agreement with the certified values (where available) at the 95% confidence level. A characteristic mass of 0.4 pg and a detection limit of 2 ng g−1, calculated for a sample mass of 1.0 mg coal, was obtained. A precision (expressed as the relative standard deviation, RSD) of <10% was typically obtained when coal samples in the mass range 0.6–1.2 mg were analyzed.
Keywords: High-resolution continuum source atomic absorption spectrometry; Graphite furnace atomic absorption spectrometry; Solid sampling; Cadmium determination; Coal analysis; Iridium permanent modifier
Coupling of SPME with MCC/UV–IMS as a tool for rapid on-site detection of groundwater and surface water contamination by G. Walendzik; J. I. Baumbach; D. Klockow (pp. 1842-1847).
The combination of headspace solid phase microextraction (HS-SPME) [1] with fast chromatographic pre-separation by means of multi-capillary columns (MCC) coupled to an ion mobility spectrometer equipped with a 10.6 eV photoionisation source was applied to rapid on-site monitoring of ground and surface water contaminations. Under field conditions, water contaminants were directly detectable down to the upper μg/L range. The potential of the developed method is illustrated by measurements of BTEX, naphthalene, chlorinated alkenes and chlorinated benzenes in water. Practical results from investigations of contaminated groundwater at a former gasworks site and groundwater from the site of a metal processing plant, focusing on the key substances benzene, naphthalene and tetrachloroethene, demonstrate the feasibility of the system for field studies.
Keywords: Ion mobility spectrometry (IMS); Headspace solid phase microextraction (HS-SPME); Multi-capillary column (MCC); Water contamination; On-site analysis; Field measurements
Processing and purity assessment of standards for the analysis of type-B trichothecene mycotoxins by R. Krska; R. C. Schothorst; H. P. van Egmond; R. D. Josephs; J. Lepschy; H. Pettersson; D. Chan; F. Berthiller; R. Schuhmacher; W. Kandler; A. Parich; E. Welzig (pp. 1848-1858).
The lack of reliable, certified calibrant solutions for the Fusarium mycotoxins deoxynivalenol (DON), 3-acetyl-DON (3-Ac-DON), 15-acetyl-DON (15-Ac-DON) and nivalenol (NIV) is a serious drawback in the already problematic area of trichothecene analysis. For this reason, purified DON, 3-Ac-DON, 15-Ac-DON and NIV standards were processed, the conditions required for their isolation and purification were optimised, and the crystalline toxins were thoroughly characterised. Several complimentary analytical methods were used to evaluate the identities of the mycotoxins and the types and amounts of impurities; results obtained from 1 H and 13 C NMR spectra, as well as from IR-spectra, were in agreement with the literature. Elemental analysis revealed that the isolated NIV occurs as monohydrate. If this is not known it results in a weighing error of approximately 5%. Differential scanning calorimetry (DSC) was only successful for 15-Ac-DON, as the other trichothecenes decomposed during measurements. No traces of chloride, nitrate and sulphate were found by means of ion chromatography (IC). As expected UV absorption spectra for DON, NIV, 3-Ac-DON and 15-Ac-DON yielded λmax values of 216, 217, 217 and 219 nm, respectively. Minor peaks due to impurities were observed by high performance liquid chromatography (HPLC) with UV detection. The main impurity peak in the DON sample was identified by LC-tandem mass spectroscopy (LC-MS/MS) as 4,7-dideoxy-NIV (7-deoxy-DON), which occurs at levels of approximately 1.4%. Gas chromatography (GC) was performed, coupled with either an electron capture detector (ECD), a flame ionisation detector (FID), or a mass spectrometric detector (MS); however, derivatisation prior to GC analysis makes the estimation of impurities difficult. LC-MS/MS was found to be unsuitable for quantifying levels of impurities. It can be concluded that high-purity (>97%) B-trichothecene standards were successfully processed and fully characterised for the first time.
Keywords: Deoxynivalenol; Mycotoxin; Trichothecenes; Reference material; Standards
High-resolution gas chromatography retention data as a basis for estimation of the octanol–water distribution coefficients (Kow) of PCB: the effect of experimental conditions by Karlheinz Ballschmiter; Diana Klingler; Stefan Ellinger; Rudolf Hackenberg (pp. 1859-1870).
