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Analytical and Bioanalytical Chemistry (v.393, #8)

Quick, efficient, effective? Meetings! by John Fetzer (pp. 1825-1827).

is the author or coauthor of over 130 research articles, reviews, and book chapters. He is a member of the International Advisory Board of Analytical and Bioanalytical Chemistry. He has worked for over 20 years as an analytical chemist for the Chevron Corporation and now runs his own consulting company, Fetzpahs Consulting, in Hercules, CA, USA. His book Career management for chemists—a guide to success in a chemistry career was published by Springer.

Pierre N. Floriano (Ed.): Microchip-based assay systems. Methods and applications by Michael Seidel (pp. 1829-1830).

John Emsley: Molecules of murder. Criminal molecules and classic cases by D. Thorburn Burns (pp. 1831-1831).

15th Conference on Applied Surface Analysis—AOFA 15 by Karl-Heinz Müller; Hubert Paulus; Mark Schülke (pp. 1833-1834).

is Professor at the University of Applied Sciences of South Westphalia, Soest department, and executive director and scientific head of the Institut für Technologie- und Wissenstransfer TWS. His scientific interests are instrumental surface analysis, the storage of hydrogen in metals, and renewable energies. is Head of the Surface-Analysis Laboratory of the Institut für Technologie- und Wissenstransfer TWS. His scientific interests are surface analysis (especially mass spectrometry) and the storage of hydrogen in metals. is scientific assistant at the University of Applied Sciences of South Westphalia in Soest. His research work and PhD thesis are focused on surface and material analysis of metal hydrides.

Three-dimensional depth profiling of molecular structures by A. Wucher; J. Cheng; L. Zheng; N. Winograd (pp. 1835-1842).

Molecular time of flight secondary ion mass spectrometry (ToF-SIMS) imaging and cluster ion beam erosion are combined to perform a three-dimensional chemical analysis of molecular films. The resulting dataset allows a number of artifacts inherent in sputter depth profiling to be assessed. These artifacts arise from lateral inhomogeneities of either the erosion rate or the sample itself. Using a test structure based on a trehalose film deposited on Si, we demonstrate that the “local” depth resolution may approach values which are close to the physical limit introduced by the information depth of the (static) ToF-SIMS method itself.

Keywords: Biological samples; Electron/ion microprobe; Mass spectrometry/ICP-MS; Thin films

Complex surface analytical investigations on hydrogen absorption and desorption processes of a TiMn₂-based alloy by Mark Schülke; Gábor Kiss; Hubert Paulus; Martin Lammers; Vaidyanath Ramachandran; Kannan Sankaran; Karl-Heinz Müller (pp. 1843-1856).

Metal hydrides are one of the most promising technologies in the field of hydrogen storage due to their high volumetric storage density. Important reaction steps take place at the very surface of the solid during hydrogen absorption. Since these reaction steps are drastically influenced by the properties and potential contamination of the solid, it is very important to understand the characteristics of the surface, and a variety of analytical methods are required to achieve this. In this work, a TiMn₂-type metal hydride alloy is investigated by means of high-pressure activation measurements, X-ray photoelectron spectroscopy (XPS), secondary neutral mass spectrometry (SNMS) and thermal desorption mass spectrometry (TDMS). In particular, TDMS is an analytical tool that, in contrast to SIMS or SNMS, allows the hydrogen content in a metal to be quantified. Furthermore, it allows the activation energy for desorption to be determined from TDMS profiles; the method used to achieve this is presented here in detail. In the results section, it is shown that the oxide layer formed during manufacture and long-term storage prevents any hydrogen from being absorbed, and so an activation process is required. XPS measurements show the oxide states of the main alloy elements, and a layer 18 nm thick is determined via SNMS. Furthermore, defined oxide layers are produced and characterized in UHV using XPS. The influence of these thin oxide layers on the hydrogen sorption process is examined using TDMS. Finally, the activation energy of desorption is determined for the investigated alloy using the method presented here, and values of 46 kJ/mol for hydrogen sorbed in UHV and 103 kJ/mol for hydrogen originating from the manufacturing process are obtained.

Keywords: Surface analysis; Hydrogen detection; Thermal desorption; Activation energy; Metal hydrides; Oxygen adsorption; Surface contamination

TOF-SIMS depth profiling and element mapping on oxidized AlCrVN hard coatings by J. Schnöller; R. Franz; C. Mitterer; H. Hutter (pp. 1857-1861).

