World Congress on Biosensors 2014

World Congress on Biosensors 2014
Biosensors 2014

Thursday 31 October 2013

Just Published: Vibrational Spectroscopy

A new issue of this journal has just been published. To see abstracts of the papers it contains (with links through to the full papers) click here:
Vibrational Spectroscopy

Selected papers from the latest issue:

Far-infrared investigation of kaolinite and halloysite intercalates using terahertz time-domain spectroscopy

30 October 2013, 21:17:54
Publication date: November 2013
Source:Vibrational Spectroscopy, Volume 69
Author(s): D. Zich , T. Zacher , J. Darmo , V. Szöcs , D. Lorenc , M. Janek
Two clay minerals from the kaolin group, namely well-ordered kaolinite and poorly ordered halloysite, were investigated by terahertz time-domain spectroscopy (THz-TDS). Both clay samples were used for preparation of their respective intercalates using dimethyl sulfoxide (DMSO) and potassium acetate (KAc) with water. The intercalates were also characterized by X-ray powder diffraction and Fourier transform infrared spectroscopy. The dielectric behaviour of clay samples was investigated in the far-infrared region of 0.2–2.7THz corresponding to about 6.7–89.9cm−1. The frequency dependence of the power absorption coefficient revealed clear absorption bands for DMSO intercalates but not for KAc with water. For kaolinite – DMSO intercalate a distinct doublet at 1.70THz (56.6cm−1) and 1.88THz (62.6cm−1), and for halloysite – DMSO intercalate a single broad band centred around 1.72THz (57.3cm−1) were found. These bands are reported for the first time in this type of intercalation substances and indicate the application potential of THz time-domain spectroscopy for use in the investigation and detection of chemical behaviour of molecular species introduced into the interlayer space of layered substances such as clays and clay minerals. Additionally, the qualitative characteristics of observed bands of DMSO intercalates in the THz region reasonably resembled the structural order/disorder of used kaolinite and halloysite samples.

Vibrational spectroscopy of phthalocyanine and naphthalocyanine in sandwich-type (na)phthalocyaninato and porphyrinato rare earth complexes. Part 15: The IR characteristics of phthalocyanine in homoleptic tetrakis(phthalocyaninato) rare earth(III)-cadmium(II) quadruple-deckers

30 October 2013, 21:17:54
Publication date: November 2013
Source:Vibrational Spectroscopy, Volume 69
Author(s): Hong Shang , Hailong Wang , Wenjun Li , Jianzhuang Jiang
The infra-red (IR) spectroscopic data for a series of twelve sandwich-type homoleptic tetrakis[2,3,9,10,16,17,23,24-octa(octyloxy)phthalocyaninato] rare earth(III)-cadmium(II) quadruple-decker complexes [Pc(OC8H17)8]M[Pc(OC8H17)8]Cd[Pc(OC8H17)8]M[Pc(OC8H17)8] (M=Y, Pr–Yb except Pm) have been collected with resolution of 2cm−1 and their interpretation in terms tried by analogy with the IR characteristics of bis(phthalocyaninato) cerium double-decker [Pc(OC8H17)8]Ce[Pc(OC8H17)8] in which the macrocyclic ligands exist as the phthalocyanine dianion. Similar to the bis/tris(phthalocyaninato) rare earth sandwich counterparts, all the absorptions contributed primarily by or at least containing contribution from the vibrations of pyrrole or isoindole stretching, breathing or deformation or aza stretching in the IR spectra of these quadruple-decker compounds show dependent nature on the rare earth ionic size. The shift toward higher energy direction in the frequencies of these vibrations along with the decrease of the rare earth radii reveals the effective and increasing π–π interactions in these quadruple-decker sandwich compounds in the same order. Nevertheless, the decreased sensitivity of the frequencies of the above mentioned vibration modes in particular the weak absorption band due to the isoindole stretching at 1414–1416cm−1 for the quadruple-decker on rare earth metal size in comparison with corresponding band for bis(phthalocyaninato) rare earth counterparts indicates the relatively weaker π–π interaction in these quadruple-deckers than in the double-deckers.

Raman spectroscopy analysis of pigments on Diego Velázquez paintings

30 October 2013, 21:17:54
Publication date: November 2013
Source:Vibrational Spectroscopy, Volume 69
Author(s): P.C. Gutiérrez-Neira , F. Agulló-Rueda , A. Climent-Font , C. Garrido
Raman micro-spectroscopy has been used for the identification of the pigments used by the Spanish painter Diego Velázquez (1599–1650), considered one of the greatest painters in art history. The set of cross-sectional samples studied belongs to paintings of the Museo del Prado collection and correspond to the three known periods of the artist's activity. We have obtained information on the chemical composition and crystal structure of the pigments used for various colours. The results are consistent with previous elemental composition determined by other analytical methods.

