Latest news ...

Loading...

World Congress on Biosensors 2014

World Congress on Biosensors 2014
Biosensors 2014

Tuesday, 31 January 2012

Just Published: Chemometrics and Intelligent Laboratory Systems

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:
Chemometrics and Intelligent Laboratory Systems
http://rss.sciencedirect.com/publication/science/5232
Selected papers from the latest issue:

Achieving bilinearity in non-bilinear augmented first order kinetic data applying calibration transfer

29 January 2012, 02:21:49Go to full article
Publication year: 2012
Source: Chemometrics and Intelligent Laboratory Systems, Available online 28 January 2012
Maryam Khoshkam, Frans van den Berg, Mohsen Kompany-Zareh
In this paper a calibration transfer method is used to achieve bilinearity for augmented first order kinetic data. First, the proposed method is investigated using simulated data and next the concept is applied to experimental data. The experimental data consists of spectroscopic monitoring of the first order degradation reaction of carbaryl. This component is used for control of pests in fruits, vegetables, forages, cotton and other crops. It is highly toxic and likely human carcinogen, and is lethal to many non-target beneficial insects. The kinetic experiment is performed at different pH-values and emission wavelengths using an excitation wavelength equal to 275 nm. Rate constants of different data matrices at different pH values were calculated based on a hard modeling method. Analysis of simulated and experimental data shows that if there is a deviation from bilinearity, applying the model based methods to augmented datasets leads to inaccurate results. The application of a calibration transfer method as an additional step in the hard modeling procedure improves the results, and accurate estimation of reaction rate constants are obtained. The proposed method was compared to Local Spectra Mode of Analysis (LSMA) which was proposed by Puxtyet al. A comparison of the results shows that the proposed method is more efficient than LSMA and leads to less uncertainty in estimated rate constants and less percent error in the relative residuals.

Highlights

► Calibration transfer method is used to achieve bilinearity in augmented first order kinetic data for first time. ► The data were analyzed based on hard modelling methods. ► calibration transfer was used as an extra step inside the procedure. ► It is shown that using calibration transfer in hard modelling methods improve the results. ► A general and simple method is proposed for correction of non-bilinearity in full rank systems.

Filling andD-optimal designs for the correlated Generalized Exponential models

29 January 2012, 02:21:49Go to full article
Publication year: 2012
Source: Chemometrics and Intelligent Laboratory Systems, Available online 28 January 2012
J.M. Rodríguez-Díaz, M.T. Santos-Martín, H. Waldl, M. Stehlík
The aim of this paper is to provide guidelines for the statistically efficient estimation of parameters of a modified Arrhenius model for chemical kinetics. A modified Arrhenius model is used for instance by modeling a flux of methane in troposphere or by chemical kinetics for reactions at membranes.D-optimal and filling designs for the Generalized Exponential Model with correlated observations are studied, considering the exponential covariance with or without nugget effect. Both equidistant and exact designs for small samples are examined, studying the behavior of different types of filling designs when a greater number of observations is preferred. Probably the main lesson we can learn is that theD-optimal design is analytically peculiar and these designs can be practically obtained only by numerical computation; however, specially two point locallyD-optimal designs are very interesting, since they may help us to find a reasonable range for filling designs. The latter ones are probably only applicable when seeking for a higher number of design points. It is an interesting issue that very often the best designs do not use the whole design interval, but only a part of it; this should be taken into account by practitioners when they design their experiments. The second important observation is the large bias of the ML estimator of the correlation parameter. From the theoretical point of view this is not surprising since variance and correlation parameters are not simultaneously identifiable. We develop a bias reduction method and illustrate its effectiveness. We also provide practical implications for chemometrics.

Highlights

► We study several design issues for modified Arrhenius modell ► We consider correlation between measurements. ► We provide applications to a flux of methane in troposphere. ► Two point designs are important for choice of temperature region. ► Special filling designs are very effective.

Use of chemometric tools to estimate the effects of the addition of yeast, glucose-oxidase, soybean or horse bean flours to wheat flour on biochemical bread dough characteristics

25 January 2012, 01:24:57Go to full article
Publication year: 2012
Source: Chemometrics and Intelligent Laboratory Systems, Available online 24 January 2012
A. Boussard, C.B.Y. Cordella, L. Rakotozafy, G. Moulin, F. Buche, ...
This work aimed to use chemometric tools to estimate and understand the interaction effects of yeast (Y), glucose oxidase (G) and horse bean (HB) or soybean (SB) flours on the biochemical characteristics of wheat bread dough. Mixing was carried out with wheat flour alone or supplemented with different ingredients (alone or in combination) such as Y, G and HB (1%) or SB (0.5%) flour. The biochemical factors related to lipid oxidation - lipid components and lipoxygenase (LOX) activity - were quantified in the initial flour and in dough after mixing. Thus, the polyunsaturated fatty acids (PUFA) either in the free form (free-PUFA) or present in triacylglycerol (PUFA-TAG), the primary oxidation products of linoleic acid (LH) such as hydroxyacid (HODE), hydroperoxide (HPODE) and ketodiene (KODE) and the carotenoid pigments were analyzed. Two experimental designs were built to quantify the effects on lipid oxidation of the different ingredients and their interactions with a limited number of experiments. Results were analyzed by using multivariate chemometrical methods, principal component analysis (PCA), statistical methods (Pareto chart) and Mahalanobis distance (MD). The HODE and KODE levels are dependent on the LOX botanical origin. In our conditions and in terms of lipid oxidation, the dough biochemical characteristics are not affected by the presence of G (without added glucose) in the formulation whatever the other ingredients were.

Optimised PCR plates for all thermal cyclers and sequencers

Manufactured from polypropylene for extra rigidity the Porvair Sciences range of high quality PCR plates are compatible with the majority of 96- and 384-well block PCR and sequencing instruments, including FAST sequencers.

Summarised in an easy-to-use selection guide - the Porvair PCR plate range of standard or low profile 96-well PCR plates are available in specific optimised formats (full, half or no skirt), with well volumes of 100-200 microlitres. Designed for higher throughput assays, where samples are often at a premium, Porvair 384-well PCR plates offer a working well volume of only 30 microlitres. To ensure full compatibility with robotic systems the 384-well PCR plates offer a full plate skirt and high rigidity to minimise distortion before and after thermal cycling.  Black alphanumeric printing on all PCR plates ensures easy well identification.

