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Analytical and Bioanalytical Chemistry (v.387, #2)

Quorum sensing: bacterial chatting by Ursula Obst (pp. 369-370).

is Head of the Department of Environmental Microbiology at the National Research Center Karlsruhe and also Associate Professor at the Technical University of Karlsruhe. Educated as a microbiologist, her interests are focussed on biofilm bacteria, environmental microbiology, and molecular biological and biochemical detection methods.

The effect of the chemical, biological, and physical environment on quorum sensing in structured microbial communities by Alexander R. Horswill; Paul Stoodley; Philip S. Stewart; Matthew R. Parsek (pp. 371-380).

As researchers attempt to study quorum sensing in relevant clinical or environmental settings, it is apparent that many factors have the potential to affect signaling. These factors span a range of physical, chemical, and biological variables that can impact signal production, stability and distribution. Optimizing experimental systems to natural or clinical environments may be crucial for defining when and where quorum sensing occurs. These points are illustrated in our case study of S. aureus signaling in biofilms, where signal stability may be affected by the host environment. The basic signaling schemes have been worked out at the molecular level for a few of the major quorum-sensing systems. As these studies continue to refine our understanding of these mechanisms, an emerging challenge is to identify if and when the local environment can affect signaling.

Keywords: Clinical/Biomedical analysis; Cell systems/Single cell analysis; Biosensors; Biofilm; Quorum sensing

New insights into the regulatory mechanisms of the LuxR family of quorum sensing regulators by William Nasser; Sylvie Reverchon (pp. 381-390).

Bacteria use small signal molecules, referred to as autoinducers, in order to monitor their population density and coordinate gene expression in a process named quorum sensing. In Gram-negative bacteria, acylated homoserine lactones are the most common autoinducer used for cell-to-cell communication. Increasing evidence that many different functions are controlled by acylated homoserine lactone quorum sensing has stimulated intensive investigations into the physiology, molecular biology and biochemistry that underlie this process. Here we review our current understanding of the molecular mechanisms used by the transcriptional regulators responsive to acylated homoserine lactone autoinducers to control gene expression and the structural modifications induced by acylated homoserine lactones binding specifically on these regulators.

Keywords: Quorum sensing; Cell population density; Bacterial autoinducer; Acylated homoserine lactone; LuxR; Transcriptional regulation; Enzymes; Pharmaceuticals; Nucleic acids (DNA|RNA)

Beyond quorum sensing: the complexities of prokaryotic parliamentary procedures by Anne K. Dunn; Eric V. Stabb (pp. 391-398).

Bacterial quorum-sensing regulatory systems can be summarized in a simple model wherein an autoinducer molecule accumulates in cultures and stimulates regulatory changes in gene expression upon reaching a critical threshold concentration. Although quorum sensing was originally thought to be an isolated phenomenon governing the regulation of a handful of processes in only a few bacteria, it is now considered to be a widespread mechanism for coordinating bacterial gene expression. Over decades of research, investigations of autoinducer-mediated regulation have revealed that these systems are far more complicated than originally appreciated, and such discoveries have accelerated recently with the application of molecular and genomic tools. The focus of this review is to highlight recent advances describing complexities that go beyond the simple model of quorum sensing. These complexities include the regulation of autoinducer production and degradation, the presence of multiple quorum-sensing systems in individual bacteria that regulate diverse genes, often in coordination with other regulatory elements, and the influence of interorganismal interactions on quorum sensing.

Keywords: Vibrio fischeri ; Pseudomonas aeruginosa ; Acyl homoserine lactone; AI-2; Bioluminescence

Microbial interactions in Staphylococcus epidermidis biofilms by Dietrich Mack; Angharad P. Davies; Llinos G. Harris; Holger Rohde; Matthias A. Horstkotte; Johannes K.-M. Knobloch (pp. 399-408).

Medical device-associated infections, most frequently caused by coagulase-negative staphylococci, especially Staphylococcus epidermidis, are of increasing importance in modern medicine. The formation of adherent, multilayered bacterial biofilms is the most important factor in the pathogenesis of these infections, which regularly fail to respond to appropriate antimicrobial therapy. Progress in elucidating the factors functional in elaboration of S. epidermidis biofilms and the regulation of their expression with a special emphasis on the role of quorum sensing are reviewed. Significant progress has been made in recent years, which provides the rationale for developing better preventive, therapeutic and diagnostic measures.

Keywords: Staphylococcus epidermidis ; Quorum sensing; Polysaccharide intercellular adhesin; Biomaterial-related infection; Biofilms

The role of quorum sensing in the pathogenicity of the cunning aggressor Pseudomonas aeruginosa by Thomas Bjarnsholt; Michael Givskov (pp. 409-414).

Recent decades have revealed that many bacterial species are capable of communicating with each other, and this observation has been largely responsible for a paradigm shift in microbiology. Whereas it was previously believed that bacteria lived as individual cells, it is now acknowledged that bacteria preferentially live in communities in the form of primitive organisms in which the behavior of individual cells is coordinated by cell–cell communication, known as quorum sensing (QS). Bacteria use QS for regulation of the processes involved in their interaction with each other, their environment, and, particularly, higher organisms We have focused on Pseudomonas aeruginosa, an opportunistic pathogen producing more than 30 QS-regulated virulence factors. P. aeruginosa causes several types of nosocomial infection, and lung infection in cystic fibrosis (CF) patients. We review the role of QS in the protective mechanisms of P. aeruginosa and show how disruption of the QS can be used as an approach to control this cunning aggressor.

Keywords: Quorum sensing; Quorum sensing inhibition; Pseudomonas aeruginosa ; Biofilm

Quorum sensing in Erwinia species by Anne M. L. Barnard; George P. C. Salmond (pp. 415-423).

The term quorum sensing (QS) refers to the ability of bacteria to regulate gene expression according to the accumulation of signalling molecules that are made by every cell in the population. The erwiniae group of bacteria are often phytopathogens and the expression of a number of their important virulence determinants and secondary metabolites is under QS control. The erwiniae utilise two types of QS signalling molecules: N-acyl homoserine lactones and AI-2-type signalling molecules. Here, we review the regulatory networks involving QS in the soft rot erwiniae.

Keywords: Erwinia ; Quorum sensing; N-Acyl homoserine lactone; Carbapenem antibiotic; Virulence

Convergence of hormones and autoinducers at the host/pathogen interface by Kendra P. Rumbaugh (pp. 425-435).