Prediction of glycoprotein secondary structure using ATR-FTIR

30 October 2013, 21:17:54
Publication date: November 2013
Source:Vibrational Spectroscopy, Volume 69
Author(s): S.P. Lewis , A.T. Lewis , P.D. Lewis
Glycoproteins are important biomolecules with a diverse array of structural and signaling functions in biology. Determination of glycoprotein secondary structure is becoming increasingly important in aiding the understanding of how these molecules function in biological environments and disease. Furthermore, glycoproteins such as mucins are being evaluated in various nano-engineering processes that require knowledge of how the underlying secondary structure might alter in different target environments. We have developed an analytical procedure for predicting the secondary structures of glycoprotein using ATR-FTIR on dry film. Using Bovine submaxillary mucin (BSM) as a glycoprotein model, we determined the additive infrared spectral pattern of acetyl amino sugars and amino acids that could contribute to the absorbance in the Amide I band of BSM through empirical data. We show through subtraction of these spectra how the absorbance pattern of the protein backbone can be determined in order to predict glycoprotein secondary structure. The analysis predicted a predominant pattern of random coil, beta sheet and beta turn secondary structure for BSM after carbohydrate and amino acid spectral subtraction in agreement with other methods. Our relatively simple approach can be applied to predict secondary structure in other glycoproteins.

Structure and vibrational spectroscopy of the fenbufen–β-cyclodextrin inclusion complex

30 October 2013, 21:17:54
Publication date: November 2013
Source:Vibrational Spectroscopy, Volume 69
Author(s): Ferenc Billes , Antonio Hernanz , Hans Mikosch , Ioan Bratu
The structure and host–guest interactions in the inclusion complex (179 atoms) of β-cyclodextrin with fenbufen are studied. Fenbufen, the biphenyl derivative γ-oxo-(1,1′-biphenyl)-4-butanoic acid, is a widespread analgesic and non-steroidal anti-inflammatory drug. Its inclusion complex with β-cyclodextrin improves the oral bioavailability and entails fewer side-effects. Optimized molecular structures, atomic net charges and vibrational spectra have been computed for the host and guest molecules, as well as for the inclusion complex. The functional density theory with the B3LYP/3-21+G method/basis set has been applied. The calculated vibrational frequencies have not been scaled, and the simulated spectra have been compared with those obtained experimentally. The host–guest interactions have been investigated in detail.

Synthesis and mesomorphic investigation of calamitic liquid crystalline system ethyl-[4-(4′-decyloxy)benzoyloxy]-benzoate (4-EDBB): A temperature dependent micro-Raman study and DFT calculations

30 October 2013, 21:17:54
Publication date: November 2013
Source:Vibrational Spectroscopy, Volume 69
Author(s): Rajib Nandi , K. Vikram , Sachin Kumar Singh , Bachcha Singh , Ranjan K. Singh
A new liquid crystalline material containing diester linking group ethyl-[4-(4′-decyloxy)benzoyloxy]-benzoate (4-EDBB) was synthesized. The phase transition temperatures were noted by differential scanning calorimetry (DSC), the texture pattern were observed by polarizing optical microscopy (POM) and temperature dependent Raman study was employed to observe the transitions as well as to understand the molecular rearrangement during phase transition. The transitions were observed with all the three techniques but the Raman signature of crystal→smectic A transition is many fold and more precise and accurate. The correlation between intermolecular interaction and phase behaviour has been discussed using temperature dependence Raman data of CH in-plane bending and CO stretching vibrations. With the help of DFT method the possible dimers of 4-EDBB were optimized and the rotational isomers were also investigated. There exists weak hydrogen bonds at room temperature, which breaks as the temperature is increased causing the CH in-plane bending to shift lower and CO stretching vibrations to shift higher. The discussion of the temperature dependent Raman data reveals that at crystal→smectic A transition as a result of intra-molecular rotation the molecules transform from trans- to cis- conformer.

Identification of the early postmortem metabolic state of porcine M. semimembranosus using Raman spectroscopy

30 October 2013, 21:17:54
Publication date: Available online 26 October 2013
Source:Vibrational Spectroscopy
Author(s): Rico Scheier , Jürgen Köhler , Heinar Schmidt
The metabolic conditions in the early postmortem muscle determine meat quality. Raman spectroscopy is shown to follow the early postmortem metabolism (0.5–10 h) of porcine M. semimembranosus (N = 10). To this end the Raman spectra, pH and lactate kinetics were measured in the laboratory. Raman difference spectra were utilized to identify the spectral changes and to assign them to metabolic and structural alterations in the pre-rigor (50 to 120min) and rigor (2 to 8.5 h) phases. In the Raman spectra, the decreasing pH was indicated by three signals assigned to phosphorylated metabolites and inorganic phosphate. Furthermore, the degradation of glycogen to lactate and a reduction of signal intensity of α-helical proteins were revealed. In the pre-rigor phase, degradation of phosphocreatine to creatine and reduction of oxy- to deoxymyoglobin was found. In the rigor phase, additionally, degradation of ATP to inosine monophosphate (IMP) was observed. Good agreement was achieved between measured and simulated Raman difference spectra. In the pre-rigor and rigor time frame, normal and deviating meat quality could be distinguished based on signals of phosphocreatine, ATP, IMP and α-helical proteins. This work provides a deeper understanding and the first semi-quantitative description of the early postmortem Raman spectra of meat which show potential for the non-invasive and early detection of the metabolic state of meat, and hence for the identification of deviating meat qualities.