Produced in Class 10,000 clean room conditions - Porvair range of PCR plates are certified free of pyrogens as well as DNAse and RNAse enzyme activity enabling routine achievement of excellent PCR results. Porvair PCR plates are based upon a well design where the liquid meniscus comes below the plate surface eliminating sample carryover problems when using a plate lid.

Available in bulk packs of 50 individually wrapped plates - Porvair Sciences 96-well and 384-well PCR plates reduce the cost of Polymerase Chain Reaction (PCR) analysis without compromising performance.

Established in 1992, Porvair Sciences Ltd. has developed internationally recognised expertise in microplate technology and manufacturing serving applications in Drug Discovery, Combinatorial Chemistry, Solid Phase Extraction, Protein Purification, High Throughput Screening, Environmental Analysis, Proteomics and Genomics.   Porvair Sciences Ltd. is a wholly owned subsidiary of Porvair plc.

For a copy of the Thermal Cycler compatibility guide and further information on PCR plates from Porvair Sciences Ltd. please telephone +44-1372-824290 or email int.sales@porvair-sciences.com

Insights in Lyophilisation European Seminars Announced by SP Scientific

In response to customer demand - SP Scientific has announced that it will bring its popular LyoLearn educational seminars in freeze drying techniques, to Europe, in May 2012.

Drawing upon leading international experts including Dr Henning Gieseler of Gilyos GmbH and Dr Michael Pikal of the University of Connecticut - 'Insights in Lyophilisation: Current Best Practices & New Research Trends' will provide an informed introduction to practical aspects of freeze drying and new freeze drying trends on the horizon.

This series of one-day seminars** to be held in Basle, Stockholm and Amsterdam will provide the novice with a basic freeze drying overview and the expert with up-to-date information on a wide range of topics of interest to the lyophilisation scientist. Scheduled question and answer sessions will provide attendees with the opportunity to have their own specific questions and concerns addressed. 

The seminar morning session will cover basic principles of freeze-drying.  Topics covered will include formulation design, physicochemical characterization and corresponding analytical procedures, the freezing step, primary drying and secondary drying.

The afternoon session will focus upon new research trends in lyophilisation. Topics covered will include the current state of controlled nucleation in freeze drying, optical coherence tomography based freeze drying microscopy, specific surface area measurements, quality by design, scale-up and new insights into heat transfer characteristics of tubing and molded vials.

For further information, or to reserve the early-bird discount price for the educational seminars, visit the SP Scientific website** or contact the company on +1-845-255-5000 x2311 / shireen.scott@spscientific.com

Just Published: Journal of Chromatography A

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:

Ozone removal in the collection of carbonyl compounds in air

30 January 2012, 23:15:07Go to full article
Publication year: 2012
Source: Journal of Chromatography A, Available online 30 January 2012
Shigehisa Uchiyama, Yohei Inaba, Naoki Kunugita
The most widely used method for measuring carbonyl compounds in air is 2,4-dinitrophenylhydrazine (DNPH) derivatization followed by high-performance liquid chromatography (HPLC). However, substantial negative interference caused by the presence of ozone in air has been reported. To avoid the influences of ozone, a potassium iodide scrubber (KI-scrubber) is commonly used. However, when air sampling using a DNPH-cartridge and a KI-scrubber is performed under conditions of high humidity, moist potassium iodide in the KI-scrubber traps carbonyls before they reach the DNPH-cartridge. Moreover, wet KI reacts with I2to form KI3and this oxidative reagent moves to the DNPH-cartridge and destroys the DNPH and DNPhydrazone derivatives. In order to alleviate these problems, new ozone scrubbers (BPE-scrubber, HQ-scrubber) have been developed. BPE-scrubber and HQ-scrubber consist of silica gel particles impregnated withtrans-1,2-bis-(2-pyridyl) ethylene (BPE) and hydroquinone (HQ), respectively. BPE reacts with ozone to form pyridine aldehyde and HQ reacts with ozone to form benzoquinone. The amounts of reducing agent in silica gel (130 mg) for ozone scrubber are 1% w/w for BPE-cartridge; 0.2% w/w for HQ-scrubber. These scrubbers can be used in air containing 140 μg/mof ozone for 24 h at a flow rate of 200 mL/min. When the relative humidity exceeded 80%, KI in the KI-scrubber was gradually moistened and changed to yellow in color. Peak abundance of formaldehyde, acetaldehyde and acetone DNPhydrazones were diminished to 25%, 15%, 2%, respectively, compared with the BPE-scrubber or HQ-scrubber. When using a BPE-scrubber or HQ-scrubber, decomposition of DNPH and DNPhydrazones were not observed at a wide range of relative humidities (3 - 97%).

Highlights

► New ozone scrubbers for the collection of carbonyl compounds are described. ► New ozone scrubbers are able to collect carbonyl compounds under high humidity conditions. ► New ozone scrubbers are able to measure simultaneously ozone and carbonyl compounds in air.

Operational-Modes of Field-Flow Fractionation in Microfluidic Channels

30 January 2012, 23:15:07Go to full article
Publication year: 2012
Source: Journal of Chromatography A, Available online 30 January 2012
T.N. Shendruk, G.W. Slater
Through a careful consideration of the retention ratio for Field-Flow Fractionation (FFF), we show that a single unified ideal retention theory can predict a wide range of separation behaviours including hydrodynamic chromatography, normal-mode FFF and steric-mode FFF by introducing the concept of adevice retention ratio. We determine the critical device retention parameter above which normal-mode does not exist and there is no clear distinction between hydrodynamic chromatograghy and steric-mode FFF. Numerical analysis of the elution order as a function of particle size quantitatively predicts the transitions between these regimes. The resulting map of the operational-modes shows each of the regions and their connectivity, and so may guide future device design. By extending this analysis to account for the variation of stress over particle surfaces, a hitherto unreported regime calledFaxén-modeFFF is predicted, which has the same elution order as normal-mode FFF. This mode arises when particle sizes approach the channel height, as occurs when microfluidic devices are utilized for FFF. The transition from steric-mode to Faxén-mode FFF is numerically mapped and approximations for each transition is presented.

Highlights

► Particle size is explicitly included in an ideal retention theory for FFF. ► We map the transition from normal-mode to steric-mode FFF. ► We show the hydrodynamic chromatography limit and map the transition to normal-mode. ► We predict a new FFF regime for microfluidic devices called Faxén-mode FFF.