V-alloyed AlCrN hard coatings were deposited on silicon wafers (Si (100)) by reactive arc evaporation in a commercial coating system at 500 °C for 10 min, resulting in a coating thickness of ∼500 nm. The chemical composition of the stoichiometric coatings is constant at approximately Al_0.70Cr_0.05V_0.25N regardless of the applied bias voltage during deposition. Coatings synthesized at a low bias of −40 V show a dual-phase structure (hexagonal close-packed and face-centered cubic (fcc)), whereas coatings deposited at a high bias of −150 V have a metastable single-phase structure (face-centered cubic). All samples were oxidized for 15 min under 20 mbar O₂ atmosphere and at four different temperatures (550, 600, 650, and 700 °C). The oxidized coatings were subject to depth profiling and element mapping by a time of flight secondary ion mass spectrometry instrument, equipped with a Bi-cluster analysis gun and Cs⁺-sputter gun. The evaluation of the in-depth distribution of several elements and species points out distinctive differences in the oxidation behavior of the two different coatings, whereas element mapping shows the formation of islands made of oxidized vanadium and aluminum species as the top-most layer of the single-phase (fcc) coating at temperatures above 650 °C.

Keywords: TOF-SIMS; Depth profiling; Element mapping; AlCrVN; Hard coatings; Vanadium oxides

X-ray diffraction and scanning electron microscopy of galvannealed coatings on steel by P. Schmid; K. Uran; F. Macherey; M. Ebert; H.-J. Ullrich; D. Sommer; F. Friedel (pp. 1863-1870).

The formation of Fe–Zn intermetallic compounds, as relevant in the commercial product galvannealed steel sheet, was investigated by scanning electron microscopy and different methods of X-ray diffraction. A scanning electron microscope with high resolution was applied to investigate the layers of the galvannealed coating and its topography. Grazing incidence X-ray diffraction (GID) was preferred over conventional Bragg–Brentano geometry for analysing thin crystalline layers because of its lower incidence angle α and its lower depth of information. Furthermore, in situ experiments at an environmental scanning electron microscope (ESEM) with an internal heating plate and at an X-ray diffractometer equipped with a high-temperature chamber were carried out. Thus, it was possible to investigate the phase evolution during heat treatment by X-ray diffraction and to display the growth of the ζ crystals in the ESEM.

Keywords: X-ray diffraction; Grazing incidence X-ray diffraction; Environmental scanning electron microscopy; Fe–Zn phase formation; High-temperature in situ observation

Quasi in situ XPS investigations on intercalation mechanisms in Li-ion battery materials by S. Oswald; K. Nikolowski; H. Ehrenberg (pp. 1871-1877).

New concepts for Li-ion batteries are of growing interest for high-performance applications. One aim is the search for new electrode materials with superior properties and their detailed characterization. We demonstrate the application of X-ray photoelectron spectroscopy (XPS) to investigate electrode materials (LiCoO₂, LiCrMnO₄) during electrochemical cycling. The optimization of a “quasi in situ” analysis, by transferring the samples with a transport chamber from the glove box to the XPS chamber, and the reliability of the experiments performed are shown. The behavior of characteristic chemical species at the electrodes and the changes in oxidation states of LiCrMnO₄ during cycling is discussed. The formation of Cr⁶⁺ is suspected as a possible reason for irreversible capacity loss during charging up to complete Li deintercalation (approximately 5.2 V). Figure Scheme of a quasi in situ XPS experiment on Li-ion battery electrode material

Keywords: X-ray photoelectron spectroscopy; Interface/surface analysis; Ion chromatography/ion exchange; Li-ion batteries

Chemical and structural characterisation of DGEBA-based epoxies by time of flight secondary ion mass spectrometry (ToF-SIMS) as a preliminary to polymer interphase characterisation by Sven Passlack; Alexander Brodyanski; Wolfgang Bock; Michael Kopnarski; Melanie Presser; Paul Ludwig Geiß; Gunnar Possart; Paul Steinmann (pp. 1879-1888).

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) has become a powerful tool in the field of surface analysis since it provides information about the top few monolayers of a sample, i.e. on the chemical composition of the sample surface. Thus, the general question arises whether a surface-sensitive technique like ToF-SIMS would be appropriate to detect systematic chemical and/or structural changes in organic bulk polymers caused by varying a chemical content of the initial components or by tracking, e.g. curing processes in such materials. It is shown that careful sample preparation and the use of multivariate methods permit the quantitative acquisition of chemical and structural information about bulk polymers from the secondary ion signals. The hardener concentration and a cross-linking coefficient in diglycidyl ether of bisphenol A based epoxies were determined by ToF-SIMS measurements on samples with different resin to hardener ratio and varying curing time. In future work, we will use the developed method to investigate the local composition of adhesively bonded joints. In particular, the mapping of the chemical and structural properties in the so-called interphase will then be of interest.

Keywords: Surface analysis; Mass spectrometry; SIMS; Polymer; Interphase

Investigation of polymer thin films by use of Bi-cluster-ion-supported time of flight secondary ion mass spectrometry by Christoph J. Straif; Herbert Hutter (pp. 1889-1898).