Most living organisms possess sophisticated cell-signaling networks in which lipid-based signals modulate biological effects such as cell differentiation, reproduction and immune responses. Acyl homoserine lactone (AHL) autoinducers are fatty acid-based signaling molecules synthesized by several Gram-negative bacteria that are used to coordinate gene expression in a process termed “quorum sensing” (QS). Recent evidence shows that autoinducers not only control gene expression in bacterial cells, but also alter gene expression in mammalian cells. These alterations include modulation of proinflammatory cytokines and induction of apoptosis. Some of these responses may have deleterious effects on the host’s immune response, thereby leading to increased bacterial pathogenesis. Prokaryotes and eukaryotes have cohabited for approximately two billion years, during which time they have been exposed to each others’ soluble signaling molecules. We postulate that organisms from the different kingdoms of nature have acquired mechanisms to sense and respond to each others signaling molecules, and we have named this process interkingdom signaling. We further propose that autoinducers, which exhibit structural and functional similarities to mammalian lipid-based hormones, are excellent candidates for mediating this interkingdom communication. Here we will compare and contrast bacterial QS systems with eukaryotic endocrine systems, and discuss the mechanisms by which autoinducers may exploit mammalian signal transduction pathways.

Keywords: Quorum sensing; Autoinducer; P. aeruginosa ; Interkingdom signaling; Endocrine disruption

Quorum-sensing systems in staphylococci as therapeutic targets by Niamh Harraghy; Sylvain Kerdudou; Mathias Herrmann (pp. 437-444).

The staphylococci are an ever-present threat in our world, capable of causing a wide range of infections, and are a persistent presence in the clinical environment. As the number of antimicrobial compounds effective against staphylococci decreases, because of the acquisition and spread of antibiotic resistance, there is a growing need for novel therapeutic molecules. Intra and inter-species communication (quorum sensing) is a biologically significant phenomenon that has been associated with virulence, intracellular survival, and biofilm formation. Quorum sensing molecules of staphylococci and other species (e.g. Pseudomonas aeruginosa) can inhibit virulence factor production and/or growth of staphylococci, leading to the possibility that interference with staphylococcal quorum-sensing systems could be a way of controlling the diverse infections caused by the staphylococci. In this article, we discuss the potential of quorum-sensing systems of staphylococci as therapeutic targets.

Keywords: Staphylococcus aureus ; Staphylococcus epidermidis ; Quorum sensing; agr ; Therapeutics

Bacterial quorum sensing and interference by naturally occurring biomimics by Diane McDougald; Scott A. Rice; Staffan Kjelleberg (pp. 445-453).

Bacteria are able to coordinate gene expression as a community through the secretion and detection of signalling molecules so that the members of the community can simultaneously express specific behaviours. This mechanism of regulation of behaviour appears to be a key trait for adaptation to specific environments and has been shown to regulate a variety of important phenotypes, from virulence factor production to biofilm formation to symbiosis related behaviours such as bioluminescence. The ability to communicate and communally regulate gene expression is hypothesised to have evolved as a way for organisms to delay expression of phenotypes until numerical supremacy is reached. For example, in the case of infection, if an invading microorganism were to express virulence factors too early, the host may be able to mount a successful defence and repel the invaders. There is growing evidence that bacterial quorum sensing (QS) systems are involved in cross-kingdom signalling with eukaryotic organisms and that eukaryotes are capable of actively responding to bacteria in their environment by detecting and acting upon the presence of these signalling molecules. Likewise, eukaryotes produce compounds that can interfere with QS systems in bacteria by acting as agonists or antagonists. An exciting new field of study, biomimetics, takes inspiration from nature’s models and attempts to design solutions to human problems, and biomimics of QS systems may be one such solution. This article presents the acylated homoserine lactone and autoinducer 2 QS systems in bacteria, the means of intercepting or interfering with bacterial QS systems evolved by eukaryotes, and the rational design of synthetic antagonists. Figure Natural products, furanones, from the red alga Delisea pulchra inhibit the quorum sensing regulated production of violacein by Chromobacterium violaceum

Keywords: Quorum sensing; N-acylated homoserine lactone; Autoinducer 2; Virulence; Quorum sensing antagonist; Biomimic

Identification of bacterial N-acylhomoserine lactones (AHLs) with a combination of ultra-performance liquid chromatography (UPLC), ultra-high-resolution mass spectrometry, and in-situ biosensors by Agnes Fekete; Moritz Frommberger; Michael Rothballer; Xiaojing Li; Matthias Englmann; Jenoe Fekete; Anton Hartmann; Leo Eberl; Philippe Schmitt-Kopplin (pp. 455-467).

N-Acylated homoserine lactones (AHLs) are produced by Gram-negative bacteria as communication signals and are frequently studied as mediators of the “quorum sensing” response of bacterial communities. Several reports have recently been published on the identification of AHLs from different species and attempts have been made to study their role in natural habitats, for example the surface of plant roots in the rhizosphere. In this article, different analytical methods, including bacterial biosensors and chromatographic techniques, are reviewed. A concept for assignment of the structures of AHLs is also presented. The retention behaviour of derivatives of AHLs containing β-keto or hydroxyl groups and/or double bonds has been evaluated in relation to the separation behaviour of AHLs with saturated and unsubstituted alkanoyl chains. Samples have also been analysed by high resolution mass spectrometry (Fourier-transform ion-cyclotron-resonance mass spectrometry, FTICR-MS), nano liquid chromatography–electrospray ionization ion trap mass spectrometry (nano-LC–MS) and by the aid of a biosensor. The results obtained from ultra performance liquid chromatography (UPLC), FTICR-MS, nano-LC–MS, and bioassays have been compared to attempt structural characterisation of AHL without chemical synthesis of analytical standards. The method was used to identify the major AHL compound produced by the rhizosphere bacterium Acidovorax sp. N35 as N-(3-hydroxydecanoyl)homoserine lactone.

Keywords: N-Acylhomoserine lactones; Biosensing; Chromatography; UPLC; FTICR-MS

Analysis of the hierarchy of quorum-sensing regulation in Pseudomonas aeruginosa by Victoria E. Wagner; Luen-Luen Li; Vincent M. Isabella; Barbara H. Iglewski (pp. 469-479).

Quorum-sensing in Pseudomonas aeruginosa is known to regulate several aspects of pathogenesis, including virulence factor production, biofilm development, and antimicrobial resistance. Recent high-throughput analysis has revealed the existence of several layers of regulation within the QS-circuit. To address this complexity, mutations in genes encoding known or putative transcriptional regulators that were also identified as being regulated by the las and/or rhl QS systems were screened for their contribution in mediating several phenotypes, for example motility, secreted virulence products, and pathogenic capacity in a lettuce leaf model. These studies have further elucidated the potential contribution to virulence of these genes within the QS regulon.

