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Analytica Chimica Acta (v.710, #)

Editorial Board (pp. iii).

Microfabricated disposable lab-on-a-chip sensors with integrated bismuth microelectrode arrays for voltammetric determination of trace metals by Christos Kokkinos; Anastasios Economou; Ioannis Raptis (pp. 1-8).

Display Omitted► Disposable lab-on-a chip devices with integrated metal electrodes were fabricated. ► The working electrode was an microelectrode array consisting of bismuth microdisks. ► The sensors were tested for the voltammetric determination of Pb(II), Cd(II), Ni(II). ► The sensors are environmentally friendly and exhibit enhanced analytical features.This work reports the fabrication of disposable three-electrode cells with integrated metal-film electrodes. The devices were fabricated by a multi-step micro-fabrication approach combining sputtering for the deposition of metals and the dielectric material (SiO₂) on the surface of a silicon wafer and photolithography for the definition of the geometry of the sensors. The working electrode was a microelectrode array consisting of bismuth microdisks while the reference and counter electrode strips were made of Ag and Pt, respectively. The utility of these devices was tested for the trace determination of Pb(II) and Cd(II) by anodic stripping voltammetry and Ni(II) by adsorptive stripping voltammetry. The detection of these trace metals was carried out in unstirred and undeoxygenated solutions exhibiting sub-μgL⁻¹ limits of detection and enhanced analytical characteristics compared to conventional bismuth-film electrodes.

Keywords: Bismuth electrodes; Microelectrode arrays; Microfabrication; Stripping analysis; Trace metals

Molecular criteria for discriminating museum Asian lacquerware from different vegetal origins by pyrolysis gas chromatography/mass spectrometry by Anne-Solenn Le Hô; Martine Regert; Olivier Marescot; Chloé Duhamel; Juliette Langlois; Tetsuo Miyakoshi; Christophe Genty; Michel Sablier (pp. 9-16).

Display Omitted► Chemical geobotanical markers of Asian lacquers to discriminate vegetal species. ► Conservation of ancient lacquerware relies to a knowledge on their materials. ► Small specimens have to be extracted from the art works to preserve them.This paper focuses on the identification of several chemical markers of vegetal species of Oriental lacquers with the aim at providing a methodology consistent with sampling restrictions necessarily applied in the field of cultural heritage. The method proposed is based on rapid and easy single step thermally assisted hydrolysis–methylation (THM) pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) analysis that can be carried out with a minimum amount of matter (typically 10μg for a sample collected on a museum or an archaeological object).The main contribution of this study is to provide multiple molecular criteria for discriminating the three Asian species used for making lacquers, namely Rhus verniciflua Stokes, Rhus succedanea and Melanorrhoea usitata. Because these trees grow in specific areas, identifying the species involved in ancient lacquer coatings also provides geobotanical data and fruitful information on the exchange networks and trading routes developed by ancient societies.With this purpose, a systematic study of all pyrolysis products of lacquer coatings was carried out on modern dried lacquer films from authentified provenance. It was demonstrated that the whole pyrolysis products play a significant role in identifying the vegetal species. The chemotaxonomic value of homologous series of alkanes, alkenes and benzene derivatives, rarely explored until now, was assessed. It was shown that the combination of data related to five distinct groups of pyrolytic markers (composition and/or distribution of alkanes, alkenes and benzene, alkenyl-, alkylcatechol and phenol derivatives) provided new strong criteria to establish vegetal origin and provenance of Asian artworks, even though they have been largely altered over time.Case studies of archaeological Chinese lacquered artefacts and Japanese Buddhistic altar were thereafter successfully investigated to address informative potential and efficiency of these criteria on ancient and degraded lacquer coatings.

Keywords: Asian lacquer; Geobotanical markers; Thermally assisted hydrolysis–methylation; Pyrolysis-gas chromatography–mass spectrometry; Cultural heritage

Bioanalytical chromatographic methods for the determination of catechol- O-methyltransferase inhibitors in rodents and human samples: A review by Daniela Gonçalves; Gilberto Alves; Patrício Soares-da-Silva; Amílcar Falcão (pp. 17-32).

