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Analytical and Bioanalytical Chemistry (v.393, #1)

The scientists of today: revisiting Leonardo in a global environment by Sylvia Daunert (pp. 1-3).

is the Gill Eminent Professor of Analytical and Biological Chemistry, the 2004–2005 Distinguished Professor from the College of Arts and Sciences at the University of Kentucky, and a 2005–2006 University of Kentucky Research Professor. Dr Daunert’s research interests lie in the area of bioanalytical chemistry, at the interface between analytical chemistry, molecular biology, and bioengineering. More specifically, her group employs recombinant DNA technology to design new molecular diagnostic tools and biosensors based on genetically engineered proteins and cells for applications in biomedical and environmental fields. Additionally, the research of her group focuses on the design of sensing arrays for the detection of molecules in small volumes and microfluidic platforms, and in the development of smart biomaterials for responsive drug delivery systems. Dr Daunert has served as Editor of Analytical and Bioanalytical Chemistry since its inception in 2001.

Meet the contributors (pp. 5-12).

Expensive equipment—a guide to purchasing by Richard Turle (pp. 13-14).

, a graduate of the University of London and the University of Waterloo, is Chief of the Analysis and Air Quality Division, Environmental Science and Technology Centre of Environment Canada in Ottawa, Canada. He manages a laboratory with 45 researchers, chemists and technologists who are responsible for developing analytical methods for measuring air pollution and new regulations as well as analysing thousands of samples annually for the National Air Pollution Surveillance programme, stack and vehicle emission samples and for compliance and enforcement. He is interested in quality assurance and accreditation as well as methods for measuring air quality and methods for regulations.

How to use time more efficiently by John Fetzer (pp. 15-16).

is the author or co-author of over 130 research articles, reviews, and book chapters. He is a member of the International Advisory Board of Analytical and Bioanalytical Chemistry. Dr Fetzer 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.

Monitoring nanoparticles in the environment by B. M. Simonet; M. Valcárcel (pp. 17-21).

The presence of nanoparticles in the environment can have important implications for both environmental and human health. Nanoscience and nanotechnology are expected to change industrial production and the economy as we know them today. However, nanotechnologies can also be a source of risks. The increasing use of nanoparticles in industrial applications will inevitably lead to the release of such materials into the environment. Accurately assessing the environmental risks posed by nanoparticles requires using effective quantitative analytical methods to determine their mobility, reactivity, ecotoxicity and persistency, many of which have still to be developed. This overview describes some methodological aspects relating to the fields of nanoparticle analysis, nanometrology and analytical chemistry.

Keywords: Nanoparticle analysis; Environmental risks; Analytical chemistry

Combining microchip and cell technology for creation of novel biodevices by Kae Sato; Yo Tanaka; Björn Renberg; Takehiko Kitamori (pp. 23-29).

Microchip technology has matured over the years into an important field in which novel technologies are being constantly invented, and down-sizing and incorporation of already existing methodologies into the microscale is increasing assay performance and bearing the promise of future total integration for simple, widespread use. One rapidly growing sub-discipline of the microchip research field is focused around the integration of microchip technology and cell biology. In this review, we recapitulate progress here at the Kitamori laboratory in direct relation to cell and microchip technologies, and show some examples of successful integration of the two, going from controlled patterning of cells, on-chip cell culture stimulation, and cardiovascular systems on a chip, to bio-microdevices integrating cardiovascular cells and microtechnology to create novel biodevices such as biocompatible, miniature pumps.

Keywords: Microchemical chip; MicroTAS; Cultured cells; Bioassay; Biodevice

Lipid imaging with cluster time-of-flight secondary ion mass spectrometry by Alain Brunelle; Olivier Laprévote (pp. 31-35).

This brief article provides an overview of the current state of the art in biological imaging mass spectrometry using cluster time-of-flight secondary ion mass spectrometry (TOF–SIMS). Recent and spectacular improvements in terms of sensitivity of TOF–SIMS imaging methods have allowed many biological applications to recently be successfully tested, such as mapping of lipid disorders in human muscles of a patient suffering from dystrophy, localization of surfactins after the swarming of bacteria on a surface, or lipid mapping over whole-body animal sections.

Keywords: Mass spectrometry imaging; Lipids; Cluster ion source; TOF–SIMS

Hydrophilic and amphiphilic water pollutants: using advanced analytical methods for classic and emerging contaminants by Walter Giger (pp. 37-44).

Organic pollutants are a highly relevant topic in environmental science and technology. This article briefly reviews historic developments, and then focuses on the current state of the art and future perspectives on the qualitative and quantitative trace determination of polar organic contaminants, which are of particular concern in municipal and industrial wastewater effluents, ambient surface waters, run-off waters, atmospheric waters, groundwaters and drinking waters. The pivotal role of advanced analytical methods is emphasized and an overview of some contaminant classes is presented. Some examples of polar water pollutants, which are discussed in a bit more detail here, are chosen from projects tackled by the research group led by the author of this article.

Keywords: Emerging contaminants; Liquid chromatography; Mass spectrometry; Surfactants; Antibiotics; Perfluorinated compounds; Benzotriazoles

Completely automated open-path FT-IR spectrometry by Peter R. Griffiths; Limin Shao; April B. Leytem (pp. 45-50).

Atmospheric analysis by open-path Fourier-transform infrared (OP/FT-IR) spectrometry has been possible for over two decades but has not been widely used because of the limitations of the software of commercial instruments. In this paper, we describe the current state-of-the-art of the hardware and software that constitutes a contemporary OP/FT-IR spectrometer. We then describe advances that have been made in our laboratory that have enabled many of the limitations of this type of instrument to be overcome. These include not having to acquire a single-beam background spectrum that compensates for absorption features in the spectra of atmospheric water vapor and carbon dioxide. Instead, an easily measured “short path-length” background spectrum is used for calculation of each absorbance spectrum that is measured over a long path-length. To accomplish this goal, the algorithm used to calculate the concentrations of trace atmospheric molecules was changed from classical least-squares regression (CLS) to partial least-squares regression (PLS). For calibration, OP/FT-IR spectra are measured in pristine air over a wide variety of path-lengths, temperatures, and humidities, ratioed against a short-path background, and converted to absorbance; the reference spectrum of each analyte is then multiplied by randomly selected coefficients and added to these background spectra. Automatic baseline correction for small molecules with resolved rotational fine structure, such as ammonia and methane, is effected using wavelet transforms. A novel method of correcting for the effect of the nonlinear response of mercury cadmium telluride detectors is also incorporated. Finally, target factor analysis may be used to detect the onset of a given pollutant when its concentration exceeds a certain threshold. In this way, the concentration of atmospheric species has been obtained from OP/FT-IR spectra measured at intervals of 1 min over a period of many hours with no operator intervention.

Keywords: Atmospheric monitoring; Open-path; Fourier-transform infrared; Automatic operation; Baseline correction; Wavelet transforms; Nonlinear response correction; Target factor analysis

Optimal coherent control of sensitivity and selectivity in spectrochemical analysis by David S. Moore (pp. 51-56).

The number and breadth of coherently controlled chemical processes are escalating exponentially since the recent convergence of stable broadband ultrafast laser sources, robust pulse shaping devices, and closed-loop optimization routines. We show here how these methods can also be applied to spectrochemical analysis. We discuss the basics of optimal coherent control and describe their use, both present and future, to enhance the sensitivity and/or selectivity of several different spectroscopic analytical methods.