Keywords: Quorum-sensing; Pseudomonas aeruginosa ; Virulence; Regulation

The quorum-sensing molecule N-3-oxododecanoyl homoserine lactone (3OC12-HSL) enhances the host defence by activating human polymorphonuclear neutrophils (PMN) by Christof Wagner; Sabine Zimmermann; Gerald Brenner-Weiss; Friederike Hug; Birgit Prior; Ursula Obst; Gertrud Maria Hänsch (pp. 481-487).

The P. aeruginosa quorum-sensing molecule N-3-oxododecanoyl homoserine lactone (3OC12-HSL) interacts not only with bacteria, but also with mammalian cells, among others with those of the immune defence system. We focussed on the possible interaction of 3OC12-HSL with human polymorphonuclear neutrophils (PMN), because these cells are the first to enter an infected site. We found that 3OC12-HSL attracts PMN, and up-regulates expression of receptors known to be involved in host defence, including the adhesion proteins CD11b/CD18 and the immunoglobulin receptors CD16 and CD64. Furthermore, the uptake of bacteria (phagocytosis), which is crucial for an efficient defence against infection, was enhanced. Thus, recognising and responding to 3OC12-HSL not only attracts the PMN to the site of a developing biofilm, but also reinforces their defence mechanisms, and hence could be a means to control the infection in an early stage and to prevent biofilm formation.

Keywords: Quorum sensing; PMN; Functional activity; Homoserine lactone; Host defence

Analysing traces of autoinducer-2 requires standardization of the Vibrio harveyi bioassay by Ramiro Vilchez; André Lemme; Verena Thiel; Stefan Schulz; Helena Sztajer; Irene Wagner-Döbler (pp. 489-496).

Autoinducer-2 (furanosyl borate diester) is a biologically active compound whose role as a universal bacterial signalling molecule is currently under intense investigation. Because of its instability and the low concentrations of it found in biological samples, its detection relies at present on a bioassay that measures the difference in the timing of the luminescence of the Vibrio harveyi BB170 sensor strain with and without externally added AI-2. Here we systematically investigated which parameters affected the fold induction values of luminescence obtained in the bioassay and developed a modified protocol. Our experiments showed that growth and luminescence of V. harveyi BB170 are strongly influenced by trace elements. In particular, addition of Fe³⁺ within a certain concentration range to the growth medium of the preinoculum culture improved the reproducibility and reduced the variance of the bioassay. In contrast, trace elements and vitamins introduced directly into the bioassay caused inhibitory effects. The initial density and luminescence of the sensor strain are very important and the values required for these parameters were defined. Borate interferes with the detection of AI-2 by giving false positive results. The response of V. harveyi BB170 to chemically synthesized AI-2 in the bioassay is nonlinear except over a very small concentration range; it is maximum over three orders of magnitude and shows inhibition above 35 μM. Based on the modified protocol, we were able to detect AI-2 in the absence of inhibitors with maximum fold induction values for the positive control (chemically synthesized AI-2) of >120 with a standard deviation of ~30% in a reliable and reproducible way.

Keywords: Quorum sensing; Autoinducer-2; Vibrio harveyi ; Bioassay; Luminescence

Comprehensive profiling of N-acylhomoserine lactones produced by Yersinia pseudotuberculosis using liquid chromatography coupled to hybrid quadrupole–linear ion trap mass spectrometry by Catharine A. Ortori; Steve Atkinson; Siri Ram Chhabra; Miguel Cámara; Paul Williams; David A. Barrett (pp. 497-511).

A method for the comprehensive profiling of the N-acylhomoserine lactone (AHL) family of bacterial quorum-sensing molecules is presented using liquid chromatography (LC) coupled to hybrid quadrupole–linear ion trap (QqQLIT) mass spectrometry. Information-dependent acquisition (IDA), using triggered combinations of triple-quadrupole and linear ion trap modes in the same LC-MS/MS run, was used to simultaneously screen, quantify and identify multiple AHLs in a single sample. This MS method uses common AHL fragment ions attributed to the homoserine moiety and the 3-oxo-, 3-hydroxy- or unsubstituted acyl side chains, to identify unknown AHLs in cell-free culture supernatants in an unbiased manner. This LC-MS technique was applied to determine the relative molar ratios of AHLs produced by Yersinia pseudotuberculosis and the consequences of inactivating by mutation either or both of the AHL synthase genes (ypsI and ytbI) on AHL profile and concentration. The Y. pseudotuberculosis wild type but not the ypsI ytbI double mutant produced at least 24 different AHLs with acyl chains ranging from C4 to C15 with or without 3-oxo or 3-hydroxy substituents. YtbI, in contrast to YpsI, could direct the synthesis of all of the AHLs identified. The most abundant and hence most biologically relevant Y. pseudotuberculosis AHLs were found to be the 3-oxo-substituted C6, C7 and C8 AHLs and the unsubstituted C6 and C8 compounds. The LC-QqQLIT methodology is broadly applicable to quorum-sensing signal molecule analysis and can provide comprehensive AHL profiles and concentrations from a single sample and simultaneously collect confirmatory spectra for each AHL identified.

Keywords: Yersinia ; Quorum sensing; N-Acylhomoserine lactones; LC-MS; Quadrupole linear ion trap

Use of quantitative real-time RT-PCR to analyse the expression of some quorum-sensing regulated genes in Pseudomonas aeruginosa by Thomas Schwartz; Sandra Walter; Silke-Mareike Marten; Frank Kirschhöfer; Michael Nusser; Ursula Obst (pp. 513-521).

P. aeruginosa living in biofilm populations sends out diffusive signalling molecules, called autoinducers, for example acylated homoserine lactone (AHL) or the P. aeruginosa quinolone signal (PQS). So far, two quorum-sensing systems, LasR and VsmR, have been identified in P. aeruginosa, both of which are required for all virulence determinants. The expression of specific genes involved in quorum-sensing regulatory mechanisms has been analysed with molecular biology methods. Real-time quantitative PCR is a highly sensitive and powerful technique for quantification of nucleic acids. Expression of the genes vsmR, lasI, and PA4296 was studied by use of reverse transcriptase and subsequent quantitative real-time PCR of the cDNAs. In parallel, expression of ribosomal 16S rRNA, used as a housekeeping gene that was constitutively expressed in all analyses, was also monitored. Biofilm was compared with planktonic bacteria, and in contrast to vsmR and Pa4296, the lasI gene was found to be down-regulated in biofilm. Extended experiments were run with synthetic signal molecules inducing regulated processes in bacterial populations. It was shown that the genes under investigation were up-regulated in mature biofilm in the presence of the signal molecule N-(3-oxododecanoyl)-l-homoserine lactone.

