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Analytica Chimica Acta (v.721, #)
Electrochemical stripping analysis of nanogold label-induced silver deposition for ultrasensitive multiplexed detection of tumor markers by Guosong Lai; Lili Wang; Jie Wu; Huangxian Ju; Feng Yan (pp. 1-6).
Display Omitted► A multiplexed immunoassay is proposed by stripping analysis of deposited silver. ► The silver deposition enhancement greatly improves detection sensitivity. ► The proposed method avoids the interference of dissolved oxygen. ► This method eliminates the electrochemical cross talk between adjacent immunosensors.A multiplexed electrochemical immunoassay method was developed for simultaneous ultrasensitive measurement of tumor markers based on electrochemical stripping analysis of silver nanoparticles (Ag NPs). The Ag NPs were deposited on a disposable immunosensor array with a reduction reaction catalyzed by nanogold labels. The immunosensor array was prepared by covalently immobilizing capture antibodies on chitosan modified screen-printed carbon electrodes. Through a sandwich-type immunoreaction, antibody-functionalized Au NPs were captured onto immunosensor surface to induce the silver deposition from a silver enhancer solution. The deposited Ag NPs could be directly measured by anodic stripping analysis in KCl solution. The catalytic deposition enhanced the analytical sensitivity for detection of protein markers. The interference of dissolved oxygen could be avoided as the detection was performed with positive stripping potential range. Using carcinoembryonic antigen and α-fetoprotein as model analytes, the proposed multiplexed immunoassay method showed wide linear ranges of three orders of magnitude with the detection limits down to 3.5 and 3.9pgmL−1, respectively. The localized silver deposition, as well as the stripping detection process, eliminated completely the electrochemical cross talk between adjacent immunosensors. The immunosensor array exhibited acceptable reproducibility, stability and accuracy, showing a promising potential in multianalyte determination for clinical application.
Keywords: Biosensor; Multiplexed immunoassay; Stripping analysis; Gold nanoparticle; Silver deposition; Screen-printed electrode
Probing protein interactions with hydrogen/deuterium exchange and mass spectrometry—A review by Andrew J. Percy; Martial Rey; Kyle M. Burns; David C. Schriemer (pp. 7-21).
Display Omitted► Protein chemistry generates mass shifts useful for structure–function studies. ► H/DX supports a powerful mass shift method for protein interaction analysis. ► H/DX mass shifts are useful for determining binding data ( Kd, off-rates). ► Improved H/DX–MS workflows can accommodate complex protein systems.Assessing the functional outcome of protein interactions in structural terms is a goal of structural biology, however most techniques have a limited capacity for making structure–function determinations with both high resolution and high throughput. Mass spectrometry can be applied as a reader of protein chemistries in order to fill this void, and enable methodologies whereby protein structure–function determinations may be made on a proteome-wide level. Protein hydrogen/deuterium exchange (H/DX) offers a chemical labeling strategy suitable for tracking changes in “dynamic topography” and thus represents a powerful means of monitoring protein structure–function relationships. This review presents the exchange method in the context of interaction analysis. Applications involving interface detection, quantitation of binding, and conformational responses to ligation are discussed, and commentary on recent analytical developments is provided.
Keywords: Mass spectrometry; H/D exchange; Protein; Protein interaction
Speciation of mercury in fish samples by flow injection catalytic cold vapour atomic absorption spectrometry by Yanlin Zhang; Samuel B. Adeloju (pp. 22-27).
Display Omitted► Successful speciation of inorganic and organic Hg with Fe3+, Cu2+ and thiourea as catalysts. ► Best sensitivity enhancement and similar sensitivity for MeHg and Hg2+ with Fe3+. ► Successful use of Hg2+ as the primary standard for quantification of inorganic and total-Hg. ► Quantitative extraction of Hg and MeHg with 2M HCl which contained thiourea. ► Integration with FIA for rapid analysis with a sample throughput of 180h−1.A rapid flow injection catalytic cold vapour atomic absorption spectrometric (FI-CCV-AAS) method is described for speciation and determination of mercury in biological samples. Varying concentrations of NaBH4 were employed for mercury vapour generation from inorganic and mixture of inorganic and organic (total) Hg. The presence of Fe3+, Cu2+ and thiourea had catalytic effect on mercury vapour generation from methylmercury (MeHg) and, when together, Cu2+ and thiourea had synergistic catalytic effect on the vapour generation. Of the two metal ions, Fe3+ gave the best sensitivity enhancement, achieving the same sensitivity for MeHg and inorganic Hg2+. Due to similarity of resulting sensitivity, Hg2+ was used successfully as a primary standard for quantification of inorganic and total Hg. The catalysis was homogeneous in nature, and it was assumed that the breaking of the CHg bond was facilitated by the delocalization of the 5 d electron pairs in Hg atom. The extraction of MeHg and inorganic mercury (In-Hg) in fish samples were achieved quantitatively with hydrochloric acid in the presence of thiourea and determined by FI-CCV-AAS. The application of the method to the quantification of mercury species in a fish liver reference material DOLT-4 gave 91.5% and 102.3% recoveries for total and methyl mercury, respectively. The use of flow injection enabled rapid analysis with a sample throughput of 180h−1.
Keywords: Inorganic mercury; Methylmercury; Flow injection; Cold vapour atomic absorption spectrometry; Catalyst; Fish
A new formulation to estimate the variance of model prediction. Application to near infrared spectroscopy calibration by E. Fernandez-Ahumada; J.M. Roger; B. Palagos (pp. 28-34).