Keywords: Coherent control; Ultrafast lasers; Pulse shaping; Closed-loop optimization; Spectrochemical analysis

Element-tagged immunoassay with inductively coupled plasma mass spectrometry for multianalyte detection by Maria Careri; Lisa Elviri; Alessandro Mangia (pp. 57-61).

The multianalyte immunoassay approach is currently attracting increasing attention due to its high sample throughput, short assay time, low sample consumption and reduced overall cost per assay. This paper reviews progress in the field of multianalyte immunoassays using inductively coupled plasma mass spectrometry, as well as applications of this approach in different fields. Examples related to the combination of protein microarray technology with the multitag approach of the immunoassay ICP-MS method and to the use of ICP-MS in the field of imaging are described. A novel strategy that involves tagging antibodies for ICP-MS detection in sensitive multitag bioassays is also presented. Finally, the outlook for this promising technique is discussed.

Keywords: Bioanalytical methods; Element-tagged multianalyte immunoassay; Inductively coupled plasma mass spectrometry; Laser ablation; Protein microarray; Imaging mass spectrometry

Capillary-based microfluidic analysis systems by Qun Fang; Meng Sun; Yan-Zhen Huang (pp. 63-66).

An overview of the recent development of high-throughput capillary-based microfluidic analysis systems (CBMAS) is presented. The advantages and applications of these systems are discussed and illustrated by recent results obtained in the authors’ group and other groups. A possible outlook for CBMAS is discussed.

Keywords: Microfluidics; Microfabrication; Capillary electrophoresis; Electrophoresis; Flow injection

Rapid test strips for analysis of mycotoxins in food and feed by Rudolf Krska; Alexandra Molinelli (pp. 67-71).

An overview is given on recent trends and applications of rapid immunodiagnostic tests for screening of food and feed for mycotoxins. Different test formats are discussed, and challenges in the development of lateral-flow devices for on-site determination of mycotoxins, with requirements such as being robust, fast, and cost-effective, are briefly elucidated.

Keywords: Mycotoxins; Lateral-flow device; Immunodiagnostic assay; Rapid test; Food analysis; Feed analysis

Determining biological noise via single cell analysis by Edgar A. Arriaga (pp. 73-80).

Single cell analysis techniques describe the cellular heterogeneity that originates from fundamental stochastic variations in each of the molecular processes underlying cell function. The quantitative description of this set of variations is called biological noise and includes intrinsic and extrinsic noise. The former refers to stochastic variations directly involved with a given process, while the latter is due to environmental factors associated with other processes. Mathematical models are successful in predicting noise trends in simple biological systems, but it takes single cell techniques such as flow cytometry and time lapse microscopy to determine and dissect biological noise. This review describes several approaches that have been successfully used to describe biological noise.

Keywords: Biological noise; Extrinsic noise; Gene regulation function; Flow cytometry; Intrinsic noise; Single cell analysis; Time lapse microscopy

Ecotoxicity and analysis of nanomaterials in the aquatic environment by Marinella Farré; Krisztina Gajda-Schrantz; Lina Kantiani; Damià Barceló (pp. 81-95).

Nanotechnology is a major innovative scientific and economic growth area. However nanomaterial residues may have a detrimental effect on human health and the environment. To date there is a lack of quantitative ecotoxicity data, and recently there has been great scientific concern about the possible adverse effects that may be associated with manufactured nanomaterials. Nanomaterials are in the 1- to 100-nm size range and can be composed of many different base materials (carbon, silicon and metals, such as gold, cadmium and selenium) and they have different shapes. Particles in the nanometer size range do occur both in nature and as a result of existing industrial processes. Nevertheless, new engineered nanomaterials and nanostructures are different because they are being fabricated from the “bottom up”. Nanomaterial properties differ compared with those of the parent compounds because about 40–50% of the atoms in nanoparticles (NPs) are on the surface, resulting in greater reactivity than bulk materials. Therefore, it is expected that NPs will have different biological effects than parent compounds. In addition, release of manufactured NPs into the aquatic environment is largely an unknown. The surface properties and the very small size of NPs and nanotubes provide surfaces that may bind and transport toxic chemical pollutants, as well as possibly being toxic in their own right by generating reactive radicals. This review addresses hazards associated and ecotoxicological data on nanomaterials in the aquatic environment. Main weaknesses in ecotoxicological approaches, controversies and future needs are discussed. A brief discussion on the scarce number of analytical methods available to determinate nanomaterials in environmental samples is included.

Keywords: Nanomaterials; Nanoparticles; Nanotubes; Fullerenes; Quantum dot; Toxicity

Mass spectrometric approaches in impaired driving toxicology by Hans H. Maurer (pp. 97-107).

Driving under the influence of prescribed or illegal drugs increases the risk of having road accidents, just like driving under the influence of alcohol. In forensic toxicology, an increasing number of blood samples must be analyzed for drugs. Immunoassays tailored for a limited number of drugs (of abuse) are usually applied as prescreening tests at the roadside and/or in the laboratory. However, many other common drugs, such as anesthetics, antidepressants, antiepileptics, antihistamines, newer designer drugs, herbal drugs, neuroleptics (antipsychotics), opioids, or sedative-hypnotics, can also impair drivers. Therefore, this paper reviews multianalyte single-stage and tandem gas or liquid chromatography–mass spectrometry (GC-MS or LC-MS) procedures for the screening, identification, and validated quantification of such drugs in blood that have been reported since 2003. Basic information about the biosample assayed, workup, chromatography, the mass spectral detection mode, and validation data is summarized in tables. The pros and cons of the reviewed procedures are critically discussed, particularly with respect to their probable usefulness in impaired driving toxicology.

Keywords: Drug; Blood; Mass spectrometry; Impaired driving; Toxicology; DUID

Nanobioanalytical luminescence: Förster-type energy transfer methods by Aldo Roda; Massimo Guardigli; Elisa Michelini; Mara Mirasoli (pp. 109-123).

Förster resonance energy transfer-based analytical techniques represent a unique tool for bioanalysis because they allow one to detect protein–protein interactions and conformational changes of biomolecules at the nanometer scale, both “in vitro” and “in vivo” in cells, tissues and organisms. These techniques are applied in diverse fields, from the detection and quantification of ligands able to bind to proteins or receptors to the development of RET-based whole-cell biosensors, microscope imaging techniques and “in vivo” whole-body imaging for the monitoring of physiological and pathological processes. However, their quantitative performances need further improvements and, even though RET measurement principles and procedures have been continuously improved, in some cases only qualitative or semiquantitative information can be obtained. In this review we report recent applications of RET-based analytical techniques and discuss their advantages and limitations. Figure RET-based techniques allow analysis of protein–protein interactions and conformational changes of biomolecules at the nanometer scale

Keywords: Fluorescence/luminescence; Biosensors; Bioassays; Fluorescence resonance energy transfer; Bioluminescence resonance energy transfer; Protein–protein interaction

Resonance energy transfer methods of RNA detection by Kyle A. Cissell; Eric A. Hunt; Sapna K. Deo (pp. 125-135).