Separation of alcohol soluble sorghum proteins using non-porous cation-exchange columns

30 January 2012, 23:15:07Go to full article
Publication year: 2012
Source: Journal of Chromatography A, Available online 29 January 2012
Deidre L. Blackwell, Scott R. Bean
Kafirins, the storage proteins and major protein of the cereal grain sorghum, play an important nutritional role for millions of people in parts of Africa and Asia. Kafirins are non-water soluble, being soluble only in the presence of detergents or aqueous alcohol mixtures and are among the most hydrophobic of the cereal proteins. Limited Mwheterogeneity of kafirins reduces their resolution when separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Charge based separation techniques have been shown to have improved resolution of kafirins, but due to the nature of their solubility, ion-exchange (IE)- HPLC has not been widely used to separate these proteins. To overcome issues of solubility, two different mobile phases were evaluated. The first mobile phase was based on 60% acetonitrile at acidic pH using guanidine-hydrochloride (Gdn-HCl) gradients to elute the proteins from a non-porous cation-exchange column. The second mobile phase tested consisted of 60% acetonitrile using an increasing concentration gradient of a triethylamine phosphate (TEAP) buffer at pH 3.0. The type of alkylation reagent used to stabilize kafirin extracts prior to analysis was found to have an impact on the IE-HPLC separations with the reagent 4-vinylpyridine providing the best resolution. Separations of kafirins in the TEAP mobile phase system resulted in 10 major peaks being resolved. Combining IE-HPLC with reverse phase (RP)- HPLC into 2D separations revealed that the α-kafirins clustered into three major groups not readily apparent in either 1D separation.

An improved hollow fiber solvent-stir bar microextraction for the preconcentration of anabolic steroids in biological matrix with determination by gas chromatography-mass spectrometry

30 January 2012, 23:15:07Go to full article
Publication year: 2012
Source: Journal of Chromatography A, Available online 29 January 2012
Wei Liu, Lan Zhang, Liangbiao Fan, Zian Lin, Yimin Cai, ...
In this paper, a convenient and self-assembled hollow fiber solvent-stir bar microextraction (HF-SSBME) device was developed, which could stir by itself. In the extraction process, the proposed device made the solvent “bar” not floating at the sample solutionorand exposing to air while organic solvents outside hollow fiber always wrapped with donor phase solvent, which reduced the vaporization of organic solvents. This design could improve the precisions and recoveries of experiments. For evaluating the device, seven anabolic steroids (prasterone, 5α-androstane-3α, 17β-diol, methandriol, 19-norandrostenediol, androstenediol, methyltestosterone and methandienone) were used as model analytes and extraction conditions such as type and volume of organic solvents, agitation speed, extraction time, extraction temperature and salt addition were studied in detail. Under the optimum conditions (15 μL toluene, 40 °C, stirring at 750 rpm for 30 min with 1.5 g sodium chloride addition in 20.0 mL donor phase), the linear ranges of anabolic steroids were 0.25-200 ng mLwith gas chromatograph-mass spectrometry. The limits of detection were lower than 0.10 ng mL. The recoveries and precisions in spiked urine and hair samples were between 73.97%-93.56% and 2.18%-4.47% (n = 5). HF-SSBME method combined the intrinsical merits of hollow fiber with the superiority of the proposed self-stirring device which can be developed to two-phase, three-phase and in-situ derivatization modes with wide prospect of application. Besides, the pedestal of this proposed device can be converted to fix stir bar in stir bar sorptive extraction (SBSE) method.

Highlights

► A new self-assembled hollow fiber solvent-stir bar microextraction device was developed. ► The proposed device can reduced the vaporization of organic solvents. ► This design could improve the precisions and recoveries of experiments. ► For evaluating the device, anabolic steroids were used as model analytes ► This device could be used in multiple mode of solvent bar microextraction.

Preparation and Characterization of Methacrylate-Based Monolith for Capillary Hydrophilic Interaction Chromatography

30 January 2012, 23:15:07Go to full article
Publication year: 2012
Source: Journal of Chromatography A, Available online 29 January 2012
Ming-Luan Chen, Li-Man Li, Bi-Feng Yuan, Qiao Ma, Yu-Qi Feng
In current study, poly(methacrylic acid-co-ethylene glycol dimethacrylate) (MAA-co-EDMA) monolith was successfully prepared for capillary hydrophilic liquid chromatography (cHILIC). The polymerization was optimized by changing the ratio of MAA to EDMA, the type and amount of porogen. The characterization indicated that “hydrophilic” monolithic column possessed homogeneous column bed, good permeability and narrow pore size distribution. Under HILIC mode, the “hydrophilic” monolith prepared with PEG and DMSO showed stronger hydrophilicity than the “hydrophobic” monolith prepared with dodecanol and toluene. Finally, the “hydrophilic” monolith was applied in the separation of tryptic digests of bovine serum albumin (BSA) withcHILIC-ESI-qTOF-MS system. Our results revealed that 49 peptides were identified with 50% sequence coverage under HILIC mode, which was much better than the peptides identified using particulate-packed commercial column with RPLC-ESI-qTOF-MS system or “hydrophobic” monolith withcHILIC-ESI-qTOF-MS system. Taken together, the “hydrophilic” monolithic column prepared in current study, demonstrated the excellent chromatographic performance on the separation of complex samples, which offers the potential application of the monolith on proteomics study.

Highlights

► A novel hydrophilic monolithic column was described. ► The monolith was optimized in details by using different types of porogen. ► The effect of porogens on surface property and porous structure was investigated. ► The monolith efficiently separated BSA tryptic digests oncHILIC-ESI-qTOF-MS.

Optimization of an Improved Single-Column Chromatographic Process for the Separation of Enantiomers

29 January 2012, 02:05:45Go to full article
Publication year: 2012
Source: Journal of Chromatography A, Available online 26 January 2012
Kazi Monzure Khoda, Bijan Medi, Mohammad Amanullah
This work addresses optimization of an improved single-column chromatographic (ISCC) process for the separation of guaifenesin enantiomers. Conventional feed injection and fraction collection systems have been replaced with customized components facilitating simultaneous separation and online monitoring with the ultimate objective of application of an optimizing controller. Injection volume, cycle time, desorbent flow rate, feed concentration, and three cut intervals are considered as decision variables. A multi-objective optimization technique based on genetic algorithm (GA) is adopted to achieve maximum productivity and minimum desorbent requirement in the region constrained by product specifications and hardware limitations. The optimization results along with the contribution of decision variables are discussed using Pareto fronts that identify non-dominated solutions. Optimization results of a similar simulated moving bed process have also been included to facilitate comparison with a continuous chromatographic process.

Highlights

► Conceptual design of an improved single-column chromatographic separation (ISCC) process has been presented. ► The ISCC process has been optimized using a multi-objective evolutionary algorithm. ► Results show that the proposed fraction collection scheme and overlapped peaks can enhance productivity and decrease desorbent requirement.