Display Omitted► We discuss the bioanalytical aspects for tolcapone and entacapone. ► Liquid chromatography methods for nitecapone were also reviewed. ► We also focused the COMT inhibitors in development, nebicapone and opicapone. ► The review provides appropriate background for development of new analytical methods. ► The pharmacokinetics of COMT inhibitors with bioanalytical interest were addressed.In the past years, it has been recognised that the levodopa therapy may be improved with therapeutic regimens including a catechol- O-methyltransferase (COMT) inhibitor. At the present time, tolcapone and entacapone are the only two COMT inhibitors available in the market. However, further COMT inhibitors are under development for Parkinson's disease, namely nebicapone and opicapone (formerly known as BIA 9-1067). In addition, the nitecapone, another well-known COMT inhibitor, is also in preclinical development but for neuropathic pain. Since the 1990s different liquid chromatography methods have been developed and validated to quantify tolcapone, entacapone, nitecapone, nebicapone and some metabolites in biological samples, particularly in plasma samples obtained from rodent and human species. These bioanalytical methods have been primarily used to support pharmacokinetic assays with such COMT inhibitors in non-clinical and clinical studies. As these inhibitors present hydrophobic groups in their chemical structures, reversed-phase liquid chromatography has been used as the major approach for the determination of such compounds, especially high-performance liquid chromatography coupled to ultraviolet detection (HPLC-UV), electrochemical detection (HPLC-ECD) and mass spectrometry detection (HPLC–MS). Regarding the sample preparation, the traditional liquid–liquid extraction (LLE) and solid-phase extraction (SPE) were also the most widely used procedures for extraction of the analytes of interest prior to the analysis of samples. Thus, this review aimed to gather, for the first time, sufficient background information about the bioanalytical chromatographic methods which have been already developed and applied for the determination of tolcapone, entacapone, nitecapone, nebicapone and their metabolites. Moreover, some pharmacokinetic aspects of the COMT inhibitors with interest from a bioanalytical perspective were also addressed.

Keywords: Bioanalytical chromatographic methods; Tolcapone; Entacapone; Nitecapone; Nebicapone; Catechol-; O; -methyltransferase inhibitors

Lanthanides determination in red wine using ultrasound assisted extraction, flow injection, aerosol desolvation and ICP-MS by Fabrina R.S. Bentlin; Clarissa M.M. dos Santos; Érico M.M. Flores; Dirce Pozebon (pp. 33-39).

Display Omitted► Ultrasound was investigated and applied for red wine samples preparation. ► Aliquots of 50μL of sample were nebulized and transported to plasma. ► FI and pneumatic nebulization/aerosol desolvation were used. ► LODs of the ICP-MS method for lanthanides determination were at ngL⁻¹ level. ► Lanthanides concentration allowed red wines classification.This paper deals with the determination of the fourteen naturally occurring elements of the lanthanide series in red wine. Ultrasound (US) was used for sample preparation prior lanthanides determination using ICP-MS. Flow injection (FI) and pneumatic nebulization/aerosol desolvation were used for nebulization of aliquots of 50μL of sample and its subsequent transportation to plasma. Sample preparation procedures, matrix interference and time of sonication were evaluated. Better results for lanthanides in red wine were obtained by sonication with US probe for 90s and sample 10-fold diluted. The limits of detection of La, Ce, Nd, Sm, Gd, Pr, Eu, Tb, Dy, Ho, Er, Tm, Lu and Yb were 6.57, 10.8, 9.97, 9.38, 2.71, 1.29, 1.22, 0.52, 2.35, 0.96, 2.30, 0.45, 0.24 and 1.35ngL⁻¹, respectively. Red wines of different varieties from three countries of South America were discriminated according to the country of origin by means of multivariate analysis of lanthanides concentration.

Keywords: Red wine; Flow injection; Sonication; Lanthanides; ICP-MS; Aerosol desolvation

Enhanced chromatographic fingerprinting of herb materials by multi-wavelength selection and chemometrics by J. Ricardo Lucio-Gutiérrez; J. Coello; S. Maspoch (pp. 40-49).