The semi-experimental approach to approximating physicochemical data relevant to environmental distribution (vapor pressure and gas–octanol distribution) by correlation with gas chromatography (GC) retention data has been extended to the determination of Kow values. We estimated Kow values >104 for polychlorinated biphenyls (PCB), which are often derived by liquid chromatography, by correlation with gas chromatographic retention data. Selecting a set of reference compounds with known Kow values for relative retention time (RRT) correlation enables easy and accurate semi-empirical calculation of further Kow values for a given group of congeners. The RRT/log Kow correlation is validated in this paper with regard to the following gas chromatographic conditions: (1) isothermal versus temperature-programmed elution, (2) the possible effect of the polarity of the stationary phase, and (3) the effect of the format of the standardized GC retention data. The advantages of our Kow(GC) method can be summarized as follows: complex mixtures can be analyzed, only amounts in the nanogram-range or less are required, Kow values of isomers can be determined and the exact structure of compounds need not be known. Normalized GC retention data of persistent organic pollutants are readily available. The quality of the Kow values obtained by the GC method compares well with that for other Kow estimation methods. It depends mainly on the accuracy of the Kow data of the structurally correlated compounds used as standards for the correlation cohort. The Kow(GC) data for all 209 PCB congeners are given.
Keywords: Kow values; Relative retention time; Total surface area; Polychlorinated biphenyls
Quantification of phytochelatins in plants by reversed-phase HPLC–ESI–MS–MS by M. H. A. El-Zohri; R. Cabala; H. Frank (pp. 1871-1876).
An on-line HPLC–ESI–MS–MS method has been developed for determination of glutathione and phytochelatins (PC) in plant tissues. For sample pretreatment, dithiothreitol (DTT) must be added at the very beginning, as an anti-oxidant. Optimization of instrumental conditions i.e. composition of HPLC mobile phase, ionization efficiency of the electrospray interface, and MS–MS detection in the multiple ion-monitoring mode, are the central aspects of this work. A polystyrene-packed column was found to be superior to a standard silica-packed reversed-phase column. A concave quadratic gradient of ammonium formate buffer and acetonitrile was found to be optimum. The limits of quantitation were 0.2 μmol kg−1 plant tissue for glutathione and PC. The method has been applied to analysis of tissue samples from Vicia faba grown in Cd-containing nutrient solutions.
Keywords: Phytochelatins; Glutathione; On-line HPLC–ESI–MS–MSVicia faba
Direct determination of total sulfur in wine using a continuum-source atomic-absorption spectrometer and an air–acetylene flame by Mao Dong Huang; Helmut Becker-Ross; Stefan Florek; Uwe Heitmann; Michael Okruss (pp. 1877-1881).
Determination of sulfur in wine is an important analytical task, particularly with regard to food safety legislation, wine trade, and oenology. Hitherto existing methods for sulfur determination all have specific drawbacks, for example high cost and time consumption, poor precision or selectivity, or matrix effects. In this paper a new method, with low running costs, is introduced for direct, reliable, rapid, and accurate determination of the total sulfur content of wine samples. The method is based on measurement of the molecular absorption of carbon monosulfide (CS) in an ordinary air–acetylene flame by using a high-resolution continuum-source atomic-absorption spectrometer including a novel high-intensity short-arc xenon lamp. First results for total sulfur concentrations in different wine samples were compared with data from comparative ICP–MS measurements. Very good agreement within a few percent was obtained.
Keywords: Continuum source; Atomic-absorption spectrometry; Sulfur determination; Wine analysis
Potential analytical applications of gated artificial ion channels by L. Husaru; R. Schulze; G. Steiner; T. Wolff; W. D. Habicher; R. Salzer (pp. 1882-1888).
Biosensors based on natural ion channels combine a biological recognition mechanism with a physical transduction technique in a very selective and sensitive manner. This kind of molecular sensor will contribute to drug screening and environmental screening. Key information about channel gating, ion transport, and molecular mechanism is provided by the patch-clamp technique, commonly used for electrophysiological analysis. Here we report the synthesis of light-gated artificial ion channels, necessary constituents for construction of biosensors based on natural ion channels. The artificial gated ion channels described here are based on calix[4]resorcinarene. Opening and closing of the artificial ion channel is achieved by azo groups, which work like a lid. Azo groups alter their conformation on irradiation with light, and are chemically quite stable. Addition of a gate function will enhance the potential of synthetic channels to be used in sensors as molecular switches.