Quantitation of RNA is important in diagnostics, environmental science, and basic biomedical research. RNA is considered a signature for pathogen identification, and its expression profile is linked with disease pathogenesis, allowing for biomarker identification. RNA-based diagnostics is an emerging field of research. This expansion of interest in studying RNA has generated demand for its accurate and sensitive detection. Several methods have therefore been developed to detect RNA. Resonance energy transfer methods of RNA detection are highly promising in terms of simplicity and high sensitivity. In this review, we have focused on the latest developments in resonance energy transfer methods of RNA detection that utilize various probe designs. The probe designs discussed here are molecular beacons, quenched autoligation probes, and linear oligonucleotide probes. Resonance energy transfer methods based on both fluorescence and bioluminescence detection are discussed.

Keywords: RNA detection; Molecular beacons; Quenched autoligation probes; Fluorescence resonance energy transfer; Bioluminescence resonance energy transfer

Modeling of retention of adrenoreceptor agonists and antagonists on polar stationary phases in hydrophilic interaction chromatography: a review by Kiyokatsu Jinno; Noel S. Quiming; Nerissa L. Denola; Yoshihiro Saito (pp. 137-153).

Retention prediction models for reversed-phase liquid chromatography (RPLC) have been extensively studied owing to the fact that RPLC remains the most widely used chromatographic technique especially in the field of pharmaceutical and biomedical analyses. However, RPLC is not always the method of choice for the analysis of some compounds that have high polarity. Hydrophilic interaction chromatography (HILIC) has been gaining interest in the last few years as an alternative option to RPLC for the analysis of polar and hydrophilic analytes. HILIC is a variant of normal-phase liquid chromatography, but utilizes water in a water-miscible organic solvent as the eluent in conjunction with a hydrophilic stationary phase. The present review aims to summarize recent contributions on the development of retention prediction models for a group of basic analytes, namely, the adrenoreceptor agonists and antagonists, on different polar stationary phases. The use of multiple linear regression and artificial neural networks in model building is highlighted.

Keywords: Adrenoreceptor agonists/antagonists; Artificial neural network; Diol column; Hydrophilic interaction chromatography; Multiple linear regression; Poly(vinyl alcohol)-bonded phase; Unmodified silica phase

Advances in the separation, sensitive detection, and characterization of heparin and heparan sulfate by Albert K. Korir; Cynthia K. Larive (pp. 155-169).

Elucidation of the relationship between the structure and biological function of the glycosaminoglycans (GAGs) heparin and heparan sulfate (HS) presents an important analytical challenge mainly due to the difficulty in determining their fine structure. Heparin and HS are responsible for mediation of a wide range of biological actions through specific binding to a variety of proteins including those involved in blood coagulation, cell proliferation, differentiation and adhesion, and host–pathogen interactions. Therefore, there is a growing interest in characterizing the microstructure of heparin and HS and in elucidating the molecular level details of their interaction with peptides and proteins. This review discusses recent developments in the analytical methods used for sensitive separation, detection, and structural characterization of heparin and HS. A brief discussion of the analysis of contaminants in pharmaceutical heparin is also presented.

Keywords: Heparin; Heparan sulfate; Oversulfated chondroitin sulfate; Glycosaminoglycan; Capillary electrophoresis; Fluorescence; Mass spectrometry; Reversed-phase ion-pairing liquid chromatography–mass spectrometry; NMR; Capillary isotachophoresis–NMR

Targeted next-generation sequencing by specific capture of multiple genomic loci using low-volume microfluidic DNA arrays by Stephan Bau; Nadine Schracke; Marcel Kränzle; Haiguo Wu; Peer F. Stähler; Jörg D. Hoheisel; Markus Beier; Daniel Summerer (pp. 171-175).

We report a flexible method for selective capture of sequence fragments from complex, eukaryotic genome libraries for next-generation sequencing based on hybridization to DNA microarrays. Using microfluidic array architecture and integrated hardware, the process is amenable to complete automation and does not introduce amplification steps into the standard library preparation workflow, thereby avoiding bias of sequence distribution and fragment lengths. We captured a discontiguous human genomic target region of 185 kb using a tiling design with 50mer probes. Analysis by high-throughput sequencing using an Illumina/Solexa 1G Genome Analyzer revealed 2150-fold enrichment with mean per base coverage between 4.6 and 107.5-fold for the individual target regions. This method represents a flexible and cost-effective approach for large-scale resequencing of complex genomes.

Keywords: Next-generation sequencing; Sequencing-by-synthesis; Microarrays; Microfluidics; Sequence enrichment; gDNA Library preparation

Cholera toxin subunit B detection in microfluidic devices by Natinan Bunyakul; Katie A. Edwards; Chamras Promptmas; Antje J. Baeumner (pp. 177-186).

Fluorescence and electrochemical microfluidic biosensors were developed for the detection of cholera toxin subunit B (CTB) as a model analyte. The microfluidic devices were made from polydimethylsiloxane (PDMS) using soft lithography from silicon templates. The polymer channels were sealed with a glass plate and packaged in a polymethylmethacrylate housing that provided leakproof sealing and a connection to a syringe pump. In the electrochemical format, an interdigitated ultramicroelectrode array (IDUA) was patterned onto the glass slide using photolithography, gold evaporation and lift-off processes. For CTB recognition, CTB-specific antibodies were immobilized onto superparamagnetic beads and ganglioside GM₁ was incorporated into liposomes. The fluorescence dye sulforhodamine B (SRB) and the electroactive compounds potassium hexacyanoferrate (II)/hexacyanoferrate (III) were used as detection markers that were encapsulated inside the liposomes for the fluorescence and electrochemical detection formats, respectively. Initial optimization experiments were carried out by applying the superparamagnetic beads in microtiter plate assays and SRB liposomes before they were transferred to the microfluidic systems. The limits of detection (LoD) of both assay formats for CTB were found to be 6.6 and 1.0 ng mL⁻¹ for the fluorescence and electrochemical formats, respectively. Changing the detection system was very easy, requiring only the synthesis of different marker-encapsulating liposomes, as well as the exchange of the detection unit. It was found that, in addition to a lower LoD, the electrochemical format assay showed advantages over the fluorescence format in terms of flexibility and reliability of signal recording.

Keywords: Biosensor; Microfluidic; Cholera toxin; Liposomes; Electrochemical detection

Suitability of infrared spectroscopic imaging as an intraoperative tool in cerebral glioma surgery by Stephan B. Sobottka; Kathrin D. Geiger; Reiner Salzer; Gabriele Schackert; Christoph Krafft (pp. 187-195).

Infrared spectroscopic imaging is a promising intraoperative tool which enables rapid, on-site diagnosis of brain tumors during neurosurgery. A classification model was recently developed using infrared spectroscopic images from thin tissue sections to grade malignant gliomas, the most frequent class of primary brain tumor. In this study the model was applied to 54 specimens from six patients with inhomogeneous gliomas composed of regions with different tumor density and morphology. The resection was controlled using neuronavigation which transfers the findings obtained by preoperative magnetic resonance imaging (MRI) into the operating field. For comparison, all specimens were independently evaluated by histopathology after hematoxylin and eosin staining. The infrared-derived grading agreed with histopathology and MRI findings for almost all specimens. With regard to histopathological assessment, sensitivities of 100% (22/22) and 93.1% (27/29) and specificities of 96.9% (31/32) and 88.0% (22/25) were achieved, depending on whether the classification was based on the predominant or maximal tumor grade, respectively, in the specimen. Altogether, in 98% (53/54) of all specimens the decision to continue or not continue tumor resection could have been made according to the infrared spectroscopic classification. This retrospective study clearly demonstrates that infrared spectroscopic imaging may help to define tumor margins intraoperatively and to detect high-grade tumor residues for achieving more radical tumor resection. MRT-guided tumor resection (left) is combined with infrared spectroscopy-based tissue classification (middle, right). With regard to histopathological assessment, sensitivities of 100% and 93.1% and specificities of 96.9% and 88.0% were achieved for 54 specimens. (TIF 47.1 KB)

Keywords: FTIR imaging; Neurosurgery; Neuropathology; Magnetic resonance imaging

Towards a nondestructive chemical characterization of biofilm matrix by Raman microscopy by Natalia P. Ivleva; Michael Wagner; Harald Horn; Reinhard Niessner; Christoph Haisch (pp. 197-206).