Vibrational spectra and static vibrational contribution to first hyperpolarizability of naphthopyrans – A combined experimental and DFT study

30 October 2013, 21:17:54
Publication date: Available online 21 October 2013
Source:Vibrational Spectroscopy
Author(s): Kadali Chaitanya , Xue Hai Ju , B. Mark Heron , Christopher D. Gabbutt
Two pairs of isomeric photochromic naphthopyrans were investigated by FT-IR and FT-Raman spectroscopy and by Density Functional Theory (DFT) methods. The vibrational frequencies and contribution to first hyperpolarizabilities of the four naphthopyrans were determined at the B3LYP/6-31G (d, p) level. Comparison of the experimental and theoretical vibrational frequencies of the naphthopyrans was made. The assignments of the vibrational spectra have been carried out with the help of normal co-ordinate analysis (NCA). These results show that the ratio between pure vibrational contribution to the electronic contribution of first hyperpolarizability ( β v / β e ) increases when the 4-methoxyphenyl groups in the symmetrical isomers is replaced by 4-morpholinophenyl and phenyl group resulting in an asymmetrically substituted isomer pair. At the static limit, the low vibrational frequency modes have dominating contributions to the vibrational dipole polarizability and first hyperpolarizability.

Vibrational spectra of a ferrocenyl phosphine derivative chemisorbed on 3-aminopropylsilyl modified silica gel

30 October 2013, 21:17:54
Publication date: Available online 16 October 2013
Source:Vibrational Spectroscopy
Author(s): Vladimir Ivanovski , Miha Bukleski , Martyna Madalska , Evamarie Hey-Hawkins
Samples of silica gel dried at different temperatures, silica gel modified with 3-aminopropylsilyl (APS) and silica gel modified with APS and further with a ferrocenyl phosphine derivative were investigated by DRIFT, transmission FTIR and MicroRaman spectroscopy. The reaction between 3-aminopropyltrimethoxysilane (APTMS) and silica gel was mainly identified by the diminishing or vanishing intensity of the stretching band of the free OH groups in the silica gel. Further chemical reaction of the APS groups with a ferrocenyl phosphine derivative (suitable as ligand in homogeneous catalysis) was identified in the IR spectra by the appearance of the C=N stretching band of the formed Schiff base, and diminishing intensity of the δ(NH2) modes. According to the IR spectra the reaction of the ferrocenyl phosphine derivative with the APS-modified silica gel is almost quantitative. From the recorded IR and Raman spectra, conclusions concerning the substitution of APTMS methoxy groups during the chemisorption on silica gel were derived. Through deconvolution of the complex Raman band in the siloxy stretching region of the APS-modified silica gel, the newly formed siloxy bond was identified.

Electric Field Standing Wave Effects in FT-IR Transflection Spectra of biological tissue sections: simulated models of experimental variability

30 October 2013, 21:17:54
Publication date: Available online 3 October 2013
Source:Vibrational Spectroscopy
Author(s): Tomasz P. Wrobel , Barbara Wajnchold , Hugh J. Byrne , Malgorzata Baranska
The so-called electric field standing wave effect (EFSW) has recently been demonstrated to significantly distort FT-IR spectra acquired in a transflection mode, both experimentally and in simulated models, bringing into question the appropriateness of the technique for sample characterization, particularly in the field of spectroscopy of biological materials. The predicted effects are most notable in the regime where the sample thickness is comparable to the source wavelength. In this work, the model is extended to sample thicknesses more representative of biological tissue sections and to include typical experimental factors which are demonstrated to reduce the predicted effects. These include integration over the range of incidence angles, varying degrees of coherence of the source and inhomogeneities in sample thickness. The latter was found to have the strongest effect on the spectral distortions and, with inhomogeneities as low as 10% of the sample thickness, the predicted distortions due to the standing wave effect are almost completely averaged out. As the majority of samples for biospectroscopy are prepared by cutting a cross section of tissue resulting in a high degree of thickness variation, this finding suggests that the standing wave effect should be a minor distortion in FT-IR spectroscopy of tissues. The study has important implications not only in optimization of protocols for future studies, but notably for the validity of the extensive studies which have been performed to date on tissue samples in the transflection geometry

Gamma ray induced changes on vibrational spectroscopic properties of strontium alumino-borosilicate glasses

30 October 2013, 21:17:54
Publication date: Available online 25 September 2013
Source:Vibrational Spectroscopy
Author(s): A. Rupesh Kumar , T.G.V.M. Rao , K. Neeraja , M. Rami Reddy , N. Veeraiah
The present investigation reports the effect of influence of aluminum ions on radiation damage of strontium borosilicate glasses studied by means of spectroscopic (viz., optical absorption (OA), infrared and Raman spectra). The composition of the glasses chosen for the study is 40SrO–xAl2O3–(15-x) B2O3–40SiO2(x=5, 7.5, 10), all in mol%. The glasses were synthesized by conventional melt quenching method. Later, the samples were exposed to gamma (γ) radiation dose of strengths 10 kGy and 30 kGy with a dose rate of 1.5Gy/s using 60Co as radiation source. The infrared spectra (IR), Raman spectra and optical absorption (OA) spectra of the samples were recorded at ambient temperature before and after irradiation. The OA spectra of the pre-irradiated samples do not exhibit any absorption bands in the UV–vis. regions and IR and Raman spectra exhibited conventional vibrational bands due to different borate, silicate AlO4 and AlO6 structural units. The OA spectra of post irradiated samples exhibited a broad absorption band in the wavelength region 600–750nm; it is attributed to electron trapped color centres. The intensity of this peak is observed to increase with increase of the γ-ray dose. Considerable changes in the intensities of various bands in the IR and Raman spectra were also observed. The changes were explained based on structural modifications taking place in the glass network due to γ-ray irradiation and finally it is concluded that the glasses mixed with 10.0 mol% of Al2O3 are relatively more radiation resistant. 