Determination of benzothiazoles and benzotriazoles by using ionic liquid stationary phases in gas chromatography mass spectrometry. Application to their characterization in wastewaters

29 January 2012, 02:05:45Go to full article
Publication year: 2012
Source: Journal of Chromatography A, Available online 26 January 2012
Carmen Domínguez, Carolina Reyes-Contreras, Josep M. Bayona
Benzothiazoles (BTHs) and benzotriazoles (BTRs) belong to a high production volume chemicals widely used in both industrial and household applications. Since they are recalcitrant to biodegradation, they are widespread in the environment. However, the BTHs and BTRs determination in environmental matrices is hindered by the coelution with coextracted organic matter and the poor selectivity in mass spectrometry due to the low mass of their diagnostic ions. Accordingly, this study examines the selectivity and suitability of new commercially available ionic liquid (IL) stationary phases for GC-MS and their application to the determination of BTHs and BTRs in wastewater samples. Five different IL columns were tested and the best results in terms of resolution, peak symmetry and analysis time were obtained with the SLB-IL59.

Highlights

► Ionic liquid stationary phases bleeding do not interfere with the benzothiazoles and benzotriazoles diagnostic ions by GC-MS. ► The SLB-IL59 allows the complete elution of 6 benzotriazoles and benzothiazoles analyzed. ► The SLB-IL59 provides suitable peak symmetry and resolution between all the target analytes. ► The SLB-IL59 has been successfully applied to their determination in wastewaters by GC-MS.

Monday, 30 January 2012

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:

Establishing forensic search methodologies and geophysical surveying for the detection of clandestine graves in coastal beach environments

29 January 2012, 02:20:08Go to full article
Publication year: 2012
Source: Forensic Science International, Available online 28 January 2012
Jamie K. Pringle, Claire Holland, Katie Szkornik, Mark Harrison
A 2010 UK police search for a clandestine burial highlighted the need for more information and quantitative data to aid coastal beach searches. This study aimed to address this by establishing relevant forensic search methodologies to aid the search for clandestine coastal burial sites, using the North West English coastline as a search area. A set of parameters were established, including criteria such as tidal range, proximity to vehicular access points and distance from inhabited areas, which may inform forensic searches by prioritising likely locations of clandestine burials. Three prioritised coastal locations were subsequently identified: (1) coastal dunes at Formby, (2) coastal dunes and (3) beach foreshore at Southport, all sites part of the Liverpool City Region in the United Kingdom. At all locations, simulated clandestine graves were hand-dug by spades into which a naked adult-sized, metal-jointed fiberglass mannequin was buried at 0.5 m below ground level. Trial geophysical surveys were then undertaken with the aim of identifying the optimal geophysical instrumentation and technique to deploy in such environments. GPR data showed 450 MHz frequency antennae to be optimal, with significantly poor data obtained from the foreshore area due to saline seawater. Electrical resistivity and magnetic susceptibility surveys were successful in coastal environments in target detection (albeit not in non-vegetated sand dunes), with resistivity fixed-offset configurations deemed optimal. The latter survey successes may be due to the recent disturbed ‘grave’ rather than the target, which itself is of interest in terms of identifying the most recent clandestine burials.

Investigation of morphine and morphine glucuronide levels and cytochrome P450 isoenzyme 2D6 genotype in codeine-related deaths

29 January 2012, 02:20:08Go to full article
Publication year: 2012
Source: Forensic Science International, Available online 28 January 2012
Joachim Frost, Arne Helland, Ivar S. Nordrum, Lars Slørdal
Compared to morphine and morphine-6-glucuronide (M6G), codeine and its other major metabolites codeine-6-glucuronide and norcodeine have weak affinity to opioid μ-receptors. Analgesic effects of codeine are thus largely dependent on metabolic conversion to morphine by the polymorphic cytochrome P450 isoenzyme 2D6 (CYP2D6). How this relates to toxicity and post-mortem whole blood levels is not known. This paper presents a case series of codeine-related deaths where concentrations of morphine, M6G and morphine-3-glucuronide (M3G), as well as CYP2D6 genotype, are taken into account. Post-mortem toxicological specimens from a total of 1444 consecutive forensic autopsy cases in Central Norway were analyzed. Among these, 111 cases with detectable amounts of codeine in femoral blood were identified, of which 34 had femoral blood concentrations exceeding the TIAFT toxicity threshold of 0.3 mg/L. Autopsy records of these 34 cases were retrieved and reviewed. In the 34 reviewed cases, there was a large variability in individual morphine to codeine concentration ratios (M/C ratios), and morphine levels could not be predicted from codeine concentrations, even when CYP2D6 genotype was known. 13 cases had codeine concentrations exceeding the TIAFT threshold for possibly lethal serum concentrations (1.6 mg/L). Among these, 8 individuals had morphine concentrations below the toxic threshold according to TIAFT (0.15 mg/L). In one case, morphine as well as M6G and M3G concentrations were below the limit of detection. A comprehensive investigation of codeine-related fatalities should, in addition to a detailed case history, include quantification of morphine and morphine metabolites. CYP2D6 genotyping may be of interest in cases with unexpectedly high or low M/C ratios.

Evaluation of human brain damage in fatalities due to extreme environmental temperature by quantification of basic fibroblast growth factor (bFGF), glial fibrillary acidic protein (GFAP), S100β and single-stranded DNA (ssDNA) immunoreactivities

29 January 2012, 02:20:08Go to full article
Publication year: 2012
Source: Forensic Science International, Available online 28 January 2012
Qi Wang, Takaki Ishikawa, Tomomi Michiue, Bao-Li Zhu, Da-Wei Guan, ...
Fatalities due to extreme environmental temperatures involving hypothermia (cold exposure) and hyperthermia (heat stroke) might present with poor or nonspecific morphological pathologies, which are insufficient to establish the cause of death in forensic practice. The present study immunohistochemically investigated basic fibroblast growth factor (bFGF), glial fibrillary acidic protein (GFAP), S100β and single-stranded DNA (ssDNA) in the parietal lobe and hippocampus of the brain in fatalities from hypothermia (n = 15) and hyperthermia (n = 18), and compared them to those of controls (n = 39), including acute death due to ischemic heart disease, mechanical asphyxiation and drowning. In addition, S100β concentration in cerebrospinal fluid (CSF) was measured. Characteristic findings in hypothermia cases were higher glial bFGF immunopositivity in the cerebral cortex and white matter, and higher S100β immunopositivity in the cerebral cortex with a lower CSF S100β concentration. Hyperthermia showed lower glial GFAP and S100β immunopositivities in the white matter, and higher neuronal ssDNA immunopositivity in the cerebral cortex and hippocampus, accompanied by high glial bFGF and S100β immunopositivities in the cerebral cortex. These findings suggest neuroprotective glial responses without marked neuronal or glial damage in fatal hypothermia, and diffuse neuronal apoptosis despite initiation of neuroprotective cortical astrocyte responses, accompanied by glial damage in the white matter, in fatal hyperthermia. These markers may be useful for evaluating brain damage and responses in fatalities due to extreme environmental temperatures.