Display Omitted► A new expression for prediction uncertainty estimation in linear regressions is proposed. ► It is the first one adapted to particularities of near infrared spectra. ► It clearly splits the sources of uncertainty and manages different types of error. ► A test on NIR spectra of feed stuff shows its advantages. ► Estimated values of the expression are in accordance with those of a resampling method.Evaluation of uncertainty affecting predictions is a major trend in analytical chemistry and chemometrics. Several approximate expressions and resampling methods have been proposed for the estimation of prediction uncertainty when using multivariate calibration. This article proposes a new expression for the variance of prediction, adapted to near infrared spectroscopy specificities and particularly to the spectral error structure, induced by the high colinearity of the variables. The proposed analytical expression enables a detailed evaluation of the different contributions and components of uncertainty affecting the model. An application to real data of feedstuff near infrared spectra related to protein content has shown its advantages.
Keywords: Prediction uncertainty; Multivariate calibration; NIR spectroscopy
Potential antioxidant compounds in Mallotus species fingerprints. Part II: Fingerprint alignment, data analysis and peak identification by C. Tistaert; B. Dejaegher; G. Chataigné; C. Rivière; N. Nguyen Hoai; M. Chau Van; J. Quetin-Leclercq; Y. Vander Heyden (pp. 35-43).
Display Omitted► Indication of peaks responsible for the antioxidant activity of Mallotus species (O-PLS). ► Development of a warping strategy based on correlation optimised warping. ► Evaluation of a multivariate model prior and after alignment for indicative and predictive purposes. ► LC–MS analyses of the indicated peaks.Some Mallotus species are commonly used as traditional medicine (TM) ingredients in Vietnam and China, but only a few are studied for their activities. In Part I, high-performance liquid chromatography (HPLC) fingerprints of 39 Mallotus samples (17 species) were developed and, because of the complexity of and the large differences between the samples, it was chosen to analyse the unaligned fingerprints. The peaks, potentially responsible for the antioxidant activity in given Mallotus species, were indicated by the regression coefficients from an orthogonal projections to latent structures (O-PLS) model. In the present study, an in depth discussion on the need for alignment of the Mallotus fingerprints for the indication of the potentially active compounds is made, as well as an experimental analysis and identification of the previously indicated peaks by HPLC–mass spectrometry (HPLC–MS). Additionally, to thoroughly study and discuss the alignment problem, the modelling and prediction of the antioxidant activity of green tea samples based on HPLC fingerprints were also considered.
Keywords: Fingerprints; Alignment; Peak identification; Multivariate calibration
Fractions of Rechtschaffner matrices as supersaturated designs in screening experiments aimed at evaluating main and two-factor interaction effects by R. Cela; R. Phan-Tan-Luu; M. Claeys-Bruno; M. Sergent (pp. 44-54).
Display Omitted► The first supersaturated matrices allowing the estimation of main effects and two-factor interactions are presented. ► An efficient procedure for the construction of optimal fractions of Rechtschaffner matrices is proposed. ► Efficient and practical procedures for the resolution of these supersaturated matrices are developed. ► The usefulness of these matrices is demonstrated in simulation experiments as well as using literature real life data.Optimal fractions of resolution V design matrices proposed by Rechtschaffner in 1967 are developed and applied as supersaturated designs in screening experiments. Rechtschaffner matrices allow evaluation of all main factors and two-factor interactions, which in many real-world studies are of practical significance. However, the number of experimental runs increases rapidly with the number of factors in the matrices, which are therefore impractical for more than 5–6 factors. On the contrary, saturated fractions based on Hadamard matrices, which are commonly applied in screening studies, cannot evaluate the interaction effects. Here, a procedure for selecting the optimum fractions of Rechtschaffner matrices is presented and provides supersaturated matrices that are well adapted to a variety of problems, thus allowing the development of screening studies with a relatively small number of experiments. The procedures developed to derive the size-reduced matrices and to evaluate the active factors are discussed and compared in terms of efficiency and reliability, by means of simulation studies and application to a real problem. These fractions are the first supersaturated design matrices capable of estimating interaction effects. Additionally, one important advantage of these supersaturated matrices is that they enable development of follow-up procedures in cases of inconclusive results, by enlarging the matrix and eventually resolving the full Rechtschaffner matrix of departure when it is necessary to evaluate the active factors and their interactions.
Keywords: Experimental design; Screening designs; Supersaturated designs; Rechtschaffner matrices
Simultaneous electrochemical sensing of ascorbic acid, dopamine and uric acid at anodized nanocrystalline graphite-like pyrolytic carbon film electrode by Mojtaba Hadi; Ahmad Rouhollahi (pp. 55-60).
Display Omitted► The nanocrystalline pyrolytic carbon film electrode as an electrochemical biosensor. ► The sensor for simultaneous detection of ascorbic acid, dopamine, and uric acid. ► Electrochemical pretreatment enhances the sensitivity and resolution.Nanocrystalline graphite-like pyrolytic carbon film (PCF) electrode fabricated by a non-catalytic chemical vapor deposition (CVD) process was used for the simultaneous electrochemical sensing of ascorbic acid (AA), dopamine (DA), and uric acid (UA). The electrode was studied with respect to changes in electrocatalytic activity caused by a simple and fast electrochemical pretreatment. The anodized electrode exhibited excellent performance compared to many chemically modified electrodes in terms of detection limit, linear dynamic range, and sensitivity. Differential pulse voltammetry (DPV) was used for the simultaneous determination of ternary mixtures of DA, AA, and UA. Under optimum conditions, the detection limits were 2.9μM for AA, 0.04μM for DA, and 0.03μM for UA with sensitivities of 0.078, 5.345, and 6.192AM−1, respectively. The peak separation was 219mV between AA and DA and 150mV between DA and UA. No electrode fouling was observed and good reproducibility was obtained in all the experiments. The sensor was successfully applied for the assay of DA in an injectable drug and UA in human urine by using standard addition method.