Display Omitted► We describe an approach for multi-wavelength fingerprinting. ► PCA was used to conduct the alignment of complex chromatographic data. ► Multi-wavelength fingerprints increased the sample's data information. ► Improved results on fingerprinting V. officinalis were demonstrated. ► General success rates of a classification above 90% were achieved by SIMCA and PLS-DA.A strategy for multi-wavelength chromatographic fingerprinting of herbal materials, using high performance liquid chromatography with a UV–Vis diode array detector is presented. Valeriana officinalis was selected to show the proposed methodology since it is a widely used commercially available herbal drug, and because misfit with other valerian species is a current issue. The enhanced fingerprints were constructed by compiling into a single data vector the chromatograms from four wavelengths (226, 254, 280 and 326nm), at which characteristic chemical constituents of studied herbs presented maximum absorbance. Chromatographic data pretreatment included baseline correction, normalization and correlation optimized warping. A simplex optimization was performed to retrieve the optimal values of the parameters used in the warping. General success rates of a classification above 90% were achieved by soft independent modeling of class analogy (SIMCA) and partial least squares discriminant analysis (PLS-DA). The sensitivity and specificity of constructed models were above 94%. Tests on laboratory-made mixtures showed that it is possible to detect adulterations or counterfeits with 5% foreign herbal material, even if it is from the Valerianaceae family. The results suggest that the proposed enhanced fingerprinting approach can be used to authenticate herb materials with complex chromatographic profiles.

Keywords: Valeriana officinalis; HPLC-fingerprinting; Multi-wavelength; Authenticity; Chemometrics

Determination of arsenate in natural pH seawater using a manganese-coated gold microwire electrode by Kristoff Gibbon-Walsh; Pascal Salaün; Constant M.G. van den Berg (pp. 50-57).

Display Omitted► Determination of arsenic(V) in water of neutral pH. ► An unusual redox couple of elemental Mn/As^V reduces As^V to As^III. ► Novel manganese coated gold microwire electrode.Direct electrochemical determination of arsenate (As^V) in neutral pH waters is considered impossible due to electro-inactivity of As^V. As^III on the other hand is readily plated as As⁰ on a gold electrode and quantified by anodic stripping voltammetry (ASV). We found that the reduction of As^V to As^III was mediated by elemental Mn on the electrode surface in a novel redox couple in which 2 electrons are exchanged causing the Mn to be oxidised to Mn^II. Advantage is taken of this redox couple to enable for the first time the electrochemical determination of As^V in natural waters of neutral pH including seawater by ASV using a manganese-coated gold microwire electrode. Thereto Mn is added to excess (∼1μM Mn) to the water leading to a Mn coating during the deposition of As on the electrode at a deposition potential of −1.3V. Deposition of As⁰ from dissolved As^V caused elemental Mn to be re-oxidised to Mn^II in a 1:1 molar ratio providing evidence for the reaction mechanism. The deposited As^V is subsequently quantified using an ASV scan. As^III interferes and should be quantified separately at a more positive deposition potential of −0.9V. Combined inorganic As is quantified after oxidation of As^III to As^V using hypochlorite. The microwire electrode was vibrated during the deposition step to improve the sensitivity. The detection limit was 0.2nM As^V using a deposition time of 180s.

Keywords: Anodic stripping voltammetry; Arsenate; Arsenic; Microwire electrode; Arsenic speciation

Dispersion of multi-wall carbon nanotubes in polyhistidine: Characterization and analytical applications by Pablo R. Dalmasso; María L. Pedano; Gustavo A. Rivas (pp. 58-64).

Display Omitted► Polyhistidine (Polyhis) is an efficient dispersing agent of MWCNT. ► MWCNT/Polyhis ratio and sonication time are critical variables when dispersing MWCNT. ► MWCNT–Polyhis deposited at GCE largely catalyzes the oxidation of ascorbic acid. ► GCE/MWCNT–Polyhis allows the selective and sensitive quantification of UA and Do.We report for the first time the use of polyhistidine (Polyhis) to efficiently disperse multiwall carbon nanotubes (MWCNTs). The optimum dispersion MWCNT–Polyhis was obtained by sonicating for 30min 1.0mgmL⁻¹ MWCNTs in 0.25mgmL⁻¹ Polyhis solution prepared in 75:25 (v/v) ethanol/0.200M acetate buffer solution pH 5.00. The dispersion was characterized by scanning electron microscopy, and by cyclic voltammetry and amperometry using ascorbic acid as redox marker. The modification of glassy carbon electrodes with MWCNT–Polyhis produces a drastic decrease in the overvoltage for the oxidation of ascorbic acid (580mV) at variance with the response observed at glassy carbon electrodes modified just with Polyhis, where the charge transfer is more difficult due to the blocking effect of the polymer. The reproducibility for the sensitivities obtained after 10 successive calibration plots using the same surface was 6.3%. The MWCNT-modified glassy carbon electrode demonstrated to be highly stable since after 45 days storage at room temperature the response was 94.0% of the original. The glassy carbon electrode modified with MWCNT–Polyhis dispersion was successfully used to quantify dopamine or uric acid at nanomolar levels, even in the presence of large excess of ascorbic acid. Determinations of uric acid in human blood serum samples demonstrated a very good correlation with the value reported by Wienner laboratory.

