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:

Sensors & Actuators A: Physical
http://rss.sciencedirect.com/publication/science/5282

Selected papers from the latest issue:

Optimal design of a four-sensor probe system to measure the flow properties of the dispersed phase in bubbly air–water multiphase flows

07 August 2013, 09:38:33

Publication date: 15 October 2013
Source:Sensors and Actuators A: Physical, Volume 201
Author(s): S.R. Pradhan , R. Mishra , K. Ubbi , T. Asim
This paper presents a systematic investigation on the design and development of a four-sensor probe system to be used for air–water multiphase flow measurements. A mathematical model is presented which can be used to determine the optimum axial separation of the front sensor with respect to three rear sensors within a four sensor probe system. This system can be used to measure flow properties of the dispersed phase in bubbly air–water flows accurately. Paper also presents a sensitivity analysis to determine the minimum sampling frequency requirements in the data collection process, so that associated errors in various output parameters can be minimized, for the given values of sensors co-ordinates. A particularly novel feature of this paper is development of a unique digital signal processing scheme to enable the accurate computation of different flow characteristics. This paper also presents validation of four-sensor probe measurements from a flow visualization and measurement system which relies on using two high speed cameras mounted orthogonally. The results obtained from validation experiments show very high degree of similarity in measured flow variables from the two systems. This indicates that the four-sensor probe system developed in this study can be used with confidence to measure parameters of a dispersed multiphase flow. The flow characteristics obtained from the four-sensor probe system when used in a multiphase flow system are also presented. The results indicate a unique flow pattern corresponding to bubbles of different sizes in air–water flows.

Non-contact crack detection of high-speed blades based on principal component analysis and Euclidian angles using optical-fiber sensors

07 August 2013, 09:38:33

Publication date: 15 October 2013
Source:Sensors and Actuators A: Physical, Volume 201
Author(s): Zhongsheng Chen , Yongmin Yang , Yong Xie , Bin Guo , Zheng Hu
High-speed rotating blades are key mechanical components in turbo-machinery. High cycle fatigues often induce blade cracks and ultimately the loss of blades. Effort has being made to measure on-line blade vibrations and promptly detect potential cracks. Traditional contacting methods are difficult to satisfy the needs of on-line testing, enduring extreme conditions and non-invasion. Nowadays non-contact vibration measurement at blade tips by optical sensing has become a promising approach. In this paper a blade tip-timing (BTT) method using four optical-fiber sensors is presented and all-blade vibration displacements are derived in detail. Blade vibration signals collected by the BTT method are typical sub-sampled signals, so a signal reconstruction method is proposed based on the Shannon sampling theorem. Next nine candidate vibration parameters are calculated to form the crack feature space and principal component analysis (PCA) is used to extract principal components from it. Then Euclidian angles of principal components are defined to detect cracks. In the end, an experimental set-up is built and a small crack is cut on a blade artificially. Collected data are analyzed to testify the proposed method and the experimental results demonstrate its effectiveness.

Theoretical modeling, simulation and experimental studies of fiber optic bundle displacement sensor

07 August 2013, 09:38:33

Publication date: 15 October 2013
Source:Sensors and Actuators A: Physical, Volume 201
Author(s): Supriya S. Patil , P.B. Buchade , A.D. Shaligram
This paper reports unified mathematical model of fiber optic bundle displacement sensor (FOBDS) based on ray tracing technique. The sensor response for concentric, random and hemispherical fiber bundle configurations is simulated using the developed model. The sensor performance parameters viz. sensitivity and linear operating range are calculated by differentiating the sensor response curve. It is observed that for a fiber bundle having two crowns of fibers with central illuminating fiber, sensitivity varies as 0.22, 0.42, 0.47 and linear operating range varies as 40mm, 22mm and 45mm for concentric, random and hemispherical configurations respectively. These results are validated by performing experiments with the developed sensor probe. Experimental results are almost matching the simulated results. After comparing the results for three configurations, it is concluded that the hemispherical configuration is best suitable configuration for sensor showing concurrent improvement in both the sensor performance parameters.

Network modeling of multiple-port, multiple-vibration-mode transducers and resonators

07 August 2013, 09:38:33

Publication date: 15 October 2013
Source:Sensors and Actuators A: Physical, Volume 201
Author(s): Michael L. Kuntzman , Donghwan Kim , Nishshanka N. Hewa-Kasakarage , Karen D. Kirk , Neal A. Hall
A modeling procedure is presented for multiple-port, multiple-vibration-mode transducers. Unique features of the procedure include the use of modal coordinates to describe deformations of the mechanical structure, the use of a network analog for each vibration mode of the structure, and the selection of modal velocity, rather than a particular physical velocity on the structure, as the mechanical flow variable in each modal network. Finite element analysis is used only to compute a discrete set of salient circuit parameters, with all other analysis and design computations performed using the networks. The approach is computationally efficient and assists with providing insights into the design of actuators and micromechanical resonators, where the generation and suppression of particular vibration modes may be important. A micromachined, multiple-port piezoelectric microphone with in-plane directivity is presented as a case study to demonstrate application of the procedure. Model verification is performed by comparing simulated and measured port-to-port transfer functions over a frequency range spanning several vibration modes of the device. The modeling procedure can address multiple-port sensor response to distributed loadings, selective excitation and suppression of modes in actuator applications, and mixed sensing and actuator applications such as the demonstrated port-to-port measurements.