Keywords: Gated calixresorcinarene; Photo switch; Ion channel
Label-free characterisation of oligonucleotide hybridisation using reflectometric interference spectroscopy by Florian Pröll; Bernd Möhrle; Michael Kumpf; Günter Gauglitz (pp. 1889-1894).
The potential of a label-free detection method, reflectometric interference spectroscopy (RIfS), for temperature-dependent DNA hybridisation experiments (for example in single nucleotide polymorphism (SNP) analysis) is investigated. Hybridisations of DNA, peptide nucleic acid (PNA), and locked nucleic acid (LNA) to a single stranded DNA were measured for several temperatures, and the melting curves and temperatures were calculated from the changes in optical thickness obtained. These measurements were performed by hybridising surface-immobilised single stranded oligomers with their complementary ssDNA or with ssDNA containing SNPs at different temperatures. DNA was compared to its analogue oligomers PNA and LNA due to their stability against nuclease. A comparison of melting temperatures demonstrated the higher binding affinities of the DNA analogues. Moreover, a continuous melting curve was obtained by first hybridising the functionalised surface with its complementary DNA at room temperature and then heating up in-flow. Measurement of the continuous melting curve was only possible due to the insensitivity of the RIfS method towards temperature changes. This is an advantage over other label-free detection methods, which are based on determining the refractive index.
Keywords: DNA; Peptide nucleic acid (PNA); Locked nucleic acid (LNA); Reflectometric interference spectroscopy (RIfS); Melting temperature; Melting curve
TIRF-based biosensor for sensitive detection of progesterone in milk based on ultra-sensitive progesterone detection in water by Jens Tschmelak; Nina Käppel; Guenter Gauglitz (pp. 1895-1903).
We report on recent advances of our immunoassay for the hormone progesterone in cow’s milk. Detection is based on total internal reflectance fluorescence (TIRF), the binding-inhibition assay with an immobilized progesterone derivative, and a commercially available monoclonal antibody to progesterone as biological recognition element. The fully automated River Analyzer (RIANA) biosensor for unattended, cost-effective, and continuous monitoring of environmental pollution therefore was adapted for sensitive determination of progesterone in milk. First, the sensitivity and robustness of the existing progesterone assay for water analysis were improved, resulting in a detection limit (LOD) of only 0.2 pg mL−1 and a quantification limit (LOQ) of only 2.0 pg mL−1. These extraordinary results are the lowest detection and quantification limits for progesterone determination using biosensors yet reported in the literature. Second, the accurate indicator of ovulation was calibrated and detected in three different types of milk (UHT milk, fresh milk, and raw milk). For commercial milk and randomly procured raw milk nominal levels of progesterone are typically in the range 5–15 ng mL−1. Limits of detection (LOD) achieved for added progesterone (i.e. spiked samples) were between 45.5 and 56.1 pg mL−1 depending on milk type. Having in mind the 1:10 dilution factor, these results are still a success. For the first time a commercially available antibody was incorporated into an immunoassay for progesterone detection in bovine milk, giving a detection limit below 1 ng mL−1 for a fully automated biosensor. Thus the outstanding progress made with this biosensor in environmental monitoring and water analysis has now been successfully adapted to milk analysis for use in the field of reproduction management.
Keywords: TIRF - Total Internal Reflectance Fluorescence; Optical Immunosensor; On-line Biosensor; Dairy Reproduction Management; River Analyzer (RIANA); Milk Analysis
Sensitive detection of organophosphates in river water by means of a piezoelectric biosensor by J. Halámek; Jan Přibyl; A. Makower; P. Skládal; F. W. Scheller (pp. 1904-1911).