In this study, the applicability of Raman microscopy (RM) for nondestructive chemical analysis of biofilm matrix, including microbial constituents and extracellular polymeric substances (EPS), has been assessed. The examination of a wide range of reference samples such as biofilm-specific polysaccharides, proteins, microorganisms, and encapsulated bacteria revealed characteristic frequency regions and specific marker bands for different biofilm constituents. Based on received data, the assignment of Raman bands in spectra of multispecies biofilms was performed. The study of different multispecies biofilms showed that RM can correlate various structural appearances within the biofilm to variations in their chemical composition and provide chemical information about a complex biofilm matrix. The results of RM analysis of biofilms are in good agreement with data obtained by confocal laser scanning microscopy (CLSM). Thus, RM is a promising tool for a label-free chemical characterization of different biofilm constituents. Moreover, the combination of RM with CLSM analysis for the study of biofilms grown under different environmental conditions can provide new insights into the complex structure/function correlations in biofilms.

Keywords: Biofilm matrix; Extracellular polymeric substances (EPS); Raman microscopy (RM); Confocal laser scanning microscopy (CLSM)

Analytical characterization of chitosan nanoparticles for peptide drug delivery applications by E. Ieva; A. Trapani; N. Cioffi; N. Ditaranto; A. Monopoli; L. Sabbatini (pp. 207-215).

Chitosan-cyclodextrin hybrid nanoparticles (NPs) were obtained by the ionic gelation process in the presence of glutathione (GSH), chosen as a model drug. NPs were characterized by means of transmission electron microscopy and zeta-potential measurements. Furthermore, a detailed X-ray photoelectron spectroscopy study was carried out in both conventional and depth-profile modes. The combination of controlled ion-erosion experiments and a scrupulous curve-fitting approach allowed for the first time the quantitative study of the GSH in-depth distribution in the NPs. NPs were proven to efficiently encapsulate GSH in their inner cores, thus showing promising perspectives as drug carriers.

Keywords: Nanoparticle; Chitosan; X-ray photoelectron spectroscopy; Drug delivery system; Glutathione

Enantioselective visualization of D-alanine in rat anterior pituitary gland: localization to ACTH-secreting cells by Sachise Etoh; Kenji Hamase; Akiko Morikawa; Tomohiro Ohgusu; Kiyoshi Zaitsu (pp. 217-223).

The cellular localization of D-alanine (D-Ala) in the rat pituitary gland, the tissue containing the highest amount of D-Ala, has been clarified for the first time by enantioselective visualization of D-Ala using our own established mouse monoclonal antibody against D-Ala. D-Ala immunopositive cells were present predominantly in the anterior lobe, while no intense staining was observed in the intermediate and posterior lobes. The anterior pituitary gland contains five types of cells secreting specific hormones (growth hormone, adrenocorticotropic hormone (ACTH), gonadotropic hormone, prolactin, and thyroid-stimulating hormone), and the double staining results indicated that D-Ala is localized to the ACTH-secreting cells. The localization of D-Ala is clearly different from that of D-aspartic acid (D-Asp), which is observed in the prolactin cells. Considered together with our previous findings that D-Ala is localized to the insulin-secreting beta-cells in the pancreas, and both ACTH and insulin are typical regulatory hormones of blood glucose, D-Ala is suggested to have some functional relationships to blood glucose level regulation in mammals.

Keywords: D-Alanine; D-Aspartic acid; Enantioselective analysis; Immunohistochemical localization; ACTH; Anterior pituitary gland

Electrocatalytic sulfite biosensor with human sulfite oxidase co-immobilized with cytochrome c in a polyelectrolyte-containing multilayer by Roberto Spricigo; Roman Dronov; Fred Lisdat; Silke Leimkühler; Frieder W. Scheller; Ulla Wollenberger (pp. 225-233).

An efficient electrocatalytic biosensor for sulfite detection was developed by co-immobilizing sulfite oxidase and cytochrome c with polyaniline sulfonic acid in a layer-by-layer assembly. QCM, UV–Vis spectroscopy and cyclic voltammetry revealed increasing loading of electrochemically active protein with the formation of multilayers. The sensor operates reagentless at low working potential. A catalytic oxidation current was detected in the presence of sulfite at the modified gold electrode, polarized at +0.1 V (vs. Ag/AgCl 1 M KCl). The stability of the biosensor performance was characterized and optimized. A 17-bilayer electrode has a linear range between 1 and 60 µM sulfite with a sensitivity of 2.19 mA M⁻¹ sulfite and a response time of 2 min. The electrode retained a stable response for 3 days with a serial reproducibility of 3.8% and lost 20% of sensitivity after 5 days of operation. It is possible to store the sensor in a dry state for more than 2 months. The multilayer electrode was used for determination of sulfite in unspiked and spiked samples of red and white wine. The recovery and the specificity of the signals were evaluated for each sample. Figure Schematic of the bioelectrocatalytic sulfite sensor: sulfite oxidase (green) oxidizes sulfite to sulfate and transfers electrons via heme b ₅ to cyt c (red) and thence to the gold electrode

Keywords: Bioelectrocatalysis; Sulfite; Sulfite oxidase; Cytochrome c; Multilayer

Water-compatible molecularly imprinted polymer for the selective recognition of fluoroquinolone antibiotics in biological samples by Elena Benito-Peña; Sofia Martins; Guillermo Orellana; María Cruz Moreno-Bondi (pp. 235-245).

A novel water-compatible molecularly imprinted polymer (MIP), prepared with enrofloxacin (ENR) as the template, has been optimised for the selective extraction of fluoroquinolone antibiotics in aqueous media. The results of a morphological characterisation and selectivity tests of the polymer material for ENR and related derivatives are reported. High affinity for the piperazine-based fluoroquinolones marbofloxacin, ciprofloxacin, norfloxacin and ofloxacin was observed, whereas no retention was found for nonrelated antibiotics. Various parameters affecting the extraction efficiency of the polymer have been optimised to achieve selective extraction of the antibiotics from real samples and to reduce nonspecific interactions. These findings resulted in a MISPE/HPLC-FLD method allowing direct extraction of the analytes from aqueous samples with a selective wash using just 50% (v/v) organic solvent. The method showed excellent recoveries and precision when buffered urine samples fortified at five concentration levels (25–250 ng mL⁻¹ each) of marbofloxacin, ciprofloxacin, norfloxacin, enrofloxacin and sarafloxacin were tested (53–88%, RSD 1–10%, n = 3). Moreover, the biological matrix of the aqueous samples did not influence the preconcentration efficiency of the fluoroquinolones on the MIP cartridges; no significant differences were observed between the recovery rates of the antibiotics in buffer and urine samples. The detection limits of the whole process range between 1.9 and 34 ng mL^–1 when 5-mL urine samples are processed. The developed method has been successfully applied to preconcentration of norfloxacin in urine samples of a medicated patient, demonstrating the ability of the novel MIP for selective extraction of fluoroquinolones in urine samples.