SAW-RFID enabled temperature sensor

07 August 2013, 09:38:33

Publication date: 15 October 2013
Source:Sensors and Actuators A: Physical, Volume 201
Author(s): Along Kang , Chenrui Zhang , Xiaojun Ji , Tao Han , Ruisheng Li , Xianwei Li
Wireless sensors based on surface acoustic wave (SAW) technology has its own advantages over its counterparts. In this paper, a novel SAW radio frequency identification (RFID) enabled temperature sensor is proposed for industrial applications, in which short measurement range but high accuracy is usually required. The encoding scheme for the sensor using pulse positions combined with phase information is adopted, and then the relationship between the length of a time slot and the decoding errors is deduced to ensure the sensor can be accurately identified, even though ambient temperature fluctuates. In order to solve the phase ambiguity problem involved in temperature measurements more efficiently and reduce the cost of obtaining the unwrapping temperature characteristic curves in the calibration process, an analytical procedure for calculating the variation of phase delay differences with respect to temperature has been proposed. A self-developed burst transceiver supporting online data analysis is also presented. The experimental results demonstrate the effectiveness and practicality of the proposed SAW-RFID enabled temperature sensing scheme, and the prototype sensor within a temperature-controlled oven 2m away from the center of the transceiver antenna in a horizontal orientation achieves an accuracy of ±0.3°C in the temperature range 0–40°C.

Heated atomic force microscope cantilever with high resistivity for improved temperature sensitivity

07 August 2013, 09:38:33

Publication date: 15 October 2013
Source:Sensors and Actuators A: Physical, Volume 201
Author(s): Joseph O. Liu , Suhas Somnath , William P. King
We report a heated atomic force microscope cantilever with a heater region engineered to have high temperature sensitivity. The high resistivity (HR) heater region is phosphorous-doped silicon with a doping concentration of 1×10¹⁶ cm⁻³ and a resistivity of 0.53Ω-cm. The heater has a temperature coefficient of resistance of 102ΩC⁻¹ over the temperature range 100–300°C, which is more than one order magnitude higher compared to heated cantilevers from previous publications. When used for thermal sensing of substrate nanotopography, the HR cantilever has a sensitivity of 0.37mV/nm at 300°C. Because the HR cantilever has high sensitivity at relatively low temperatures, it can be used to measure substrates that cannot withstand high temperatures, demonstrated here as a polymer film grating of thickness 110nm.

Investigations on non-linear temperature-dependent electro-mechanical response of 1–3 type piezocomposites

07 August 2013, 09:38:33

Publication date: 15 October 2013
Source:Sensors and Actuators A: Physical, Volume 201
Author(s): R. Jayendiran , A. Arockiarajan
An investigation on temperature-dependent behaviour of 1–3 piezocomposites is carried out under electro-mechanical coupled loading condition for different fiber volume fractions and bulk piezoceramics. Effective properties of 1–3 piezocomposite are measured using resonance based method for different operating temperatures. A simple homogenization technique is proposed for predicting the effective properties of 1–3 piezocomposites at elevated temperatures. A thermodynamically consistent uni-axial non-linear constitutive model is developed to predict thermo-electro-mechanical behavior of 1–3 piezocomposites. The predicted effective properties are incorporated in the proposed uni-axial model. The responses of piezocomposites subjected to electric field and mechanical stress are calculated and compared with experimental observations for room and elevated temperatures.

Mechano-electrical conversion for harvesting energy with hybridization of electrostrictive polymers and electrets

07 August 2013, 09:38:33

Publication date: 15 October 2013
Source:Sensors and Actuators A: Physical, Volume 201
Author(s): Fouad Belhora , Pierre-Jean Cottinet , Abdelowahed Hajjaji , Daniel Guyomar , M’hammed Mazroui , Laurent Lebrun , Yahia Boughaleb
In recent years, electroactive polymers have been widely used as smart materials. Electromechanical applications are currently focused on energy harvesting, including the development of autonomous device. During the last few years, electrostrictive polymers have been investigated as for energy harvesting. However, for energy scavenging, a static field is necessary, a solution to avoid this problem involves the hybridization of electrostrictive polymers with electrets. The present work has been dedicated to the analytical modeling based on electrostatic and electrostrictive equations. An experimental study was carried out on polyurethane and P(VDF-TrFE-CFE) films, either without filler or filled with carbon nanopowder.

Development of a lead-zirconate-titanate (PZT) thin-film microactuator probe for intracochlear applications

07 August 2013, 09:38:33

Publication date: 15 October 2013
Source:Sensors and Actuators A: Physical, Volume 201
Author(s): Chuan Luo , G.Z. Cao , I.Y. Shen
In this paper, we present design, fabrication, and testing results of a small-scale piezoelectric lead-zirconate-titanate (PZT) thin-film microactuator probe that could be implanted in the inner ear for hearing rehabilitation. The PZT probe would generate a pressure wave directly stimulating perilymph in the cochlea to provide acoustic stimulation. Specifically, the PZT probe is 1-mm wide, 10-mm long, and 0.4-mm thick with a PZT thin-film diaphragm at the tip of the probe serving as an acoustic actuator. The diaphragm size is 0.8mm×0.8mm and the probe is packaged with parylene of 0.25-μm thickness. The design effort includes finite element simulations to determine thickness of the parylene package as well as back-of-the-envelope calculations of implantation depth of the PZT probe. The fabrication work includes deposition of a PZT thin film via sol–gel processes, deep reaction ion etching to form an array of vibrating PZT diaphragms, dicing the wafer to release the PZT probes, and application of parylene layer to package the PZT probes. The testing effort includes measurements of actuator velocity (via a laser Doppler vibrometer) and impedance (via an impedance analyzer) in air and in water. After the PZT probe is submerged in water, its displacement gradually increases and saturates at around 2h. Impedance measurements also show a similar trend. To explain these phenomena, we hypothesize that water infiltrates into the PZT thin film via diffusion, thus increasing the dielectric constant of the PZT film. SEM images reveal numerous nano-pores on PZT and probe surfaces, indirectly supporting the hypothesis. The PZT probe functions in water for 55h without breaking down.

