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:

A computationally efficient numerical model of the offset of CMOS-integrated vertical Hall devices

05 April 2012, 09:29:18

Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 178
T. Kaufmann, M.C. Vecchi, P. Ruther, O. Paul
This paper describes a computationally efficient numerical model to study effects determining the offset of five-contact vertical Hall sensors (VHS). It applies a two-dimensional finite element model implemented in COMSOL Multiphysics and allows to take into account the junction field effect (JFE) altering the depletion layer width between n-well and p-doped regions as well as resistive asymmetries due to contact shifts. Doping profiles of realistic devices were extracted using SYNOPSYS TCAD simulations based on three sets of process parameters with different doping doses of the n-well and p⁺-diffusions. The VHS offset was compared with experimental results obtained using complementary metal oxide semiconductor (CMOS)-based VHS and analyzed as a function of the input voltage. It was shown that the linear offset components are modeled adequately by resistive imbalances caused by lateral contact shifts in the nanometer range. The JFE in turn is responsible for the nonlinear effects of dominantly quadratic dependence on the input voltage. Both effects contribute additively to the overall offset. According to the simulations, the nonlinear contribution is strongly reduced at higher n-well doping concentrations.

Electromechanical performance of poly(vinylidene fluoride)/carbon nanotube composites for strain sensor applications

05 April 2012, 09:29:18

Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 178
A. Ferrreira, J.G. Rocha, A. Ansón-Casaos, M.T. Martínez, F. Vaz, S. Lanceros-Mendez
This paper reports on the piezoresistive behavior of polymer based nanocomposites, composed of poly(vinylidene fluoride) – PVDF and carbon nanotubes (CNTs). The samples were prepared by hot pressing with CNT sample concentrations up to loadings of 10wt.%. The phase present in the polymer was the α-phase. The correlation between the electrical resistivity and mechanical solicitations is presented in this work for the different composites and for varying mechanical solicitations. The values of the gauge factor, ranging up to 6.2, and the linearity of the response over a wide strain range shows the viability of these materials to be used as piezoresistive sensors. The stability of the signal, the time response and the temperature behavior were also evaluated. The observed electrical and electromechanical behavior can be explained in the framework of the percolation theory.

Numerical study of a ferrule-top cantilever optical fiber sensor for wind-tunnel applications and comparison with experimental results

05 April 2012, 09:29:18

Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 178
A. Cipullo, G. Gruca, K. Heeck, F. De Filippis, D. Iannuzzi, A. Minardo, L. Zeni
We present a numerical analysis of an air flow velocity sensor based on a fiber-optic ferrule-top cantilever. The device forms a low-finesse Fabry–Perot interferometer, with one of the two reflecting surfaces constituted by a cantilever beam. Under the effect of the flow pressure, the cantilever bends producing a change in the cavity length of the Fabry–Perot and therefore a modification of its optical response. The numerical analysis, performed by use of finite-element method (FEM), is then compared with a set of experimental results obtained in a small wind-tunnel.

ZnO nanorods grown on polymer substrates as UV photodetectors

05 April 2012, 09:29:18

Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 178
I-Chuan Yao, Tseung-Yuen Tseng, Pang Lin
Vertical well-aligned and uniform ZnO nanorods were successfully prepared on low cost and flexible PET polymer substrate by aqueous solution method under various growth conditions. Current–voltage (I–V) and current–time (I–t) relationships measurements demonstrate that the photocurrent can be increased by more than 25 times upon UV illumination (λ =365nm) with a power density of 70μW/cm². The photocurrents can be repeatedly and reproducibly switched by modulating UV exposure with power densities of 25–70μW/cm². The fast response time (100s) and rapid recovery time (120s) are achieved in UV turn-on/off switching measurements. Owing to the good performance including mechanical flexibility, nondestructive properties, high reliability and multilevel photoresponse, the well-aligned ZnO nanorods grown on transparent and flexible PET polymer substrates have high potential for UV photodetector applications.

Gold nano-particle-based thermal sensors fabricated using microspotting and DEP techniques

05 April 2012, 09:29:18

Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 178
Siu Ling Leung, Minglin Li, Wen J. Li, John D. Mai
We show that pearl chains of gold nano-particles (Au NPs) are formed consistently between microelectrodes by combining microspotting and dielectrophoretic (DEP) techniques. Experimental results on various sized Au particles and DEP parameters, including voltage and frequency, are reported in this paper to explore the critical parameters in controlling the pearl chain formation (PCF) process between microelectrodes. PCF is observed from 10kHz to 5MHz for 100nm diameter Au NPs, and 100kHz to 10MHz for 10nm Au NPs. Variations in formation rate are detected when the applied voltage and particle size varies. At higher voltages, PCF occurs at a higher rate and the formation time decreases. The optimum frequency for Au NPs PCF shifts to a higher frequency region when the particle size decreases. Theoretical analysis is carried out by calculating the DEP force with AC electrokinetics to explain the observations at DEP frequencies ranging from 10Hz to 10MHz. Finally, Au NP chains formed between the microelectrodes are shown to vary in resistance consistent with predictions for a simplified model of an impinging jet system, indicating that these Au particle sensors could potentially be used to precisely measure localized temperatures and other localized thermal phenomena.