The investigation and analysis of polymer thin films with Bi n ⁺, n = 1–7 cluster ions has been demonstrated by means of static secondary ion mass spectrometry (SIMS). The highly specific signal enhancement of these primary ions combined with the individual fragmentation pattern of poly(4-vinylphenol) and poly(methyl methacrylate) is the basic principle for a modified approach of data reduction derived from the well-established g-SIMS procedure. Based on mass spectra, which correspond to different cluster ion sizes, not only a clear distinction between the two polymers is feasible but also a further simplification of the data can be demonstrated. It has been successfully proven that characteristic polymer-relevant species can be refined out of the large amount of unspecific and highly fragmented secondary ions, which are usually present in SIMS spectra. Therefore, a more precise and direct interpretation of complex organic fragments becomes feasible, which consequently enables the investigation of even more sophisticated samples.

Keywords: ToF-SIMS; Bi cluster ions; g-SIMS; Polymer; Signal enhancement

Characterization of the morphology and composition of commercial negative resists used for lithographic processes by B.-E. Schuster; A. Haug; M. Häffner; M. M. Blideran; M. Fleischer; H. Peisert; D. P. Kern; T. Chassé (pp. 1899-1905).

We present a spectroscopic and microscopic characterization of the chemical composition, structure, and morphology of two commercial negative resists using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). For this purpose, films of a novolak-based resist (ma-N 2400) and hydrogen silsesquioxane (HSQ) are treated under different conditions (temperature, deep ultraviolet (DUV) exposure, CHF₃ plasma). Topographic AFM images show that both heating and DUV exposure strongly affect the surface morphology of as-prepared ma-N 2400 resist films. These different treatment conditions also lead to decreasing roughnesses, which indicates structural reorganization. Furthermore, the decrease of the photoactive compound (bisazide) in the ma-N 2400 resist films, observed in FTIR spectra, suggests cross-linking of the resist after CHF₃ plasma treatment, heating, or DUV exposure. XPS measurements on different CHF₃ plasma-treated surfaces reveal that a structurally homogeneous fluorine-containing polymer is generated that is responsible for an enhanced etch resistance. FTIR measurements of HSQ films show a correlation between the degree of HSQ cross-linking and baking time.

Keywords: Negative photoresist; Hydrogen silsesquioxane; Morphology; FTIR; AFM; XPS

Application of XPS and ToF-SIMS for surface chemical analysis of DNA microarrays and their substrates by Nora Graf; Thomas Gross; Thomas Wirth; Wilfried Weigel; Wolfgang E. S. Unger (pp. 1907-1912).

The chemical composition of the functional surfaces of substrates used for microarrays is one of the important parameters that determine the quality of a microarray experiment. In addition to the commonly used contact angle measurements to determine the wettability of functionalized supports, X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) are more specific methods to elucidate details about the chemical surface constitution. XPS yields information about the atomic composition of the surface, whereas from ToF-SIMS, information on the molecular species on the surface can be concluded. Applied on printed DNA microarrays, both techniques provide impressive chemical images down to the micrometer scale and can be utilized for label-free spot detection and characterization. Detailed information about the chemical constitution of single spots of microarrays can be obtained by high-resolution XPS imaging. Figure Eye-catching image for the graphical online abstract

Keywords: Microarrays; Surface analysis; XPS; ToF-SIMS; Chemical imaging

Operation and application of a new time-of-flight e-gas secondary neutral mass spectrometer (ToF–SNMS) by M. Kopnarski; J. Lösch; L. Simeonov (pp. 1913-1916).

The low-pressure rf plasma of a secondary neutral mass spectrometer (e-gas SNMS) was connected with a time-of-flight (ToF) mass spectrometer for the first time. As opposed to ToF–SIMS in e-gas SNMS, the primary ion pulse cannot be used for triggering the flight time measurement. Therefore, an extraction pulse is used which at a defined time loads an ion package from the beam of the post-ionised particles into the ToF spectrometer. The newly developed ToF–SNMS system is described, and first experimental results are presented.

Keywords: Mass spectrometer; Plasma; SNMS; Time-of-flight; Cluster

TOF-S-SIMS molecular depth profiling of organic bilayers using mechanical wear test methodology by Roel De Mondt; Luc Van Vaeck; Andreas Heile; Heinrich F. Arlinghaus; Frank Vangaever; Jens Lenaerts (pp. 1917-1921).

Recent publications on static secondary ion mass spectrometry (S-SIMS) focus on molecular depth profiling by using polyatomic or ultra-low energy monoatomic projectiles. Since their applicability depends on the relationship between the ion yield and the depth, which is hard to obtain without extensive studies, a combination of a wear test method with S-SIMS surface analysis was performed in the current study. Using this non-sputtering procedure, the relation between the signal intensity and the local concentration remains in principle the same as that at the surface (which is easy to determine). Mechanical erosion was successfully applied to expose sub-surface material from organic multilayers. Through surface analysis with S-SIMS on the gradually exposed deeper planes, molecular depth profiles could be obtained. The study was conducted on a model system relevant to offset printing, consisting of two polymer layers, containing dyes and a surfactant, cast on an Al substrate. Figure Concept of mechanical erosion followed by S-SIMS surface analysis to obtain molecular depth profiles

Keywords: Organic; Static SIMS; Depth profiling; Molecular; Polymer

Application of TEM and XPS in the interpretation of the kinetics of deuterium evolution from ultrathin TiD y/Pd films evaporated on quartz by W. Lisowski; E. G. Keim (pp. 1923-1929).