Keywords: Carbon nanotubes dispersion; Polyhistidine; Glassy carbon electrode; Ascorbic acid; Dopamine; Uric acid

Multi-class pesticide analysis in human hair by gas chromatography tandem (triple quadrupole) mass spectrometry with solid phase microextraction and liquid injection by Guillaume Salquèbre; Claude Schummer; Maurice Millet; Olivier Briand; Brice M.R. Appenzeller (pp. 65-74).

Display Omitted► SPME and GC–MS/MS were combined for the detection of 22 pesticides in human hair. ► High sensitivity was obtained despite of dealing with 7 different chemical classes. ► All the field samples analyzed here contained target pesticides. ► Some pesticides never analyzed in hair so far were detected here at high levels. ► This work will help studying pesticide exposure and associated biological effects.A method for the simultaneous detection and quantification of 22 pesticides from different chemical classes was developed using solid-phase microextraction (SPME) and gas chromatography tandem (triple quadrupole) mass spectrometry. Pesticides were extracted from 50mg of pulverized hair with acetonitrile. The extract was submitted to two successive steps of direct immersion-SPME at 30°C and 90°C or to a liquid injection without SPME in order to obtain optimized conditions for each of the 22 analytes investigated. Validation parameters were significantly influenced by both the injection mode (SPME vs liquid injection) and the temperature of SPME. Limits of quantification ranged from 0.05pgmg⁻¹ for trifluralin to 10pgmg⁻¹ for pentachlorophenol. The application of the validated method to the analysis of samples collected from non-occupationally exposed volunteers demonstrated the presence of pesticides in all the samples tested. Altogether, 13 different analytes were detected at concentration above the limit of quantification.

Keywords: Pesticides; Hair; GC–MS/MS; SPME; Human biomonitoring; Exposure

Multiple headspace solid-phase microextraction after matrix modification for avoiding matrix effect in the determination of ethyl carbamate in bread by Chang-Wen Ye; Xue-Na Zhang; Yuan-Li Gao; Yu-long Wang; Si-Yi Pan; Xiu-Juan Li (pp. 75-80).

Display Omitted► Multiple headspace SPME for eliminating matrix effect in solid samples analysis. ► A novel polyethylene glycol/hydroxy-terminated silicone oil fiber is used. ► The bread is desiccated by mixing with anhydrous sodium sulphate.This study presents the potential of multiple headspace solid-phase microextraction (multiple HS-SPME) for the quantification of analytes in solid samples. Multiple HS-SPME shares the same advantages as SPME. It also enables a complete recovery of the target compound and therefore the matrix effect, which commonly appears in SPME-based analysis, is avoided. A method based on multiple HS-SPME for the determination of the toxic contaminant ethyl carbamate (EC) in bread samples has been developed and validated, using gas chromatography with flame ionization detector. A novel polyethylene glycol/hydroxy-terminated silicone oil fiber was prepared for the first time and subsequently used instead of commercial ones because of its high extraction ability and good operational stability. An important problem still remained in multiple HS-SPME of EC in fresh bread samples. The adsorption of EC by water in the samples caused low transport of analyte to the headspace, which made multiple HS-SPME invalidated. Mixing with anhydrous sodium sulphate, the sensitivity of the method was improved and the problem was solved. The proposed method showed satisfactory linearity (0.15–1500μgg⁻¹), precision (1.6%, n=5) and limit of detection (0.041μgg⁻¹). Good recoveries, from 92.5 to 103.4%, were observed at three spiking levels. The method was applied to 14 bread samples. The multiple HS-SPME technique offers several advantages including reducing the manipulation time and cost, and avoiding analyte losses, especially in the analysis of a large number of samples in different matrices.

Keywords: Multiple headspace solid-phase microextraction; Ethyl carbamate; Bread; Matrix modification; Polyethylene glycol; Matrix effect

Native vs photoinduced chemiluminescence in dimethoate determination by M. Catalá-Icardo; J.L. López-Paz; C. Choves-Barón; A. Peña-Bádena (pp. 81-87).