Design, fabrication and characterization of high temperature piezoelectric vibration sensor using YCOB crystals

05 April 2012, 09:29:18

Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 178
Kyungrim Kim, Shujun Zhang, Giovanni Salazar, Xiaoning Jiang
A shear-mode piezoelectric accelerometer using YCa4O(BO3)3 single crystals (YCOB) was designed, fabricated and successfully tested for high temperature vibration sensing applications. Dynamic modeling of the accelerometer was presented first, followed by YCOB single crystal sample preparation, sensor assembly and experimental setup establishment. The prototyped accelerometer was tested at temperatures ranging from room temperature to 1000°C and at frequencies ranging from 50Hz to 350Hz. The sensitivity of the prototype was found to be 5.9±0.06pC/g throughout the tested frequency, temperature and acceleration ranges. In addition, YCOB piezoelectric accelerometers retained the same sensitivity at 1000°C for a dwell time of 9h, exhibiting a high stability and reliability.

Thermal conductivity detector compact Spice model based on experimental measurements and 3D simulations

05 April 2012, 09:29:18

Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 178
F. Rastrello, P. Placidi, A. Scorzoni, E. Cozzani, M. Messina, I. Elmi, S. Zampolli, G.C. Cardinali
In this paper a novel compact Spice model of a thermal conductivity detector (TCD) is presented and validated against an extensive experimental characterization and 3D simulations. The TCD used is based on the ultra low power (ULP) technology and it has been electrically characterized with different helium and nitrogen gas flow rates, via a microfluidic experimental setup. Extraction of global electro-thermal parameters, exploited for the development of the Spice model, has been performed by using both 3D electro-thermal FEM simulations made with COMSOL Multyphisics^® and experimental measurements. The first result we discuss is the good agreement between 3D FEM simulations of the device, made with COMSOL Multiphysics^®, and the experiments, with a maximum error of 2.9% for He flow rate of 9sccm and around 1.8% for the N2 carrier gas at each considered flow rate. We have demonstrated that the Spice model can reproduce very well the FEM simulations for all the gas flow rates and the operating power values taken into consideration, using simulation parameters extracted from FEM data itself. Results of the Spice model compare well also with the real behavior of a TCD device for both the used gases, using parameters either extracted from FEM simulations or calibrated with experimental measurements, with a maximum error of 0.9% for the He flow rate of 0.29sccm and a maximum error of 0.8% for the N2 flow rate of 10.3sccm. The novelty of the proposed approach is to provide a useful instrument for the electronic designer who wants to incorporate a Spice electro-thermal model in a simulation environment. The TCD can initially be simulated with an electro-thermal FEM model for a reduced number of operating conditions, then the Spice model can be calibrated and exploited for the electronic design. After device production, the Spice model can eventually be optimized using the experimental results, thus improving the accuracy of the whole electronic circuit simulation.

Variation in phase transformation paths of NiTi films as a function of film thickness

05 April 2012, 09:29:18

Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 178
Ashvani Kumar, Devendra Singh, Davinder Kaur
NiTi shape memory alloy thin films of different thickness have been grown on silicon (100) substrates using dc magnetron co-sputtering. Differences in microstructure such as crystallinity, grain size, grain size distribution and surface roughness of these films were studied using X-ray diffractrometer (XRD) and atomic force microscope (AFM). The influence of film thickness on phase transformation behavior was studied using four probe resistivity method. NiTi films exhibited mainly three kinds of transformation behaviors i.e. incomplete, constrained and complete austenite to martensite phase transformation for the films having lower (≤300nm), intermediate (0.6–1.1μm) and higher (2.3μm) thickness, respectively. It is proposed that the constrained or incomplete transformation could be due to the special constraints (resistance force) introduced by the inter-diffusion of film, higher number of grain boundaries and increased level of the intrinsic defects. The level of actuation force can be tuned by choosing the different transformation paths that can have immense technological importance in the fabrication of various types of MEMS devices.

High-speed CMOS magnetic angle sensor based on miniaturized circular vertical Hall devices

05 April 2012, 09:29:18

Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 178
M. Banjevic, B. Furrer, M. Blagojevic, R.S. Popovic
We present a high-speed CMOS integrated magnetic angle sensor consisting of two 8-contact circular vertical Hall devices (CVHD). The biasing and sensing of the Hall voltage is rotated clockwise for the first device, and counter clockwise for the second one. The output voltages of the two devices are processed separately in two channels and they act as a reference signal one to another. The output of the sensor is a pulse width modulated signal whose width is proportional to twice the angle enclosed between the in-plane magnetic induction vector and the reference axis. The information on the angle is directly present in the pulse width modulated signal without the need for either arctg function implementation or complicated angle detection algorithms. The sensor's concept together with optimized interface and signal conditioning electronics allows for very high bandwidth. The measurement range of the sensor is 0–90°, with possibility for further extension. The sensor achieves tracking the angle of the in-plane magnetic vector oscillating at up to 200kHz (12,000,000rpm), or equivalently, having an angular speed of 628,000rad/s. To our knowledge, this is the highest bandwidth of a completely CMOS integrated magnetic angle sensor. The maximum absolute error for these speeds is ±4° without any calibration, the response time is 1μs, and the angular resolution is 0.5°.