Keywords: Gene expression; RT-PCR; Quorum sensing; Pseudomonas aeruginosa ; Biofilm

Metabonomics, metabolomics, and metabolic profiling by Cynthia K. Larive (pp. 523-523).

is Professor of Analytical Chemistry at the University of California Riverside. She has an active research program involving bioanalytical and environmental analytical applications of NMR spectroscopy (for more information see http://www.chem.ucr.edu/faculty/larive/larive.html ). Professor Larive is also active in curricular reform and the promotion of undergraduate research. She is editor-in-chief and principal investigator of the Analytical Sciences Digital Library ( http://www.asdlib.org ), an internet-based resource for instructors, students, and practitioners of analytical chemistry. This digital library is a collection of peer-reviewed websites on topics including pedagogical approaches, analytical techniques, applications, and classroom resources.

Comparing and combining NMR spectroscopy and mass spectrometry in metabolomics by Zhengzheng Pan; Daniel Raftery (pp. 525-527).

Improving NMR sensitivity by use of salt-tolerant cryogenically cooled probes by Lora C. Robosky; Michael D. Reily; Daina Avizonis (pp. 529-532).

Beyond blood sugar: the potential of NMR-based metabonomics for type 2 human diabetes, and the horse as a possible model by Michael S. Hodavance; Sarah L. Ralston; István Pelczer (pp. 533-537).

Metabonomic analysis is a powerful tool for identifying and characterizing metabolic disorders, for example type 2 diabetes and the metabolic syndrome. Nuclear magnetic resonance (NMR) spectroscopy is an essential tool for such analysis, with special benefits. The review assesses the current status and potential of NMR-based metabonomics of type 2 diabetes. The horse is proposed as a possible model for studying this condition and disease. Some examples are shown of horse blood analyses by NMR.

Keywords: Metabonomics; Type 2 diabetes; Horses; Glucose tolerance; Insulin resistance; NMR

Principal component analysis of urine metabolites detected by NMR and DESI–MS in patients with inborn errors of metabolism by Zhengzheng Pan; Haiwei Gu; Nari Talaty; Huanwen Chen; Narasimhamurthy Shanaiah; Bryan E. Hainline; R. Graham Cooks; Daniel Raftery (pp. 539-549).

Urine metabolic profiles of patients with inborn errors of metabolism were examined with nuclear magnetic resonance (NMR) and desorption electrospray ionization mass spectrometry (DESI–MS) methods. Spectra obtained from the study of urine samples from individual patients with argininosuccinic aciduria (ASA), classic homocystinuria (HCY), classic methylmalonic acidemia (MMA), maple syrup urine disease (MSUD), phenylketonuria (PKU) and type II tyrosinemia (TYRO) were compared with six control patient urine samples using principal component analysis (PCA). Target molecule spectra were identified from the loading plots of PCA output and compared with known metabolic profiles from the literature and metabolite databases. Results obtained from the two techniques were then correlated to obtain a common list of molecules associated with the different diseases and metabolic pathways. The combined approach discussed here may prove useful in the rapid screening of biological fluids from sick patients and may help to improve the understanding of these rare diseases.

Keywords: Nuclear magnetic resonance (NMR); Desorption electrospray ionization (DESI); Mass spectrometry; Metabolomics; Inborn errors of metabolism; Principal component analysis (PCA)

Combined Fourier-transform infrared imaging and desorption electrospray-ionization linear ion-trap mass spectrometry for analysis of counterfeit antimalarial tablets by Camilla Ricci; Leonard Nyadong; Facundo M. Fernandez; Paul N. Newton; Sergei G. Kazarian (pp. 551-559).

This paper reports use of a combination of Fourier-transform infrared (FTIR) spectroscopic imaging and desorption electrospray ionization linear ion-trap mass spectrometry (DESI MS) for characterization of counterfeit pharmaceutical tablets. The counterfeit artesunate antimalarial tablets were analyzed by both techniques. The results obtained revealed the ability of FTIR imaging in non-destructive micro-attenuated total reflection (ATR) mode to detect the distribution of all components in the tablet, the identities of which were confirmed by DESI MS. Chemical images of the tablets were obtained with high spatial resolution. The FTIR spectroscopic imaging method affords inherent chemical specificity with rapid acquisition of data. DESI MS enables high-sensitivity detection of trace organic compounds. Combination of these two orthogonal surface-characterization methods has great potential for detection and analysis of counterfeit tablets in the open air and without sample preparation.

Keywords: Fake drugs; Malaria; Chemical imaging; Mass spectrometry; Forensic; Artesunate

Cavities generated by self-organised monolayers as sensitive coatings for surface acoustic wave resonators by Peter Lieberzeit; Wolfgang Greibl; Michael Jenik; Franz L. Dickert; Gerhard Fischerauer; Wolf-Eckhart Bulst (pp. 561-566).

Silanisation of quartz substrate surfaces with a mixture of two chlorosilanes, namely trimethylchlorosilane and 7-octenyldimethylchlorosilane, leads to sensitive coatings for volatile organic compounds (VOC) on surface acoustic wave (SAW) devices. In this way we created monolayers of molecular cavities engulfing the analytes according to host–guest chemistry directly on the device surfaces, and also confirmed the occurrence of such cavities by molecular modelling. We monitored the binding process of the silanes by using Fourier transform infrared (FTIR) spectrometry and atomic force microscopy (AFM). In order to increase the stiffness of the cavities, we crosslinked the terminal double bonds of the long spacers by heating the surface in the presence of a radical initiator. Compared to SAW delay lines silanised with trimethylchlorosilane, devices modified with the binary silane mixture lead to substantially higher frequency shifts when exposed to solvent vapour streams. Nearly instantaneous responses can be observed, which e.g. allows xylene detection down to a few ppm. Interaction of o-xylene with a silanised quartz surface

Keywords: SAW; VOC detection; Self-assembled monolayers; Quartz surfaces; Chlorosilanes

Biosensor incorporating cell barrier architectures for detecting Staphylococcus aureus alpha toxin by Gargi Ghosh; Leonidas G. Bachas; Kimberly W. Anderson (pp. 567-574).