Robot-Compatible Automatic Dry Down Station

Porvair Sciences will officially launch the UltraVap Mistral robot-compatible automatic dry down station at Biotechnica 2013 (Hannover, Germany).

Drawing upon Porvair’s market leading position in nitrogen blow down evaporation – the UltraVap Mistral offers a simple, turnkey solution for integrating an automatic dry down step into your automated liquid handling protocol.  The UltraVap Mistral is fully optimised to work with robotic liquid handling systems from suppliers including Beckman, Hamilton and Tecan and features a new “shuttle” design capable of serving and retrieving microplates to and from the robot deck without further need for off-deck handling.

With a built in colour TFT display and easy to use graphical interface, the UltraVap Mistral is Porvair’s most advance evaporator yet. Integrated method storage for 32 protocols and 5-step evaporation ramp programming combine to make the UltraVap Mistral faster and easier to use than any other blow down evaporator on the market. A wide choice of needle heads, integrated fume extraction and the possibility to connect multiple units via Ethernet all set the Mistral apart in this class of evaporator.

For further information please visit www.porvair-sciences.com/en/services-menu/equipment/ultravap-rc-microplate-evaporator/ or contact Porvair Sciences on +44-1978-666240 /  int.sales@porvair-sciences.com.

Wednesday 30 October 2013

Just Published: Trends in Analytical Chemistry

A new issue of this journal has just been published. To see abstracts of the papers it contains (with links through to the full papers) click here:

Selected papers from the latest issue:

Voltammetric determination of mercury(II)

30 October 2013, 08:30:24
Publication date: November 2013
Source:TrAC Trends in Analytical Chemistry, Volume 51
Author(s): Chao Gao , Xing-Jiu Huang
Monitoring mercury provides a real challenge in analytical and environmental science, yet solutions are urgently needed due to the adverse effects of mercury on human health and the environment. Electrochemical techniques, more specifically voltammetric techniques, for determination of mercury(II) [Hg(II)] have inherent advantages. We review the state of the art in voltammetric determination of Hg(II) through quantitatively comparing different approaches classified according to the type of working electrode used. As much modern electroanalysis uses nanomaterials for the design of optimal electrode surfaces, this aspect is covered fully.

Advances for sensitive, rapid and selective extraction in different configurations of solid-phase microextraction

30 October 2013, 08:30:24
Publication date: November 2013
Source:TrAC Trends in Analytical Chemistry, Volume 51
Author(s): Ali Mehdinia , Mohammad Ovais Aziz-Zanjani
Since its introduction in 1990s, different configurations of solid-phase microextraction (SPME) have been evaluated for different applications, and can be classified into the static and dynamic techniques. The current review briefly discusses the development of the techniques applied to reduce extraction time and/or to enhance extraction efficiency. It is also reviews selective microextraction techniques, such as molecularly-imprinted polymer, immunoaffinity, restricted access material and aptamer sol-gel SPME.

Extraction and determination methodologies for benzotriazole UV stabilizers in personal-care products in environmental and biological samples

30 October 2013, 08:30:24
Publication date: November 2013
Source:TrAC Trends in Analytical Chemistry, Volume 51
Author(s): S. Montesdeoca-Esponda , T. Vega-Morales , Z. Sosa-Ferrera , J.J. Santana-Rodríguez
Benzotriazole UV stabilizers (BUVSs) are emerging contaminants that are mutagenic, toxic, pseudo-persistent, bioaccumulative and with significant estrogenic activity. However, the use of BUVSs in personal-care products (PCPs) is one of the primary ways that they enter the environment, often in “hot-spots” of discharge, such as wastewater-treatment plants (WWTPs). We present an overview of the current methods employed in the trace analysis of BUVSs in different types of environmental and biological samples. We compare and discuss potential advantages and disadvantages of each step involved in the analytical procedure.

Graphene as a new sorbent in analytical chemistry

30 October 2013, 08:30:24
Publication date: November 2013
Source:TrAC Trends in Analytical Chemistry, Volume 51
Author(s): Rafal Sitko , Beata Zawisza , Ewa Malicka
In the past three years, we have seen intense interest grow in graphene (G) and graphene oxide (GO) as new sorbents in analytical chemistry. This article focuses on the adsorptive properties of G and GO and their application in preconcentrating organic compounds and trace-metal ions, including trace analysis of water, food, biological and environmental samples using chromatography and spectroscopy techniques. Some methods of modification or chemical functionalization of G and GO are also discussed. The article shows that G, GO and their derivatives or composites can be very attractive as sorbents due to their adsorption capacities being much higher than those of any of the currently reported sorbents.

Recent progress of capillary electrophoresis in studying the speciation of actinides

30 October 2013, 08:30:24
Publication date: November 2013
Source:TrAC Trends in Analytical Chemistry, Volume 51
Author(s): A.R. Timerbaev , R.M. Timerbaev
This article reviews recent applications of the method for actinide-speciation analysis, with emphasis on using capillary-electrophoresis-separation schemes integrated with inductively coupled plasma mass-spectrometry detection. Also brought into focus are studies in which the speciation information acquired is complemented by relevant thermodynamic data on complexation of actinides with naturally-occurring ligands.