Experimental and theoretical studies on MEMS piezoelectric vibrational energy harvesters with mass loading

05 April 2012, 09:29:18

Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 178
Robert Andosca, T. Gus McDonald, Vincent Genova, Steven Rosenberg, Joseph Keating, Cole Benedixen, Junru Wu
Experimental and theoretical investigations on micro-scale multi-morph cantilever piezoelectric vibrational energy harvesters (PZEHs) of the MicroElectroMechanical Systems (MEMS) are presented. The core body of a PZEH is a “multi-morph” cantilever, where one end is clamped to a base and the other end is free. This “fixed-free” cantilever system including a proof-mass (also called the end-mass) on the free-end that can oscillate with the multi-layer cantilever under continuous sinusoidal excitations of the base motion. A partial differential equation (PDE) describing the flexural wave propagating in the multi-morph cantilever is reviewed. The resonance frequencies of the lowest mode of a multi-morph cantilever PZEH for some ratios of the proof-mass to cantilever mass are calculated by either solving the PDE numerically or using a lumped-element model as a damped simple harmonic oscillator; their results are in good agreement (disparity≤0.5%). Experimentally, MEMS PZEHs were constructed using the standard micro-fabrication technique. Calculated fundamental resonance frequencies, output electric voltage amplitude V and output power amplitude P with an optimum load compared favorably with their corresponding measured values; the differences are all less than 4%. Furthermore, a MEMS PZEH prototype was shown resonating at 58.0±2.0Hz under 0.7 g (g =9.81m/s²) external excitations, corresponding peak power reaches 63μW with an output load impedance Z of 85kΩ. This micro-power generator enabled successfully a wireless sensor node with the integrated sensor, radio frequency (RF) radio, power management electronics, and an advanced thin-film lithium-ion rechargeable battery for power storage at the 2011 Sensors Expo and Conference held in Chicago, IL. In addition, at 58Hz and 0.5, 1.0 g excitations power levels of 32, and 128μW were also obtained, and all these three power levels demonstrated to be proportional to the square of the acceleration amplitude as predicted by the theory. The reported P at the fundamental resonance frequency f 1 and acceleration G-level, reached the highest “Figure of Merit” [power density×(bandwidth/resonant frequency)] achieved amongst those reported in the up-to-date literature for high quality factor Q f MEMS PZEH devices.

Capacitive humidity sensors based on the dielectrophoretically manipulated ZnO nanorods

05 April 2012, 09:29:18

Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 178
Leping Chen, Jian Zhang
In this paper, the capacitive relative humidity sensors based on dielectrophoretically manipulated ZnO nanostructure were constructed and studied. The humidity-sensitive ZnO nanorods were first synthesized by the thermal decomposition technique and deposited among the micromachined electrodes pairs via dielectrophoretic manipulation. The manipulated samples were detected as the capacitive sensors in which the nanostructured ZnO acted as the sensing elements. The capacitive humidity sensors were constructed by detecting the variations of the ZnO dielectric constant changing with the humidity environment. The results showed that the sensor had high humidity sensitivity, good stability, fast response/recovery time and well reproducibility. The dielectrophoresis manipulation can also improve the sensitivity of the sensor efficiently.

A temperature sensor based on a MWCNT/SEBS nanocomposite

05 April 2012, 09:29:18

Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 178
G. Matzeu, A. Pucci, S. Savi, M. Romanelli, F. Di Francesco
The fabrication of a temperature sensor based on multi-walled carbon nanotubes (MWCNTs)/styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) triblock copolymer composite is reported. The device was realized by drop casting 10μl of a MWCNTs dispersion in a toluene solution of SEBS onto gold electrodes fabricated onto a polyimide support. Thermogravimetric and electrical resistance measurements highlighted a good reproducibility of film composition and sensing properties. A negative temperature coefficient with an absolute value comparable to the highest values in metals was measured when a substantial amount of MWCNTs was incorporated into the nanocomposite (40% by weight), and a five-fold increase was observed close to the percolation threshold. Though such sensitivity seems to be partly lost after the first heating, the results allowed us to be optimistic about the feasibility of realizing nanocomposite films with temperature sensitivities comparable to that of common thermistors in the range 20–60°C.

Torsion sensor based on the coil-less fluxgate effect

05 April 2012, 09:29:18

Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 178
S. Atalay, N. Bayri, A. Fidan, F.E. Atalay, V. Yagmur
The torsion dependence of the coil-less fluxgate properties of amorphous (Co0.94Fe0.06)72.5Si12.5B15 wire was investigated. The results show that the second harmonic of the output voltage from the wire ends, U wire, varied linearly at the ±30π rad/m torsion range for as-cast wire and ±5π rad/m torsion range for annealed wire. It was also found that if the sample was annealed at higher torsion, the curve shifted negatively or positively depending on the direction of torsion applied during the annealing. Most importantly, the output signal changed its sign as the direction of external torsion reversed, and therefore the proposed torsion sensor could detect whether torsion was in the negative or positive (clockwise or anti-clockwise) direction.