Alpha toxin is a common virulent factor of Staphylococcus aureus and is believed to play crucial roles in pathogenicity induced by S. aureus. Alpha toxin is also known to induce permeability to endothelial cell monolayers in vitro due to the formation of interendothelial gaps. The present study is directed towards measuring alpha toxin using a whole-cell-based biosensor. The biosensor, consisting of a confluent monolayer of human umbilical vein endothelial cells (HUVECs) on a potassium ion-selective electrode, takes advantage of cell permeability dysfunction to detect the presence of small quantities of alpha toxin. When a confluent monolayer of cells was formed on the membrane surface, the response of the electrode toward the marker ion, potassium, was inhibited. Upon exposing this sensor to varying concentrations of alpha toxin for 20 min, an increase in sensor response to potassium was observed. The response thus obtained was indirectly related to the concentration of alpha toxin. The detection limit of this sensor for alpha toxin was found to be 0.1 ng/ml. Cell monolayers were stained with silver nitrate to quantify the formation of intercellular gaps as well as to study the effect of this toxin on HUVECs morphology. A strong positive correlation was observed between the response obtained from the biosensor and the area of the intercellular gaps. Silver staining also revealed the tendency of cells to round up upon being exposed to alpha toxin. Figure Measuring alpha toxin using a whole-cell-based biosensor

Keywords: Potassium-selective electrodes; Biosensor; Alpha toxin; Intercellular gaps; Silver staining

Investigation, by single photon ionisation (SPI)–time-of-flight mass spectrometry (TOFMS), of the effect of different cigarette-lighting devices on the chemical composition of the first cigarette puff by Thomas Adam; Richard R. Baker; Ralf Zimmermann (pp. 575-584).

Soft single-photon ionisation (SPI)–time-of-flight mass spectrometry (TOFMS) has been used to investigate the effect of different cigarette-lighting devices on the chemical composition of the mainstream smoke from the first cigarette puff. Lighting devices examined were a Borgwaldt electric lighter, a propane/butane gas lighter, a match, a candle, and the burning zone of another cigarette. To eliminate the effects of the different masses of tobacco burnt by use of the different lighting methods a normalisation procedure was performed which enabled investigation of changes in the chemical patterns of the resulting smoke. When another cigarette was used as the lighting device, elevated levels of ammonia and other nitrogen-containing substances were observed. These are high in the sidestream smoke of the cigarette used for lighting and would be drawn into the mainstream smoke of the cigarette being lit. In contrast, smoke from the cigarette lit by the electric lighter contained slightly higher normalised amounts of isoprene. Lighting the cigarette by use of a candle resulted in larger amounts of substances, e.g. benzene, which most probably originated from thermal decomposition of wax. The composition of the first puff of smoke obtained by use of the three lighting methods with open flames (gas lighter, match, and candle) was usually similar whereas the composition of the smoke produced by use of the electric lighter and the cigarette as the lighter were more unique. The chemical patterns generated by the different lighting devices could, however, be separated by principal-component analyses. Two additional test series were also studied. In the first the cigarette was lit with an electric lighter, then extinguished, the ash was cut off, and the cigarette was re-lit. In the second the cigarette was heated in an oven to 80 °C for 5 min before being lit. These treatments did not result in changes in the chemical composition compared with cigarettes lit in the ordinary way. Figure Time-of-flight mass spectrometry (TOFMS) has been used to investigate the effect of different cigarette-lighting devices on the chemical composition of the mainstream smoke from the first cigarette puff

Keywords: Single-photon ionisation; Cigarette smoke; Tobacco; Principal-component analysis; First puff

Development of a novel luminol chemiluminescent method catalyzed by gold nanoparticles for determination of estrogens by Yongxin Li; Ping Yang; Po Wang; Lun Wang (pp. 585-592).

It has been found that gold nanoparticles (nano-Au) enhance the chemiluminescence (CL) of the luminol–hydrogen peroxide system and that estrogens inhibit these CL signals in alkaline solution. CL spectra, UV–visible spectra, X-ray photoelectron spectra (XPS), and transmission electron microscopy (TEM) were used to investigate the mechanism of the CL enhancement. On the basis of the inhibition, a flow-injection CL method has been established for determination of three natural estrogens. Under the optimized conditions, the linear range for determination of the estrogens was 0.07 to 7.0 μmol L⁻¹ for estrone, 0.04 to 10 μmol L⁻¹ for estradiol, and 0.1 to 10 μmol L⁻¹ for estriol. The detection limits were 3.2 nmol L⁻¹ for estrone, 7.7 nmol L⁻¹ for estradiol, and 49 nmol L⁻¹ for estriol, with RSD of 2.9, 2.6, and 1.8%, respectively. This method has been used for analysis of estrogens in commercial tablets and in urine samples from pregnant women.

Keywords: Gold nanoparticles; Luminol; Estrogens; Chemiluminescence

Simultaneous determination of losartan, EXP-3174 and hydrochlorothiazide in plasma via fully automated 96-well-format-based solid-phase extraction and liquid chromatography–negative electrospray tandem mass spectrometry by Filomila Kolocouri; Yannis Dotsikas; Constantinos Apostolou; Constantinos Kousoulos; Yannis L. Loukas (pp. 593-601).

An automated, sensitive and high-throughput liquid chromatographic/electrospray tandem mass spectrometric (LC–MS/MS) assay was developed for the simultaneous determination of losartan (LOS), its major circulating metabolite EXP-3174 and hydrochlorothiazide (HCTZ) in human plasma. LOS and HCTZ coexist in the same drug formulation, and this is the first method that enables the simultaneous determination of both drugs along with the active metabolite of LOS. Since these drugs have different physicochemical properties, the employment of a liquid–liquid extraction (LLE) protocol was precluded. A fully automated solid-phase extraction (SPE) protocol, based on 96-well format plates, was used to isolate these compounds and furosemide (internal standard, IS) from plasma. Washing and elution steps were amended accordingly in order to minimize any matrix effect from components of the plasma without reducing the elution of the molecules of interest. The compounds were eluted from a C18 column and detected with an API 3000 triple-quadrupole mass spectrometer using negative electrospray ionization and multiple reaction monitoring (MRM). The assay was linear over the range 1.00–400 ng/mL for LOS and EXP-3174 and 0.500–200 ng/mL for HCTZ, respectively, when 200 μl of plasma was used in the extraction. The overall intra- and interassay variations were within acceptance limits. The analysis time for each sample was 4 min, and more than 300 samples could be analyzed in one day by running the system overnight. The assay was simple, highly sensitive, selective, precise, fast, and it enables the reliable determination of LOS, EXP-3174 and HCTZ in pharmacokinetic or bioequivalence studies after per os administration of a single tablet containing both drugs.