The kinetics of thermal evolution of deuterium from ultrathin TiD y/Pd bilayer films has been studied by means of thermal desorption mass spectrometry (TDMS). Using a combination of transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy, we made a study of the complex structural and chemical transformations of the TiD y/Pd film as a result of TDMS-induced evolution of deuterium and simultaneous annealing of this film. Both preparation and TDMS processing of the TiD y/Pd bilayer films were performed in situ under UHV conditions. It was found that the high-temperature TDMS processing of an ultrathin TiD y/Pd film, which was carried out in a relatively short time, leads to a significant film structure transformation. Energy-filtered TEM mapping of cross-section images and EDX analysis revealed extensive interdiffusion of Ti and Pd within the Ti–Pd bi-layer film. This process leads to a progressive change in chemical composition within the surface and subsurface area of the film during the TDMS processing. As the temperature of TDMS heating increases, segregation of Ti at the Pd top layer surface becomes significant. As a result, the kinetics of deuterium desorption is progressively changed during TDMS; at lower temperatures, the kinetics is limited by recombinative processes at the Pd surface, at temperatures beyond 500 K, it becomes dominated by interdiffusion of Ti into the Pd surface.

Keywords: Palladium; Titanium deuteride; SEM; TEM; XPS

An XPS analytical approach for elucidating the microbially mediated enargite oxidative dissolution by M. Fantauzzi; G. Rossi; B. Elsener; G. Loi; D. Atzei; A. Rossi (pp. 1931-1941).

In this work, the microbe-mediated oxidative dissolution of enargite surfaces (Cu₃AsS₄) was studied on powdered samples exposed to 9K nutrient solution (pH 2.3) inoculated by Acidithiobacillus ferrooxidans initially adapted to arsenopyrite. These conditions simulate the acid mine environment. The redox potential of the inoculated solutions increased up to +0.72 V vs normal hydrogen electrode (NHE), indicating the increase of the Fe³⁺ to Fe²⁺ ratio, and correspondingly the pH decreased to values as low as 1.9. In the sterile 9K control, the redox potential and pH remained constant at +0.52 V NHE and 2.34, respectively. Solution analyses showed that in inoculated medium Cu and As dissolved stoichiometrically with a dissolution rate of about three to five times higher compared to the sterile control. For the first time, X-ray photoelectron spectroscopy (XPS) was carried out on the bioleached enargite powder with the aim of clarifying the role of the microorganisms in the dissolution process. XPS results provide evidence of the formation of a thin oxidized layer on the mineral surface. Nitrogen was also detected on the bioleached surfaces and was attributed to the presence of an extracellular polymer substance layer supporting a mechanism of bacteria attachment via the formation of a biofilm a few nanometers thick, commonly known as nanobiofilm. Figure SEM image of enargite is in the background of the figure; in foreground the scheme of the dissolution mechanism in presence of microorganisms showing a sulphur enriched layer; the mechanism is supported by the presence of the high binding energy signal in the S2p photoelectron spectrum (upper-right).

Keywords: XPS surface analysis; Toxic mine effluents; Enargite; A. ferrooxidans ; Bioleaching; Mineral sulfides dissolution; Extracellular polymer substance

Aptamer-based electrochemical biosensor for Botulinum neurotoxin by Fang Wei; Chih-Ming Ho (pp. 1943-1948).

We have developed an aptamer-based electrochemical sensor for detection of Botulinum neurotoxin, where steric hindrance is applied to achieve specific signal amplification via conformational change of the aptamer. The incubation time and potassium concentration of the reaction buffer were found to be key parameters affecting the sensitivity of detection of the recognition of Botulinum neurotoxin by the aptamer. Under optimized experimental conditions, a high signal-to-noise ratio was obtained within 24 h with a limit of detection (LOD) of 40 pg/ml by two standard deviation cutoffs above the noise level.

Keywords: Aptamer; Botulinum neurotoxin; Biosafety; Electrochemical biosensors; Steric hindrance; Conducting polymer; Bioanalytical methods; Bioassays; Biosensors

Screening hydrolysis products of sulfur mustard agents by high-performance liquid chromatography with inductively coupled plasma mass spectrometry detection by Karolin K. Kroening; Douglas D. Richardson; Scott Afton; Joseph A. Caruso (pp. 1949-1956).