Keywords: Water-compatible molecularly imprinted polymers; Fluoroquinolones; Antibiotics; Solid-phase extraction; Urine samples

Determination of biogenic amines in food samples using derivatization followed by liquid chromatography/mass spectrometry by Susanne Bomke; Bettina Seiwert; Lukas Dudek; Stefan Effkemann; Uwe Karst (pp. 247-256).

A liquid chromatography (LC)/mass spectrometry method was developed for the determination of selected biogenic amines in various fish and other food samples. It is based on a precolumn derivatization of the amines with succinimidylferrocenyl propionate under formation of the respective amides and their reversed-phase liquid-chromatographic separation with subsequent electrospray ionization mass-spectrometric detection. Deuterated putescine, cadaverine, and histamine are added prior to the derivatization as internal standards that are coeluted, thus allowing excellent reproducibility of the analysis to be achieved. Depending on the analyte, the limits of detection were between 1.2 and 19.0 mg/kg, covering between 2 and 3 decades of linearity. The limit of detection and the linear range for histamine are suitable for the surveillance of the only defined European threshold for biogenic amines in fish samples. Compared with the established ortho-phthalaldehyde (OPA)/LC/fluorescence method, the newly developed method allows an unambiguous identification of the biogenic amines by their mass spectra in addition to only retention times, a fivefold acceleration of the separation, and independency from the sample matrix owing to the isotope-labeled internal standards. Various fish, calamari, and salami samples were successfully analyzed with the new method and validated with an independent OPA/LC/fluorescence method.

Keywords: Biogenic amines; Derivatization; Ferrocene; Liquid chromatography; Mass spectrometry; Stable isotopes

Study of multiple binding constants of dexamethasone with human serum albumin by capillary electrophoresis–frontal analysis and multivariate regression by Peng Zhao; Guijie Zhu; Weibing Zhang; Lihua Zhang; Zhen Liang; Yukui Zhang (pp. 257-261).

Studies into the interactions between drugs and human serum albumin (HSA) are extremely important for drug discovery, since HSA behaves as a carrier for external drugs and internal biological molecules. In this paper, to evaluate the pharmacokinetic and pharmacodynamic properties of dexamethasone (DXM), the interaction between DXM and HSA was studied by capillary electrophoresis–frontal analysis (CE-FA). According to the Klotz equation, four binding sites between DXM and HSA were obtained, and the average binding constant was 1.05 × 10³ M⁻¹. Furthermore, according to multiple equilibrium theory, based on the assumption that there are two types of binding site, the binding constant at one site was calculated to be 3.539 × 10³ M⁻¹, and the average of the other three was 1.234 × 10³ M⁻¹. In addition, to obtain the detailed binding information at each binding site, new equations were deduced by multivariate regression. The four binding constants of DXM and HSA were calculated to be 5.558 × 10¹ M⁻¹, 2.158 × 10⁴ M⁻¹, 7.312 × 10³ M⁻¹ and 2.043 × 10³ M⁻¹, respectively, which is helpful for detailed studies into the interactions between drugs and proteins with multiple binding sites. Figure Electropherograms of DXM sodium phosphate and HAS mixtures for different protein to drug concentration ratios, obtained by CE-FA

Keywords: Binding constant; Human serum albumin; Dexamethasone; Capillary electrophoresis–frontal analysis

Determination of selected β-receptor antagonists in biological samples by solid-phase extraction with cholesterolic phase and LC/MS by Bogusław Buszewski; Tomasz Welerowicz; Eugenia Tęgowska; Tadeusz F. Krzemiński (pp. 263-272).

A new method is presented for the determination of five selected β-receptor antagonists by HPLC, which emphasizes sample preparation via retention on a new type of silica gel sorbent used for solid-phase extraction (SPE). Sorbents of this type were obtained by the chemical modification of silica gels of various porosities by cholesterol ligands. The cholesterol-based packing material was investigated by spectroscopic methods and elemental analysis. The recoveries obtained with the extraction procedure were optimum over a relatively broad sample pH range (3.08–7.50). Analytical factors such as the sample loading, the washing step and elution conditions, the concentration of β-receptor antagonists to be extracted, and the type of sorbent were found to play significant roles in the sample preparation procedure and would therefore need to be controlled to achieve optimum recoveries of the analytes. Under optimum conditions, the recoveries of nadolol, acebutolol, esmolol, oxprenolol and propranolol from spiked buffers, blood and urine were reproducible and dependent on the polarity or hydrophilicity of the compounds. The above analytes were determined by reverse-phase high-performance liquid chromatography (HPLC) with UV and ESI-ion trap mass spectrometry (MS) detection. The described method was found to be suitable for the routine measurement of compounds that are both polar and basic, and can be applied for the analysis of biological samples such as urine and blood in clinical, toxicological or forensic laboratories. The recovery measurements were performed on spiked human urine and serum, and on real samples of mouse blood serum.

Keywords: Propranolol; Acebutolol; Esmolol; Oxprenolol; Nadolol; Cholesterolic stationary phase; SPE; LC/MS

Nylon-6 capillary-channeled polymer (C-CP) fibers as a hydrophobic interaction chromatography stationary phase for the separation of proteins by Rayman D. Stanelle; R. Kenneth Marcus (pp. 273-281).

Nylon-6 capillary-channeled polymer (C-CP) fibers are used as the stationary phase for the hydrophobic interaction chromatography (HIC) separation of a synthetic protein mixture composed of ribonuclease A, lysozyme, and holotransferrin. Nylon is a useful polymer phase for HIC as it has an alkyl backbone, while the amide functionality is hydrophilic (in fact ionic) in nature. The combination of a nonporous polymer surface of the fiber phases and high column permeability yields very efficient mass transfer characteristics, as exhibited by narrowing of peak widths with increases in mobile phase linear velocity. Retention factors and resolution were evaluated at flow rates ranging from 0.5 to 9 mL/min (linear velocities of ca. 2 to 15 mm/s) and at gradient slopes between 3.3 and 20 %B/min. Optimum resolution was achieved by employing fast flow rates (9 mL/min) and slow gradients (3 %B/min), also resulting in the highest peak capacities.

Keywords: Capillary-channeled polymer; Hydrophobic interaction chromatography; Fibers; Protein

Characterization of surface-confined ionic liquid stationary phases: impact of cation and anion identity on retention by David S. Van Meter; Nyoté J. Oliver; A. Björn Carle; Sabine Dehm; Thomas H. Ridgway; Apryll M. Stalcup (pp. 283-294).

A series of surface-confined ionic liquid (SCIL) stationary phases for high-performance liquid chromatography were synthesized in-house. The synthesized phases were characterized by the linear solvation energy relationship (LSER) method to determine the effect of residual linking ligands and the role of the cation and the anion on retention. Statistical analysis was utilized to determine whether the system coefficients returned from multiple linear regression analysis of chromatographic retention data for a set of 28 neutral aromatic probe solutes were significantly different. Examination of the energetics of retention via κ−κ plots agrees with the results obtained from the LSER analysis. Residual linking ligands were determined to contribute reversed-phase-type retention character to the chromatographic system. Furthermore, retention on the SCIL phases was observed to be more profoundly affected by the identity of the anion than by that of the cation.