Non-contact temperature determination of embedded magnetic phases of hard coatings by exploitation of the magnetic hysteresis

05 April 2012, 09:29:18

Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 178
Claas Thede, Steffen Chemnitz, Iulian Teliban, Christoph Bechtold, Christian Klever, Michael Stüber, Eckhard Quandt
A non-contact temperature sensor is described which is based on the temperature dependency of the hysteresis of a magnetic phase embedded in a non-magnetic hard coating. For the measurement principle the technique of frequency mixing is used, with extension toward phase sensitivity as indicator for the temperature. The sensor's capabilities such as selectivity and sensitivity are investigated on TiN–FeCo magnetic multilayers. The sensor has been proven for temperatures up to 500°C and shows capabilities for higher temperatures.

Deposition and characterization of thick graded index SixOyFz films with low stress

05 April 2012, 09:29:18

Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 178
Aron Michael, Abdullah Al Hafiz, Tom Puzzer, Chee Yee Kwok
This paper develops deposition techniques that are suitable for realizing low stress thick and crack free fluorine doped graded index silica (Si x O y F z ) films by the hollow cathode plasma enhanced chemical vapour deposition (HC-PECVD) system from a mixture of SiH4/O2/CF4. Silica films are deposited by varying O2, SiH4, CF4 flow rates, and RF powers. The refractive index, stress, deposition rate, chemical bonding state and chemical composition of such films have been investigated. The results indicate that low stress thick graded index silica film can be deposited by either (i) employing RF power below a certain value, which we shall refer it as ‘threshold RF power’ or (ii) increasing O2/SiH4 flow rate ratios. The threshold RF power is found to be 200W using 50sccm of O2, and 20sccm of SiH4. At RF powers below this threshold value, no oxygen deficiency is observed in the film even at a higher CF4 flow rate. On the other hand, stressed silicon rich film results at CF4 flow rates of 10sccm when the RF power is increased to 300W. By increasing O2 flow rate to 100sccm and decreasing SiH4 flow rate to 15sccm, the plasma at 300W RF power remains not oxygen deficient for up to 50sccm of CF4 flow rates. These deposition parameters are employed to deposit 28μm thick 1-D GRIN lens with a net stress of only 30MPa (compressive), and the graded index profile is optically tested. Moreover, the effect of moisture on such films has been investigated and a simple preventative measure is proposed.

Effects of wire properties on the field-tunable behaviour of continuous-microwire composites

05 April 2012, 09:29:18

Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 178
F.X. Qin, H.X. Peng, M.H. Phan, L.V. Panina, M. Ipatov, A. Zhukov
The microwire composites consisting of continuous Co-rich amorphous glass-coated ferromagnetic microwires embedded in a E-glass prepreg matrix were fabricated, and the influences of wire periodicity (b), composition and radius on the field-tunable properties have been systematically investigated in a broad microwave frequency range of 0.9–18GHz. It has been found that the field tunability, effective operational frequency and field of the composites are strongly dependent on these factors. With decreasing b from 15 to 7mm, the field tunability of effective permittivity (n ɛ ) increases from 0.77% to 16%m/A by more than 20 times. The detected cups and resonances of the transmission and reflection spectra are identified. Their changes with wire periodicity have been shown to be due to a combination of the dielectric and magnetic response arising from the interactions between microwave and microwires and microwires by themselves. The best possible field tunability occurs below the plasma frequency. The effective magnetic field for realisation of the field-tunable properties has been found to be about 500A/m, which is associated with the anisotropy field. In addition, field tunability is found to be positively correlated with the magnetic softness and GMI properties of the wire fillers, which are determined by the wire composition and geometry. These findings are of practical importance in developing multifunctional microwire composites for a broad range of engineering applications, such as structural health monitoring, NDT and microwave tunable devices.

Silicon anisotropic etching in TMAH solutions containing alcohol and surfactant additives

05 April 2012, 09:29:18

Publication year: 2012
Source:Sensors and Actuators A: Physical, Volume 178
Irena Zubel, Małgorzata Kramkowska, Krzysztof Rola
Wet chemical etching of Si(100) and Si(110) wafers in TMAH solutions containing Triton X-100 and alcohol additives was studied in a wide range of alcohol concentrations. TMAH solutions containing butanol-2 and ternary solutions composed of TMAH+Triton+alcohol, used in the experiments, had not been investigated before. The phenomena associated with the presence of surfactant and alcohol additives in etching solutions were analyzed and the mechanism including co-solving of surfactant molecules in alcohol and interplay in the adsorbing mechanism was proposed. The influence of these phenomena on the etching rates and morphologies of Si(100) and Si(110) was discussed. The addition of alcohol, especially butanol-2, to a TMAH solution resulted in significant improvement of the etched surface finish. The roughness of Si(110) surfaces etched in TMAH+butanol solutions was superior to the roughness of the surfaces etched in TMAH+Triton. The best surface roughness parameters of Si(110) (Ra=0.0322μm and RMS=0.0549μm), measured with an optical profilometer on the area of 1.6mm×1.6mm, were achieved after etching in a ternary solution of TMAH+Triton+butanol. This solution appears to be a good candidate in applications where high quality finish of etched surfaces is required on a substantially high area.