Sulfur mustard (HD), bis(2-chloroethyl)sulfide, is one of a class of mustard agents which are chemical warfare agents. The main chemical warfare hydrolysis degradation products of sulfur mustards are: thiodiglycol, bis(2-hydroxyethylthio)methane, 1,2-bis(2-hydroxyethylthio)ethane, 1,3-bis(2-hydroxyethylthio)propane, and 1,4-bis(2-hydroxyethylthio)butane. The aim of this study is to identify these five hydrolysis degradation products utilizing reversed-phase high-performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (ICP-MS) for element-specific sulfur detection using a collision/reaction cell and electrospray ionization mass spectrometry to confirm the identification. To date, this is the first study utilizing ICP-MS with ³²S element-specific detection for the analysis of vesicant chemical warfare agent degradation products.

Keywords: ICP-MS; ESI-MS; Displacement chromatography; Mustard gas; Displacer; Sulfur detection

Simultaneous quantification of nicotine, opioids, cocaine, and metabolites in human fetal postmortem brain by liquid chromatography tandem mass spectrometry by Diaa M. Shakleya; Marilyn A. Huestis (pp. 1957-1965).

A validated method for simultaneous LCMSMS quantification of nicotine, cocaine, 6-acetylmorphine (6AM), codeine, and metabolites in 100 mg fetal human brain was developed and validated. After homogenization and solid-phase extraction, analytes were resolved on a Hydro-RP analytical column with gradient elution. Empirically determined linearity was from 5–5,000 pg/mg for cocaine and benzoylecgonine (BE), 25–5,000 pg/mg for cotinine, ecgonine methyl ester (EME) and 6AM, 50-5000 pg/mg for trans-3-hydroxycotinine (OH-cotinine) and codeine, and 250–5,000 pg/mg for nicotine. Potential endogenous and exogenous interferences were resolved. Intra- and inter-assay analytical recoveries were ≥92%, intra- and inter-day and total assay imprecision were ≤14% RSD and extraction efficiencies were ≥67.2% with ≤83% matrix effect. Method applicability was demonstrated with a postmortem fetal brain containing 40 pg/mg cotinine, 65 pg/mg OH-cotinine, 13 pg/mg cocaine, 34 pg/mg EME, and 525 pg/mg BE. This validated method is useful for determination of nicotine, opioid, and cocaine biomarkers in brain.

Keywords: LCMSMS; Brain; Fetal; Cocaine; Opiate; Nicotine

Identification of β-carotene in an evaporitic matrix—evaluation of Raman spectroscopic analysis for astrobiological research on Mars by Petr Vítek; Jan Jehlička; Howell G. M. Edwards; Kateřina Osterrothová (pp. 1967-1975).

Since evaporitic rocks on the Martian surface could (or still can) serve as potential habitats for microbial life on Mars, there is a reasonable possibility that these rocks may sustain molecular remnants as evidence for the presence of extinct or extant living organisms on Mars and that β-carotene could be a suitable biomarker. In this paper, Raman microspectrometry was tested as a nondestructive method of determining the lowest detectable β-carotene content in experimentally prepared evaporitic matrices—namely, gypsum, halite and epsomite. Two excitation wavelengths were compared—514.5 nm, because of the resonance Raman enhancement in the carotenoid analysis, and 785 nm, as a more universal wavelength now much used in the detection of biomolecules terrestrially. Mixtures were measured directly as well as with a laser beam penetrating the crystals of gypsum and epsomite. We have obtained β-carotene signals at the 0.1 to 10 mg kg⁻¹ level—the number of registered β-carotene Raman bands differed depending on the particular mineral matrix and the excitation wavelength. Concentrations of β-carotene of about one order of magnitude higher were identified when analysed through single crystals of gypsum and epsomite, respectively.

Keywords: Raman spectroscopy; Astrobiology; β-Carotene; Biomarkers; Evaporites; Mars

A liquid chromatography tandem mass spectrometry method for the simultaneous quantification of 20 drugs of abuse and metabolites in human meconium by Teresa R. Gray; Diaa M. Shakleya; Marilyn A. Huestis (pp. 1977-1990).

A method for the simultaneous quantification of 20 cocaine, amphetamine, opiate, and nicotine analytes in meconium, the first neonatal feces, by liquid chromatography tandem mass spectrometry was developed and validated. Specimen preparation included methanol homogenization and solid phase extraction. Two injections were required to achieve sufficient sensitivity and linear dynamic range. Linearity ranged from 0.5–25 up to 500 ng/g (250 ng/g p-hydroxymethamphetamine), and correlation coefficients were >0.996. Imprecision was <10.0% CV, analytical recovery 85.5–123.1%, and extraction efficiencies >46.7% at three concentrations across the linear range. Despite significant matrix effects of −305.7–40.7%, effects were similar for native and deuterated analytes. No carryover, endogenous or exogenous interferences were observed, with analyte stability at room temperature, 4 °C, and −20 °C and on the autosampler >70%, except for 6-acetylmorphine, hydrocodone, oxycodone, and morphine. Method applicability was demonstrated by analyzing meconium from drug-exposed neonates.