Keywords: Nanostructured carbon film; Ascorbic acid; Uric acid; Dopamine; Simultaneous determination
Microporous silica with nanolayer structure coated with renewable organic solvent film as a novel extracting phase: A combination of solid- and liquid-phase microextraction by Mohammad Saraji; Bahman Farajmand (pp. 61-67).
Display Omitted► In this work combination of liquid- and solid-phase microextraction was applied as a novel extraction method. ► Flower-like microporous silica was created on the surface of a stainless steel wire. ► The silica layer was coated with an organic solvent with enough vapor pressure to be easily evaporated inside the GC injector. ► The organic solvent was used as a renewable extracting phase in SPME. ► The new extracting phase was compared with two commercial SPME fibers and SDME method.A new method based on combination of solid- and liquid-phase microextraction was developed. For the first time, porous flower-like silica microstructures with nanometric layers were created on the surface of the stainless steel wire by a new facile hydrothermal process. The fiber, coated with a suitable organic solvent, was applied for microextraction of some organophosphorus pesticides from aqueous samples followed by gas chromatography-nitrogen phosphorous detection. Method detection limits were between 0.6 and 3ngL−1. Relative standard deviations for intra- and inter-day precision were 4.4–7.3% and 5.1–7.8%, respectively. Fiber-to-fiber reproducibility for five prepared fibers was 6.3–8.4%. Tap, river and waste water samples were analyzed for evaluation of the method in real sample analysis. Relative recoveries for spiked tap, river and waste water samples were in the range of 94–101%, 89–97% and 82–103%, respectively. In addition, the method was compared with two commercial solid-phase microextraction (SPME) fibers, single drop microextraction (SDME) and liquid-phase microextraction (LPME). The present method showed higher extraction efficiency as compared with SDME, LPME and commercial SPME fibers.
Keywords: Microporous silica; Solid-phase microextraction; Liquid-phase microextraction; Water analysis; Organophosphorus compounds
Preparation, evaluation and characterization of quercetin-molecularly imprinted polymer for preconcentration and clean-up of catechins by María del Mar Castro López; M.C. Cela Pérez; María Sonia Dopico García; José Manuel López Vilariño; María Victoria González Rodríguez; Luis F. Barral Losada (pp. 68-78).
Display Omitted► Specificity and selectivity MIPs developed for the catechins contained in extracts. ► Inherent bleeding is avoided using quercetin as template. ► Fast and high adsorption in a homogeneous surface onto the MIP is observed. ► External film diffusion step is the limiting step of the adsorption process. ► Adsorption could be described as strong hydrogen bonds comparable to chemisorption.Molecularly imprinted polymer (MIP) for solid extraction and preconcentration of catechins have been successfully prepared by a thermal polymerization method using quercetin as template, 4-vinylpyridine as functional monomer and ethylene glycol dimethacrylate as crosslinker. A solution mixture of acetone and acetonitrile was used as porogen. Systematic investigations of the influence of monomer, cross-linker, porogen, as well as polymerization conditions on the properties of the MIPs were carried out. The quercetin MIPs were evaluated according to their selective recognition properties for quercetin, structurally related compounds (catechin, epigallocatechin gallate and epicatechin) and a unrelated compound of similar molecular size (α-tocopherol). Good binding was observed for quercetin, catechin and epigallocatechin gallate with an optimized MIP in a solid phase extraction system. Adsorption and kinetic characteristics were evaluated for catechins which indicated that the synthesized polymer had high adsorption capacity and contained homogeneous binding sites. Chemical and morphological characterization of the MIP was investigated by FTIR, SEM and BET, which confirmed a high degree of polymerization. Finally, the MIP was successfully applied to the clean-up and preconcentration of catechins from several natural samples.
Keywords: Abbreviations; EC; (−)-epicatechin; EGCG; (−)-epigallocatechin gallate; Quer; (−)-quercetin dihydrate; C; (+)-catechin hydrate; TRIM; 1,1,1-tris(hydroxymethyl)-propantrimethacrylat tech; AIBN; 2,2′-Azobis(2-methylpropionitrile); 4-Vpy; 4-vinylpiridine; α-TOCO; alpha-tocopherol; BJH; Barret–Joyner–Halenda method; BET; Brunauer–Emmett–Teller method; Caff; Caffeine; DC; degree of monomeric conversion; K; p; distribution coefficients; EGDMA; ethylene glycol dimethacrylate; preI; initial imprinting value for the template during the synthesis step; I; imprinting factor; MAA; methacrylic acid; MIPs; molecularly imprinted polymers; NIPs; non-imprinted polymers; SEM; scanning electron microscope; S; selectivity factor; SPE; solid phase extraction; MISPE; SPE involving a molecular imprinted polymer; T:M:Cr; template:monomer:crosslinker ratioMolecularly imprinted polymer; Quercetin; Catechins; Isotherm; Kinetics; Physical characterization; Natural samples
Optimization of headspace solid-phase microextraction for analysis of β-caryophyllene in a nanoemulsion dosage form prepared with copaiba ( Copaifera multijuga Hayne) oil by Daiane de O. Dias; Mariana Colombo; Regina G. Kelmann; Tatiane P. De Souza; Valquiria L. Bassani; Helder F. Teixeira; Valdir F. Veiga Jr.; Renata P. Limberger; Letícia S. Koester (pp. 79-84).