Keywords: Losartan; Hydrochlorothiazide; Solid-phase extraction; Mass spectrometry; 96 deep well

Comparison of performance of partial least squares regression, secured principal component regression, and modified secured principal component regression for determination of human serum albumin, γ-globulin and glucose in buffer solutions and in vivo blood glucose quantification by near-infrared spectroscopy by Bo-Yan Li; Sumaporn Kasemsumran; Yun Hu; Yi-Zeng Liang; Yukihiro Ozaki (pp. 603-611).

The performances of three multivariate analysis methods—partial least squares (PLS) regression, secured principal component regression (sPCR) and modified secured principal component regression (msPCR)—are compared and tested for the determination of human serum albumin (HSA), γ-globulin, and glucose in phosphate buffer solutions and blood glucose quantification by near-infrared (NIR) spectroscopy. Results from the application of PLS, sPCR and msPCR are presented, showing that the three methods can determine the concentrations of HSA, γ-globulin and glucose in phosphate buffer solutions almost equally well provided that the prediction samples contain the same spectral information as the calibration samples. On the other hand, when some potential spectral features appear in new measurements, sPCR and msPCR outperform PLS significantly. The reason for this is that such spectral features are not included during calibration, which leads to a degradation in PLS prediction performance, while sPCR and msPCR can improve their predictions for the concentrations of the analytes by removing the uncalibrated features from the original spectra. This point is demonstrated by successfully applying sPCR and msPCR to in vivo blood glucose measurements. This work therefore shows that sPCR and msPCR may provide possible alternatives to PLS in cases where some uncalibrated spectral features are present in measurements used for concentration prediction.

Keywords: Human serum albumin; γ-Globulin; Glucose; Secured principal component regression (sPCR); Moving window partial least squares regression (MWPLSR)

Chemiluminescent detection of DNA hybridization using gold nanoparticles as labels by Zheng-Ping Li; Cheng-Hui Liu; Yong-Shan Fan; Xin-Rui Duan (pp. 613-618).

A chemiluminescent (CL) detection method has been developed for DNA hybridization. The assay relies on a sandwich-type DNA hybridization in which gold nanoparticles modified with alkylthiol-capped oligonucleotide strands are used as probes to monitor the presence of the specific target DNA. The $$ { ext{AuCl}}^{ - }_{4} $$ , which is the dissolving product of the gold nanoparticles anchored on the DNA hybrids, serves as an analyte in the H₂O₂–luminol– $$ { ext{AuCl}}^{ - }_{4} $$ CL reaction for the indirect measurement of the target DNA. The combination of the remarkable sensitivity of the CL analysis with the large number of $$ { ext{AuCl}}^{ - }_{4} $$ released from each DNA hybrid allows a detection limit at levels as low as 0.1 pM of the target DNA. Moreover, with a further silver amplification step, the detection limit will be pushed down to the femtomolar domain.

Keywords: Chemiluminescent; DNA hybridization; Gold nanoparticles; Silver amplification

A diagnostic tool for determining the quality of accuracy validation. Assessing the method for determination of nitrate in drinking water by L. Escuder-Gilabert; E. Bonet-Domingo; M. J. Medina-Hernández; S. Sagrado (pp. 619-625).

Realistic internal validation of a method implies the performance validation experiments under intermediate precision conditions. The validation results can be organized in an X Nr×Ns (replicates×runs) data matrix, analysis of which enables assessment of the accuracy of the method. By means of Monte Carlo simulation, uncertainty in the estimates of bias and precision can be assessed. A bivariate plot is presented for assessing whether the uncertainty intervals for the bias (E ± U(E)) and intermediate precision (RSDi ± U(RSDi) are included in prefixed limits (requirements for the method). As a case study, a method for determining the concentration of nitrate in drinking water at the official level set by 98/83/EC Directive is assessed by use of the proposed plot.

Keywords: Accuracy validation; Intermediate precision; Uncertainty estimation; Monte Carlo simulation

Analytical speciation as a tool to assess arsenic behaviour in soils polluted by mining by M. J. Ruiz-Chancho; J. F. López-Sánchez; R. Rubio (pp. 627-635).

A study is performed to evaluate the occurrence of arsenic in polluted soils using acidic extractions and liquid chromatography–hydride generation–atomic fluorescence spectrometry (LC–HG–AFS) for speciation analysis. Seven soil samples were collected in an abandoned area polluted by mining in the Eastern Pyrenees (Spain), and two uncontaminated soils were taken for reference purposes. Moreover, the total arsenic content is evaluated in two different sieved fractions in order to obtain information on the possible particle-size-dependent association of arsenic with soil components. Soil samples were extracted with both phosphoric and ascorbic acids and the stabilities of the extracted species were studied. The arsenic species were determined by LC–HG–AFS. In addition, the ability of soil grinding to effect species change is also assessed. Arsenite and arsenate were found in the polluted soils, but only arsenate was found in the unpolluted soils. The quality of the results was assessed through a mass balance calculation and by analysing two soil Certified Reference Materials. Valuable information regarding arsenic occurrence in the studied soils is obtained from the speciation results. The presence of arsenite in the extracts can be attributed to arsenopyrite residues, whereas the presence of arsenate indicates release from weathered material. Figure Abandoned mining polluted area in Eastern Pyrenees

Keywords: Arsenic; Speciation; Soil; Sample pretreatment; Hyphenated techniques

Characterisation of betalain patterns of differently coloured inflorescences from Gomphrena globosa L. and Bougainvillea sp. by HPLC–DAD–ESI–MS n by Florian Kugler; Florian C. Stintzing; Reinhold Carle (pp. 637-648).

In the present study, the betaxanthin (bx) and betacyanin patterns of differently coloured inflorescences from Gomphrena globosa L. and Bougainvillea sp. have been investigated in detail by applying reversed phase high-performance liquid chromatography–diode array detection (HPLC–DAD) coupled with positive ion electrospray mass spectrometry. Histidine-bx was found to be the predominant betaxanthin of Gomphrena globosa inflorescences. Furthermore, arginine-bx was detected as a novel betaxanthin, which to the best of our knowledge has not been reported as a pigment that occurs naturally so far. Dopa-bx was the major betaxanthin of Bougainvillea sp., although several minor betaxanthins were also present, including lysine-bx and putrescine-bx, novel betaxanthins hitherto not observed naturally. Remarkable differences in the betacyanin patterns between the purple, red and orange varieties were observed for both Gomphrena and Bougainvillea inflorescences. Hence, both the betacyanin profiles and the relative betaxanthin:betacyanin ratios determine the broad colour palette of Gomphrena petals and Bougainvillea bracts.