Leading European Biobank Reports On Micronic Sample Storage

Europe's largest biorepository - Biobank Graz (Graz, Austria) has reported on its use of sample storage consumables and data management software from Micronic Europe to safeguard its blood, serum and plasma samples.

Biobank Graz is a non-profit making service facility of the Medical University Graz, which supports the search for the underlying causes of disease and improvements in disease diagnosis and therapy. Over the medium to long term this is expected to contribute to an improvement in the quality of healthcare available to the general population. Whilst Biobank Graz primarily services Medical University Graz internal academics, it also offers its services to external academic and industrial partners within the framework of research collaborations. Biobank Graz collection of over 5 million human samples is based on many years of preparatory work and on existing sample collections from the research projects of different clinics and institutes.

Dr Karine Sargsyan, COO of Biobank Graz commented "After a comprehensive evaluation of commercially available consumables we selected Micronic 0.75 ml and 1.2ml tubes together with screw caps and Roborack storage racks to provide high integrity, long-term storage of our human blood, serum and plasma samples at -80° C ". A key determinant of our selection was that Micronic laser etched tube codes proved most stable to a barrage of tests including temperature stability, solvent / chemical resistance, moisture ingress and impact / wear - a fact borne out that we have only experienced an incredible 1 unreadable code in over 100,000 stored samples over the last 3½ years ". She added "Our scientists have also appreciated the flexibility and ease-of-use of Micronic's tube scanning and data management software together with the excellent support provided by the company".

Micronic 0.75ml and 1.2ml sample storage tubes are manufactured from medical grade polypropylene in a fully automated Class 7 cleanroom environment ensuring they exhibit absolute product consistency, near zero contaminants and compliance with US and European Pharmacopoeia tests. The tubes resist many organic solvents (DMSO, methanol, dichloromethane), may be autoclaved clean and can be repeatedly freeze-thawed without loss of product performance. A unique 2D code on the bottom of each tube provides an easy and unambiguous means of storing and identifying samples.  The optimised internal shape of each Micronic sample storage tube ensures the lowest possible dead volume and maximum sample recovery.  Designed to fit 96 individual tubes into a standard footprint rack optimises use of valuable freezer space and ensures automation compatibility.

For further information relating to Biobank Graz please visit www.medunigraz.at/biobank. For further information on sample storage solutions for biobanking applications please contact Micronic on telephone +31-320-277070 or email sales@micronic.com.

Just Published: Journal of Pharmaceutical and Biomedical Analysis

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:

Journal of Pharmaceutical and Biomedical Analysis
http://rss.sciencedirect.com/publication/science/5266

Selected papers from the latest issue:

Microdialysis combined with liquid chromatography–tandem mass spectrometry for the determination of levo-tetrahydropalmatine in the rat striatum

04 April 2012, 10:36:45

Publication year: 2012
Source:Journal of Pharmaceutical and Biomedical Analysis, Volumes 64–65
Chen Wang, Shu Li, Yuanjun Tang, Shuowen Wang, Yalin Zhang, Guorong Fan, Liqin Li, Yi Zhang
Levo-tetrahydropalmatine (l-THP), one of the main active alkaloids isolated from Rhizoma corydalis, was recently found to elicit profound effects on the dopaminergic system in the striatum, which plays an important role in regulating nociception. A rapid and sensitive method based on microdialysis combined with liquid chromatography–tandem mass spectrometry was developed for the determination of l-THP in the rat striatum. Microdialysis probes were stereotactically placed in the striatal hemisphere, and l-THP was measured from the microdialysates collected using LC–MS/MS. Reverse-phase LC separation was accomplished on a Diamonsil™ C18 column (50mm×2.1mm ID, 5μm) with the mobile phase composed of methanol–water (50:50, v/v) at a flow rate of 0.2ml/min. The method had a chromatographic total run time of 5min. Detection was performed in electrospray positive mode and quantification was executed in selected reaction monitoring mode. The following transitions were monitored: m/z 356.0→191.9 for l-THP and 256.0→167.1 for the internal standard diphenhydramine. The method was sensitive with a lower limit of quantitation (LLOQ) of 0.1ng/ml for l-THP, with good linearity in the range of 0.1–1000ng/ml (r ² ≥0.999). All the validation data, such as accuracy, precision, and inter-day repeatability were within the required limits. The method was successfully applied to pharmacokinetic study of the l-THP in the rat striatum.