Some practical applications of magnetohydrodynamic pumping

07 August 2013, 09:38:33

Publication date: 15 October 2013
Source:Sensors and Actuators A: Physical, Volume 201
Author(s): Champak Das , Guochun Wang , Forrest Payne
Magnetohydrodynamic pumping provides a unique opportunity to mobilize fluids inside a channel using very low power and without employing any external moving parts. In this paper, we illustrate certain unique applications of these pumps such as sample injection, fluid flow in packed bed, and on-chip assay development, all of which are relevant to point-of-care diagnostic device design and fabrication. A linear flow velocity of 5cm/min was obtained using four on-board pumps in a closed loop of circumferential track length of 10cm (channel cross section of 0.5mm×0.5mm), whereas it dropped to 1.8mm/min in a packed bed column operated by a single pump. Finally, these pumps were integrated with silicon immunoassay chips to evaluate the feasibility of transporting electro active species with these pumps from source to electrochemical detection site.

Cantilever resonator based on the electrostriction effect in Gd-doped ceria

07 August 2013, 09:38:33

Publication date: 15 October 2013
Source:Sensors and Actuators A: Physical, Volume 201
Author(s): Roman Korobko , Ellen Wachtel , Igor Lubomirsky
Thin films of Ce0.8Gd0.2O1.9, which have recently been shown to demonstrate giant electrostriction, are proposed as the active material for miniature cantilever resonators and actuators. In the absence of strain, these films have an electrostriction coefficient within the range of 2–10kPa/(kV/cm)², as compared with the somewhat larger values for the best commercial electrostrictors (e.g. PbMn 1 / 3 Nb 2 / 3 O 3 , 62kPa/(kV/cm)². At the same time, Ce0.8Gd0.2O1.9 films can generate stress >70MPa which is competitive with materials currently in use and only limited by the strength of the film-substrate interface. In this report, we investigate two aspects of the practical application of Ce0.8Gd0.2O1.9 as a resonator: the fabrication conditions and the frequency dependence of the electrostrictive behavior. We show that the films can display electromechanical response with frequencies up to 6kHz. With respect to fabrication, we show that Ce0.8Gd0.2O1.9 films have a number of technological advantages when compared to the lead titanate based materials currently in use: (a) they can be deposited on a variety of metal contacts and substrates, including silicon; (b) they do not require high temperature processing; and (c) because Ce0.8Gd0.2O1.9 has cubic symmetry, it can in principle be used as a polycrystalline film with arbitrary texture and does not require poling. In addition, neither Ce nor Gd nor their oxides are toxic; the oxides have very low vapor pressure; and the cations, being highly charged do not diffuse into Si. Consequently, Ce0.8Gd0.2O1.9 films may be readily and advantageously integrated into existing semiconductor fabrication technologies. 

Fully Automated Drying or Concentration of Very Large Volumes

Genevac has announced the launch of the ROCKET 4D – a fully automated system for automatic drying or concentration of very large volumes (a few to 100 litres) in one operation with no user interaction. Simply load your sample, select a method, press start, and walk away – the system will do the rest.

Compact in size the ROCKET 4D allows you to dry or concentrate your samples with complete confidence as it uses proprietary vacuum technology to suppress solvent bumping and foaming – problems associated with sample loss when using large scale rotary evaporators.

Rocket 4D comes as standard with a single, 5 litre 316 stainless steel vessel for drying or concentrating product. This has detachable handles and is easily lifted into and out of the evaporator. Access to the dried or concentrated product in the vessel is very easy. Dried products can be scooped out, or where enhanced user protection is needed, re-dissolved while the vessel is still in the system. Liquid products can be easily drained via a drain port in the side of the rotor, using a dedicated pouring stand.

Users wishing to dry volumes larger than five litres require the ‘Autofeed’ option, which enables the Rocket 4D to draw in product from the user’s own external supply. The Rocket 4D controls product feed, drying and the discharge of condensed waste solvent without any external intervention. The autofeed system has an integrated rinse circuit which enables dried products to be automatically re-dissolved in a small volume of solvent at the end of the process. Alternatively, the same circuit can be used under manual control for solvent exchange, by selecting a different solvent for re-dissolve.

Cleaning the Rocket 4D between cycles is also very straightforward. The PTFE feed tubing is easily detached for cleaning or replacement and the vessel can be readily cleaned, wiped, inspected and even put in a dishwasher. It’s all so easy compared with handling large glass evaporator flasks!

The ROCKET 4D also includes powerful cold traps that maximise solvent recovery protecting the environment and improving drying of samples.

For further information including a full product brochure please visit www.Genevac.com/Rocket4D  or contact the company on +44-1473-240000 / salesinfo@genevac.co.uk

Just Published: Sensors & Actuators B: Chemical

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:

Sensors & Actuators B: Chemical
http://rss.sciencedirect.com/publication/science/5283

A fluorescent colorimetric pH sensor and the influences of matrices on sensing performances

06 August 2013, 10:08:24

Publication date: November 2013
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Yanqing Tian , Emily Fuller , Summer Klug , Fred Lee , Fengyu Su , Liqiang Zhang , Shih-hui Chao , Deirdre R. Meldrum
A fluorescent colorimetric pH sensor was developed by a polymerization of a monomeric fluorescein based green emitter (SM1) with a monomeric 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran derived red emitter (SM2) in poly(2-hydroxyethyl methacrylate)-co-polyacrylamide (PHEMA-co-PAM) matrices. Polymerized SM1 (PSM1) in the polymer matrices showed bright emissions at basic conditions and weak emissions at acidic conditions. Polymerized SM2 (PSM2) in the polymer matrices exhibited a vastly different response when compared to PSM1. The emissions of PSM2 are stronger under acidic conditions than those under basic conditions. When SM1 and SM2 were polymerized in the same polymer matrix, a dual emission sensor acting as a ratiometric pH sensor (PSM1,2) was successfully developed. Because the PSM1 and PSM2 exhibited different pH responses and separated emission windows, the changes in the emission colors were clearly observed in their dual color sensor of PSM1,2, which changed emission colors dramatically from green at pH 7 to red at pH 4, which was detected visually and/or by using a color camera under an excitation of 488nm. In addition to the development of the dual color ratiometric pH sensor, we also studied the effects of different matrix compositions, crosslinkers, and charges on the reporting capabilities of the sensors (sensitivity and pK a).