Keywords: Linear solvation energy relationship; Retention mechanisms; Surface-confined ionic liquids; Ionic liquids; Reversed-phase high-performance liquid chromatography; κ−κ plots

Particle size characterization by quadruple-detector hydrodynamic chromatography by Amandaa K. Brewer; André M. Striegel (pp. 295-302).

Particle size and shape and their distribution directly influence a variety of end-use material properties related to packing, mixing, and transport of powders, solutions, and suspensions. Many of the techniques currently employed for particle size characterization have found limited applicability for broadly polydisperse and/or nonspherical particles. Here, we introduce a quadruple-detector hydrodynamic chromatography (HDC) method utilizing static multiangle light scattering (MALS), quasi-elastic light scattering (QELS), differential viscometry (VISC), and differential refractometry (DRI), and apply the technique to characterizing a series of solid and hollow polystyrene latexes with diameters in the approximate range of 40–400 nm. Using HDC/MALS/QELS/VISC/DRI, we were able to determine a multiplicity of size parameters and their polydispersity and to monitor the size of the particles across the elution profile of each sample. Using self-similarity scaling relationships between the molar mass and the various particle radii, we were also able to ascertain the shape of the latexes and the shape constancy as a function of particle size. The particle shape for each latex was confirmed by the dimensionless ratio ρ ≡ R G,z/R H,z which, in addition, provided information on the structure (compactness) of the latexes as a function of particle size. Solid and hollow polystyrene latex samples were also differentiable using these methods. Extension of this method to nonspherical, fractal objects should be possible.

Keywords: Polymers; Separations/instrumentation; Separations/theory; High performance liquid chromatography

Enantioselective complexation of carbamoylated quinine and quinidine with N-blocked amino acids: vibrational and electronic circular dichroism study by Ondřej Julínek; Marie Urbanová; Wolfgang Lindner (pp. 303-312).

Infrared absorption (IR) and vibrational and electronic circular dichroism (VCD and ECD, respectively) spectra of tert-butylcarbamoylquinine (t-BuCQN) and pseudoenantiomeric tert-butylcarbamoylquinidine (t-BuCQD), denoted as selectors (SO), complexed with chiral (S) and (R)-3,5-dinitrobenzoylleucine (DNB-Leu) and achiral 3,5-dinitrobenzoylglycine (DNB-Gly), denoted as selectands (SA), in methanol and acetonitrile, with the spectra of pure SA and SO are reported. H–D exchange of exchangeable hydrogen atoms of SA and SO in deuterated methanol which occurs in IR and VCD experiments is exploited to identify Amide II and Amide III vibrational modes. The formation of preferentially bound complexes composed of sterically compatible combinations of DNB-Leu and SO are manifested by increased intensity of VCD bands assigned to vibrations of amide, carbamate, quinoline, and dissociated carboxylate group and also by increased ECD signals. The VCD technique revealed similarities between the strongly bound diastereomeric complex of chiral DNB-Leu and SO and the complex of achiral DNB-Gly and SO, highlighting the leading role of SO in the formation of SA–SO complex. Figure Vibrational circular dichroism study: Interaction markers typical of the binding between the quinine selector and the derivatized amino acid selectand

Keywords: Diastereomeric complexes; Quinine derivatives; N-Derivatized amino acids; DNB derivatives; Vibrational circular dichroism; Electronic circular dichroism

A study of the interaction between enantiomers of zolmitriptan and hydroxypropyl-beta-cyclodextrin by capillary electrophoresis by Nannan Pang; Zhengxiang Zhang; Yu Bai; Huwei Liu (pp. 313-320).

The enantioresolution of zolmitriptan was performed using cyclodextrin (CD)-modified capillary zone electrophoresis (CZE) with hydroxypropyl-β-CD (HP-β-CD) as the chiral selector. The influence of experimental conditions on the enantioseparation of zolmitriptan, such as pH, temperature, applied voltage, and concentrations of running electrolyte and CD, was systematically investigated, obtaining a baseline separation of two enantiomers by the use of a 25 mM sodium dihydrogen phosphate (SDPH) running electrolyte (pH 2.4) containing 30 mM HP-β-CD at 15 °C. Binding constants for each enantiomer–HP-β-CD pair at different temperatures, as well as thermodynamic parameters for binding, were calculated. A nonlinear van’t Hoff plot was obtained, indicating that the thermodynamic parameters of complexation were temperature-dependent for zolmitriptan enantiomers. The significant contribution of the enthalpy difference to the Gibbs free energy change suggested a stereomeric barrier mechanism for chiral recognition. Figure Resolution of zolmitriptan enantiomers was achieved by using CD-modified CZE

Keywords: Binding constant; Capillary zone electrophoresis; Enantioseparation; Zolmitriptan; Cyclodextrin

Chiral separation of raltitrexed by cyclodextrin-modified micellar electrokinetic chromatography by Yi Liu; Xiaofang Fu; Chao Ma; Jiasheng Zhong; Yiping Liao; Huwei Liu (pp. 321-326).

A rapid and effective method was developed for the chiral separation of raltitrexed (RD) enantiomers by carboxymethyl-beta-cyclodextrin (CM-β-CD)-modified micellar electrokinetic chromatography (MEKC). Optimization of conditions including the type and concentration of the chiral selector, concentration of sodium dodecyl sulfate (SDS), pH and concentration of the background electrolyte (BGE), capillary temperature, and applied voltage was investigated. The enantiomers of raltitrexed could be separated with satisfactory resolution and linear response by using 75 mM Tris-phosphate at pH 8.0 containing 30 mM SDS and 8 mM CM-β-CD as buffer system. Furthermore, the usefulness of this method was demonstrated in a purity test of a real synthetic drug sample. Figure Chiral separation of raltitrexed by CM-β-CD MEKC was optimized and applied to test the purity of a synthetic drug sample

Keywords: Raltitrexed; Chiral separation; Micellar electrokinetic chromatography; Carboxymethyl-β-cyclodextrin

Retention time prediction of compounds in Grob standard mixture for apolar capillary columns in temperature-programmed gas chromatography by Yasar Thewalim; Fredrik Aldaeus; Anders Colmsjö (pp. 327-334).

This paper presents an extension of a previous investigation in which the behavior of nonpolar compounds in temperature-programmed gas chromatographic runs was predicted using thermodynamic (entropy and enthalpy) parameters derived from isothermal runs. In a similar manner, entropy and enthalpy parameters were determined for a Grob standard mixture of compounds with widely varying chemical characteristics. These parameters were used to predict the retention times and chromatographic behaviors of the compounds on four gas chromatography capillary columns: three that had phenyl-based stationary phases (with degrees of substitution of 0%, 5% and 50%) and one with (50%) cyanopropyl substitution. The predictions matched data empirically obtained from temperature-programmed chromatographic runs for all of the compounds extremely well, despite the wide variations in polarity of both the compounds and stationary phases. Thus, the results indicate that such simulations could greatly reduce the time and material costs of chromatographic optimizations.

Keywords: Gas chromatography; Grob standard mixture; Retention time; Retention order; Prediction

Titanium levels in the organs and blood of rats with a titanium implant, in the absence of wear, as determined by double-focusing ICP-MS by Alejandro Sarmiento-González; Jorge Ruiz Encinar; Juan M. Marchante-Gayón; Alfredo Sanz-Medel (pp. 335-343).