Development and validation of an alpha fetoprotein immunoassay using Gyros technology

04 April 2012, 10:36:45

Publication year: 2012
Source:Journal of Pharmaceutical and Biomedical Analysis, Volumes 64–65
Allison M. Given, Pamela M. Whalen, Peter J. O’Brien, Chad A. Ray
Circulating alpha fetoprotein (AFP) is a diagnostic and prognostic biomarker for hepatocellular carcinoma (HCC) with potential utility as a pharmacodynamic endpoint in rodent tumor models. This application is limited, however, by low sample volumes, highlighting the need for sensitive, sample-sparing biomarker assay methods. In order to improve the utility of AFP as an oncology biomarker, we developed a method for AFP using the Gyrolab™, an automated microimmunoassay platform. Commercially available antibodies were screened to identify optimal combinations that were then used in a multi-factorial design of experiments (DOE) to optimize reaction conditions. Analytical validation included assessments of accuracy and precision (A&P), and dilutional linearity/hook effect, as well as reagent and sample stability. The method is reliable, with total error, a measure of accuracy and precision, less than 30% for all concentrations tested. AFP concentrations were measurable in diseased mice and undetectable in normal mice. Therefore, this novel, low volume AFP immunoassay is suitable for pre-clinical drug development, where its miniaturized format facilitates serial sampling in rodent models of cancer.

Simultaneous determination of antidementia drugs in human plasma: Procedure transfer from HPLC–MS to UPLC–MS/MS

04 April 2012, 10:36:45

Publication year: 2012
Source:Journal of Pharmaceutical and Biomedical Analysis, Volumes 64–65
Muriel Noetzli, Nicolas Ansermot, Maria Dobrinas, Chin B. Eap
A previously developed high performance liquid chromatography mass spectrometry (HPLC–MS) procedure for the simultaneous determination of antidementia drugs, including donepezil, galantamine, memantine, rivastigmine and its metabolite NAP 226-90, was transferred to an ultra performance liquid chromatography system coupled to a tandem mass spectrometer (UPLC–MS/MS). The drugs and their internal standards ([²H7]-donepezil, [¹³C,²H3]-galantamine, [¹³C2,²H6]-memantine, [²H6]-rivastigmine) were extracted from 250μL human plasma by protein precipitation with acetonitrile. Chromatographic separation was achieved on a reverse phase column (BEH C18 2.1mm×50mm; 1.7μm) with a gradient elution of an ammonium acetate buffer at pH 9.3 and acetonitrile at a flow rate of 0.4mL/min and an overall run time of 4.5min. The analytes were detected on a tandem quadrupole mass spectrometer operated in positive electrospray ionization mode, and quantification was performed using multiple reaction monitoring. The method was validated according to the recommendations of international guidelines over a calibration range of 1–300ng/mL for donepezil, galantamine and memantine, and 0.2–50ng/mL for rivastimgine and NAP 226-90. The trueness (86–108%), repeatability (0.8–8.3%), intermediate precision (2.3–10.9%) and selectivity of the method were found to be satisfactory. Matrix effects variability was inferior to 15% for the analytes and inferior to 5% after correction by internal standards. A method comparison was performed with patients’ samples showing similar results between the HPLC–MS and UPLC–MS/MS procedures. Thus, this validated UPLC–MS/MS method allows to reduce the required amount of plasma, to use a simplified sample preparation, and to obtain a higher sensitivity and specificity with a much shortened run-time.

Tentative identification of phase I metabolites of HU-210, a classical synthetic cannabinoid, by LC–MS/MS

04 April 2012, 10:36:45

Publication year: 2012
Source:Journal of Pharmaceutical and Biomedical Analysis, Volumes 64–65
Unyong Kim, Ming Ji Jin, Jaeick Lee, Sang Beom Han, Moon Kyo In, Hye Hyun Yoo
(6aR,10aR)-9-(Hydroxymethyl)-6,6-dimethyl-3-(2-methyloctan-2-yl)-6a,7,10,10a-tetrahydrobenzo[c]chromen-1-ol (HU-210) is a synthetic cannabinoid, with a classical cannabinoid structure similar to Δ⁹-tetrahydrocannabinol (Δ⁹-THC). In this study, the in vitro metabolism of HU-210 was investigated in human liver microsomes to characterize associated phase I metabolites. HU-210 was incubated with human liver microsomes, and the reaction mixture was analyzed using LC–MS/MS. HU-210 was metabolized in human liver microsomes, yielding about 24 metabolites. These metabolites were structurally characterized on the basis of accurate mass analyses and MS/MS fragmentation patterns. The major metabolic route for HU-210 was oxygenation. Metabolites M1–M7 were identified as mono-oxygenated metabolites; M8–M15, mono-hydroxylated metabolites; M16–M20, di-oxygenated metabolites; and M21–M24, di-hydroxylated metabolites. These results provide evidence for in vivo HU-210 metabolism, and they may be applied to the analysis of HU-210 and its relevant metabolites in biological samples.