AC electro-osmotic micromixer using a face-to-face, asymmetric pair of planar electrodes

06 August 2013, 10:08:24

Publication date: November 2013
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Jhih-Lin Chen , Wei-Hung Shih , Wen-Hsin Hsieh
This paper is the first to report the mixing performance of an AC electro-osmotic (AC-EO) micromixer based on the two sets of vortices generated by a face-to-face, asymmetric pair of planar electrodes. The larger top electrode of the asymmetric electrode pair was rectangular (30×60mm²) and the much smaller bottom electrode was also rectangular (500×700μm²) and featured two protrusions. Due to the highly three-dimensional flow pattern generated by the unique shape of the face-to-face electrode pair, the mixing enhancement factor (mixing time by diffusion/mixing time by the micromixer) exhibited by the reported micromixer ranged from 290 to 360 and the mixing performance values were uniform across the entire height of the fluid cavity. The usefulness of the mixer in hybridizing single-stranded deoxyribonucleic acids and mixing Escherichia coli with RNA stains was also demonstrated experimentally. A numerical investigation was conducted to study the three-dimensional AC-EO flow patterns induced by the face-to-face, asymmetric electrode pair. This analysis made it possible to identify a detailed flow pattern and the formation mechanism of the vortices. The confluence of inward AC-EO flows from the edges of the bottom-electrode protrusion locally induced a large inward-pumping force and was responsible for the formation of the four vortices at the four corners of the bottom electrode. The numerical and experimental results of this research provide information that will be useful in future applications and research in the area of microfluidic manipulation.

Modification of a QCN sensor by SiO2 nanoparticles and MIP for telone determination: Improving its selectivity and sensitivity

06 August 2013, 10:08:24

Publication date: November 2013
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): A. Mirmohseni , M. Rastgouy-Houjaghan
A quartz crystal nanobalance (QCN) sensor was developed for the selective determination of telone in aqueous solutions. Telone imprinted nanocomposite was synthesized using SiO2 nanopowders and acrylic acid. FTIR spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) were employed to characterize the morphology and microstructure of the SiO2-MIP nanocomposite. The prepared SiO2-MIP nanocomposite particles were coated on quartz crystal electrode to form complementary structures for the template recognition of telone. The SiO2-MIP coated electrode was used to determine telone levels in solution. The developed sensor demonstrated a high selectivity and sensitivity (4.96Hz per mgL⁻¹) for telone. It can also be used for telone determination in the concentration range between 1 to 40mgL⁻¹. Furthermore, a good reproducibility, R.S.D.=1.66% (n =5) was observed. During its photocatalytic degradation by UV/ZnO, telone residue process was measured by the developed sensor and GC to validate the accuracy of the developed sensor in real world situation. According to the results of the t-test, QCN sensor and GC spectroscopy measurement results enjoy good agreement. Therefore, a fabricated sensing system has the potential for real sample application.

Slime mould tactile sensor

06 August 2013, 10:08:24

Publication date: November 2013
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Andrew Adamatzky
Slime mould Physarum polycephalum is a single cells visible by unaided eye. The cells shows a wide spectrum of intelligent behaviour. By interpreting the behaviour in terms of computation one can make a slime mould based computing device. The Physarum computers are capable to solve a range of tasks of computational geometry, optimisation and logic. Physarum computers designed so far lack of localised inputs. Commonly used inputs — illumination and chemo-attractants and -repellents — usually act on extended domains of the slime mould's body. Aiming to design massive-parallel tactile inputs for slime mould computers we analyse a temporal dynamic of P. polycephalum's electrical response to tactile stimulation. In experimental laboratory studies we discover how the Physarum responds to application and removal of a local mechanical pressure with electrical potential impulses and changes in its electrical potential oscillation patterns.

Highly sensitive gallia-SnO2 nanocomposite sensors to CO and ethanol in presence of methane

06 August 2013, 10:08:24

Publication date: November 2013
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Minoo Bagheri , Abbas Ali Khodadadi , Ali Reza Mahjoub , Yadollah Mortazavi
Responses of gallia-SnO2 nanocomposite sensors, containing 0–50wt% Ga2O3 calcined at 500–850°C, to CO, methane and ethanol are investigated. The gallia-SnO2 samples were prepared via a facile co-precipitation method using stannic chloride and gallium nitrate aqueous solutions without any template and characterized by XRD, EDX, TEM, PL and BET surface area techniques. The samples containing up to 25wt% gallia and calcined at 500°C indicate that only tetragonal rutile structure of SnO2 is formed. The Ga4SnO8 and β-Ga2O3 phases are observed for the samples containing 50wt% Ga2O3 and calcined at 850 and 1050°C, respectively. The average particle sizes of the nanocomposites gradually decrease from 21.6 to 6.7nm, as their gallia contents increase from 0 to 25wt%. The highest responses of 315 and 119 are observed for 300ppm CO and ethanol by the sensors containing 5 and 1wt% Ga2O3, respectively. The sensors containing 25wt% Ga2O3 calcined at 850°C and 50wt% gallia calcined at 500 and 850°C are selective to CO and show negligible responses to ethanol and methane.