Analytical applications of chemiluminescence-detection systems assisted by magnetic microparticles and nanoparticles

30 October 2013, 08:30:24
Publication date: November 2013
Source:TrAC Trends in Analytical Chemistry, Volume 51
Author(s): Mortaza Iranifam
Analytical applications of chemiluminescence detection systems based on magnetic microparticles and nanoparticles (MMP-CL and MNP-CL) have attracted growing interest in research and commercial fields. This article reviews the literature on the analytical applications of MMP-CL and MNP-CL systems, illustrated by different reaction strategies, such as immunoassay and hybridization labels in diverse fields (e.g., clinical and pharmaceutical, environmental or food analysis).

Sampling uncertainty of wastewater monitoring estimated in a collaborative field trial

30 October 2013, 08:30:24
Publication date: November 2013
Source:TrAC Trends in Analytical Chemistry, Volume 51
Author(s): Magda Cotman , Albin Pintar
This case study gives practical guidance on how uncertainty in monitoring programs can be reduced in wastewater sampling. Seventeen sampling teams took part in a trial. The monitoring consisted of both field and laboratory measurements. The variabilities between reported results of participants in the trial, expressed as coefficients of variation (CVs), were found to be 8.5% for chemical oxygen demand (COD), 9.5% for total suspended solids (TSS) and 14.5% for sulfate ion, respectively.

Applications of nanomaterials in potentiometric sensors

30 October 2013, 08:30:24
Publication date: November 2013
Source:TrAC Trends in Analytical Chemistry, Volume 51
Author(s): Tanji Yin , Wei Qin
Nanomaterials play an important role in the fabrication of chemosensors and biosensors, due to their unique physical and chemical properties, such as large surface area/volume ratio, good conductivity, excellent electrocatalytic activity and high mechanical strength. We review recent advances in the applications of these nanomaterials in potentiometric sensors. We highlight the development of stable solid-state polymeric membrane ion-selective electrodes (ISEs). We describe ISEs based on ionophore-modified nanomaterials. Also, we present highly-sensitive potentiometric biosensors based on nanomaterials.

Ionic liquids in dispersive liquid-liquid microextraction

30 October 2013, 08:30:24
Publication date: November 2013
Source:TrAC Trends in Analytical Chemistry, Volume 51
Author(s): María J. Trujillo-Rodríguez , Priscilla Rocío-Bautista , Verónica Pino , Ana M. Afonso
In this review, we summarize the most recent analytical developments aimed at employing Ionic liquids (ILs) in dispersive liquid-liquid microextraction (DLLME). Four main operation modes can be distinguished: (1) conventional IL-DLLME; (2) temperature-controlled IL-DLLME; (3a) ultrasound-assisted, (3b) microwave-assisted or (3c) vortex-assisted IL-DLLME; and, (4) in-situ IL-DLLME. In these modes, the dispersive solvent can be an organic solvent, a surfactant, or a hydrophilic IL. In some cases, a dispersive solvent is not even necessary. We discuss practical applications of IL-DLLME to determine metals and organic compounds in a variety of samples.

Electrochemiluminescence quenching of tris(2,2′-bipyridyl)ruthenium

30 October 2013, 08:30:24
Publication date: November 2013
Source:TrAC Trends in Analytical Chemistry, Volume 51
Author(s): Baomei Huang , Xibin Zhou , Zhonghua Xue , Xiaoquan Lu
Electrochemiluminescence (ECL) of tris(2,2′-bipyridyl)ruthenium [ Ru ( bpy ) 3 2 + ] has received considerable attention over broad applications due to its remarkably high sensitivity and extremely wide dynamic range. This review presents the state of ECL quenching of Ru ( bpy ) 3 2 + . After a brief introduction of the ECL of Ru ( bpy ) 3 2 + , we discuss in detail ECL-quenching co-reactants, the ECL-quenching mechanism and applications of ECL quenching coupled with capillary electrophoresis and flow-injection analysis.

Validation of a sampling procedure

30 October 2013, 08:30:24
Publication date: November 2013
Source:TrAC Trends in Analytical Chemistry, Volume 51
Author(s): Małgorzata Bodnar , Jacek Namieśnik , Piotr Konieczka
Each step of the analytical procedure influences the final results in a significant way. In the majority of cases, the analytical procedure encompasses sampling because the analysis of the entire object (material) is usually impossible, so it is necessary to include the uncertainty related to sampling procedure in the uncertainty-budget calculations. This article describes two basic ways of estimating sampling uncertainty (i.e. experimental and modeling). There is also an example that shows how to estimate uncertainty using analysis of variance (ANOVA).

First international comparative study of volatile fatty acids in aqueous samples by chromatographic techniques: Evaluating sources of error

30 October 2013, 08:30:24
Publication date: November 2013
Source:TrAC Trends in Analytical Chemistry, Volume 51
Author(s): F. Raposo , R. Borja , J.A. Cacho , J. Mumme , K. Orupõld , S. Esteves , J. Noguerol-Arias , S. Picard , A. Nielfa , P. Scherer , I. Wierinck , E. Aymerich , C. Cavinato , D.C. Rodriguez , N. García-Mancha , P.N.T. Lens , V. Fernández-Cegrí
This first international proficiency-testing scheme evaluated the analytical performance and the state of practice in measurement of volatile fatty acids in aqueous samples. Gas chromatography and high-performance liquid chromatography were used by 25 laboratories from 15 different countries. Two reference materials were selected for analysis. The performance of each laboratory was assessed by the internationally-accepted z-score. The overall performance was rather poor. Among the causes of poor analytical performance, human errors and inadequate calibration were probably the major problems encountered.