Pharmacokinetics and disposition study of calf thymus DNA in rats by applying 3H-labeling method

04 April 2012, 10:36:45

Publication year: 2012
Source:Journal of Pharmaceutical and Biomedical Analysis, Volumes 64–65
Shuoye Yang, Qiuyang Zhang, Jiayin Chen, Deen Han, Di Zhao, Xijing Chen
A tritium(³H)-labeling method with high specificity was established to investigate the pharmacokinetics and disposition of the calf thymus DNA (ctDNA) in rats. The plasma pharmacokinetics, tissue distribution, mass balance and excretion were characterized in SD rats, respectively. Rats were injected i.v. with radiolabeled ctDNA with the dose of 40μCi/kg in each independent experiment. ³H-labeled ctDNA was eliminated rapidly in plasma, with the half-life estimated from 9 to 13h and preferentially accumulated in liver and lung, its concentration in all the tissues investigated decreased to very low level after 24h. ctDNA exhibited 80.8% accumulative recovery, excretion of radiolabel in urine and bile was nearly complete by 72h, which shown as the main excretion pathways, and the total recovery of excretion reached 77.9% within three days. In conclusion, ctDNA was rapidly eliminated in plasma and would not accumulate in tissues, parent ctDNA and its radioactive metabolites can be recovered almost completely in schedule time. All the results indicated that the in vitro use of ctDNA is safe and will not bring out potential risk.

Development of a rapid method for the determination and confirmation of nitroimidazoles in six matrices by fast liquid chromatography–tandem mass spectrometry

04 April 2012, 10:36:45

Publication year: 2012
Source:Journal of Pharmaceutical and Biomedical Analysis, Volumes 64–65
Ádám Tölgyesi, Virender K. Sharma, Szabolcs Fekete, Jenő Fekete, Andrea Simon, Szilvia Farkas
A rapid liquid chromatography–tandem mass spectrometric (LC–MS/MS) method was developed to identify and to quantify nitroimidazoles, metronidazole (MNZ), ronidazole (RNZ) and dimetridazole (DMZ) and their corresponding hydroxy metabolites, MNZ-OH and 2-hydroxymethyl-1-methyl-5-nitroimidazole (HMNNI) in plasma, milk, muscle, egg, honey and feed samples. The same sample clean-up procedure including a novel solid-phase extraction (SPE) on polymeric Strata-SDB cartridges was used for each matrix. The analytes were separated on Kinetex XB C-18 core–shell type HPLC column using isocratic elution mode with a mobile phase containing 0.1% formic acid in water/methanol (88/12, v/v, pH 2.6) at a flow rate of 0.7ml/min. The main advantage of the developed method is that the analysis time of only 3min, which is about three to ten times shorter than in other reported HPLC methods. The developed method was validated using a matrix-comprehensive in-house validation strategy. The matrix effect of LC–MS/MS analysis was also investigated. Results are presented from the successful application of the developed method to an incurred pork meat certified reference material and to incur porcine plasmas in a proficiency test in year 2011.

Development and validation of non-aqueous capillary electrophoresis methods to analyze boronic esters and acids

04 April 2012, 10:36:45

Publication year: 2012
Source:Journal of Pharmaceutical and Biomedical Analysis, Volumes 64–65
Mindy B. Forst, Anne M. Warner
Boronic esters and acids are potential intermediates in the manufacture of many active pharmaceutical ingredients (API). Accurate quantitation of the intermediate is necessary to assure the stoichiometry of the reaction. The analysis of these compounds is challenging due to their labile nature. For example, the boronic ester can hydrolyze to the acid during storage, when exposed to moisture in the air, during sample preparation and analysis, and thus give erroneous ester results. Traditional analytical techniques like gas chromatography (GC), normal phase chromatography (NPLC), hydrophilic interaction chromatography (HILIC), and reversed phase liquid chromatography (RPLC) have been utilized but with noted limitations such as poor peak shape, variation in retention times, and evidence of hydrolysis. All of these limitations impact accurate quantitation needed for selected situations. For the proprietary boronic ester evaluated here, these traditional techniques were insufficient for the accurate determination of assay and residual boronic acid. Non-aqueous capillary electrophoresis (NACE) is an accurate quantitative technique that can be used to analyze boronic esters and their corresponding acids without the limitations noted for traditional analytical techniques. The present study describes the development of methodology for the determination of the potency of a proprietary boronic ester as well as methodology for the determination of residual boronic acid in the ester. In addition, nine model boronic ester and acid pairs with a range in polarity, based on the electronic properties of the attached side group, were tested to evaluate and demonstrate the general applicability of these conditions. Under the conditions used for potency, all ten pairs had a resolution between the boronic ester and acid of greater than 1.5, acceptable peak shape for the boronic ester (tailing factor of less than 2.0), and a run time of less than 3min. In addition, this work describes the development of methodology to determine residual levels of boronic acids in the corresponding boronic ester. Using the ten boronic ester and acid pairs, eight of the ten pairs were shown to have acceptable sensitivity (S/N of 10 or better at 0.5%) and spike recoveries (within the range of 80–120%). The potential for hydrolysis during analysis was also addressed by using a subset of the ten boronic ester and acid pairs and spiking water into the diluent. There was no observed conversion of the ester to the acid. The lack of hydrolysis during analysis and the high success in separating and validating these methods for the boronic ester and acid pairs supports the utility of NACE as a technique for the analysis of boronic esters and acids.