Quantitative monitoring of corticosteroids in cosmetic products manufactured in Korea using LC–MS/MS

29 January 2012, 02:20:08Go to full article
Publication year: 2012
Source: Forensic Science International, Available online 27 January 2012
Yun Sik Nam, Il Keun Kwon, Yeonhee Lee, Kang-Bong Lee
Some cosmetic products manufactured in Korea for the treatment of eczema, seborrhea and psoriasis have been suspected to contain anti-inflammatory corticosteroids such as prednisolone, hydrocortisone, betamethasone, dexamethasone and triamcinolone acetonide without these ingredients being indicated on the label. Due to their severe side effects such as permenent skin atopy, these corticosteroids have to be monitored in cosmetic products from a forensic point of view. Many cosmetic product samples (N = 65) have been collected from both local and online markets in Korea. The corticosteroid content of these samples was analyzed by LC–MS/MS with diagnostic ions (m/z).Linearity was studied with 0.1–10 μg/mL range in all corticosteroids. Good correlation coefficients (r ≥ 0.997) were found and the limits of quantification were 4.68–7.97 ng/mL for each of the corticosteroids. At three different concentrations spanning the linear dynamic ranges, mean recoveries were 97.2–113.5%and precisions (RSD) for intra-day and inter-day analysis were less than 8.9%. Also, accuracy (Bias %) was less than 11.8%.The results showed that between 0.76–0.94 μg/g levels of prednisolone were detected in four cosmetic products and triamcinolone acetonidewas detected with a concentration in the range of 11.5–272 μg/g in nine samples. This fact reveals that some manufacturers have arbitrarily added these corticosteroids in their cosmetic products without indicating them on the label. Thus, these cosmetic products have to be monitored and if proven illegal preparations removed from the market.

Factitious disorder comorbid with bipolar I disorder. A case report

27 January 2012, 22:24:17Go to full article
Publication year: 2012
Source: Forensic Science International, Available online 27 January 2012
Antonio Del Casale, Stefano Ferracuti, Chiara Rapinesi, Daniele Serata, Alessio Simonetti, ...
We describe a case of factitious disorder with physical and psychological symptoms comorbid with bipolar I disorder in a 37-year-old woman. Since the onset of bipolar disorder, which occurred at the age of 31, she increasingly complained of physical symptoms, compulsively seeking medical and surgical interventions. She has been hospitalised several times and her Munchausen-type factitious disorder recently appeared to be developing into Munchausen by proxy, involving her 11-year-old daughter. The patient adhered poorly to stabilising and antipsychotic drug treatment and did not improve through the years. We here analyse her mood phases, which were always associated with changes in the quality of factitious symptoms, according to whether the disorder was in its depressive phase (somatic complaints and suicidal ideation prevail), or in its manic or mixed phase (medical intervention-seeking and manipulation of clinicians to obtain surgical interventions). We also briefly discuss some important forensic issues to consider in similar cases, mainly stemming from the psychotic aspects of these two co-occurring disorders. Clinicians should be aware of some patients’ ability to produce signs and symptoms of physical and/or psychological illness and consult psychiatrists before giving consent to invasive diagnostic procedures or surgery.

Just Published: Sensors & Actuators A: Physical

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:

Sharp silicon tips with different aspect ratios in wet etching/DRIE and surfactant-modified TMAH etching

27 January 2012, 22:07:35Go to full article
Publication year: 2012
Source: Sensors and Actuators A: Physical, Available online 27 January 2012
Bin Tang, Kazuo Sato, Miguel A. Gosálvez
A simple, high yield method of surfactant-modified wet anisotropic etching for the fabrication of sharp silicon tips is proposed in the applications of scanning probe microscope (SPM) and vacuum microelectronics. The formation of this new tip has been explained as the change in the local etch rate brought about by the strong adsorption of surfactant molecules in the apex of a silicon tip. In order to understand this point, the different etch rates of the same orientations tested on the hemispherical silicon (with curvature) and flat samples (no curvature) are investigated, and the adsorption thicknesses (or densities) of surfactants on various silicon surfaces measured by an ellipsometer are obtained. Tips with different aspect ratios (0.8:1 and 6:1) have been successfully fabricated on silicon (100) and (111) by the combination of etching in pure tetramethylammonium hydroxide (TMAH) or deep reactive ion etching (DRIE) and etching in surfactant-modified TMAH solutions, having the advantages of good uniformities, low temperatures, low costs and complementary metal oxide semiconductor (CMOS)-compatible. The apex of each resultant tip after the treatment in surfactant-added wet etchants typically can have a radius of curvature of 4∼5 nm on silicon (100) or even ≤2 nm on silicon (111) without any subsequent oxide sharpening process.

An array of 100 μm x 100 μm Dielectric Elastomer Actuators with 80% Strain for Tissue Engineering Applications

27 January 2012, 22:07:35Go to full article
Publication year: 2012
Source: Sensors and Actuators A: Physical, Available online 27 January 2012
Samin Akbari, Herbert Shea
Biological cells modulate their behavior, express genes, proliferate or differentiate in response to mechanical strains ranging from 1 to 20%. There currently exists no technique to apply strain to many targeted individual cells in a larger culture in order to perform parallelized high throughput testing. Dielectric Elastomer Actuators (DEAs) are compliant devices capable of generating large percentage strains with sub-second response time, ideally suited by their compliance for cell manipulation. We report an array of 100 μm x 100 μm DEAs reaching up to 80% in-plane strain at an electric field of 240 V/μm. The miniaturized DEAs are made by patterning 100 μm wide compliant ion-implanted gold electrodes on both sides of a 30 μm thick polydimethylsiloxane (PDMS) membrane. We report the important effect of uniaxial prestretch of the membrane on the microactuators’ performance; the largest strain is achieved by prestretching uniaxially by 175%. Each actuator is intended to have a single cell adhered to it in order to periodically stretch the cells to study the effect of mechanical stimulation on its biochemical responses. To avoid short-circuiting all the top electrodes by the conductive saline cell growth medium, a 20 μm thick biocompatible PDMS layer is bonded on the actuators. In this configuration, 37% strain is achieved at 3.6 kV with sub-second response. This device can be used as a high throughput single cell stretcher to apply relevant biological periodic strains to individual cells in a single experiment