Display Omitted► A SPME-CG method is proposed for β-caryophyllene assay in nanoemulsions containing copaiba oil. ► SPME parameters were optimized for efficient β-caryophyllene extraction. ► The stability-indicating capability and specificity of the method were satisfied. ► Nanoemulsions partially protected β-caryophyllene under stressing conditions. ► The proposed method presents linearity, lows LOD and LOQ, good precision, accuracy and robustness.Recent studies have shown the anti-inflammatory activity of Copaiba oils may be addressed to the high content of β-caryophyllene, the most common sesquiterpene detected, especially in the Copaifera multijuga Hayne species. In the present study, nanoemulsions were proposed as a delivery system for copaiba oil in view to treat locally inflamed skin. This article describes the optimization and validation of a stability-indicating SPME-GC method, for β-caryophyllene analysis in the nanoemulsions produced by high pressure homogenization. SPME methods are performed with PDMS (polydimethylsiloxane) fiber (100μm). Three SPME parameters were evaluated by a three-level-three-factor Box–Behnken factorial design as potentially affecting the technique efficiency. According to the results obtained, the best conditions to extract β-caryophyllene were: (i) sampling temperature of 45°C, (ii) sampling time of 20min and (iii) no NaCl addition. Results coming from the forced degradation tests showed a reduction of β-caryophyllene peak area when both caryophyllene methanolic solution and nanoemulsions were exposed to acid hydrolysis, UV-A irradiation, oxidative (H2O2) and thermolitic (60°C) conditions. Such reduction occurred in lower extent in the nanoemulsions, suggesting a protective effect of the formulation to β-caryophyllene content. Since no degradation products were detected in the same retention time of β-caryophyllene, the specificity of the method was demonstrated. The method was linear in the range of 0.14–0.68μgmL−1 of β-caryophyllene ( r2>0.999), and was also validated for precision (R.S.D.≤5.0%), accuracy (97.85–101.87%) and robustness. Finally, the method was applied to quantification of β-caryophyllene content in the developed formulations.
Keywords: Copaiba oil; Nanoemulsion; β-Caryophyllene; Headspace solid-phase microextraction; Validation
Highly sensitive polymerase chain reaction-free quantum dot-based quantification of forensic genomic DNA by Yu Kyung Tak; Won Young Kim; Min Jung Kim; Eunyoung Han; Myun Soo Han; Jong Jin Kim; Wook Kim; Jong Eun Lee; Joon Myong Song (pp. 85-91).
Display Omitted► Genomic DNA quantification were performed using a quantum dot-labeled Alu sequence. ► This probe provided PCR-free determination of human genomic DNA. ► Qdot-labeled Alu probe-hybridized genomic DNAs had a 2.5-femtogram detection limit. ► Qdot-labeled Alu sequence was used to assess DNA samples for human identification.Forensic DNA samples can degrade easily due to exposure to light and moisture at the crime scene. In addition, the amount of DNA acquired at a criminal site is inherently limited. This limited amount of human DNA has to be quantified accurately after the process of DNA extraction. The accurately quantified extracted genomic DNA is then used as a DNA template in polymerase chain reaction (PCR) amplification for short tandem repeat (STR) human identification. Accordingly, highly sensitive and human-specific quantification of forensic DNA samples is an essential issue in forensic study. In this work, a quantum dot (Qdot)-labeled Alu sequence was developed as a probe to simultaneously satisfy both the high sensitivity and human genome selectivity for quantification of forensic DNA samples. This probe provided PCR-free determination of human genomic DNA and had a 2.5-femtogram detection limit due to the strong emission and photostability of the Qdot. The Qdot-labeled Alu sequence has been used successfully to assess 18 different forensic DNA samples for STR human identification.
Keywords: Abbreviations; PCR; polymerase chain reaction; Qdot; quantum dot; STR; short tandem repeat; CODIS; Combined DNA Index System; a-NP; alpha-naphthyl phosphaste; AcP; acid phosphatase; LMG; Leucomalachite green; SM; semen; qRT-PCR; quantitative real-time polymerase chain reaction; ATP; adenosine triphosphate; LIF; laser-induced fluorescence; DI; dye intercalationForensic DNA samples; Quantum dot; Alu; sequence; STR human identification
Fluorimetric detector and sensor for flow analysis made of light emitting diodes by Łukasz Tymecki; Magdalena Rejnis; Marta Pokrzywnicka; Kamil Strzelak; Robert Koncki (pp. 92-96).
Display Omitted► Flow-through fluorimetric detector made of three LEDs only is presented. ► The detector applied in FIA manifold is useful for pharmaceutical analysis. ► Solid phase spectrometry with the detector leads to optosensor development.Two compact optoelectronic fluorimetric devices operating according to the paired-emitter-detector-diode concept have been developed. The fluorimetric detector, fabricated of three light emitting diodes only, has been applied for the development of fluorimetric optosensor by further integration with sensing solid phase. In these investigations as a model analyte and as a model sensing layer useful for solid phase spectrometry, riboflavin and C18-silica have been chosen, respectively. Both developed analytical devices have been applied for non-stationary fluorimetric measurements performed under conditions of flow injection analysis. The presented flow-through detector and sensor operating under given flow conditions offer riboflavin determination in mgL−1 and μgL−1 ranges of concentration, respectively.
Keywords: Fluorimetry; Detector; Sensor; Solid phase spectrometry; Paired emitter detector diode; Flow analysis; Riboflavin
Exploiting adsorption and desorption at solid–liquid interface for the fluorometric monitoring of glibenclamide in adulterated drinks by David S.M. Ribeiro; João A. Lopes; João L.M. Santos; João A.V. Prior (pp. 97-103).