A promising gold nanocluster fluorescent sensor for the highly sensitive and selective detection of S2−

06 August 2013, 10:08:24

Publication date: November 2013
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Ma-Lin Cui , Jia-Ming Liu , Xin-Xing Wang , Li-Ping Lin , Li Jiao , Zhi-Yong Zheng , Li-Hong Zhang , Shu-Lian Jiang
Bright red-emissive gold nanoclusters (AuNCs) were synthesized by a facile one-pot approach in aqueous solution using bovine serum albumin (BSA) as a protecting agent. A new BSA-AuNC fluorescent sensor for the detection of S²⁻ has been designed based on the sharp fluorescence quenching of BSA-AuNCs, which results from the degradation of its structure due to the formation of Au2S by the reaction between Au and S²⁻. The proposed highly sensitive (the detection limit [LD] was 0.029μM) and selective sensor was applied to the detection of S²⁻ in the presence of high concentrations of different anions in aqueous solution, and the results were in good agreement with those determined by electrochemical methods. The sensor is shown to be environmentally friendly, simple, responsive and practical. Meanwhile, the morphological changes of BSA-AuNCs and BSA-AuNCs-S²⁻ were characterized by high-resolution transmission electron microscopy (HRTEM). Furthermore, the sensing mechanism for the detection of S²⁻ is discussed.

Flavone modified-β-cyclodextrin as a highly selective and efficient fluorescent chemosensor for Cu2+ ions and l-histidine

06 August 2013, 10:08:24

Publication date: November 2013
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Ismail Abulkalam Azath , Kasi Pitchumani
7-Aminoflavone modified β-cyclodextrin with a hydrazinecarbothioamide linker is synthesised for the first time and characterised by NMR, ESI-MS and elemental analysis. NOESY as well as emission spectra indicate the inclusion of phenyl ring inside the cyclodextrin cavity. The hydrazinecarbothioamide linker acts as the metal binding unit. This flavone modified CD selectively binds with Cu(II) over other metal ions. Binding with Cu(II) makes the complex non-fluorescent. Addition of histidine, among other amino acids, results in regeneration of the fluorescence enhancement. This is due to the fact that l-histidine displaces Cu²⁺ from Flav-CD-Cu²⁺ complex to release the free flavone resulting in regeneration of its fluorescence. This turn-on sensor can be utilised effectively to sense both Cu(II) among various metal ions and l-histidine (as well as histamine) among various amino acids.

Sensitive and selective determination of uric acid in real samples by modified glassy carbon electrode with holmium fluoride nanoparticles/multi-walled carbon nanotube as a new biosensor

06 August 2013, 10:08:24

Publication date: November 2013
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): M. Noroozifar , M. Khorasani-Motlagh , F. Zareian Jahromi , S. Rostami
A novel modified glassy carbon electrode with holmium fluoride (HoF3) nanoparticles (HoFNPs)-multiwalled carbon nanotubes (MWCNTs) is fabricated and then successfully used for the sensitive and selective determination of uric acid (UA) in the presence of ascorbic acid (AA) and dopamine (DA). HoFNPs are successfully attached on the multi-walled carbon nanotubes (MWCNTs) via the intermediate of noncovalent hydrophobic interactions of the MWCNTs surface with sodium dodecyl sulfate (SDS). A detailed investigation by transmission electron microscopy (TEM) and electrochemistry is performed in order to elucidate the preparation process and properties of the nanocomposites. TEM image shows that the particle size of HoFNPs is about 56nm. Linear calibration plot is obtained over the range 2.0×10⁻⁷–5.0×10 ⁻⁴ M (0.2–500.0μM) with a detection limit 1.6×10⁻⁷ M (0.16μM) for UA. The modified carbon electrode proves to have good sensitivity, stability and performance for determination UA in the presence of AA, DA in human blood serum and urine samples.

A simple homemade light emitting diode based photometer for chromium speciation

06 August 2013, 10:08:24

Publication date: November 2013
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Mohammad-Hossein Sorouraddin , Masoud Saadati , Hasan Karimi baneshat
A simple spectrophotometric method utilizing a homemade light emitting diode (LED) based photometer is developed for chromium (VI) and total chromium determination in water samples. The photometer is composed of an LED (white color) as light source and a programmable light-to-frequency converter (three arrays of photodiodes each with a red, green or blue filter) as a detector. The chromium speciation is based on the complex formation reaction of Cr(VI) with 1,5-diphenylcarbazide. Considering the maximum absorption wavelength of the complex, the determination was performed using green filter detector. Prior to the total chromium determination, Cr(III) was oxidized to Cr(VI) with Ce(IV). Cr(III) concentration was calculated from the difference between total Cr and Cr(VI) concentrations. Under the optimum conditions, the calibration graph was linear in 10–200μgL⁻¹ chromium concentration range. The relative standard deviation (n =5) and the limit of detection was calculated to be 2.45 and 2.99μgL⁻¹ respectively. The proposed method was successfully applied to chromium speciation in spiked water samples.