Keywords: Meconium; Drugs of abuse; Prenatal drug exposure; Liquid chromatography tandem mass spectrometry

Identification of protein binders in works of art by high-performance liquid chromatography–diode array detector analysis of their tryptic digests by Wim Fremout; Jana Sanyova; Steven Saverwyns; Peter Vandenabeele; Luc Moens (pp. 1991-1999).

Proteins in works of art are generally determined by the relative amounts of amino acids. This method, however, implies a loss of information on the protein structure and its modifications. Consequently, we propose a method based on the analysis of trypsin digests using high-performance liquid chromatography (HPLC) UV diode array detection (DAD) for painting binder studies. All reaction steps are done in the same vial; no extraction methods or sample transfer is needed, reducing the risk of sample losses. A collection of pure binders (collagen, ovalbumin, yolk and casein) as well as homemade and historical paint samples have been investigated with this method. Chromatograms of unknowns at 214 nm and 280 nm are compared with those of the reference samples as a fingerprint. There is a good agreement between many peptides, but others seem to have been lost or their retention time shifted due to small compositional changes because of ageing and degradation of the paint. The results are comparable with the results of other techniques used for binder identification on the same samples, with the additional advantage of differentiation between egg yolk and glair.

Keywords: Cultural heritage samples; Ancient art objects; Binding media; Protein binder; Tryptic digest; HPLC-DAD

Hapten synthesis and enzyme-linked immunosorbent assay for phosmet residues: assay optimization and investigation of matrix effects from different food samples by Yang Song; Yu Ge; Yan Zhang; Bing Liu; Yang Lu; Tingting Dong; Shuo Wang (pp. 2001-2008).

In this study, a panel of haptens was synthesized for immunoconjugate preparation, and several haptens for heterologous tracer conjugates were also prepared. A highly sensitive polyclonal antibody against the organophosphorus insecticide phosmet was obtained and competitive direct enzyme-linked immunosorbent assays (cd-ELISA) for this pesticide were developed. In the cd-ELISA, the limit of detection (IC₁₅) was 0.6 μg kg⁻¹ and the sensitivity (IC₅₀) was 20 μg kg⁻¹. The suitability of the ELISA for pesticide quantification in peach, apple, orange juice, and apple juice was also studied. Good accuracy and precision were obtained with mean recoveries between 78% and 102.3% and mean coefficients of variation below 13.63%. Validation of the ELISA was conducted by high-performance liquid chromatography. The correlation between the data obtained using the microwell assay and the high-performance liquid chromatography was good (R ² = 0.9849). The developed immunoassay methods were suitable for the rapid quantitative or qualitative determination of phosmet in food samples.

Keywords: Phosmet; ELISA; Polyclonal antibody; Matrix effect; Cross-reactivity

Determination of trace tetracycline antibiotics in foodstuffs by liquid chromatography–tandem mass spectrometry coupled with selective molecular-imprinted solid-phase extraction by Tao Jing; Xiao-Dan Gao; Peng Wang; Yan Wang; Yan-Fei Lin; Xiao-Zhong Hu; Qiao-Lin Hao; Yi-Kai Zhou; Su-Rong Mei (pp. 2009-2018).

A rapid, specific, and sensitive method has been developed using molecularly imprinted polymers (MIPs) as solid-phase extraction sorbents for extraction of trace tetracycline antibiotics (TCs) in foodstuffs. MIPs were prepared by precipitation polymerization using tetracycline as the template. Under the optimal condition, the imprinting factors for MIPs were 4.1 (oxytetracycline), 7.0 (tetracycline), 7.4 (chlortetracycline), 7.7 (doxycycline), respectively. Furthermore, the performance of MIPs as solid-phase extraction sorbents was evaluated and high extraction efficiency of molecularly imprinted solid-phase extraction (MISPE) procedure was demonstrated. Compared with commercial sorbents, MISPE gave a better cleanup efficiency than C18 cartridge and a higher recovery than Oasis HLB cartridge. Finally, the method of liquid chromatography–tandem mass spectrometry coupled with molecular-imprinted solid-phase extraction was validated in real samples including lobster, duck, honey, and egg. The spiked recoveries of TCs ranged from 94.51% to 103.0%. The limits of detection were in the range of 0.1–0.3 μg kg⁻¹. Chromatograms obtained by direct injection of the spiked egg extracts (5 × 10^-3 mmol L⁻¹) and purification with MISPE

Keywords: Tetracycline antibiotics; Precipitation polymerization; Molecularly imprinted solid-phase extraction; Foodstuff; Liquid chromatography–tandem mass spectrometry

Comparison of two SPME fibers for the extraction of some off-flavor cork-taint compounds in bottled wines investigated by GC–HRMS by Giuliana Bianco; Giuseppe Novario; Rosalia Zianni; Tommaso R. I. Cataldi (pp. 2019-2027).

Headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography with high-resolution mass spectrometry (GC–HRMS) was used to determine 2,4,6-trichloroanisole, 2,3,6-trichloroanisole, 2,3,4-trichloroanisole, 2,3,5,6-tetrachloroanisole, pentachloroanisole, 2,4,6-tribromoanisole, 2-methylisoborneol, and 4-ethylguaiacol in wine samples. Two types of fiber coating commonly employed for sampling trichloroanisoles in wine and cork stoppers, viz. a polar mixed 50/30 μm divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) and a nonpolar 100 μm polydimethylsiloxane (PDMS), both 1 cm in length, were compared. This study demonstrates that the most employed polar mixed fiber should not be used with ethanol–water solutions, viz. wine samples, as its coating is not chemically and mechanically robust for sample extractions, as confirmed by environmental scanning electron microscopy. Much more effective and reliable results were obtained with the PDMS fiber, which remained functional for more than 80 analyses of red and white wine samples with satisfactory extraction efficiencies. Detection limits of investigated compounds, under optimized experimental conditions, ranged from 0.2 to 0.4 ng/L at a signal-to-noise ratio of 3 and quantification limits from 0.8 to 1.5 ng/L. The proposed method was successfully applied to commercially available Italian white and red wines using 2,4,6-TCA-d₅ as the internal standard.

Keywords: Cork-taint compounds; Solid-phase microextraction; PDMS; Wines; Trichloroanisoles; GC; High-resolution mass spectrometry

Monitoring of cell cultures with LTCC microelectrode array by P. Ciosek; K. Zawadzki; J. Łopacińska; M. Skolimowski; P. Bembnowicz; L. J. Golonka; Z. Brzózka; W. Wróblewski (pp. 2029-2038).

Monitoring of cell cultures in microbioreactors is a crucial task in cell bioassays and toxicological tests. In this work a novel tool based on a miniaturized sensor array fabricated using low-temperature cofired ceramics (LTCC) technology is presented. The developed device is applied to the monitoring of cell-culture media change, detection of the growth of various species, and in toxicological studies performed with the use of cells. Noninvasive monitoring performed with the LTCC microelectrode array can be applied for future cell-engineering purposes. Figure Microelectrode array for monitoring of cell cultures

Keywords: Sensor array; Cell cultures; LTCC; Ion-selective electrodes

Certified reference material for quantification of polycyclic aromatic hydrocarbons in sediment from the National Metrology Institute of Japan by Nobuyasu Itoh; Yoshie Aoyagi; Akiko Takatsu; Takashi Yarita (pp. 2039-2049).

The National Metrology Institute of Japan has issued a certified reference material (CRM) of freshwater lake sediment for polycyclic aromatic hydrocarbon (PAHs) analyses. The certification used three extraction techniques: pressurized liquid extraction (PLE) with toluene, PLE with dichloromethane/ethyl acetate (1:1 by volume), and alkaline extraction (1 M KOH in methanol) in combination with microwave-assisted extraction. Both gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/dopant-assisted atmospheric pressure photoionization/MS (LC/DA-APPI/MS) analyses were used. Certified values are provided for 18 PAHs at 1–25 μg kg⁻¹ except for perylene (2.08 × 10³ μg kg⁻¹), and information values are provided for two. Since the values of PAHs in the CRM are much lower than those in other CRMs and are comparable to those found at sites with little human influence, the CRM is suitable for PAH monitoring in sediment and soil samples.

Keywords: Polycyclic aromatic hydrocarbons (PAHs); Certified reference material (CRM); Sediment; Quality assurance/quality control

Label-free aptamer-based colorimetric detection of mercury ions in aqueous media using unmodified gold nanoparticles as colorimetric probe by Li Li; Baoxin Li; Yingying Qi; Yan Jin (pp. 2051-2057).

We report a simple and sensitive aptamer-based colorimetric detection of mercury ions (Hg²⁺) using unmodified gold nanoparticles as colorimetric probe. It is based on the fact that bare gold nanoparticles interact differently with short single-strand DNA and double-stranded DNA. The anti-Hg²⁺ aptamer is rich in thymine (T) and readily forms T–Hg²⁺–T configuration in the presence of Hg²⁺. By measuring color change or adsorption ratio, the bare gold nanoparticles can effectively differentiate the Hg²⁺-induced conformational change of the aptamer in the presence of a given salt with high concentration. The assay shows a linear response toward Hg²⁺ concentration through a five-decade range of 1 × 10⁻⁴ mol L⁻¹ to 1 × 10⁻⁹ mol L⁻¹. Even with the naked eye, we could identify micromolar Hg²⁺ concentrations within minutes. By using the spectrometric method, the detection limit was improved to the nanomolar range (0.6 nM). The assay shows excellent selectivity for Hg²⁺ over other metal cations including K⁺, Ba²⁺, Ni²⁺, Pb²⁺, Cu²⁺, Cd²⁺, Mg²⁺, Ca²⁺, Zn²⁺, Al³⁺, and Fe³⁺. The major advantages of this Hg²⁺ assay are its water-solubility, simplicity, low cost, visual colorimetry, and high sensitivity. This method provides a potentially useful tool for the Hg²⁺ detection.