Keywords: Gomphrena globosa L.; Amaranthaceae; Bougainvillea sp.; Nyctaginaceae; Betalains

Early oriented isothermal crystallization of polyethylene studied by high-time-resolution SAXS/WAXS by N. Stribeck; A. Almendarez Camarillo; U. Nöchel; P. Bösecke; R. K. Bayer (pp. 649-661).

During cooling from the quiescent melt of a highly oriented polyethylene rod, highly oriented proto-lamellae are formed first, which are not crystalline. This is shown in scattering data which are recorded on two-dimensional detectors with a cycle time of 1 s and an exposure of 0.1 s. In the experiments small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) are registered simultaneously during the first 3 min after quenching to a crystallization temperature. A non-uniform thickness between 20 and 100 nm is characteristic for the ensemble of proto-lamellae. During the first minute of isothermal treatment the number of proto-lamellae slowly increases without a change of the thickness distribution. As crystallization starts, the crystallites are not oriented in contrast to the proto-lamellae. During crystallization the layer thickness distribution narrows. The number of lamellae rapidly increases during the following 2 min of isothermal treatment (at 128 °C and 124 °C). The results are obtained by interpretation of the WAXS and of the multidimensional chord distribution function (CDF), a model-free real-space visualization of the nanostructure information contained in the SAXS data.

Keywords: SAXS; Polyethylene; Crystallization

Simultaneous determination of β-lactamic antibiotics by a new high-performance low-pressure chromatographic system using a multisyringe burette coupled to a monolithic column (MSC) by Hilda M. González-San Miguel; Jesús M. Alpízar-Lorenzo; Víctor Cerdà (pp. 663-671).

A technique based on multisyringe chromatography (MSC) was developed to determine three β-lactamic antibiotics. Amoxicillin (AMOXI), ampicillin (AMPI) and cephalexin (CEPHA) were analyzed using a system with a very simple design and very low-cost equipment consisting of a multisyringe module, three low-pressure solenoid valves, a monolithic Chromolith Flash RP-18e column and a diode array spectrophotometric detector monitoring at 250 nm. Mobile phases containing methanol:acetic acid (0.1 M)–sodium acetate (0.1 M), pH 6.2, were tested for various ratios of methanol:acetic acid–sodium acetate, but a ratio of 10:90 gave optimum results with a flow rate of 2 ml min⁻¹. Validation parameters were evaluated for amoxicillin. The response to amoxicillin was linear over the range 0.04–0.4 mg/mL, with a correlation coefficient of 0.9996; precisions, evaluated as the repeatability for 0.04, 0.16 and 0.4 mg/mL amoxicillin, were 0.6%, 0.1% and 0.6%, respectively. Recovery from a generic formulation of amoxicillin was evaluated. The method showed selectivity in the presence of excipients commonly used in capsules, and satisfactory specificity was observed for amoxicillin and hydrolytic degradation products. The linearity was also evaluated for cephalexin and ampicillin. The conditions selected for MSC separation were compared with those for a HPLC system, and similar results were obtained in terms of chromatographic parameters but a difference in retention times was observed. Figure MSC system used for isocratic separation. MS, multisyringe burette; M, manometer; V1-V3, solenoid valves; MP, mobile phase; S, sample; W, waste; RP-18, monolithic column; DA, diode array detector; U, unused syringe.

Keywords: Multisyringe chromatography; Monolithic column; Amoxicillin; Ampicillin; Cephalexin; Validation

Application of matrix solid-phase dispersion and liquid chromatography–mass spectrometry to fungicide residue analysis in fruits and vegetables by Suli Wang; Yanjun Xu; Canping Pan; Shuren Jiang; Fengmao Liu (pp. 673-685).

A method based on matrix solid-phase dispersion (MSPD) and liquid chromatography–electrospay ionization–mass spectrometry used to analyze fifteen fungicide residues in fruits and vegetables is described. The method required only 0.5 g of sample, C₁₈-bonded silica was used as dispersant sorbent, and ethyl acetate was used as eluting solvent. Fortified recoveries in apple, orange, banana, lettuce, grape and tomato samples ranged from 71% to 102% and relative standard deviations were less than 13% with fortified levels of 0.03–1.5 mg kg⁻¹. Detection and quantification limits were 1~30 μg kg⁻¹ and 4~100 μg kg⁻¹, respectively, with linear calibration curves extending up to 15 mg kg⁻¹. The analytical characteristics of MSPD compared very favorably with those found for a classical multiresidue method: the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method. The method was applied to determine the fungicides in real samples. Liquid chromatography–tandem mass spectrometry (LC–MS–MS) was used as confirmatory tool for positive samples.

Keywords: Fruits and vegetables; Fungicide residues; Matrix solid-phase dispersion (MSPD); Liquid chromatography–mass spectrometry (LC–MS)

Sensitive measurement of ultratrace phenols in natural water by purge-and-trap with in situ acetylation coupled with gas chromatography-mass spectrometry by Ru-Song Zhao; Chuan-Ge Cheng; Jin-Peng Yuan; Ting Jiang; Xia Wang; Jin-Ming Lin (pp. 687-694).

A novel purge-and-trap method coupled with gas chromatography-mass spectrometry (GC-MS) is developed for the analysis of trace and ultratrace phenols based on their derivatization with acetic anhydride. Parameters affecting the extraction efficiency, such as purge temperature, concentration of sodium chloride, purge time, and volume of derivatization reagent, were investigated. The optimized conditions were addition of 150 μL acetic anhydride, purge time of 25 min at the purge temperature of 60 °C with 30% NaCl. The linear range was 0.2–100 μg L⁻¹ for phenols. The limits of detection (LODs) ranged from 0.08 to 0.15 μg L⁻¹ and the relative standard deviations (RSDs) for most of the phenols at the 10 μg L⁻¹level were below 10%. Natural water samples collected from a pool were successfully analyzed using the proposed method. The recovery of spiked water samples was 72.9–84.2%.

Keywords: Phenols; Acetylation; Purge-and-trap; Natural water; GC-MS

Determination of doxycycline in pharmaceuticals and human urine by micellar electrokinetic capillary chromatography by Rade Injac; Javor Kac; Samo Kreft; Borut Strukelj (pp. 695-701).