Synthesis of hierarchical SnO2 nanostructures assembled with nanosheets and their improved gas sensing properties

06 August 2013, 10:08:24

Publication date: November 2013
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Liwei Wang , Shurong Wang , Yanshuang Wang , Hongxin Zhang , Yanfei Kang , Weiping Huang
Well-defined three-dimensional (3D) hierarchical tin dioxide (SnO2) nanoflowers (NFs) constructed by two-dimensional (2D) nanosheets (NSs) are successfully fabricated by a simple one-pot low-temperature (90°C) hydrothermal strategy. The influence of the experiment parameters on the morphology of the products is investigated in detail. Field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) demonstrate that the size and shape of the 3D hierarchical SnO2 NFs can be tailored by modulating the molar ratio of OH⁻ to Sn²⁺, reaction time and reaction temperature in the process of hydrothermal synthesis. A possible formation process and growth mechanism for such fabricated 3D hierarchical SnO2 nanostructures has been proposed based on the experimental results. The gas sensing tests of the SnO2 NF sensor for several reducing volatile organic compounds (VOCs) including ethanol, n-butanol, acetone, methanol, chloroform and benzene have been performed at the relatively low operating temperature of 240°C. The excellent gas sensing performances of the unique 3D hierarchical SnO2 NFs at low operating temperature of 240°C indicate their potential application as gas sensors. The unique 3D hierarchical SnO2 NFs with high accessible surface area and commodious inter space can also be expected to use as catalyst, dye-sensitive solar cell and Li ion battery materials.

Direct nitrate sensing in water using an array of copper-microelectrodes from flat flexible cables

06 August 2013, 10:08:24

Publication date: November 2013
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Iranaldo S. da Silva , William R. de Araujo , Thiago R.L.C. Paixão , Lúcio Angnes
Nitrate determination plays a very important role in the analysis of environmental samples. In this paper, an activation procedure for nitrate sensing using a modified copper electrode made from flat flexible cables in presence of a low amount of chloride is reported. The proposed method exhibits enhanced electrocatalytic behaviour in the reduction of nitrate compared to a bare copper electrode. The proposed method showed linear response for nitrate in the concentration range 10–1070μmolL⁻¹, with a regression coefficient R ² =0.999 (n =12) and a limit of detection of 1.8μmolL⁻¹. According to the procedure based on the standard addition technique, the recovery values obtained were 93–103%, showing the accuracy of the proposed method. In addition, the proposed sensor was applied to the determination of nitrate in mineral water samples and the results are in good agreement (for a 95% confidence level according to the Student's t-test) with those obtained using the capillary electrophoresis procedure.

Electrochemical immunosensor based on graphene–polyaniline composites and carboxylated graphene oxide for estradiol detection

06 August 2013, 10:08:24

Publication date: November 2013
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Jie Li , Su Liu , Jinghua Yu , Wenjing Lian , Min Cui , Wei Xu , Jiadong Huang
A novel estradiol immunosensor based on graphene–polyaniline (GR–PANI) composites and carboxylated graphene oxide (GO) was developed. GR–PANI composites were used to enhance the electroactivity and stability of the electrode. The current response of the immunosensor was remarkably improved due to the synergistic effects of GR and PANI. Horseradish peroxidase–graphene oxide–antibody (HRP–GO–Ab) conjugates which were constructed by using the carboxylated GO as the carrier of the antibody and horseradish peroxidase as the label improved the catalytic activity for hydrogen reduction of the electrode. A competitive immunoassay was facilitated between 17β-estradiol and the HRP–GO–Ab conjugates. Based on this competitive immunoassay, the immunosensor showed a wide linear response to estradiol in the range 0.04–7.00ng/mL and a limit of detection of 0.02ng/mL (S/N=3). The developed immunosensor was successfully applied to the detection of estradiol in real samples.

Simultaneous detection of benzene and toluene using a pulsed ion mobility spectrometer

06 August 2013, 10:08:24

Publication date: November 2013
Source:Sensors and Actuators B: Chemical, Volume 188
Author(s): Stefan Zimmermann , Frank Gunzer
Ion mobility spectrometry (IMS) is a well known method for fast trace gas detection in air. Having simple instrumentation, IMS is especially suited when portability and highest sensitivity are required. However, due to competing chemical ionization processes in the reaction region of IMS, it can be difficult or even impossible to detect small amounts of certain substances in a complex mixture. A prominent example is the detection of low benzene concentrations in the presence of higher toluene concentrations. In this paper we present experimental results of simultaneous toluene and benzene detection by using a pulsed electron source for ionization and demonstrate how this can help to overcome the major issue of atmospheric pressure chemical ionization (APCI). 

Reproducible Isolation of High Quality RNA

INTEGRA has released a new video demonstrating a solid phase extraction (SPE) microplate method for reproducible, high throughput isolation of high-quality DNA-free total RNA.

Large scale gene expression screening projects require reliable high-throughput methods to isolate high quality RNA from a large number of samples. To meet this need, a growing number of commercial 96-well format RNA isolation kits are now available. Typically such kits are compatible with commonly used 96-well plate vacuum manifolds enabling the extraction (isolation) procedure to be accelerated.

The video shows how researchers use a VIAFLO 384 handheld electronic pipette in conjunction with vacuum manifold, 96-well solid phase extraction (SPE) microplate and RNA isolation kit to reproducibly extract high quality total RNA from cultured cells and bacteria.

The VIAFLO 384 is a handheld 384-channel electronic pipette that offers all the benefits of increased sample throughput as well as lower sample and reagent use without the expense of having to invest in a robotic liquid handling system. Designed to be used just like a standard handheld pipette the VIAFLO 384 requires no special skills or training to operate it. The VIAFLO 384 features INTEGRA's popular Touch Wheel™ pipette user interface enabling simple and fast programming of a wide range of pipetting modes including repeat dispense, serial dilute and mixing routines.