Surface development of molecularly imprinted polymer films to enhance sensing signals

30 October 2013, 08:30:24
Publication date: November 2013
Source:TrAC Trends in Analytical Chemistry, Volume 51
Author(s): Piyush Sindhu Sharma , Marcin Dabrowski , Francis D’Souza , Wlodzimierz Kutner
Molecular imprinting of polymers is a well-established procedure for preparing artificial recognition units of chemical sensors. This procedure can produce materials of selectivity comparable to that of their biological counterparts. Deposition of a thin film of a molecularly imprinted polymer (MIP), playing a role of recognition unit, directly on surface of the transduction unit integrates these units to result in a chemical sensor. However, a smooth and continuous thin film of such a unit limits sensitivity of the devised chemosensor because of slow diffusion of an analyte through the film towards less accessible imprinted molecular cavities in the film bulk on the one hand and a low specific surface area on the other. Therefore, this area should be increased in a controllable way by developing the film surface. For that, macroporous MIP with large surface area, deposited directly on a transducer surface, effectively enhance signals in sensing applications. This review describes in detail a growing trend to prepare MIPs with a high (surface area)-to-volume ratio to enhance the sensing signal.

Optical immunosensing of effective cardiac biomarkers on acute myocardial infarction

30 October 2013, 08:30:24
Publication date: November 2013
Source:TrAC Trends in Analytical Chemistry, Volume 51
Author(s): Mohammad Hasanzadeh , Nasrin Shadjou , Jafar Soleymani , Eskandar Omidinia , Miguel de la Guardia
This review describes: the advantages of examples of optical methods used in immunosensing of cardiac biomarkers and their reported applications, stressing their potential for future developments; evaluation of some progress toward viable cardiac-biomarker measurements for detection and diagnostics of myocardial infarction; and, trends in the development of optical immunosensors, including integrated immunosensors, and the application of nanotechnology and microfluidic technology. 

Toolkit for Nucleosome & Histone Research

AMSBIO has announced addition of new biotinylated histones and nucleosomes to its expanding range of recombinant nucleosomes, purified nucleosomes and full length histone proteins.

A nucleosome is the basic unit of DNA packaging. It consists of a segment of DNA wound around a core (“octamer”) of 8 histone proteins (two each of histones H2A, H2B, H3, and H4). The “tails” of these histone proteins stick out, where they can be modified by a number of different histone acetyltransferases, methyltransferases, PARPs, and other epigenetic enzymes. Many of these enzymes modify very specific sites e.g. EZH2, specifically tri-methylates the lysine at position 27 in the H3 histone.

AMSBIO's new line of biotinylated histone peptides have been developed for enzyme kinetic studies as well as for screening small molecular inhibitors of different histone methyltransferases in drug discovery and HTS applications.

The major difference between AMSBIO recombinant nucleosomes made in E. coli and those purified from whole cells is that the recombinant ones are unmodified. E. coli and other bacteria do not have the enzymes to methylate or acetylate the histone proteins. AMSBIO nucleosomes purified from mammalian cells are supplied methylated or acetylated on most histone sites, making them suitable substrates for demethylases.

For further information on the complete range of nucleosomes and histones available from AMSBIO please visit www.amsbio.com/Nucleosomes-and-Histone-Proteins.aspx or contact AMSBIO now on +44-1235-828200 / +1-949-768-8365 or email info@amsbio.com.

Tuesday 29 October 2013

Just Published: Talanta

A new issue of this journal has just been published. To see abstracts of the papers it contains (with links through to the full papers) click here:
Talanta

Selected papers from the latest issue:

Analysis of perphenazine and fluphenazine by capillary electrophoresis coupled with tris (2,2′-bipyridyl) ruthenium (II) electrochemiluminescence detection

29 October 2013, 09:30:12
Publication date: 15 January 2014
Source:Talanta, Volume 118
Author(s): Lei Xu , Libo Li , Jianshe Huang , Tianyan You
The coupling of end-column tris (2,2′-bipyridyl) ruthenium (II) electrochemiluminescence (ECL) detection with capillary electrophoresis (CE) was developed for the analysis of two antipsychotic drugs, perphenazine (PPH) and fluphenazine (FPH). The parameters related to CE separation and ECL detection, including the detection potential, the buffer pH value and concentration, the separation voltage, and Ru(bpy)3 2+ concentration, were investigated in detail. Under optimum conditions, PPH and FPH were well separated and detected within 11min. The linear ranges were 0.1–5μM for PPH, and 0.1–7.5μM for FPH, respectively. The limits of detection of PPH and FPH were 5 and 10nM (S/N=3). The relative standard deviations (n=3) of the ECL intensity and the migration time were less than 2.5 and 0.65% in a day, and less than 3.4 and 1.7% in different three days. The proposed method was successfully applied to determine PPH and FPH in spiked urine samples with satisfactory results.