Display Omitted► Comparison between native and photoinduced chemiluminescence of dimethoate. ► Hexadecylpyridinium enhanced greatly the chemiluminescence. ► Solid phase extraction allowed the successful determination of dimethoate in water.The determination of dimethoate using either its native chemiluminescent (CL) properties or its photoinduced chemiluminescence obtained by irradiation with a 15W low-pressure mercury lamp was studied. Thereby, two flow injection systems (FIA) with and without irradiation were exhaustively optimized and their analytical characteristics studied. Better sensitivity and selectivity was found in absence of irradiation, due to the enhancing effect of hexadecylpyridinium chloride (HPC), which acted as a sensitizer. In the developed FIA-CL system, the alkaline hydrolysis of dimethoate with NaOH was performed on-line in presence of HPC. The oxidation of the product of hydrolysis with Ce(IV) in hydrochloric medium induced chemiluminescence. The method provided a limit of detection of only 0.05ngmL⁻¹ without any pre-treatment. However, the combination with solid phase extraction allowed the removal of some potential interferents as well as the preconcentration of the pesticide. Finally, the developed method was successfully applied to natural waters with recoveries between 95 and 108%.

Keywords: Dimethoate; Photoreaction; Chemiluminescence; Flow injection; Water

Effect of dispersion on the diffusion zone in two-phase laminar flows in microchannels by Debapriya Chakraborty; Nilanjana Bose; Sukanya Sasmal; Swagata Dasgupta; Tapas K. Maiti; Suman Chakraborty; Sunando DasGupta (pp. 88-93).

Display Omitted► Interdiffusion zone of two reacting liquids in laminar flow in a microchannel. ► Effect of dispersion. ► Modelling of the near wall zone and evaluation of dispersion coefficient. ► Introduction of effective diffusivity to account for dispersion. ► Dependence of effective diffusivity on channel Peclet number.Aim of the present work is to investigate the reaction–diffusion process of a two species system under laminar flow in a T-shaped microchannel. A zone formed at the interface between the aqueous solutions of these two species is affected by advection and diffusion. Through theoretical analyses and experimental results, the effect of dispersion has been shown to influence this diffusion zone. We have defined a parameter called effective diffusivity, to account for the dispersion effects and observed it to be a function of the channel Peclet number. In the limiting case of low Peclet number, this parameter is constant and turns out to be equal to the molecular diffusivity. We have also related effective diffusivity and the dispersion coefficient through scaling estimates.

Keywords: Laminar flow; Transverse diffusion; Reaction; Dispersion; Peclet number; Effective diffusivity

Detection of singly- and doubly-charged quaternary ammonium drugs in equine urine by liquid chromatography/tandem mass spectrometry by Emmie N.M. Ho; W.H. Kwok; April S.Y. Wong; Terence S.M. Wan (pp. 94-101).

Display Omitted► A high throughput screening method for 38 singly- and doubly-charged QADs. ► QADs are difficult to be extracted and poorly retained on reversed-phase columns. ► Separation of QADs using polar group embedded C18 LC column. ► Easily expandable to accommodate more target analytes.Quaternary ammonium drugs (QADs) are anticholinergic agents some of which are known to have been abused or misused in equine sports. A recent review of literature shows that the screening methods reported thus far for QADs mainly cover singly-charged QADs. Doubly-charged QADs are extremely polar substances which are difficult to be extracted and poorly retained on reversed-phase columns. It would be ideal if a comprehensive method can be developed which can detect both singly- and doubly-charged QADs. This paper describes an efficient liquid chromatography/tandem mass spectrometry (LC/MS/MS) method for the simultaneous detection and confirmation of 38 singly- and doubly-charged QADs at sub-parts-per-billion (ppb) to low-ppb levels in equine urine after solid-phase extraction.Quaternary ammonium drugs were extracted from equine urine by solid-phase extraction (SPE) using an ISOLUTE^® CBA SPE column and analysed by LC/MS/MS in the positive electrospray ionisation mode. Separation of the 38 QADs was achieved on a polar group embedded C18 LC column with a mixture of aqueous ammonium formate (pH 3.0, 10mM) and acetonitrile as the mobile phase. Detection and confirmation of the 38 QADs at sub-ppb to low-ppb levels in equine urine could be achieved within 16min using selected reaction monitoring (SRM). Matrix interference of the target transitions at the expected retention times was not observed. Other method validation data, including precision and recovery, were acceptable. The method was successfully applied to the analyses of drug-administration samples.