Display Omitted► Glibenclamide in spiked drinks was already used to commit drug-facilitated crimes. ► The drug can be extracted through adsorption in activated charcoal. ► Eluent was developed for desortion of the drug and its fluorometric monitoring. ► Methodology implemented successfully in an automatic and miniaturized flow system. ► First work in the literature for the detection of glibenclamide in teas.Nowadays, the use of a drug to modify a person's behavior with criminal intentions has become a growing public concern. In fact, stealthy drink spiking with certain drugs can cause the incapacitation of a potential victim of assault and in extreme cases can even lead to death. Belonging to the group of drugs used to commit drug-facilitated crimes is glibenclamide, which not only exhibits high sedation secondary effects but when subject to an overdose intake can lead to intense hypoglycemic episodes that could end with death. Suicide attempts and homicides through overdose with glibenclamide have already been reported.In this work and for the first time, it was developed a new methodology for detection of glibenclamide in spiked liquid samples (teas) by fluorometry ( λex=300nm; λem=404nm). The novel methodology was also implemented in a miniaturized and portable automatic flow system based in the concept of multipumping with an in-line pre-separation unit. The separation of the drug from the liquid samples was achieved through adsorption of the drug into activated charcoal packed within a mini column followed by elution with a solution composed by ethanol, hydrochloric acid and the surfactant CTAB (70%, 1.0molL−1, 0.01molL−1, respectively). The results allowed to obtain a linear working range for glibenclamide concentrations of up to 50mgL−1 ( r=0.9999) and the detection limit was about 0.81mgL−1 of glibenclamide.
Keywords: Multipumping; Adsorption; Charcoal; Glibenclamide; Drug-facilitated crimes; Drink spiking
Analysis of intercellular calcium signaling using microfluidic adjustable laminar flow for localized chemical stimulation by Jian Sun; Ying Zheng; Xiaojun Feng; Wei Du; Bi-Feng Liu (pp. 104-109).
Display Omitted► A microfluidic device was made for intercellular calcium signals (ICS) studies. ► Localized stimulation of ATP induced ICS in contacting cells by laminar flow. ► The role of gap junction in ICS was investigated using this device.The propagation of intercellular calcium signals provides a mechanism to coordinate cell population activity, which is essential for regulating cell behavior and organ development. However, existing analytical methods are difficult to realize localized chemical stimulation of a single cell among a population of cells that are in close contact with one another for studying the propagation of calcium wave. In this work, a microfluidic method is presented for the analysis of contact-dependent propagation of intercellular calcium wave induced by extracellular ATP using multiple laminar flows. Adjacent cells were seeded ∼300μm downstream the intersection of a Y-shaped microchannel with negative pressure pulses. Consequently, the lateral diffusion distance of the chemical at cell locations was limited to ∼26μm with a total flow rate of 20μLmin−1, which prevented the interference of diffusion-induced cellular responses. Localized stimulation of the target cell with ATP induced the propagation of intercellular calcium wave among the cell population. In addition, studies on the spread of intercellular calcium wave under octanol inhibition allowed us to characterize the gap junction mediated cell–cell communication. Thus, this novel device will provide a versatile platform for intercellular signal transduction studies and high throughput drug screening.
Keywords: Microfluidic chip; Intercellular calcium signaling; Gap junction; Multiple laminar flows
Development of a candidate certified reference material of cypermethrin in green tea by Della W.M. Sin; Pui-kwan Chan; Samuel T.C. Cheung; Yee-Lok Wong; Siu-kay Wong; Chuen-shing Mok; Yiu-chung Wong (pp. 110-114).
Display Omitted► A cypermethrin CRM in green tea was developed. ► Using two isotope dilution mass spectrometry techniques for characterization. ► Certified value of 148μgkg−1 with expanded uncertainty of ±9.2%. ► Support quality assurance of pesticide residue analysis in tea to testing.This paper presents the preparation of a candidate certified reference material (CRM) of cypermethrin in green tea, GLHK-11-01a according to the requirements of ISO Guide 34 and 35. Certification of the material was performed using a newly developed isotope dilution mass spectrometry (IDMS) approach, with gas chromatography high resolution mass spectrometry (GC–HRMS) and gas chromatography–tandem mass spectrometry (GC–MS/MS). Statistical analysis (one-way ANOVA) showed excellent agreement of the analytical data sets generated from the two mass spectrometric detections. The characterization methods have also been satisfactorily applied in an Asia-Pacific Metrology Program (APMP) interlaboratory comparison study. Both the GC–HRIDMS and GC–IDMS/MS methods proved to be sufficiently reliable and accurate for certification purpose. The certified value of cypermethrin in dry mass fraction was 148μgkg−1 and the associated expanded uncertainty was 14μgkg−1. The uncertainty budget was evaluated from sample in homogeneity, long-term and short-term stability and variability in the characterization procedure. GLHK-11-01a is primarily developed to support the local and wider testing community on need basis in quality assurance work and in seeking accreditation.
Keywords: Cypermethrin; Certified reference material; Tea; Isotope dilution mass spectrometry; Pesticide residues
Comparison of liquid chromatography-microchip/mass spectrometry to conventional liquid chromatography–mass spectrometry for the analysis of steroids by Linda Ahonen; Pekka Keski-Rahkonen; Taija Saarelainen; Jenni Paviala; Raimo A. Ketola; Seppo Auriola; Matti Poutanen; Risto Kostianen (pp. 115-121).
Display Omitted►Comparison of a HPLC-Chip/MS system to a conventional LC–MS system. ► LODs for oxime-derivatized steroids slightly lower with the HPLC-Chip/MS system. ► Both methods show good linearity, quantitative performance, and repeatability. ► Development of a HPLC-Chip/MS method for analyzing non-derivatized steroids.The feasibility of a microfluidic-based liquid chromatography-electrospray ionization/mass spectrometric system (HPLC-Chip/ESI/MS) was studied and compared to a conventional narrow-bore liquid chromatography-electrospray ionization/mass spectrometric (LC-ESI/MS) system for the analysis of steroids. The limits of detection (LODs) for oxime derivatized steroids, expressed as concentrations, were slightly higher with the HPLC-Chip/MS system (50–300pM) using an injection volume of 0.5μL than with the conventional LC-ESI/MS (10–150pM) using an injection volume of 40μL. However, when the LODs are expressed as injected amounts, the sensitivity of the HPLC-Chip/MS system was about 50 times higher than with the conventional LC-ESI/MS system. The results indicate that the use of HPLC-Chip/MS system is clearly advantageous only in the analysis of low-volume samples. Both methods showed good linearity and good quantitative and chromatographic repeatability. In addition to the instrument comparisons with oxime derivatized steroids, the feasibility of the HPLC-Chip/MS system in the analysis of non-derivatized and oxime derivatized steroids was compared. The HPLC-Chip/MS method developed for non-derivatized steroids was also applied to the quantitative analysis of 15 mouse plasma samples.