Graphical abstract

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Label-free voltammetric detection of MicroRNAs at multi-channel screen printed array of electrodes comparison to graphite sensors

29 October 2013, 09:30:12
Publication date: 15 January 2014
Source:Talanta, Volume 118
Author(s): Arzum Erdem , Gulsah Congur
The multi-channel screen-printed array of electrodes (MUX-SPE16) was used in our study for the first time for electrochemical monitoring of nucleic acid hybridization related to different miRNA sequences (miRNA-16, miRNA-15a and miRNA-660, i.e, the biomarkers for Alzheimer disease). The MUX-SPE16 was also used for the first time herein for the label-free electrochemical detection of nucleic acid hybridization combined magnetic beads (MB) assay in comparison to the disposable pencil graphite electrode (PGE). Under the principle of the magnetic beads assay, the biotinylated inosine substituted DNA probe was firstly immobilized onto streptavidin coated MB, and then, the hybridization process between probe and its complementary miRNA sequence was performed at MB surface. The voltammetric transduction was performed using differential pulse voltammetry (DPV) technique in combination with the single-use graphite sensor technologies; PGE and MUX-SPE16 for miRNA detection by measuring the guanine oxidation signal without using any external indicator. The features of single-use sensor technologies, PGE and MUX-SPE16, were discussed concerning to their reproducibility, detection limit, and selectivity compared to the results in the earlier studies presenting the electrochemical miRNA detection related to different miRNA sequences.

Selective enrichment of phosphopeptides by titania nanoparticles coated magnetic carbon nanotubes

29 October 2013, 09:30:12
Publication date: 15 January 2014
Source:Talanta, Volume 118
Author(s): Yinghua Yan , Zhifang Zheng , Chunhui Deng , Xiangmin Zhang , Pengyuan Yang
Selective enrichment of phosphoproteins or phosphopeptides from complex mixtures is essential for mass spectrometry (MS)-based phosphoproteomics. In this work, for the first time, titania nanoparticles coated magnetic carbon nanotubes (denoted as MagCNTs@TiO2 composites) were synthesized through a facile but effective solvothermal reaction for selective enrichment of phosphopeptides. The MagCNTs@TiO2 material demonstrated low limit of detection (20fmol), along with an exceptional great specificity to capture phosphopeptides from a tryptic digest of the mixture of a nonphosphorylated protein BSA and a phosphorylated protein β-casein with molar ratios of BSA/β-casein up to 200:1. In addition, the high magnetic susceptibility allowed convenient separation of the target peptides by magnetic separation. Experimental results demonstrated that the MagCNTs@TiO2 composites showed excellent potential for the selective enrichment of phosphopeptides for MS analysis.

Chemical profiling of Wu-tou decoction by UPLC–Q-TOF-MS

29 October 2013, 09:30:12
Publication date: 15 January 2014
Source:Talanta, Volume 118
Author(s): Yao Qi , Shizhe Li , Zifeng Pi , Fengrui Song , Na Lin , Shu Liu , Zhiqiang Liu
Wu-tou decoction (WTD), a traditional Chinese medicine (TCM) formula, is composed of Aconiti Radix Cocta, Ephedrae Herba, Paeoniae Radix Alba, Astragali Radix and Glycyrrhiza Radix Preparata, and it has been used for more than a thousand years to treat rheumatic arthritis, rheumatoid arthritis and pain of joints, while the active constitutions of WTD are unclear. In this research, an ultra performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC–Q-TOF-MS) method in both positive and negative ion mode was established to investigate the major constitutions in WTD. A Waters ACQUITY UPLC BEH C18 column was used to separate the aqueous extract of WTD. Acetonitrile and 0.1% aqueous formic acid (v/v) were used as the mobile phase. 74 components including alkaloids, monoterpene glycosides, triterpene saponins, flavones and flavone glycosides were identified or tentatively characterized in WTD based on the accurate mass within 15ppm error and tandem MS behavior. All the constitutions were also detected in the corresponding individual herbs. These results will provide a basis for further study in vivo of WTD and the information of potential new drug structure for treating rheumatic arthritis and rheumatoid arthritis.

Stir bar sorptive extraction polar coatings for the determination of chlorophenols and chloroanisoles in wines using gas chromatography and mass spectrometry

29 October 2013, 09:30:12
Publication date: 15 January 2014
Source:Talanta, Volume 118
Author(s): Juan Ignacio Cacho , Natalia Campillo , Pilar Viñas , Manuel Hernández-Córdoba
The simultaneous determination of 14 chlorophenols (CPs) and chloroanisoles (CAs) in wine samples is carried out using stir bar sorptive extraction (SBSE) with thermal desorption and gas chromatography–mass spectrometry (TD–GC–MS), evaluating the preconcentration efficiency of two different polar extracting phases, ethylene glycol–silicone (EG–Silicone) copolymer and polyacrylate, which have recently become commercially marketed. The influence of several extraction variables on the preconcentration capacity of these two novel coatings was tested, as well as the variables affecting the thermal desorption step. The EG–Silicone extraction phase provided the best results, since it allowed the simultaneous preconcentration of both species the non-polar CAs, due to the silicone base, and the polar CPs, because of the ethylene glycol polymer. Consequently, under the finally selected conditions, CPs were determined without any derivatization step, reaching detection limits in the 0.3–1.4ngL−1 range, depending on the compound. For CAs the detection limits ranged from 0.2 to 0.5ngL−1, with good precision and recovery. Five CAs and three CPs were found in several analyzed wines, some of which can be regarded as defective considering their contents in 2,4,6-TCA and 2,6-DCA.