A highly sensitive piezoelectric biosensor has been developed for detection of cholinesterase inhibitors. The inhibitor benzoylecgonine-1,8-diamino-3,4-dioxaoctane (BZE-DADOO) was immobilized on a monolayer of 11-mercaptomonoundecanoic acid (MUA) self-assembled on the gold surface of the sensor. The binding of high-molecular-weight cholinesterase to the immobilized cocaine derivative was monitored with a mass sensitive piezoelectric quartz crystal (quartz crystal nanobalance; QCN). In the presence of an inhibiting substance in the sample, the binding of cholinesterase to the immobilized inhibitor was reduced. The decrease of the rate of mass change was proportional to the concentration of free inhibitor in the sample. This way the affinity sensor followed anti-cholinesterase toxicity and the enzyme activity of ChE was not addressed. A assay for detection of organophosphates (OP) was optimized. Regeneration of the sensor surface was achieved with 1 mol L−1 formic acid, which enabled 40 measurements with one sensor. All assays were carried out in a flow-through arrangement. The total measurement time (binding+regeneration) was 25 min and the detection limit for different OP (paraoxon, diisopropylfluorophosphate, chlorpyriphos, and chlorfenvinphos) was down to 10−10 mol L−1 (0.02 μg L−1). This sensor was used for determination of organophosphate (diisopropylfluorophosphate) levels in river water samples.
Keywords: Cholinesterase; Organophosphate; Pesticide; Piezoelectric quartz crystal; River water sample; Environmental analysis
Synthesis, analytical characterization and bioactivity of Ag and Cu nanoparticles embedded in poly-vinyl-methyl-ketone films by N. Cioffi; N. Ditaranto; L. Torsi; R. A. Picca; E. De Giglio; L. Sabbatini; L. Novello; G. Tantillo; T. Bleve-Zacheo; P. G. Zambonin (pp. 1912-1918).
The electrosynthesis of copper and silver core-shell nanoparticles (NPs) by the sacrificial anode technique, employing tetraoctylammonium (TOA) salts as base electrolyte for the first time, is described. These surfactants were selected because they combine high NP stabilizing power with useful disinfecting properties. The resulting colloids were mixed with a solution of an inert dispersing polymer and used to prepare nanostructured composite thin films. The morphologies and chemical compositions of the nanomaterials were characterized by Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). The TEM reveals that the average core diameter of the metal NPs ranges between 1.7 and 6.3 nm, as a function of the nature of the metal and of the electrosynthesis conditions, and does not change significantly upon inclusion in the polymer matrix. An appreciable concentration of the metal is detected on the nanoparticle surface by XPS. High-resolution XP spectra indicate that both copper and silver are present at zero oxidation state in all of the materials (colloids and composite films). This demonstrates the high efficiency of the surfactant at controlling the morphology and the chemical composition of the nanodispersed metal in both the as-synthesized colloid and in the polymeric dispersion. The nanocoatings are shown to exert a marked inhibitory effect on the growth of eukaryote and prokaryote target microrganisms, and experimental evidence of a synergic disinfecting effect due to the surfactant and the nanodispersed metal is provided. On the basis of these stability and bioactivity results, it is clear that Cu-NPs and Ag-NPs are suitable for application in disinfecting or antifouling paint and coating formulations.
Keywords: Nanoparticle; Copper; Silver; Disinfectant; Bioactivity; XPS; TEM
Development of new rat monoclonal antibodies with different selectivities and sensitivities for 2,4,6-trinitrotoluene (TNT) and other nitroaromatic compounds by Petra M. Krämer; Elisabeth Kremmer; Cristina M. Weber; Ioan M. Ciumasu; Stephan Forster; Antonius A. Kettrup (pp. 1919-1933).
Five new rat monoclonal antibodies (mAbs) for 2,4,6-trinitrotoluene (TNT) and other nitroaromatic compounds, including, especially, the metabolite 2-amino-4,6-dinitrotoluene (2-ADNT), are described. Five heterogeneous, competitive enzyme-linked immunosorbent assays (ELISAs) were developed. Assay 1 uses mAb DNT4 3F6 as recognition element and gives a standard curve for TNT in 40 mmol L−1 phosphate buffered saline (PBS) with a test midpoint (IC50) of 0.26±0.08 μg L−1 (n=20). Assay 2 (mAb DNT4 4G4) has an IC50 of 0.35±0.07 μg L−1 (n=18), assay 3 (mAb DNT4 1A3) has an IC50 of 0.73±0.14 μg L−1 (n=15), and assay 4 (mAb DNT4 1A7) has an IC50 of 2.32±0.70 μg L−1 (n=15). Assay 5 (mAb DNT2 4B4) is very selective for 2-ADNT and has an IC50 of 8.5±1.7 μg L−1 (n=15) in PBS. These antibodies for nitroaromatic compounds differ not only in their sensitivity but also in their selectivity. Major cross-reactants are 1,3,5-trinitrobenzene, 2-ADNT, 4-amino-2,6-dinitrotoluene (4-ADNT), 2,4-dinitroaniline, 3,5-dinitroaniline, and 2,6-dinitroaniline. Although assay 5 is not highly sensitive, the mAb DNT2 4B4 in this assay is highly selective for 2-ADNT. Of all the compounds tested, only 2,4-dinitroaniline and 3,5-dinitroaniline had relevant cross reactivities, 18% and about 26%, respectively. Two ELISAs, using mAbs DNT4 3F6 and DNT2 4B4, were used to analyze different concentrations of TNT and 2-ADNT, respectively, in three different surface water matrices (river and lake water). Both assays were affected by the matrix, but usually performed well (recovery within the range 70–120%). In addition, these ELISAs were used to analyze mixtures of TNT, 2-ADNT, and 4-ADNT, at three different concentrations, in the same water matrices. A different recognition pattern was clearly visible with both assays and depended on the cross reactivities of the corresponding mAb.