Highlights

► Fabrication and characterization of an array of 100 μm x 100 μm dielectric elastomer actuators, generating up to 80% in-plain strain. ► Presenting an effective method to pattern 100 μm wide compliant electrodes by low energy ion implantation, addressing the lack of suitable fabrication techniques to pattern μm scale compliant electrodes on silicone membranes. ► Fabrication of two layer actuators showing up to 37% strain for cell stretching applications to allow high throughput mechanotransduction studies in single cell level

GAMMA AND eLECTRON BEAM IRRADIATION EFFECTS ON The Resistance of mICROMACHINED Polycrystalline silicon BEAMS

27 January 2012, 22:07:35Go to full article
Publication year: 2012
Source: Sensors and Actuators A: Physical, Available online 24 January 2012
Lei Wang, Jieying Tang, Qing-An Huang
This paper reports gamma and electron beam irradiation effects on the resistance of polycrystalline silicon beams in MEMS. Displacement damage, injection annealing, and thermal spike are identified as causes of the gamma and electron beam irradiation effect on polycrystalline silicon. Radiation effect on grain neutral regions and grain boundary of polycrystalline silicon are also discussed. Co60 irradiation test and Electron beam irradiation were performed to identify the radiation effects on polycrystalline silicon beams. Resistances were measured by a Keithley Semiconductor Characterization with hardware modules of 4200-scs to reveal the gamma and electron irradiation effect on resistance of the microbridges. The reason for the change of the resistance was analyzed by the theory of radiation effects in solids, and the gamma and electron beam irradiation effects which induce this change were discussed.

Development of on-chip vacuum generation by gas-liquid phase transition

27 January 2012, 22:07:35Go to full article
Publication year: 2012
Source: Sensors and Actuators A: Physical, Available online 24 January 2012
K. Sugiyama, Y. Ukita, Y. Takamura
In this paper, we developed on-chip vacuum generation technique using gas-liquid phase transition. Fabricated quartz chip was composed simply of a structural vacuum chamber and a diaphragm for pressure measurement by laser displacement meter. Efficient reduction of pressure in the chamber was accomplished by the phase transition with the simple design of the fabricated chip. The pressure was reduced by decreasing the temperature of low boiling point liquid filled into the chamber after closing its valve. The lowest pressure attained to 50.8kPa(diethyl ether) or 23.2 kPa(water) at 7 min from atmospheric pressure by using diethyl ether and water, respectively. The highest performance of micro vacuum pump was achieved. The absolute pressure below 25 kPa was maintained about 20 min due to low leakage of the fabricated chip.

Highlights

► On-chip vacuum technique is developed using gas-liquid phase transition. ► Condensation by phase transition is effective for vacuumgenerationin micro chamber. ► Diaphragm vacuum sensor is integrated into micro chamber. ► The lowest pressure attained 23.2kPa by using phase transition of water. ► Fabricated chamber maintains vacuum below 25 kPa for 20 min.

AQUACOUNTER® KF Volumetric Titrator Reduces Reagent Waste

JMScience’s AQUACOUNTER® Karl Fischer Volumetric Titrator (AQV-2200S) is economical and eco-friendly with small volume titration cells requiring only 20mL of titration solvent for accurate measurements. Less reagent volume reduces waste and makes it easy to replace fresh solvent for the next measurement.

This high-end titrator is the perfect choice for a very wide range from 100 ppm to 100% water content with its maximum capability for automation and upgrades. Suitable for 100% H2O.

Combining one additional KF station with either a volumetric or coulometric module enables two different measurements to be performed at the same time. With a volumetric and coulometric channel, one can measure moisture over the entire range from 2ppm to 100% or double the sample throughput with 2 identical KFstations.  Additional compact  burets and snap buret-heads are useful for quick KFreagent exchange or back titration applications.

A two-channel option means easy “plug-and-play”. End-users can add various peripherals, such as a second channel, and the system recognizes the new channels and begins working with them immediately.  Intuitive control panel display shows current status, data and function keys and are displayed on a large, colorful screen.  Result data with curves can be viewed on your PC internet browsing program without optional software. Save and load parameters and results via USB flash memory.  A built-in thermal printer is easy to load and has high resolution printouts.

This volumetric titrator is ideal for users who: 1) have many kinds of samples to be analyzed; 2) exchange KF reagents frequently or after each measurement; 3) are eco-minded and budget-conscious.

For more information contact us at 1-800-495-1678 or visit us at www.jmscience.com

Thursday, 26 January 2012

Just Published: Journal of Chromatography A

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:

Mixed-mode solid-phase extraction followed by dispersive liquid-liquid microextraction for the sensitive determination of ethylphenols in red wines

25 January 2012, 01:09:37Go to full article
Publication year: 2012
Source: Journal of Chromatography A, Available online 24 January 2012
I. Carpinteiro, B. Abuín, I. Rodríguez, M. Ramil, R. Cela
Selectivity of mixed-mode solid-phase extraction (SPE) was combined with the concentration power of dispersive liquid-liquid microextraction (DLLME) to obtain a sensitive, low solvent consumption method for gas chromatography-mass spectrometry determination of ethylphenol off-flavours (4-ethylphenol, EP; 4-ethylguaicol, EG and 4-ethylcathecol, EC) in complex red wine samples. Under optimized conditions, limits of quantification (LOQs) between 0.3 and 0.8 ng mLwere obtained using just 5 mL of wine and 0.06 mL of 1,1,1-trichloroethane (TCE) as extractant in the DLLME step. Analytes were acetylated after SPE and previously to DLLME concentration to enhance the performance of their GC-MS determination. The overall extraction efficiency of the method was unaffected by the particular characteristics of each wine; thus, accurate results (relative recoveries from 89 to 109% for samples spiked at concentrations from 20 to 1000 ng mL) were obtained using matrix-matched standards, without requiring the use of the time consuming standard addition quantification methodology. The applicability of the method was demonstrated with the analysis of different red wines. Analytes concentrations varied from 6 to 2265 ng mL(EP), 0.8 to 251 ng mL(EG) and non-detected to 158 ng mL(EC).