Titanium (Ti) has long been regarded as an inert and biocompatible metal, ideal for biomedical applications such as dental implants or joint replacements. However, concerns about the biocompatibility of Ti have lately arisen. Unfortunately, information on reliable Ti baseline physiological levels in blood and organ tissues is still pending and the real effects of physiological corrosion as opposed to wear processes of Ti or Ti alloys implants is controversial so far. In this work a previously developed and validated methodology, based on using double-focusing inductively coupled plasma mass spectrometry (DF-ICP-MS) has been used to establish Ti basal levels in blood and organs (heart, liver, spleen, kidneys, and lungs) of Wistar rats. These data were compared with the levels found in three Wistar rats implanted with a Ti wire embedded in their femur for 18 months, in order to assign possible Ti released purely due to non-wear physiological mechanisms. Results showed that Ti content in all the selected organ tissues and blood was higher than previously determined Ti basal levels, clearly showing both corrosion of the Ti implant and systemic Ti accumulation in target tissues. These results indicate that Ti metal corrosion occurs. This seems to be the only mechanism responsible in the long term for the observed passive dissolution of Ti of the implant in the absence of wear. A comparative study of the systemic distribution of the soluble and particulate Ti potentially released from Ti implants was also carried out by intraperitoneally injection of soluble Ti(citrate)₃ and insoluble TiO₂ particles, respectively. Different systemic Ti storage was observed. Whereas soluble Ti was rapidly transported to all distal organs under study, TiO₂ particles were only accumulated in lung tissue.

Keywords: Titanium; Implants; DF-ICP-MS; Rats; Corrosion

Determination of compound-specific Hg isotope ratios from transient signals using gas chromatography coupled to multicollector inductively coupled plasma mass spectrometry (MC-ICP/MS) by Mark Dzurko; Delphine Foucher; Holger Hintelmann (pp. 345-355).

MeHg and inorganic Hg compounds were measured in aqueous media for isotope ratio analysis using aqueous phase derivatization, followed by purge-and-trap preconcentration. Compound-specific isotope ratio measurements were performed by gas chromatography interfaced to MC-ICP/MS. Several methods of calculating isotope ratios were evaluated for their precision and accuracy and compared with conventional continuous flow cold vapor measurements. An apparent fractionation of Hg isotopes was observed during the GC elution process for all isotope pairs, which necessitated integration of signals prior to the isotope ratio calculation. A newly developed average peak ratio method yielded the most accurate isotope ratio in relation to values obtained by a continuous flow technique and the best reproducibility. Compound-specific isotope ratios obtained after GC separation were statistically not different from ratios measured by continuous flow cold vapor measurements. Typical external uncertainties were 0.16‰ RSD (n = 8) for the ²⁰²Hg^/198Hg ratio of MeHg and 0.18‰ RSD for the same ratio in inorganic Hg using the optimized operating conditions. Using a newly developed reference standard addition method, the isotopic composition of inorganic Hg and MeHg synthesized from this inorganic Hg was measured in the same run, obtaining a value of δ ²⁰²Hg = −1.49 ± 0.47 (2SD; n = 10). For optimum performance a minimum mass of 2 ng per Hg species should be introduced onto the column.

Keywords: Multicollector inductively coupled plasma mass spectrometry; Mercury; Methylmercury; Isotope ratios; Transient signals; Speciation; Gas chromatography; Mass bias; Isotope fractionation

Stability of arsenic peptides in plant extracts: off-line versus on-line parallel elemental and molecular mass spectrometric detection for liquid chromatographic separation by Katharina Bluemlein; Andrea Raab; Jörg Feldmann (pp. 357-366).

The instability of metal and metalloid complexes during analytical processes has always been an issue of an uncertainty regarding their speciation in plant extracts. Two different speciation protocols were compared regarding the analysis of arsenic phytochelatin (As^IIIPC) complexes in fresh plant material. As the final step for separation/detection both methods used RP-HPLC simultaneously coupled to ICP-MS and ES-MS. However, one method was the often used off-line approach using two-dimensional separation, i.e. a pre-cleaning step using size-exclusion chromatography with subsequent fraction collection and freeze-drying prior to the analysis using RP-HPLC–ICP-MS and/or ES-MS. This approach revealed that less than 2% of the total arsenic was bound to peptides such as phytochelatins in the root extract of an arsenate exposed Thunbergia alata, whereas the direct on-line method showed that 83% of arsenic was bound to peptides, mainly as As^IIIPC₃ and (GS)As^IIIPC₂. Key analytical factors were identified which destabilise the As^IIIPCs. The low pH of the mobile phase (0.1% formic acid) using RP-HPLC–ICP-MS/ES-MS stabilises the arsenic peptide complexes in the plant extract as well as the free peptide concentration, as shown by the kinetic disintegration study of the model compound As^III(GS)₃ at pH 2.2 and 3.8. But only short half-lives of only a few hours were determined for the arsenic glutathione complex. Although As^IIIPC₃ showed a ten times higher half-life (23 h) in a plant extract, the pre-cleaning step with subsequent fractionation in a mobile phase of pH 5.6 contributes to the destabilisation of the arsenic peptides in the off-line method. Furthermore, it was found that during a freeze-drying process more than 90% of an As^IIIPC₃ complex and smaller free peptides such as PC₂ and PC₃ can be lost. Although the two-dimensional off-line method has been used successfully for other metal complexes, it is concluded here that the fractionation and the subsequent freeze-drying were responsible for the loss of arsenic phytochelatin complexes during the analysis. Hence, the on-line HPLC–ICP-MS/ES-MS is the preferred method for such unstable peptide complexes. Since freeze-drying has been found to be undesirable for sample storage other methods for sample handling needed to be investigated. Hence, the storage of the fresh plant at low temperature was tested. We can report for the first time a storage method which successfully conserves the integrity of the labile arsenic phytochelatin complexes: quantitative recovery of As^IIIPC₃ in a formic acid extract of a Thunbergia alata exposed for 24 h to 1 mg As^v L⁻¹ was found when the fresh plant was stored for 21 days at 193 K. Figure On-line HPLC–ICP-MS/ES-MS (bottom) is the preferred method for MS determination of unstable arsenic peptide complexes in plant extracts, since this avoids fractionation and subsequent freeze-drying that are responsible for loss of arsenic phytochelatin complexes in the 2D off-line method (top)

Keywords: Phytochelatins; Electrospray mass spectrometry; Inductively coupled plasma mass spectrometry; Speciation; Sample preparation; Freeze-drying; Hyphenated techniques; Chromatography; Plants

Multivariate analysis of DSC–XRD simultaneous measurement data: a study of multistage crystalline structure changes in a linear poly(ethylene imine) thin film by Hiroyuki Kakuda; Tetsuo Okada; Makoto Otsuka; Yukiteru Katsumoto; Takeshi Hasegawa (pp. 367-376).