Keywords: TNT; 2-Amino-4,6-dinitrotoluene; 4-Amino-2,6-dinitrotoluene; Nitroaromatic compounds; Immunoassay; Monoclonal antibodies; Water; Pattern recognition
Ultrafiltration behavior of selected pharmaceuticals on natural and synthetic membranes in the presence of humic-rich hydrocolloids by Peter Burba; Helma Geltenpoth; Jürgen Nolte (pp. 1934-1941).
The separation behavior of the frequently administered pharmaceuticals sulfamethoxazol (Sulfa), carbamazepine (Carba), diclofenac (Diclo), and ibuprofen (Ibu) on different natural and synthetic ultrafiltration membranes was studied. Commercially available cattle intestine natural membranes (NM), polyethersulfone (PES), and regenerated cellulose-based (RC) flat membranes (nominal cut-off 1 kDa) have been investigated as ultrafiltration membranes in a small tangential-flow ultrafiltration unit (TF-UF). First, the nominal cut-off of the NM membranes under study was assessed at approximately 5 kDa, by using polystyrenesulfonate standards for pore-size classification at low TF-UF pressure (0.25×105 Pa). Working pressures of >1.5×105 Pa strongly increased the cut-off of NM, in contrast with that of PES and RC membranes. Sulfa, Carba, Diclo and Ibu (1 mg L−1 each) in colloid-free aqueous solutions (400 mg L−1 NaCl) completely permeated through NM membranes, but less through PES and RC, which had particular sorption capability towards Diclo. The drugs were routinely determined by using high-performance liquid chromatography (HPLC). Detailed TF-UF investigation of drug retention on NM in the presence of humic hydrocolloids revealed strong interactions between aquatic humic substances (HS) and Diclo and Ibu (but not with Sulfa and Carba) causing retention of up to 80% of Diclo and Ibu, probably because of their binding to macromolecular HS. The standard deviation (SD) of both drug and HS permeation through a single NM was between 2.5 (Sulfa) and 4.0% (Diclo), in contrast with the SD of permeation through separate membranes taken from different lots [SD up to 14.0% (Diclo)], presumably caused by natural variation of the studied NM. Accordingly, membrane filtration of drug-containing water samples on cattle intestines enables both analyte/matrix separations for Carba and Sulfa in the presence of humic colloids and analytical discrimination between free and colloid-bound Diclo and Ibu fractions.
Keywords: Tangential-flow ultrafiltration; Cattle intestine membranes; Sulfamethoxazol; Carbamazepine; Diclofenac; Ibuprofen; Analyte/matrix separation; Humic hydrocolloids
Reflectometric interference spectroscopy combined with MALDI−TOF mass spectrometry to determine quantitative and qualitative binding of mixtures of vancomycin derivatives by Martin Mehlmann; Alex M. Garvin; Michael Steinwand; Günter Gauglitz (pp. 1942-1948).
This paper describes the combination of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry with label free bio-interaction analysis based on reflectometric interference spectroscopy (RIfS). The potential of this concerted approach is demonstrated by measuring the binding properties of different vancomycin-type glycopeptide antibiotic mixtures. Although RIfS is sensitive and does not require use of a label, it cannot determine which components of a mixture have bound to the surface after incubation. Fortunately, each bound species has a unique mass that can, afterwards, be determined by mass spectrometry. Thus, the screening capability of RIfS is combined with the identification capability of mass spectrometry.