Keywords: Mass spectrometry; Liquid chromatography; Microchip; Electrospray ionization; Steroids; Derivatization
Fission track–secondary ion mass spectrometry as a tool for detecting the isotopic signature of individual uranium containing particles by Fumitaka Esaka; Chi-Gyu Lee; Masaaki Magara; Takaumi Kimura (pp. 122-128).
Display Omitted► A fission track technique is combined with secondary ion mass spectrometry. ► Plasma ashing is used to prepare samples for analysis. ► The particles with higher enriched uranium are identified efficiently.A fission track technique was used as a sample preparation method for subsequent isotope abundance ratio analysis of individual uranium containing particles with secondary ion mass spectrometry (SIMS) to measure the particles with higher enriched uranium efficiently. A polycarbonate film containing particles was irradiated with thermal neutrons and etched with 6M NaOH solution. Each uranium containing particle was then identified by observing fission tracks created and a portion of the film having a uranium containing particle was cut out and put onto a glassy carbon planchet. The polycarbonate film, which gave the increases of background signals on the uranium mass region in SIMS analysis, was removed by plasma ashing with 200W for 20min. In the analysis of swipe samples having particles containing natural (NBL CRM 950a) or low enriched uranium (NBL CRM U100) with the fission track–SIMS method, uranium isotope abundance ratios were successfully determined. This method was then applied to the analysis of a real inspection swipe sample taken at a nuclear facility. As a consequence, the range of235U/238U isotope abundance ratio between 0.0276 and 0.0438 was obtained, which was higher than that measured by SIMS without using a fission track technique (0.0225 and 0.0341). This indicates that the fission track–SIMS method is a powerful tool to identify the particle with higher enriched uranium in environmental samples efficiently.
Keywords: SIMS; Uranium; Isotope abundance ratio; Individual particles; Fission track
Mapping of sulfur metabolic pathway by LC Orbitrap mass spectrometry by Yulan Rao; Margaret McCooeye; Zoltán Mester (pp. 129-136).
Display Omitted► LCMS method for the determination of free, oxidized and protein bound thiols in yeast was developed. ► In freshly harvested yeast, most of the thiols were in the reduced forms. ► The stress response of yeast to H2O2, Cd and As was studied via changes in the thiol profiles.For the first time a liquid chromatography method with high resolution mass spectrometric detection has been developed for the simultaneous determination all key metabolites of the sulfur pathway in yeast, including all thiolic (cysteine (Cys), homocysteine (HCys), glutathione (GSH), cysteinyl-glycine (Cys-Gly), γ-glutamyl-cysteine (Glu-Cys)) and non-thiolic compounds (methionine (Met), s-adenosyl-methionine (AdoMet), s-adenosyl-homocysteine (AdoHcy), and cystathionine (Cysta)). The developed assay also permits the speciation and selective determination of reduced, oxidized and protein bound fractions of all of the five thiols. Iodoacetic acid (IAA) was chosen as the derivatizing reagent. Thiols were extracted from sub-mg quantities of yeast using hot 75% ethanol. The detection limits were in the range of 1–12nmolL−1 for standard solution (high femotomole, absolute), except AdoMet (116nmolL−1), which was unstable. In freshly harvested yeast, most of the thiols were in the reduced forms and low levels of protein-bound GSH and Glu-Cys were found. In a selenium enriched yeast, the thiols were mainly in the oxidized forms, and a significant amount of protein-bound Cys, HCys, GSH, Cys-Gly and Glu-Cys were found. The method was also applied to the metabolic study of the adaptive response of Saccharomyces cerevisiae to hydrogen peroxide, cadmium, and arsenite, and the change in concentration of thiols in the sulfur pathway was monitored over a period of 4h.
Keywords: Thiol; Yeast; LTQ-Orbitrap mass spectrometry; Oxidative stress; Metabolic study
Development and validation of an open screening method for diuretics, stimulants and selected compounds in human urine by UHPLC–HRMS for doping control by A. Jiménez Girón; K. Deventer; K. Roels; P. Van Eenoo (pp. 137-146).
Display Omitted► A new doping control screening method using UHPLC–HRMS is presented. ► Screening was performed in full scan MS with scan-to-scan polarity switching within a single run. ► Sample preparation was minimized by a direct 10-fold dilution of the urine. ► Detection limits were compliant with the imposed MRPLs by WADA.A new doping control screening method for the analysis of diuretics and stimulants using ultra high pressure liquid chromatography–high resolution Orbitrap mass spectrometry has been developed. The screening was performed in full scan MS with scan-to-scan polarity switching which allowed to detect more than 120 target analytes. Sample preparation was limited to 10-fold dilution of the urine into the internal standard solution followed by injection. Total run time per sample was 10min. Validation of the method yielded detection limits for diuretics between 25 and 250ngmL−1 and for stimulants between 5 and 500ngmL−1. The screening method has been implemented in routine doping control.
Keywords: Liquid chromatography; High resolution mass spectrometry; Screening; Polarity switching; Doping; Urine
High-performance liquid chromatography with fluorescence detection and ultra-performance liquid chromatography with electrospray tandem mass spectrometry method for the determination of indoleamine neurotransmitters and their metabolites in sea lamprey plasma by Huiyong Wang; Erin J. Walaszczyk; Ke Li; Yu-Wen Chung-Davidson; Weiming Li (pp. 147-153).