A multivariate analytical technique has been applied to the analysis of simultaneous measurement data from differential scanning calorimetry (DSC) and X-ray diffraction (XRD) in order to study thermal changes in crystalline structure of a linear poly(ethylene imine) (LPEI) film. A large number of XRD patterns generated from the simultaneous measurements were subjected to an augmented alternative least-squares (ALS) regression analysis, and the XRD patterns were readily decomposed into chemically independent XRD patterns and their thermal profiles were also obtained at the same time. The decomposed XRD patterns and the profiles were useful in discussing the minute peaks in the DSC. The analytical results revealed the following changes of polymorphisms in detail: An LPEI film prepared by casting an aqueous solution was composed of sesquihydrate and hemihydrate crystals. The sesquihydrate one was lost at an early stage of heating, and the film changed into an amorphous state. Once the sesquihydrate was lost by heating, it was not recovered even when it was cooled back to room temperature. When the sample was heated again, structural changes were found between the hemihydrate and the amorphous components. In this manner, the simultaneous DSC–XRD measurements combined with ALS analysis proved to be powerful for obtaining a better understanding of the thermally induced changes of the crystalline structure in a polymer film. Figure DSC–XRD combined with ALS analysis provides a powerful method for elucidating thermally induced changes of crystalline structure in a polymer film

Keywords: Differential scanning calorimetry; Multivariate analysis; Augmented alternative least-squares technique; Polymer film; Diffraction methods (X-ray)

Isotopic fractionation of mercury induced by reduction and ethylation by Lu Yang; Ralph E. Sturgeon (pp. 377-385).

Isotope ratio measurements characterizing ²⁰²Hg/²⁰⁰Hg in NIST SRM 3133 Mercury Standard Solution were undertaken by multicollector inductively coupled plasma mass spectrometry employing NIST SRM 997 Tl for mass bias correction by use of the slope and the intercept obtained from a natural logarithmic plot of each session of measurements of ²⁰²Hg/²⁰⁰Hg against ²⁰⁵Tl/²⁰³Tl. The calculated value of 1.285333 ± 0.000192 (mean and one standard deviation, n = 40) for the mass bias corrected ²⁰²Hg/²⁰⁰Hg was then used for mass bias correction of other Hg isotope pairs. Ratios of 0.015337 ± 0.000011, 1.68770 ± 0.00054, 2.3056 ± 0.0015, 1.3129 ± 0.0013, 2.9634 ± 0.0038, and 0.67937 ± 0.0013 (expanded uncertainty, k = 2) were obtained for ¹⁹⁶Hg/¹⁹⁸Hg, ¹⁹⁹Hg/¹⁹⁸Hg, ²⁰⁰Hg/¹⁹⁸Hg, ²⁰¹Hg/¹⁹⁸Hg, ²⁰²Hg/¹⁹⁸Hg, and ²⁰⁴Hg/¹⁹⁸Hg, respectively. Reduction of Hg(II) to Hg⁰ in solutions of SRM 3133 was then undertaken using SnCl₂, NaBH₄, UV photolysis in the presence of formic acid, and ethylation of Hg(II) using NaBEt_4. These reactions induced significant isotope fractionation with maximum values of 1.17 ± 0.07, 1.08 ± 0.09, 1.34 ± 0.07, and 3.59 ± 0.09‰ (one standard deviation, 1SD, n = 5) for δ ^202/198Hg relative to the initial isotopic composition in the solution following 85–90% reduction of the Hg by SnCl₂, NaBH₄, UV photolysis, and ethylation with NaBEt₄, respectively. Mass-dependent fractionation was found to be dominant for all reduction processes. Figure Mass dependence of fractionation for all samples from Hg fractionation experiments using NaBEt₄. Solid lines are the theoretically predicted MDF based on δ′ ^202/198 Hg using equation 7. Error bars displayed are one standard deviation of the mean of 5 measurements of each sample

Keywords: Isotope ratios; Multicollector inductively coupled plasma mass spectrometry; Mass-independent fractionation; Isotopic fractionation; Mercury reduction; Mercury ethylation

Determination of trace inorganic anions in seawater samples by ion chromatography using silica columns modified with cetyltrimethylammonium ion by Xiao-Lin Jiang; Lee Wah Lim; Toyohide Takeuchi (pp. 387-391).

Conventional silica columns dynamically modified with cetyltrimethylammonium ions were evaluated for the determination of UV-absorbing bromide, nitrate, and nitrite in seawater samples. Cetyltrimethylammonium, which is a quaternary ammonium ion, was dynamically introduced onto silica surfaces. The first layer of the modifier was introduced by electrostatic interaction, whereas the second layer was introduced by hydrophobic interaction. The latter layer worked as the anion-exchange sites. The modified conventional silica columns could be used for separation of inorganic anions. Separation of authentic mixture of five anions was achieved within 17 min. The addition of 0.1 mM cetyltrimethylammonium ion to the eluent improved the repeatability of the retention time. Seawater samples could be directly injected onto the prepared conventional silica columns, and bromide, nitrate, and nitrite levels were determined to be 69, 0.13, and 0.016 ppm, respectively.

Keywords: Ion chromatography; Silica columns; Cetyltrimethylammonium ion; Inorganic anions; Seawater

Sulfur trace determination in petroleum products by isotope dilution ICP-MS using direct injection by thermal vaporization (TV-ICP-IDMS) by Jens Heilmann; Klaus G. Heumann (pp. 393-397).

An accurate, sensitive, and fast method for direct determination of total sulfur in petroleum products after thermal vaporization of an isotope-diluted sample was developed by using ICP-MS. ³⁴S-labelled dibenzothiophene spike was used for the isotope dilution step. The isotope-diluted sample was injected into a thermal vaporizer which was directly connected by a heated transfer line to the plasma torch. Sample transport was achieved by using a helium gas flow, and the isotope ratio ³⁴S/³²S was determined within seconds after injection. No other sample preparation other than the simple and fast isotope dilution step, which enables accurate and sensitive determination of sulfur at high sample throughputs, is necessary. Thus, this technique fits all needs for routine analyses. Validation of the TV-ICP-IDMS method was carried out by analyzing the certified gas oil reference materials BCR672 and BCR107. Comparison of results for noncertified low- and high-boiling samples, obtained from an ICP-IDMS microwave-assisted digestion method, also resulted in very good agreement. The low detection limit of 40 ng/g and the large dynamic range of TV-ICP-IDMS fulfill all necessities to allow analysis of sulfur in different petroleum products, e.g., even at the low concentration level of ‘sulfur-free’ gasoline.

Keywords: Sulfur trace determination; Isotope dilution ICP-MS; Petroleum products; Thermal vaporization; Routine analysis

Cross-flow microfiltration system for rapid enrichment of bacteria in water by Caroline Peskoller; Reinhard Niessner; Michael Seidel (pp. 399-404).

Permanent monitoring of waterborne pathogens is important for securing the hygiene of water. Enumerating bacteria in water at low concentrations and minute quantities demands rapid and efficient enrichment methods in order to improve the signal-to-noise ratio of subsequent determination methods. In this work an automated cross-flow microfiltration (CFM) system is presented which is usable in the field to concentrate large volumes of environmental water for analytical purposes. It was designed as a rapid enrichment apparatus achieving high recovery and high concentration factors. The efficiency of the CFM system was studied for E. coli spiked in a 10-L tap water sample. By this technique, a 10-L water sample was concentrated by a factor of 200 in 15 min. The high and consistent recovery of 91.3 ± 5.4% living cells in the concentration range 0.01 and 100 cfu mL⁻¹ is suitable for rapid enumeration of bacteria in water.

Keywords: Cross-flow microfiltration; Enrichment; Sample preparation; Drinking water; Pathogenic bacteria

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Analytical and Bioanalytical Chemistry (v.393, #1)

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Analytical and Bioanalytical Chemistry (v.393, #1)