Keywords: Quaternary ammonium drugs; Urine; Horse; Liquid chromatography/tandem mass spectrometry

Dominant structural factors for complexation and denaturation of proteins using carboxylic acid receptors by Tatsuya Oshima; Hiroshi Muto; Yoshinari Baba (pp. 102-110).

Display Omitted► Complexation accompanied by denaturation of protein with synthetic carboxylic acid receptors was investigated, to evaluate the key factors for recognition of proteins. ► TPP derivatives bearing multiple carboxylic acid groups in the side chains exhibited higher affinity than other receptors that were smaller and had fewer carboxylic acid groups. ► From the results of Job plots and slope analysis for the amount of denatured protein, formation of 1:1 complexes was confirmed.Complexation accompanied by denaturation of protein with synthetic carboxylic acid receptors was investigated, to evaluate the key factors for recognition of proteins. The synthetic receptors used were tetraphenylporphyrin (TPP) derivatives and receptors bearing multiple (2–8) carboxylic acid groups. The complexation behavior was quantified from the absorption in the far UV CD spectrum attributed to the secondary structure of the protein. TPP derivatives bearing multiple carboxylic acid groups in the side chains exhibited higher affinity than other receptors that were smaller and had fewer carboxylic acid groups. As the degree of complexation was influenced by the pH and ionic strength in aqueous solution, electrostatic interaction was one of the most important factors for the recognition of proteins. Complexation was also estimated by observation of fluorescence quenching of the TPP derivatives. The stoichiometry of the complexes between lysozyme and the porphyrins was investigated by quantitative analysis of the denaturation using CD spectra. From the results of Job plots and slope analysis for the amount of denatured protein, formation of 1:1 complexes was confirmed. The equilibrium association constants ( K_ass) for lysozyme and the TPP receptors ranged from 0.6×10⁶ to 1.1×10⁶M⁻¹. The lytic activity of lysozyme was partially lost in the presence of anionic TPP derivatives, due to complexation and denaturation.

Keywords: Denaturation; Protein surface recognition; Tetraphenylporphyrin; Protein; Circular dichroism

Label-free genotyping of cytochrome P450 2D6*10 using ligation-mediated strand displacement amplification with DNAzyme-based chemiluminescence detection by Hong-Qi Wang; Zhan Wu; Yan Zhang; Li-Juan Tang; Ru-Qin Yu; Jian-Hui Jiang (pp. 111-117).

Display Omitted► We report a homogeneous label-free CYP2D6*10 genotyping technique. ► Genotyping is accomplished by ligase chain reaction. ► The technique is based on ligation-mediated strand displacement amplification. ► The signal of detection is DNAzyme-catalyzed chemiluminescence.Genotyping of cytochrome P450 monooxygenase 2D6*10 (CYP2D6*10) plays an important role in pharmacogenomics, especially in clinical drug therapy of Asian populations. This work reported a novel label-free technique for genotyping of CYP2D6*10 based on ligation-mediated strand displacement amplification (SDA) with DNAzyme-based chemiluminescence detection. Discrimination of single-base mismatch is firstly accomplished using DNA ligase to generate a ligation product. The ligated product then initiates a SDA reaction to produce aptamer sequences against hemin, which can be probed by chemiluminescence detection. The proposed strategy is used for the assay of CYP2D6*10 target and the genomic DNA. The results reveal that the proposed technique displays chemiluminescence responses in linear correlation to the concentrations of DNA target within the range from 1pM to 1nM. A detection limit of 0.1pM and a signal-to-background ratio of 57 are achieved. Besides such high sensitivity, the proposed CYP2D6*10 genotyping strategy also offers superb selectivity, great robustness, low cost and simplified operations due to its label-free, homogeneous, and chemiluminescence-based detection format. These advantages suggest this technique may hold considerable potential for clinical CYP2D6*10 genotyping and association studies.

Keywords: Genotyping; Cytochrome P450 monooxygenase 2D6*10; DNA ligase; Strand displacement amplification; Single nucleotide polymorphism

Cobalt hexacyanoferrate modified multi-walled carbon nanotubes/graphite composite electrode as electrochemical sensor on microfluidic chip by Xinchun Li; Zuanguang Chen; Yuwen Zhong; Fan Yang; Jianbin Pan; Yajing Liang (pp. 118-124).