Sensitivity comparison of UPLC–MS/MS and HPLC/FLD method for the determination of melatonin.Display Omitted► Compared two sensitive analytical methods: HPLC/FLD and UPLC/MS/MS. ► Reported firstly on the measurements of neurotransmitters in the sea lamprey by two methods. ► Studied recovery and matrix effects of SPE and LLE. ► Determined four indoleamine neurotransmitters. ► Analyzed plasma samples from sea lampreys.We present a comparison of two sensitive methods, HPLC with fluorescence detector (HPLC/FLD) and UPLC with electrospray tandem mass spectrometry (UPLC/MS/MS), for the determination of indoleamine neurotransmitters (NTs) and their metabolites in sea lamprey plasma samples. Liquid–liquid extraction (LLE) and solid-phase extraction (SPE) were also tested for recovery and matrix effect. The recoveries of SPE determined by HPLC/FLD and UPLC/MS/MS ranged from 75 to 123% and 78 to 105%, respectively, while the recoveries of LLE ranged from 45 to 73% and 48 to 75%, respectively. SPE combined with HPLC/FLD and UPLC/MS/MS to determine the target analytes in plasma samples were validated of the sensitivity, reproducibility, accuracy and precision. Both methods exhibited excellent linearity in the range of 0.2–50ngmL−1 for all analytes. The limits of detection (LOD) varied from 0.04ngmL−1 to 0.13ngmL−1 for HPLC/FLD method and 0.003ngmL−1 to 0.02ngmL−1 for UPLC/MS/MS method. The inter-day accuracy ranged from 82.5 to 127.0% for HPLC/FLD and 93.0 to 113.0% for UPLC/MS/MS. The inter-day precision ranged from 9.9 to 32.3% for HPLC/FLD and 5.4 to 13.2% for UPLC/MS/MS. These results demonstrated that the values obtained by both methods were within the satisfactory range and the UPLC/MS/MS method provided more accurate and precise measurements than HPLC/FLD method. The comparison is of great importance to determine the available detectors, considering the complexity and expensiveness versus quality parameters. These two methods were applied to the analysis of four important indoleamine neurotransmitter analytes (5-hydroxytryptamine, 5-hydroxyindole-3-acetic acid, tryptamine and melatonin) in sea lamprey plasma samples.
Keywords: Neurotransmitters; Plasma; HPLC; UPLC–MS/MS; Liquid–liquid extraction; Solid phase extraction
CdTe quantum dots functionalized with 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide as luminescent nanoprobe for the sensitive recognition of bromide ion by Oluwasesan Adegoke; Eric Hosten; Cedric McCleland; Tebello Nyokong (pp. 154-161).
A bromide ion-selective modified nanoprobe sensor based on 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT)-functionalized CdTe quantum dots (QDs-4AT) showed a high selectivity and sensitivity for the determination of bromide ion using fluorescence recovery.Display Omitted► Water soluble CdTe quantum dots interact with tetramethylpiperidine-N-oxide. ► Quantum dots fluorescence is quenched by the radical. ► In the presence of bromide ions the fluorescence is restored. ► The sensor is more selective to bromine ions than other common ions.A novel bromide ion-selective modified nanoprobe sensor based on 4-amino-2,2,6,6-tetramethylpiperidine-N-oxide (4AT)-functionalized CdTe quantum dots (QDs-4AT) has been developed. Fluorescence quenching of the QDs by 4AT was observed. The functionalized QDs-4AT nanoprobe allowed a highly sensitive determination of bromide ion via analyte-induced change in the photoluminescence (fluorescence recovery) of the modified QDs. A detection limit of 0.6nM of bromide ion was obtained, while the interfering effect of other inorganic cations and anions was investigated to examine the selectivity of the nanoprobe. The linear range was between 0.01 and 0.13μM. Combined fluorescence lifetime and electron paramagnetic resonance measurements confirmed electron transfer processes between bromide ion and QDs-4AT.
Keywords: Tetramethylpiperidine-N-oxide; Fluorescence quenching; Quantum dots; Glutathione; Bromide
Selective and sensitive determination of peptides using 3,4-dihydroxyphenylacetic acid as a fluorogenic reagent by Hasina Yasmin; Takayuki Shibata; Mohammed Shafikur Rahman; Tsutomu Kabashima; Masaaki Kai (pp. 162-166).
Display Omitted► 3,4-Dihydroxyphenylacetic acid was found to produce fluorescence with peptides. ► The reaction proceeded in the presence of sodium periodate and borate buffer at 37°C. ► Peptides containing Gly at their N-termini provided stronger fluorescence. ► A lower detection limit of 0.25μmolL−1 was obtained with peptides GP and GPP. ► Almost none of the other biomolecules including proteins showed fluorescence.A novel fluorescence (FL) reaction for N-terminal Gly-containing peptides has been developed using 3,4-dihydroxyphenylacetic acid (3,4-DHPAA). The reaction of the peptides with 3,4-DHPAA was carried out in borate buffer (pH 8.0) in the presence of sodium periodate at 37°C for 10min, and the FL was measured with a spectrofluorimeter at the excitation and emission wavelengths of 370nm and 465nm, respectively. The 3,4-DHPAA reagent generated particularly strong FL for peptides containing Gly at their N-termini. When various other bio-substances, such as amino acids, sugars, nucleic bases, nucleotides, and proteins, were reacted with 3,4-DHPAA, no FL was observed. Under optimized reaction conditions, the lower detection limit of 0.25μmolL−1 was obtained for the N-terminal Gly-containing peptides of Gly-Pro (GP) and Gly-Pro-Pro (GPP), which gave 3 times greater FL intensity than that observed for the reagent blank. The proposed reaction with 3,4-DHPAA as a fluorogenic reagent is selective and sensitive for the detection of N-terminal Gly-containing peptides, and therefore, this method could be a useful tool for the determination of these particular oligopeptides.