Highlights

► Selective ethylphenols determination in red wines ► Wide linear response range ► Overall extraction yields not affected by wine sample characteristics ► High enrichment factors with low organic solvents and sample consumption.

Development of a hydrophilic interaction liquid chromatography–mass spectrometry method for detection and quantification of urea thermal decomposition by-products in emission from diesel engine employing selective catalytic reduction technology

25 January 2012, 01:09:37Go to full article
Publication year: 2012
Source: Journal of Chromatography A, Available online 24 January 2012
Mahmoud M. Yassine, Ewa Dabek-Zlotorzynska, Valbona Celo
The use of urea based selective catalytic reduction (SCR) technology for the reduction of NOx from the exhaust of diesel-powered vehicles has the potential to emit at least six thermal decomposition by-products, ammonia, and unreacted urea from the tailpipe. These compounds may include: biuret, dicyandiamine, cyanuric acid, ammelide, ammeline and melamine. In the present study, a simple, sensitive and reliable hydrophilic interaction liquid chromatography (HILIC)-electrospray ionization (ESI)/mass spectrometry (MS) method without complex sample pre-treatment was developed for identification and determination of urea decomposition by-products in diesel exhaust. Gradient separation was performed on a SeQuant® ZIC-HILIC column with a highly polar zwitterionic stationary phase, and using a mobile phase consisting of acetonitrile (eluent A) and 15 mM ammonium formate (pH 6; eluent B). Detection and quantification were performed using a quadrupole ESI/MS operated simultaneously in negative and positive mode. With 10 μL injection volume, LODs for all target analytes were in the range of 0.2-3 μg/L. The method showed a good inter-day precision of retention time (RSD <0.5%) and peak area (RSD <3%). Satisfactory extraction recoveries from spiked blanks ranged between 96 and 98%. Analyses of samples collected during transient chassis dynamometer tests of a bus engine equipped with a diesel particulate filter (DPF) and urea based SCR technology showed the presence of five target analytes with cyanuric acid and ammelide the most abundant compounds in the exhaust.

Highlights

► Exhaust from a bus engine equipped with diesel particulate filter and urea- selective reduction technology. ► Identification and quantification of urea thermal decomposition compounds in diesel emission were studied. ► A new HILIC-ESI/MS method has been developed. ► Five target analytes, with cyanuric acid and ammelide the most abundant compounds, were determined.

Evaluation of a column classification method using the separation of alfuzosin from its related substances

25 January 2012, 01:09:37Go to full article
Publication year: 2012
Source: Journal of Chromatography A, Available online 24 January 2012
Jarosław Szulfer, Alina Plenis, Tomasz Bączek
The popularity and commercial availability of reversed-phase liquid chromatographic (RP-LC) stationary phases cause analysts to be often confronted with the problem of column selection. For this reason, general test methods to characterize RP-LC columns have been extensively studied since the 1970s. This paper focuses on correlating the column classification based on a method developed at the Katholieke Universiteit Leuven (KUL method) with the selectivity obtained for a real separation. The analysis of alfuzosin hydrochloride and related compounds was carried out according to the method prescribed in the European Pharmacopoeia (Ph. Eur.) monograph. This separation was performed on 36 new RP-LC stationary phases which had been previously characterized chromatographically. For deeper comparative analysis of KUL classification of the stationary RP-LC brands and their column performance in pharmaceutical practice two chemometric tools, such as principal component analysis (PCA) and cluster analysis (CA), have been used. It was shown that stationary phase classes closely related by KUL method gave comparable separation for alfuzosin and related compounds. Therefore, the column ranking system based on the evaluation ofF-values can be considered as a helpful tool in the selection of a suitable column for pharmaceutical analyses.

Highlights

► Column classification was carried out in view of LC separation of alfuzosin and related compounds. ► We performed LC column classification based on KUL method. ► We evaluated column classification system using chemometric techniques. ► Principal component analysis and cluster analysis were applied. ► The tested classification system can be considered as efficient tools.

Ultra-Trace Level Analysis of Morpholine, Cyclohexylamine, and Diethylaminoethanol in Steam Condensate by Gas Chromatography with Multi-Mode Inlet, and Flame Ionization Detection

25 January 2012, 01:09:37Go to full article
Publication year: 2012
Source: Journal of Chromatography A, Available online 24 January 2012
J. Luong, R.A. Shellie, H. Cortes, R. Gras, T. Hayward
Steam condensate water treatment is a vital and integral part of the overall cooling water treatment process. Steam condensate often contains varying levels of carbon dioxide and oxygen which acts as an oxidizer. Carbon dioxide forms corrosive carbonic acid when dissolved in condensed steam. To neutralize the harmful effect of the carbonic acid, volatile amine compounds such as morpholine, cyclohexylamine, and diethylaminoethanol are often employed as part of a strategy to control corrosion in the water treatment process. Due to the high stability of these compounds in a water matrix, the indirect addition of such chemicals into the process via steam condensate often results in their presence throughout the process and even into the final product. It is therefore important to understand the impact of these chemicals and their fate within a chemical plant.The ability to analyze such compounds by gas chromatography has historically been difficult due to the lack of chromatographic system inertness at the trace level concentrations especially in an aqueous matrix. Here a highly sensitive, practical, and reliable gas chromatographic approach is described for the determination of morpholine, cyclohexylamine, and diethylaminoethanol in steam condensate at the part-per-billion (ppb) levels. The approach does not require any sample enrichment or derivatization.The technique employs a multi-mode inlet operating in pulsed splitless mode with programmed inlet temperature for sample introduction, an inert base-deactivated capillary column for solute separation and flame ionization detection. Chromatographic performance was further enhanced by the incorporation of 2-propanol as a co-solvent. Detection limits for morpholine, cyclohexylamine, diethylaminoethanol were established to be 100 ppb (v/v), with relative standard deviations (RSD) of less than 6% at the 95% confidence level (n = 20) and a percent recovery of 96% or higher for the solutes of interest over a range of 0.1 to 100 ppm (v/v). A complete analysis can be conducted in less than ten minutes.