Keywords: Mercury ion; Aptamer; Gold nanoparticles; Colorimetric probe

Quantification of luminally released serotonin in rat proximal colon by capillary electrophoresis with laser-induced fluorescence detection by Sheng-da Qi; Shun-lian Tian; Hong-xi Xu; Joseph J. Y. Sung; Zhao-xiang Bian (pp. 2059-2066).

Serotonin (5-hydroxytryptamine, 5-HT) plays vital roles in regulating gastrointestinal functions. Thus, the detection of 5-HT in the gastrointestinal tract is of great importance for biomedical research, medical diagnosis, and pharmaceutical therapy. This paper presents a simple, sensitive, and fast method for the quantification of luminally released serotonin in the feces and tissues of the rat proximal colon by means of capillary electrophoresis with laser-induced fluorescence detection. 5-Carboxyfluorescein N-succinimidyl ester was used for precolumn derivatization of serotonin. The optimal separation and detection conditions were obtained with an electrophoretic buffer containing 60 mM borate (pH 8.90) and an air-cooled argon-ion laser (excitation at 488 nm, emission at 520 nm). The serotonin concentrations in the feces and tissues of proximal colons were analyzed with this method, and the average values of serotonin in the feces samples were 1.951 ± 0.446 ng/mg (male) and 2.095 ± 0.533 ng/mg (female) and 1.397 ± 0.267 ng/mg in rat proximal colon tissues. The results demonstrate that this method can accurately determine luminally released 5-HT in rats.

Keywords: Serotonin; Capillary electrophoresis; Laser-induced fluorescence

Comparison in the analytical performance between krypton and argon glow discharge plasmas as the excitation source for atomic emission spectrometry by Kazuaki Wagatsuma (pp. 2067-2074).

The emission characteristics of ionic lines of nickel, cobalt, and vanadium were investigated when argon or krypton was employed as the plasma gas in glow discharge optical emission spectrometry. A dc Grimm-style lamp was employed as the excitation source. Detection limits of the ionic lines in each iron-matrix alloy sample were compared between the krypton and the argon plasmas. Particular intense ionic lines were observed in the emission spectra as a function of the discharge gas (krypton or argon), such as the Co II 258.033 nm for krypton and the Co II 231.707 nm for argon. The explanation for this is that collisions with the plasma gases dominantly populate particular excited levels of cobalt ion, which can receive the internal energy from each gas ion selectively, for example, the 3d⁷4p ³G₅ (6.0201 eV) for krypton and the 3d⁷4p ³G₄ (8.0779 eV) for argon. In the determination of nickel as well as cobalt in iron-matrix samples, more sensitive ionic lines could be found in the krypton plasma rather than the argon plasma. Detection limits in the krypton plasma were 0.0039 mass% Ni for the Ni II 230.299-nm line and 0.002 mass% Co for the Co II 258.033-nm line. However, in the determination of vanadium, the argon plasma had better analytical performance, giving a detection limit of 0.0023 mass% V for the V II 309.310-nm line.

Keywords: Glow discharge optical emission spectrometry; Argon plasma; Krypton plasma; Nickel; Cobalt; Vanadium; Excitation mechanism

Determination of trace elements in residual oil by high-resolution inductively coupled plasma mass spectrometry by Hualin Xie; Kelong Huang; Jinchun Liu; Xidu Nie; Liang Fu (pp. 2075-2080).

An analytical method using high-resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) for rapid simultaneous determination of 20 elements, including Na, Mg, Al, Ca, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Mo, Cd, Sn, Sb, Ba, and Pb elements, in residual oil was described. The sample was dissolved in HNO₃ by microwave digestion, and then the above 20 elements in the solution were analyzed directly by HR-ICP-MS. Most of the spectral interferences could be avoided by measuring in the high-resolution mode. The matrix effect caused by the sample-digesting solution and corrected by Sc, Rh, and Bi as the internal standard elements was studied in detail. The optimum condition of the determination was also tested and discussed. The result showed that the detection limits of the method were in the range of 0.014 to 11.6 μg L⁻¹; the relative standard deviation was less than 3.8% and recoveries in the samples were in the range of 88.4% to 108.0%. This method can be used to determine the trace elements in residual oil with the features of accurate, rapid, and convenient determination.

Keywords: Residual oil; HR-ICP-MS; Trace elements; Spectral interferences; Matrix effect

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Analytical and Bioanalytical Chemistry (v.393, #8)

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Analytical and Bioanalytical Chemistry (v.393, #8)