To watch the RNA isolation video please visit www.youtube.com/watch?v=qZUDG_74MgU. For further information on the VIAFLO 384 please contact INTEGRA in Europe / Asia on telephone +41-81-286-9530 / email info@integra-biosciences.com or in North / South America on telephone +1-603-578-5800 / email US@integra-biosciences.com

Just Published: Spectrochimica Acta Part B: Atomic 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:

Spectrochimica Acta Part B: Atomic Spectroscopy
http://rss.sciencedirect.com/publication/science/5287

Selected papers from the latest issue:

Obituary: Prof. Dr. Kurt Laqua (1919–2013)

01 August 2013, 11:42:42

Publication date: 1 August 2013
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 86
Author(s): Kay Niemax

Nanoscience, nanotechnology and spectrometry

01 August 2013, 11:42:42

Publication date: 1 August 2013
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 86
Author(s): Freddy C. Adams , Carlo Barbante
Nanoscience has outgrown its infancy, and nanotechnology has found important applications in our daily life — with many more to come. Although the central concepts of the nano world, namely the changes of particular physical properties on the length scale of individual atoms and molecules, have been known and developed for quite some time already, experimental advances since the 1980s and recognition of the potential of nanomaterials led to a genuine breakthrough of the inherently multidisciplinary nanoscience field. Analytical nanoscience and nanotechnology and especially the use of micro and nano electro mechanical systems, of the quantum dots and of mass spectrometry, currently provide one of the most promising avenues for developments in analytical science, derived from their two main fields of action, namely (a) the analysis of nano-structured materials and (b) their use as new tools for analysis. An overview is given of recent developments and trends in the field, highlighting the importance and point out future directions, while also touching drawbacks, such as emerging concerns about health and environmental issues.

Liquid phase microextraction for the analysis of trace elements and their speciation

01 August 2013, 11:42:42

Publication date: 1 August 2013
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 86
Author(s): Bin Hu , Man He , Beibei Chen , Linbo Xia
Trace/ultra-trace elements and their speciation analysis in complex matrices usually require sample preparation procedures to achieve sample clean-up and analyte preconcentration. Sample preparation is often the bottleneck in trace elements and their speciation analysis which has a direct impact on accuracy, precision and limits of detection and is often the rate-determining step of the analytical process. Recent trends in sample preparation include miniaturization, automation, high-throughput performance and reduction in solvent/sample consumption and operation time. Liquid-phase microextraction (LPME) technique as a novel and promising alternative in sample preparation can meet these requirements and has become a very efficient sample preparation technique. This review updates the state of art of LPME for trace elements and their speciation analysis and discusses its promising prospects. The major thrust of the article highlights the applications of LPME including single-drop microextraction (SDME), hollow fiber-liquid phase microextraction (HF-LPME), dispersive liquid liquid microextraction (DLLME) and solidified floating organic drop microextraction (SFODME) to the fields of elemental and their speciation analysis by atomic spectrometry-based methods, especially inductively coupled plasma mass spectrometry. General and specific concepts, different extraction formats and characteristics of LPME are described and compared, along with examples of recent innovations and applications presented to demonstrate its potential for trace elements and their speciation analysis in biological and environmental fields. Moreover, the application potential and an outlook on the combination of LPME and atomic spectrometry-based techniques for inorganic analysis are commentated.

Independent component analysis classification of laser induced breakdown spectroscopy spectra

01 August 2013, 11:42:42

Publication date: 1 August 2013
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 86
Author(s): Olivier Forni , Sylvestre Maurice , Olivier Gasnault , Roger C. Wiens , Agnès Cousin , Samuel M. Clegg , Jean-Baptiste Sirven , Jérémie Lasue
The ChemCam instrument on board Mars Science Laboratory (MSL) rover uses the laser-induced breakdown spectroscopy (LIBS) technique to remotely analyze Martian rocks. It retrieves spectra up to a distance of seven meters to quantify and to quantitatively analyze the sampled rocks. Like any field application, on-site measurements by LIBS are altered by diverse matrix effects which induce signal variations that are specific to the nature of the sample. Qualitative aspects remain to be studied, particularly LIBS sample identification to determine which samples are of interest for further analysis by ChemCam and other rover instruments. This can be performed with the help of different chemometric methods that model the spectra variance in order to identify a the rock from its spectrum. In this paper we test independent components analysis (ICA) rock classification by remote LIBS. We show that using measures of distance in ICA space, namely the Manhattan and the Mahalanobis distance, we can efficiently classify spectra of an unknown rock. The Mahalanobis distance gives overall better performances and is easier to manage than the Manhattan distance for which the determination of the cut-off distance is not easy. However these two techniques are complementary and their analytical performances will improve with time during MSL operations as the quantity of available Martian spectra will grow. The analysis accuracy and performances will benefit from a combination of the two approaches.

A systematic study on the influence of carbon on the behavior of hard-to-ionize elements in inductively coupled plasma–mass spectrometry

01 August 2013, 11:42:42

Publication date: 1 August 2013
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 86
Author(s): Guillermo Grindlay , Juan Mora , Margaretha de Loos-Vollebregt , Frank Vanhaecke
A systematic study on the influence of carbon on the signal of a large number of hard-to-ionize elements (i.e. B, Be, P, S, Zn, As, Se, Pd, Cd, Sb, I, Te, Os, Ir, Pt, Au, and Hg) in inductively coupled plasma–mass spectrometry has been carried out. To this end, carbon matrix effects have been evaluated considering different plasma parameters (i.e. nebulizer gas flow rate, r.f. power and sample uptake rate), sample introduction systems, concentration and type of carbon matrix (i.e. glycerol, citric acid, potassium citrate and ammonium carbonate) and type of mass spectrometer (i.e. quadrupole filter vs. double-focusing sector field mass spectrometer). Experimental results show that P, As, Se, Sb, Te, I, Au and Hg sensitivities are always higher for carbon-containing solutions than those obtained without carbon. The other hard-to-ionize elements (Be, B, S, Zn, Pd, Cd, Os, Ir and Pt) show no matrix effect, signal enhancement or signal suppression depending on the experimental conditions selected. The matrix effects caused by the presence of carbon are explained by changes in the plasma characteristics and the corresponding changes in ion distribution in the plasma (as reflected in the signal behavior plot, i.e. the signal intensity as a function of the nebulizer gas flow rate). However, the matrix effects for P, As, Se, Sb, Te, I, Au and Hg are also related to an increase in analyte ion population caused as a result of charge transfer reactions involving carbon-containing charged species in the plasma. The predominant specie is C⁺, but other species such as CO⁺, CO2 ⁺, C2 ⁺ and ArC⁺ could also play a role. Theoretical data suggest that B, Be, S, Pd, Cd, Os, Ir and Pt could also be involved in carbon based charge transfer reactions, but no experimental evidence substantiating this view has been found.