Highlights

► Volatile amines are employed to control corrosion in water treatment ► Indirect addition of these amines into process streams sometimes occurs ► We combine 3 innovations for ultra-trace amine determination in steam condensate ► Anal. of morpholine, cyclohexylamine, and diethylaminoethanol is conducted < 10 min ► Practical detection limits for the volatile amines investigated is 100 ppb (v/v)

Just Published: Biosensors & Bioelectronics

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:

Using the nanoimprint-in-metal method to prepare corrugated metal structures for plasmonic biosensors through both surface plasmon resonance and index-matching effects

25 January 2012, 01:10:19Go to full article
Publication year: 2012
Source: Biosensors and Bioelectronics, Available online 24 January 2012
Chen-Chieh Yu, Kuan-Hung Ho, Hsuen-Li Chen, Shang-Yu Chuang, Shao-Chin Tseng, ...
In this study, we prepared metallic corrugated structures for use as highly sensitive plasmonic sensors. Relying on the direct nanoimprint-in-metal method, fabrication of this metallic corrugated structure was readily achieved in a single step. The metallic corrugated structures were capable of sensing both surface plasmon resonance (SPR) wavelengths and index-matching effects. The corrugated Au films exhibited high sensitivity (ca. 800 nm/RIU), comparable with or even higher than those of other reported SPR-based sensors. Because of the unique index-matching effect, refractometric sensing could also be performed by measuring the transmission intensity of the Au/substrate SPR mode—conveniently, without a spectrometer. In the last, we demonstrated the corrugated Au film was capable of sensing biomolecules, revealing the ability of the structure to be a highly sensitive biosensor

Highlights

► Metallic corrugated structure is prepared as highly sensitive plasmonic sensors ► It can sense both surface plasmon resonance wavelength and index-matching effect ► A high sensitivity of 800 nm/RIU is achieved according to resonance wavelength shift ► Besides, the linear response of resonance intensity is adopted for sensing as well ► In the last, the structure demonstrates the ability to be a sensitive biosensor

Electrical detection of Biomolecular adsorption on Sprayed Graphene Sheets

25 January 2012, 01:10:19Go to full article
Publication year: 2012
Source: Biosensors and Bioelectronics, Available online 24 January 2012
Tamon R. Page, Yuhei Hayamizu, Christopher R. So, Mehmet Sarikaya
The binding affinities of graphite-binding peptides to a graphite surface were electrically characterized using sprayed graphene field effect transistors (SGFETs) fabricated with solution exfoliated graphene. The binding affinities of these peptides were also characterized using atomic force microscopy (AFM) and mechanically exfoliated graphene field effect transistors (GFETs) to confirm the validity of the SGFET platform. Binding constants obtainedviaGFET and AFM were comparable with those observed using SGFETs. The sprayed graphene film serves as a scalable platform to study biomolecular adsorption to graphitic surfaces

Highlights

► We fabricated graphene field effect transistors with solution exfoliated graphene ► The transistor enables us to characterize bio-molecular adsorption electrically ► We studied solid-binding peptides as a molecular calibration tool ► This sensor responded to the peptides comparably with conventional graphene sensors ► The sensorgrams are verified by atomic force microscopy

Evaluation of permselective membranes for optimization of intracerebral amperometric glutamate biosensors

25 January 2012, 01:10:19Go to full article
Publication year: 2012
Source: Biosensors and Bioelectronics, Available online 24 January 2012
 N.Wahono, S. Qin, P. Oomen, T.I.F. Cremers, M.G. de Vries, ...
Monitoring of extracellular brain glutamate concentrations by intracerebral biosensors is a promising approach to further investigate the role of this important neurotransmitter. However, amperometric biosensors are typically hampered by Faradaic interference caused by the presence of other electroactive species in the brain, such as ascorbic acid, dopamine, and uric acid. Various permselective membranes are often used on biosensors to prevent this. In this study we evaluated the most commonly used membranes, i.e. nafion, polyphenylenediamine, polypyrrole, polyaniline, and polynaphthol using a novel silica-based platinum electrodeFirst we selected the membranes with the highest sensitivity for hydrogen peroxidein vitroand an optimal selectivity against electrochemical interferents. Then we evaluated the performances of these membranes in a short lasting (3-4 hrs)in vivoexperiment. We found that bestin vitroperformance was accomplished with biosensors that were protected by a poly(m-phenylenediamine) membrane deposited onto the platinum electrode by cyclic voltammetry. However, post-implantation evaluation of these membranes showed poor selectivity against dopamine. Combination with a previously applied nafion layer did not protect the sensors against acute biofouling; indeed it was even counter effective.Finally, we investigated the ability of our biosensors to monitor the effect of glutamate transport blocker DL-TBOA on modulating glutamate concentrations in the prefrontal cortex of anaesthetized rats. The optimized biosensors recorded a rapid 35-fold increase in extracellular glutamate, and are considered suitable for further explorationin vivo

Highlights

► Several permselective membranes were studied to improve glutamate sensorsin vivoperformance ► Poly(m-PD) CV shows highest performance to repel interfering compounds ► There is no significance biofouling effect after implantation on GluOx activity ► This sensor type has the potential to be used to monitor glutamate in brain

Simultaneous determination of ascorbic acid, dopamine and uric acid using high-performance screen-printed graphene electrode

23 January 2012, 22:13:51Go to full article
Publication year: 2012
Source: Biosensors and Bioelectronics, Available online 21 January 2012
Jianfeng Ping, Jian Wu, Yixian Wang, Yibin Ying
A disposable and sensitive screen-printed electrode using an ink containing graphene was developed. This electrode combined the advantages of graphene and the disposable characteristic of electrode, which possessed wide potential window, low background current and fast electron transfer kinetics. Compared with the electrodes made from other inks, screen-printed graphene electrode (SPGNE) showed excellent electrocatalytic activity for the oxidation of ascorbic acid (AA), dopamine (DA), and uric acid (UA). Three well-defined sharp and fully resolved anodic peaks were found at the developed electrode. Differential pulse voltammetry was used to simultaneous determination of AA, DA, and UA in their ternary mixture. In the co-existence system of these three species, the linear response ranges for the determination of AA, DA, and UA were 4.0 − 4500 μM, 0.5 − 2000 μM, and 0.8 − 2500 μM, respectively. The detection limits (S/N = 3) were found to be 0.95 μM, 0.12 μM, and 0.20 μM for the determination of AA, DA, and UA, respectively. Furthermore, the SPGNE displayed high reproducibility and stability for these species determination. The feasibility of the developed electrode for real sample analysis was investigated. Results showed that the SPGNE could be used as a sensitive and selective sensor for simultaneous determination of AA, DA, and UA in biological samples, which may provide a promising alternative in routine sensing applications

Highlights

► A disposable electrode made from graphene-based screen-printing ink was proposed. ► Large potential window, low background current and fast electron transfer kinetics. ► Three well-defined and fully resolved peaks for oxidation of three species. ► High sensitivity, selectivity, stability, reproducibility and easy fabrication.