Sequential extraction of platinum, cisplatin and carboplatin from environmental samples and pre-concentration/separation using vesicular coacervative extraction and determination by continuum source ETAAS

29 October 2013, 09:30:12
Publication date: 15 January 2014
Source:Talanta, Volume 118
Author(s): Noorbasha N. Meeravali , K. Madhavi , R. Manjusha , Sunil Jai Kumar
A sequential extraction procedure is developed for the separation of trace levels of hexachloroplatinate, cisplatin and carboplatin from soil, which are then, pre-concentrated using a vesicular coacervative cloud point extraction method prior to their determination as platinum by continuum source ETAAS. Sequential extraction of carboplatin, cisplatin and hexachloroplatinate from a specific red soil is achieved by using the 20% HCl, aqua regia at room temperature and by combination of aqua regia and HF with microwave digestion, respectively. The pre-concentration of these species from the extracted solutions is based on the formation of extractable hydrophobic complexes of PtCl6 2− anionic species with free cationic head groups solubilizing sites of the Triton X-114 co-surfactant stabilized TOMAC (tri-octyl methyl ammonium chloride) vesicles through electrostatic attraction. This process separates the platinum from bulk aqueous solution into a small vesicular rich phase. The parameters affecting the extraction procedures are optimized. Under the optimized conditions, the achieved pre-concentration factor is 20 and detection limit is 0.5ngg−1 for soil and 0.02ngmL−1 for water samples. The spiked recoveries of hexachloroplatinate, cisplatin and carboplatin in water and soil extracts in the vesicular coacervative extraction are in the range of 96–102% at 0.5–1ngmL−1 with relative standard deviation of 1–3%. The accuracy of the method for platinum determination is evaluated by analyzing CCRMP PTC-1a copper–nickel sulfide concentrate and BCR 723 road dust certified reference materials and the obtained results agreed with the certified values with 95% confidence level of student t-test. The results were also compared to mixed-micelle (MM)-CPE method reported in the literature [22].

Ultrahigh resolution mass spectrometry-based metabolic characterization reveals cerebellum as a disturbed region in two animal models

29 October 2013, 09:30:12
Publication date: 15 January 2014
Source:Talanta, Volume 118
Author(s): Shuhai Lin , Basem Kanawati , Liangfeng Liu , Michael Witting , Min Li , Jiandong Huang , Philippe Schmitt-Kopplin , Zongwei Cai
In the previous reports about cognitive dysfunction, cerebellum was thought to be a less affected tissue by genetic or environmental alterations in comparison to other tissues in the brain including hippocampus under the same conditions. In this work, we investigated two types of metabolomic alterations inside the cerebellum tissue. The first one addressed the differences in the metabolomics profiles between Transgenic (Tg) CRND8 of Alzheimer's disease mice and non-transgenic (non-Tg) littermates. The second one addressed the metabolic differences between wild type mice exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and wild type mice which are not exposed to this toxic compound. For these two investigations, ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR/MS) was implemented. As a result, the significant changes of each comparison were tentatively annotated by the high mass accuracy generated from the measurements in the negative ion mode. The biosynthesis of amino acids was also enhanced pronouncedly, and perturbation of purine metabolism was also observed in Tg mice compared to non-Tg littermates. In another animal model, the reduced levels of amino acids were found whereas the intermediate levels in purine metabolism and fatty acids including fatty acid conjugated metabolites were elevated in cerebellar tissues of mice exposed to TCDD compared to control group. Collectively, it was demonstrated that FT-ICR/MS was a powerful tool for interpretation of the elemental compositions of the peaks, revealing that the metabolic perturbations in cerebellar tissues of mice were induced by either genetic manipulation or environmental factor. Therefore, the non-targeted approach, alternatively, provides various metabolic phenotypes for the systems-level mirror of the complex etiology of neurotoxicity in the cerebellum.

Multifunctional AS1411-functionalized fluorescent gold nanoparticles for targeted cancer cell imaging and efficient photodynamic therapy

29 October 2013, 09:30:12
Publication date: 15 January 2014
Source:Talanta, Volume 118
Author(s): Jun Ai , Yuanhong Xu , Baohua Lou , Dan Li , Erkang Wang
Herein, one multifunctional AS1411-functionalized fluorescent gold nanoparticles (named NAANPs) is synthesized and successfully applied for both targeted cancer cell imaging and efficient photodynamic therapy (PDT). The NAANPs are obtained by functionalizing the gold nanoparticles with AS1411 aptamer and then bound with one porphyrin derivative N-methylmesoporphyrin IX (NMM). Using HeLa cells over expressing nucleolin as representative cancer cells, the formed NAANPs can target to the cell surface via the specific AS1411-nucleolin interaction, which can discriminate the cancer cells from normal ones (e.g. HEK293) unambiguously. That the fluorescence intensity of NMM increased significantly upon binding to AS1411 G-quadruplex makes the NAANPs appropriate fluorescence reagent for cell imaging. Meanwhile, NMM can also be used as a photosensitizer, thus irradiation of the NAANPs by the white light from a common electric torch can lead to efficient production of cytotoxic reactive oxygen species for establishing a new type of PDT to cancer cells. Gold nanoparticles play the roles of both carrier and enhancer of the functional groups onto the cells. In addition, they not only possess inherently certain cytotoxicity to the cancer cells, but also boost the cellular uptake of the fluorescent groups. As a result, the efficiency of both the targeted cell imaging and PDT could be ensured.

Graphical abstract

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