Keywords: Biomolecular interaction analysis; RIfS; Label-free; MALDI−TOF
A direct solid sampling electrothermal atomic absorption spectrometric method for determination of trace elements in zirconium dioxide by Viliam Krivan; Petra Janickova (pp. 1949-1957).
A direct solid sampling electrothermal atomic absorption spectrometric method for determination of Cd, Co, Cr, Cu, Fe, Li, Mn, Ni and Zn in zirconium dioxide has been developed. Using optimised experimental conditions, very effective in-situ analyte/matrix separation was achieved without any chemical modification. After the measurement, the matrix residue could easily be tipped out from the platform. In the determination of Cr, before sampling, the platform bottom was covered with carbon powder. Quantification was performed using calibration curves measured with aqueous standard solutions pipetted onto the matrix residue from a previous sample run. Sample amounts between 0.5 and 40 mg were applied for each analysis cycle. The accuracy was determined by comparison of the results with those obtained by radiochemical neutron activation analysis and by electrothermal atomic absorption spectrometry using liquid sampling of digests and slurry sampling. For the nine elements assayed, the limits of detection achievable by this method are between 0.06 ng g−1 (Cd) and 2.3 ng g−1 (Fe).
Keywords: Electrothermal atomic absorption spectrometry; Solid sampling; Zirconium dioxide; Trace impurities
Direct analysis of Al2O3 powders by total reflection X-ray fluorescence spectrometry by Birgit U. Peschel; Ursula E. A. Fittschen; Giancarlo Pepponi; Christoph Jokubonis; Christina Streli; Peter Wobrauschek; Gerald Falkenberg; José A. C. Broekaert (pp. 1958-1964).
A direct analysis procedure for the determination of trace impurities of Ca, V, Cr, Mn, Fe, Ni, Cu, Zn and Ga in Al2O3 ceramic powders by total reflection X-ray fluorescence spectrometry (TXRF) is described. The powders were analysed in the form of slurries containing 1–10 mg mL−1 of powder. The use of the procedure in the case of powders with differing grain size and for different slurry concentrations was investigated. Three different quantification possibilities were compared, namely the use of Al as a matrix component, the use of Fe as a trace element contained in the sample or of Co added in concentrations of 200 μg g−1 as internal standard. The homogeneity of elemental distributions in sample layers deposited on the TXRF quartz carriers by evaporating 5 μL of the 10 mg mL−1 slurries was studied by scanning the 4- to 5-mm-diameter spots of two samples by synchrotron radiation TXRF at Hasylab. For powders with differing graininess but mainly finer than about a few 10 μm, no systematic influence of the grain size on the accuracy of the determinations of Ca, V, Fe, Ni, Cu and Zn could be observed. The measurement precision, however, seemed to be limited by inhomogeneous distributions of the trace elements in the samples as testified by the synchrotron radiation TXRF scans. Detection limits of the developed TXRF procedure for Ca, V, Cr, Mn, Fe, Ni, Cu, Zn and Ga were found to be in the 0.3–7 μg g−1 range and were shown to increase slightly with the grain size of the samples. Quantification using Al (matrix) as internal standard led to systematically higher values out of the accuracy required, whereas the other two approaches in all cases led to reliable results.
Keywords: Total reflection X-ray fluorescence; Al2O3Direct solids analysis
Depth profiling with modified dc-Grimm and rf-Grimm-type glow discharges operated with high gas flow rates and coupled to a high-resolution mass spectrometer by Jorge Pisonero; Ingo Feldmann; Nerea Bordel; Alfredo Sanz-Medel; Norbert Jakubowski (pp. 1965-1974).
The improved analytical capability of direct-current (dc) and radiofrequency (rf) “fast flow” glow discharges coupled to a sector field mass spectrometer (GD-SFMS) are presented. In particular, the effect of GD chamber design has been studied to obtain suitable crater shapes for depth-profile analysis of solid samples while maintaining the high sensitivity and stability of this source. In this study it was observed that the distance between the sample surface and the end of the flow tube is critical and so careful optimisation is needed. Under optimum conditions plane crater profiles, with high ion-signal sensitivity and sufficient stability, were obtained. The capability to determine qualitative and semi-quantitative depth profiles is presented here using, as model, a coated sample of certified thickness. Finally, the depth resolution achieved for qualitative depth profiles obtained by rf-GD-(SF)MS is compared with that for the well-established rf-GD optical emission spectroscopy (OES) technique.