Micellar electrokinetic capillary chromatography (MEKC) was performed at 25 °C and 30 kV (under a pressure of 15 mbar), using 30 mM borate buffer containing 60 mM sodium dodecysulfate (SDS) and 5% (v/v) methanol as background electrolyte (pH 9.0) to determine doxycycline. UV detection was at 350 nm. The method was shown to be specific, accurate (recovery was 100.3 ± 1.0%), linear over the tested range (correlation coefficient 0.9995) and precise (RSD <1.9%). The method was used to determine doxycycline in tablets, capsules and human urine after oral application.

Keywords: Doxycycline; Micellar electrokinetic capillary chromatography (MEKC); Pharmaceuticals; Human urine

A novel amperometric immunosensor based on Fe₃O₄ magnetic nanoparticles/chitosan composite film for determination of ferritin by Sheng-Fu Wang; Yu-Mei Tan (pp. 703-708).

A novel amperometric immunosensor was developed by immobilizing ferritin antibody (FeAb) on the surface of Fe₃O₄ magnetic nanoparticles/chitosan composite film modified glassy carbon electrode (GCE). This material combined the advantages of inorganic Fe₃O₄ nanoparticles with the organic polymer chitosan. The stepwise assembly procedure of the immunosensor was characterized by means of differential pulse voltammetry (DPV) and ac impedance. The K₃Fe(CN)₆/K₄Fe(CN)₆ was used as a marker to probe the interface and to determinate ferritin. The factors that could influence the performance of the resulting immunosensor were studied in detail. After the immunosensor was incubated with ferritin for 32 min at 35 °C, the DPV current decreased linearly with the logarithm of ferritin concentration in the range from 20 to 500 ng mL⁻¹ with a correlation coefficient of 0.995 and a detection limit of 7.0 ng mL⁻¹. This immunosensor was used to analyze ferritin in human serum samples. The analytical results showed that the developed immunoassay was comparable with the radioimmunoassay (RIA), and the studied immunosensor exhibited good accuracy, high sensitivity, and long-term stability for 3 weeks, which implies a promising alternative approach for detecting ferritin in clinical diagnosis.

Keywords: Amperometric immunosensor; Fe₃O₄ magnetic nanoparticles; Chitosan; Ferritin

Probing traces of hydrogen peroxide by use of a biosensor based on mediator-free DNA and horseradish peroxidase immobilized on silver nanoparticles by Fuchuang Wang; Ruo Yuan; Yaqin Chai; Dianping Tang (pp. 709-717).

A new electrochemical biosensor for determination of hydrogen peroxide (H₂O₂) has been developed by immobilizing horseradish peroxidase (HRP) on silver colloids (nanosilver) and use of a DNA-functionalized interface. In the presence of the DNA and the nanosilver the immobilized HRP gives a pair of well-defined redox peaks with an electron-transfer rate constant of 3.27 ± 0.91 s⁻¹ in pH 7.0 PBS. The presence of DNA also provides a biocompatible microenvironment for enzyme molecules, greatly amplifies the amount of HRP molecules immobilized on the electrode surface, and improves the sensitivity of the biosensor. Under optimum conditions the biosensor has electrocatalytic activity in the reduction of hydrogen peroxide with linear dependence on H₂O₂ concentration in the range 1.5 × 10⁻⁶ to 2.0 × 10⁻³ mol L⁻¹; the detection limit is 5.0 × 10⁻⁷ mol L⁻¹ at a signal-to-noise ratio of 3. The $$ K^{{{ ext{app}}}}_{{ ext{m}}} $$ value of HRP in the composite membrane was found to be 1.62 mmol L⁻¹. These results suggest that the properties of the complex film, with its bioelectrochemical catalytic activity, could make it useful for development of bioelectronic devices and for investigation of protein electrochemistry at functional interfaces.

Keywords: Electrochemical biosensor; DNA; Hydrogen peroxide; Silver nanoparticles

Analysis of domperidone in pharmaceutical formulations and wastewater by differential pulse voltammetry at a glassy-carbon electrode by M. S. El-Shahawi; S. O. Bahaffi; T. El-Mogy (pp. 719-725).

The redox characteristics of the drug domperidone at a glassy-carbon electrode (GCE) in aqueous media were critically investigated by differential-pulse voltammetry (DPV) and cyclic voltammetry (CV). In Britton–Robinson (BR) buffer of pH 2.6–10.3, an irreversible and diffusion-controlled oxidation wave was developed. The dependence of the CV response of the developed anodic peak on the sweep rate (ν) and on depolizer concentration was typical of an electrode-coupled chemical reaction mechanism (EC) in which an irreversible first-order reaction is interposed between the charges. The values of the electron-transfer coefficient (α) involved in the rate-determining step calculated from the linear plots of E _p,a against ln (ν) in the pH range investigated were in the range 0.64 ± 0.05 confirming the irreversible nature of the oxidation peak. In BR buffer of pH 7.6–8.4, a well defined oxidation wave was developed and the plot of peak current height of the DPV against domperidone concentration at this peak potential was linear in the range 5.20 × 10⁻⁶ to 2.40 × 10⁻⁵ mol L⁻¹ with lower limits of detection (LOD) and quantitation (LOQ) of 6.1 × 10⁻⁷ and 9.1 × 10⁻⁷ mol L⁻¹, respectively. A relative standard deviation of 2.39% (n = 5) was obtained for 8.5 × 10⁻⁶ mol L⁻¹ of the drug. These DPV procedures were successfully used for analysis of domperidone in the pure form (98.2 ± 3.1%), dosage form (98.35 ± 2.9%), and in tap (97.0 ± 3.6%) and wastewater (95.0 ± 2.9%) samples. The method was validated by comparison with standard titrimetric and HPLC methods. Acceptable error of less than 3.3 % was also achieved. Figure In aqueous media at pH 7.6- 8.4, the DPV and cyclic voltammetry of the drug domperidone (I) at GCE showed an irreversible and diffusion controlled oxidation wave. The values of the electron transfer coefficient (α) involved in the rate determining step were found in the range 0.64± 0.05 confirming the irreversible nature of the peak. The analysis of the drug in pure form and in wastewater samples was successfully achieved

Keywords: Electrochemical oxidation; Domperidone; Motilium tablets; Wastewater; GCE; DPV

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Analytical and Bioanalytical Chemistry (v.387, #2)

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Analytical and Bioanalytical Chemistry (v.387, #2)