Display Omitted► CoHCF nanoparticles modified MWCNTs/graphite electrode use for electrochemistry on electrophoresis microchip for the first time. ► Simultaneous, rapid, and sensitive electrochemical detection of hydrazine and isoniazid in real samples. ► An exemplary work of CME sensor assembly onto microchip for determination of analytes with environmental significance. ► Manifestation of the applicability and flexibility of CME sensor for electroanalysis on microfluidic chip.Nanomaterial-based electrochemical sensor has received significant interest. In this work, cobalt hexacyanoferrate modified multi-walled carbon nanotubes/graphite composite electrode was electrochemically prepared and exploited as an amperometric detector for microchip electrophoresis. The prepared sensor displayed rapid and sensitive response towards hydrazine and isoniazid oxidation, which was attributed to synergetic electrocatalytic effect of cobalt hexacyanoferrate and multi-walled carbon nanotubes. The sensitivity enhancement with nearly two orders of magnitude was gained, compared with the bare carbon paste electrode, with the detection limit of 0.91μM ( S/ N=3) for hydrazine. Acceptable repeatability of the microanalysis system was verified by consecutive eleven injections of hydrazine without chip and electrode treatments, the RSDs for peak current and migration time were 3.4% and 2.1%, respectively. Meanwhile, well-shaped electrophoretic peaks were observed, mainly due to fast electron transfer of electroactive species on the modified electrode. The developed microchip-electrochemistry setup was successfully applied to the determination of hydrazine and isoniazid in river water and pharmaceutical preparation, respectively. Several merits of the novel electrochemical sensor coupled with microfluidic platform, such as comparative stability, easy fabrication and high sensitivity, hold great potential for hydrazine compounds assay in the lab-on-a-chip system.

Keywords: Cobalt hexacyanoferrate; Multi-walled carbon nanotubes; Chemically modified electrode; Microfluidic chip; Hydrazine

Morphine-induced conditioned place preference in mice: Metabolomic profiling of brain tissue to find “molecular switch” of drug abuse by gas chromatography/mass spectrometry by Jiaoran Meng; Xiaodong Zhang; Hao Wu; Jing Bu; Chenyi Shi; Chunhui Deng; Yu Mao (pp. 125-130).

In this study, morphine-induced conditioned place preference (CPP) in mice was used as an animal model to explore the mechanism of context-dependent learning associated with rewarding effect of morphine. We developed a GC–MS method to investigate the metabolic differences in mice brain tissues between morphine-treated ( n=20) and control groups ( n=19). Mice brain tissue metabolites were extracted and derivatized followed by analysis with GC–MS. 21 metabolic markers related to metabolic pathway of morphine in brain tissues were found.Display Omitted► We explored the mechanism of context-dependent learning associated with rewarding effect of morphine in mice brain. ► We examined metabolomic change in morphine-treated mice by GC/MS. ► Potential biomarkers relating to rewarding effect of morphine were selected. ► Myo-inositol, nicotinamide, proline and valine were likely to play a part in intracellular morphine-related signal pathway. ► We provided a new angle to look for the molecular mechanism of drug abuse.Conditioned place preference (CPP) is a widely used model to explore the mechanism of context-dependent learning. In this work, we developed a GC–MS method to investigate the metabolites in mice brain which was used to study the mechanism of context-dependent learning associated with rewarding effect of morphine. Metabolites were extracted from brain tissues and derivatized followed by analysis by gas chromatography/mass spectrometry (GC–MS). In total, 69 peaks were identified as known compounds. By a Wilcoxon ran sum test with p value ≤0.05, 21 metabolites were selected and considered as the potential biomarkers of morphine in mice brain. Using principal component analysis (PCA) and receiver-operator characteristic (ROC) curves, a model was constructed with a combination of these 21 metabolic markers. Multivariate statistics of the model yielded separation between the two groups with an area under the curve value of 0.947. Some metabolites were further discussed in detail about their pathway. Results showed that our technique can be successfully applied to profile for biomarkers and in understanding molecular mechanisms of drug abuse.

Keywords: Metabolomic profile; Morphine-induced conditioned place preference; Biomarker; Gas chromatography/mass spectrometry

Erratum to “Development of fluorescence imaging-based assay for screening cardioprotective compounds from medicinal plants” [Anal. Chim. Acta 702 (2011) 87–94] by Yi Wang; Xiaoping Zhao; Xiumei Gao; Xiaojing Nie; Yingxin Yang; Xiaohui Fan (pp. 131-131).

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Analytica Chimica Acta (v.710, #)