Keywords: Fast-flow glow discharge; Sector field mass spectrometry; Depth-profile analysis
Parasitic ion-implantation produced by a Kaufman-type ion source used for planar etching of surfaces by Alex von Bohlen; Reinhold Klockenkämper (pp. 1975-1980).
Total reflection X-ray fluorescence spectrometry (TXRF) and photoelectron spectroscopy (XPS) were used to characterize ion-etched surfaces of Si wafers, a quartz glass and vacuum-metallized multilayer on a Si wafer. These samples were first treated with low kinetic energy ions of a broad beam Kaufman-type ion source. By repeating this method of sputtering, layers can be removed stepwise and in combination with surface analysis by TXRF a multielement depth profiling can be carried out. The depth resolution is of the order of 3 nm. Unfortunately, ion-etching leads to uncontrollable ion implantation and thus to a contamination of the samples with some ‘parasitic’ elements which may disturb the multielement characterization of the original surfaces. XPS with Ar sputtering was used to confirm the implantation of interfering elements in the freshly ion-etched samples.
Keywords: Ion etching; Ion implantation; Depth profiling; Multielement analysis; TXRF
FIA acid–base titrations with a new flow-through pH detector by H. Kahlert; J. R. Pörksen; J. Behnert; F. Scholz (pp. 1981-1986).
A pH-sensitive detector for flow-through potentiometry based on a graphite/quinhydrone composite electrode was applied for flow-injection analysis (FIA) titrations. Hydrochloric acid and acetic acid were titrated by injection of samples into a sodium hydroxide carrier solution. System conditions were optimised by variation of flow rate, injection volume and titrant concentration. The parameters sampling frequency, residence time and dispersion coefficient were determined. The evaluation of peak width (time between the two inflection points on each side of the peak), peak area and slope of the raising edge of the peak lead were studied with respect to their use for calibration. Hydrochloric acid and acetic acid could be titrated down to a concentration of 2 × 10−4 mol L−1 using 150-μL injection volumes, which is almost ten times lower than can be achieved using colour indicators and a spectrophotometric detection.
Keywords: FIA titration; pH measurement; pH detector
Infrared reststrahlen revisited: commonly disregarded optical details related to n<1 by Ernst Heiner Korte; Arnulf Röseler (pp. 1987-1992).
Spectral ellipsometry has developed into a routine method applicable to the infrared spectral range. It can give both the refractive index (n) and the absorption index (k), which has so far only been determined for a limited number of compounds. It turns out that vibrations that have a dispersion with an interval of n<1 are by no means restricted to crystals, but occur with numerous compounds including polymers and liquids. In conventional infrared spectroscopy, one usually is not aware of such a situation and so the consequences are disregarded. These include the so-called reststrahlen (residual rays) bands and specific phenomena that occur when n matches the absorption index (the Berreman effect) or the refractive index of ambient air (vanishing reflection, the Christiansen effect). These and some typical applications are discussed, including model calculations and experimental data.
Keywords: Reststrahlen; Residual rays; Refractive index; Optical constants; Infrared ellipsometry
Effect of the interface on separation in multicapillary gas chromatography-based hyphenated techniques for speciation analysis of organometallic compounds by Petru Jitaru; Adrian Birzu; Raluca Mocanu; Freddy C. Adams (pp. 1993-1998).
This paper reports the effect of transfer line (TL) internal diameter (i.d.) on gas chromatographic separation characteristics such as efficiency and speed, when a multicapillary (MC) column is used for speciation analysis of mercury. Five different TL consisting of fused-silica capillaries with 0.15, 0.20, 0.25, 0.32, and 0.53 mm i.d. are compared. The separation efficiency and total chromatographic run time are critically affected by the i.d. of the TL. Narrow capillaries (i.d.≤0.20 mm) produce minimum peak dispersion whereas wide capillaries result in narrow peaks and shorter chromatographic analysis times. A thermodynamic approach is proposed to describe the motion of the analytes through the separation column and TL. The model provides good agreement with the experimental data for high pressures (≥35 psig) and wide TL (≥0.25 mm i.d.).
Keywords: Hyphenated techniques; Multicapillary gas chromatography; Transfer line; Peak dispersion; Mercury speciation analysis