Determination of platinum group metal catalyst residues in active pharmaceutical ingredients by means of total reflection X-ray spectrometry

01 August 2013, 11:42:42

Publication date: 1 August 2013
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 86
Author(s): Eva Marguí , Ignasi Queralt , Manuela Hidalgo
The control of metal catalyst residues (i.e., platinum group metals (PGMs)) in different stages of the manufacturing processes of the active pharmaceutical ingredients (APIs) and, especially, in the final product is crucial. For API specimens, there are strict guidelines to limit the levels of metal residues based on their individual levels of safety concern. For PGMs the concentration limit has been established at 10mg/kg in the API. Therefore great effort is currently being devoted to the development of new and simple procedures to control metals in pharmaceuticals. In the present work, an analytical methodology based on benchtop total reflection X-ray fluorescence spectrometry (TXRF) has been developed for the rapid and simple determination of some PGM catalyst impurities (Rh, Pd, Ir and Pt) in different types of API samples. An evaluation of different sample treatments (dissolution and digestion of the solid pharmaceutical samples) has been carried out and the developed methodologies have been validated according to the analytical parameters to be considered and acceptance criteria for PGM determination according to the United States Pharmacopeia (USP). Limits of quantification obtained for PGM metals were in the range of 2–4mg/kg which are satisfactory according to current legislation. From the obtained results it is shown that the developed TXRF method can be implemented in the pharmaceutical industries to increase productivity of the laboratory; offering an interesting and complementary analytical tool to other atomic spectroscopic methods.

Detection of zinc and lead in water using evaporative preconcentration and single-particle laser-induced breakdown spectroscopy

01 August 2013, 11:42:42

Publication date: 1 August 2013
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 86
Author(s): Samu T. Järvinen , Jaakko Saarela , Juha Toivonen
A novel laser-induced breakdown spectroscopy (LIBS)-based measurement method for metals in water is demonstrated. In the presented technology a small amount of sodium chloride is dissolved in the sample solution before spraying the sample into a tubular oven. After water removal monodisperse dry NaCl aerosol particles are formed where trace metals are present as additives. A single-particle LIBS analysis is then triggered with a scattering based particle detection system. Benefits are the highly increased metal concentration in the LIBS focal volume and the static NaCl-matrix which can be exploited in the signal processing procedure. Emitted light from the emerged plasma plume is collected with wide angle optics and dispersed with a grating spectrometer. In an aqueous solution, the respective limits of detection for zinc and lead were 0.3ppm and 0.1ppm using a relatively low 14mJ laser pulse energy. Zn/Na peak intensity ratio calibration curve for zinc concentration was also determined and LIBS signal dependence on laser pulse energy was investigated.

A new X-ray pinhole camera for energy dispersive X-ray fluorescence imaging with high-energy and high-spatial resolution

01 August 2013, 11:42:42

Publication date: 1 August 2013
Source:Spectrochimica Acta Part B: Atomic Spectroscopy, Volume 86
Author(s): F.P. Romano , C. Altana , L. Cosentino , L. Celona , S. Gammino , D. Mascali , L. Pappalardo , F. Rizzo
A new X-ray pinhole camera for the Energy Dispersive X-ray Fluorescence (ED-XRF) imaging of materials with high-energy and high-spatial resolution, was designed and developed. It consists of a back-illuminated and deep depleted CCD detector (composed of 1024×1024pixels with a lateral size of 13μm) coupled to a 70μm laser-drilled pinhole-collimator, positioned between the sample under analysis and the CCD. The X-ray pinhole camera works in a coaxial geometry allowing a wide range of magnification values. The characteristic X-ray fluorescence is induced on the samples by irradiation with an external X-ray tube working at a maximum power of 100W (50kV and 2mA operating conditions). The spectroscopic capabilities of the X-ray pinhole camera were accurately investigated. Energy response and energy calibration of the CCD detector were determined by irradiating pure target-materials emitting characteristic X-rays in the energy working-domain of the system (between 3keV and 30keV). Measurements were performed by using a multi-frame acquisition in single-photon counting. The characteristic X-ray spectra were obtained by an automated processing of the acquired images. The energy resolution measured at the Fe–Kα line is 157eV. The use of the X-ray pinhole camera for the 2D resolved elemental analysis was investigated by using reference-patterns of different materials and geometries. The possibility of the elemental mapping of samples up to an area of 3×3cm² was demonstrated. Finally, the spatial resolution of the pinhole camera was measured by analyzing the profile function of a sharp-edge. The spatial resolution determined at the magnification values of 3.2× and 0.8× (used as testing values) is about 90μm and 190μm respectively. 

NEW Shodex HPLC Column Catalog 2013-2015

JM Science is pleased to announce the new Shodex HPLC Column catalog which features scores of application chromatograms, charts and diagrams that describe a very wide selection of separation modes such as reversed phase, hydrophilic interaction, normal phase, ligand exchange, ion exclusion, ion chromatography, size exclusion, ion exchange, hydrophobic interaction, affinity and chiral separations. HPLC columns are available in analytical, semi-micro, micro and preparative sizes and are largely based on polymeric packing materials that provide the liquid chromatographer with one of the most extensive choices of separation mechanisms combined with an equally large combination of stationary and mobile phases.

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