Keywords: Key words; Fluorescence reaction; Selective detection; N; -terminal Gly-containing peptides; 3,4-DHPAA
Development of a chemiluminescence-based quantitative lateral flow immunoassay for on-field detection of 2,4,6-trinitrotoluene by Mara Mirasoli; Angela Buragina; Luisa Stella Dolci; Massimo Guardigli; Patrizia Simoni; Angel Montoya; Elisabetta Maiolini; Stefano Girotti; Aldo Roda (pp. 167-172).
Display Omitted► A lateral flow immunoassay for TNT (2,4,6-trinitrotoluene) has been developed. ► Chemiluminescence detection allows quantitative TNT analysis. ► On-field analysis is possible by using a portable chemiluminescence imaging device.Simple, rapid and highly sensitive assays, possibly allowing on-site analysis, are required in the security and forensic fields or to obtain early signs of environmental pollution. Several bioanalytical methods and biosensors based on portable devices have been developed for this purpose. Among them, Lateral Flow ImmunoAssays (LFIAs) offer the advantages of rapidity and ease of use and, thanks to the high specificity of antigen–antibody binding, allow greatly simplifying and reducing sample pre-analytical treatments. However, LFIAs usually employ colloidal gold or latex beads as labels and they rely on the formation of colored bands visible by the naked eye. With this assay format, only qualitative or semi-quantitative information can be obtained and low sensitivity is achieved. Recently, the use of enzyme-catalyzed chemiluminescence detection in LFIA has been proposed to overcome these problems. In this work, we describe the development of a quantitative CL-LFIA assay for the detection of 2,4,6-trinitrotoluene (TNT) in real samples. Thanks to the use of a portable imaging device for CL signal measurement based on a thermoelectrically cooled CCD camera, the analysis could be performed directly on-field. A limit of detection of 0.2μgmL−1 TNT was obtained, which is five times lower than that obtained with a previously described colloidal gold-based LFIA developed employing the same immunoreagents. The dynamic range of the assay extended up to 5μgmL−1 TNT and recoveries ranging from 97% to 111% were obtained in the analysis of real samples (post blast residues obtained from controlled explosion).
Keywords: Biosensors; Chemiluminescence; Imaging; Lateral flow immunoassay; 2,4,6-Trinitrotoluene
Polymeric imidazolium ionic liquids as valuable stationary phases in gas chromatography: Chemical synthesis and full characterization by Jaime González-Álvarez; Domingo Blanco-Gomis; Pilar Arias-Abrodo; Daniel Díaz-Llorente; Nicolás Ríos-Lombardía; Eduardo Busto; Vicente Gotor-Fernández; María Dolores Gutiérrez-Álvarez (pp. 173-181).
Display Omitted► Synthesis and characterization of seven new polymeric ionic liquids. ► Application of these ionic liquids as stationary phases in gas chromatography. ► Good thermal stabilities (240–300°C) achieved. ► High column efficiencies obtained (3120–4200plates/m). ► Excellent separations attained for compound mixtures, including xylene isomers.Seven new functionalized polymerizable ionic liquids were chemically prepared, and later applied for the preparation of polymeric stationary phases in gas chromatography. These coated GC columns, which exhibited good thermal stabilities (240–300°C) and very high efficiencies (3120–4200plates/m), have been characterized using the Abraham solvation parameter model. The chromatographic behavior of these polymeric IL columns has been deeply studied observing excellent selectivities in the separation of many organic substances such as alkanes, ketones, alcohols, amines or esters in mixtures of polar and non polar solvents or fragrances. Remarkably, the challenging separation of xylene isomers has been possible using a bis(trifluoromethylsulfonyl)amide based imidazolium IL coated column as a gas chromatography stationary phase.
Keywords: Chemical synthesis; Gas chromatography; Polymeric ionic liquids; Solvation parameter model; Stationary phases
Characterization of At− species in simple and biological media by high performance anion exchange chromatography coupled to gamma detector by A. Sabatié-Gogova; J. Champion; S. Huclier; N. Michel; F. Pottier; N. Galland; Z. Asfari; M. Chérel; G. Montavon (pp. 182-188).
Display Omitted► First identification of an astatine species under reducing conditions bearing one single negative charge, most probably At−. ► Astatide identified in human serum. ► Proposition of a method for assessing the stability of211At-labeled biological molecules in nuclear medicine.Astatine is a rare radioelement belonging to the halogen group. Considering the trace amounts of astatine produced in cyclotrons, its chemistry cannot be evaluated by spectroscopic tools. Analytical tools, provided that they are coupled with a radioactive detection system, may be an alternative way to study its chemistry. In this research work, high performance anion exchange chromatography (HPAEC) coupled to a gamma detector (γ) was used to evaluate astatine species under reducing conditions. Also, to strengthen the reliability of the experiments, a quantitative analysis using a reactive transport model has been done. The results confirm the existence of one species bearing one negative charge in the pH range 2–7.5. With respect to the other halogens, its behavior indicates the existence of negative ion, astatide At−. The methodology was successfully applied to the speciation of the astatine in human serum. Under fixed experimental conditions (pH 7.4–7.5 and redox potential of 250mV) astatine exists mainly as astatide At− and does not interact with the major serum components. Also, the method might be useful for the in vitro stability assessment of211At-labeled molecules potentially applicable in nuclear medicine.
Keywords: Astatine; Speciation; Ion-exchange; Human serum