The effects of dynamic changes of malonyl ginsenosides on evaluation and quality control of Panax ginseng C.A. Meyer

04 April 2012, 10:36:45

Publication year: 2012
Source:Journal of Pharmaceutical and Biomedical Analysis, Volumes 64–65
Zhi Liu, Yu Li, Xiang Li, Chang-Chun Ruan, Li-Juan Wang, Guang-Zhi Sun
To clarify the effects of malonyl ginsenosides (MGR) on evaluation and quality control of Panax ginseng, the contents of neutral and malonyl ginsenosides from P. ginseng were examined by high-performance liquid chromatography equipped with UV-VIS detector (HPLC-UV) during extraction, processing and storage. Several solvents, including water, ethanol, methanol, and n-butanol were used in the cold-soaked extraction (CSE). Among the four extraction solvents, methanol was found to be the most efficient. CSE was compared with other extraction methods such as Soxhlet extraction (SE), heat reflux extraction (HRE), ultrasonic-assisted extraction (UAE), and microwave-assisted extraction (MAE). The content of MGR showed significant differences, higher in CSE and UAE; lower in MAE and HRE; no MGR could be detected after SE. However, the total contents of neutral and malonyl ginsenosides were not different. Meanwhile, white ginseng, stored at 25°C in air of low humidity, showed a marked decrease in the concentration of MGR from 1.19% to 0.63% but with an increase in the neutral ginsenosides from 1.12% to 1.53% after 0–9-month storage. The results indicated that MGR changed dynamically in P. ginseng with different extraction solvents, extraction methods and increasing storage time. The total ginsenosides was not only underestimated but also determined imprecisely by ignoring malonyl ginsenosides. On the basis of our results, we suggest that malonyl ginsenosides should be transformed into the corresponding neutral ginsenosides during sample preparation for quality control and evaluation of P. ginseng. Then the content of six neutral ginsenosides in samples was used as the true level of total ginsenosides. The results reported here might provide useful information for accurate evaluation and quality control of P. ginseng.

Characterization and identification of baccharane glycosides in Impatientis Semen by rapid-resolution liquid chromatography with electrospray ionization quadrupole time-of-flight tandem mass spectrometry

04 April 2012, 10:36:45

Publication year: 2012
Source:Journal of Pharmaceutical and Biomedical Analysis, Volumes 64–65
Yu Fu, Wen Gao, Jun-jie Yu, Jun Chen, Hui-jun Li, Ping Li
Baccharane glycosides represent a group of rare saponins in plant kingdom and have been regarded as chemical marker for quality control of Impatientis Semen. Based on the structural skeleton, the baccharane glycosides were classified into three types: hosenkol A, hosenkol B and hosenkol C type. In this study, a rapid-resolution liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (RRLC/ESI-Q-TOF MS/MS) was performed to investigate the fragmentation behaviours of baccharane glycosides from Impatientis Semen. In full scan mass spectrum, the accurate determination of molecular formula was obtained by the predominant ion [M+COO]⁻ in negative mode. In the MS/MS spectrum, fragmentation reactions of the [M+H]⁺ acquired in positive mode were recorded to provide abundant structural information on the aglycone and glycosyl moieties. The characteristic ion for hosenkol A and hosenkol B type glycosides was at m/z 399, while for hosenkol C type glycosides the diagnostic ion was at m/z 381. Neutral losses of monosaccharide, disaccharide, H2O and C3H4 were observed for stepwise structural characterization. As a result, 19 compounds including 9 target saponins and 10 non-target saponins were rapidly screened out in ethanol extract of Impatientis Semen, and 5 of them were found to be novel baccharane glycosides.

Analysis of cycloserine and related compounds using aqueous normal phase chromatography/mass spectrometry

04 April 2012, 10:36:45

Publication year: 2012
Source:Journal of Pharmaceutical and Biomedical Analysis, Volumes 64–65
Joseph J. Pesek, Maria T. Matyska, Andy Dang
A new approach is evaluated for the analysis of cycloserine, a strongly hydrophilic drug. The method utilized is aqueous normal phase chromatography with a silica hydride-based stationary phase and mass spectrometry for detection. The samples are analyzed to determine the number of components and they are identified when possible. In addition, the composition change is monitored with respect to time and sample solvent. Analyses using both gradient and isocratic conditions are presented. The repeatability of inter- and intraday analyses is also determined.

Comparative determination of sibutramine as an adulterant in natural slimming products by HPLC and HPTLC densitometry

04 April 2012, 10:36:45

Publication year: 2012
Source:Journal of Pharmaceutical and Biomedical Analysis, Volumes 64–65
Etil Ariburnu, Mehmet Fazli Uludag, Huseyin Yalcinkaya, Erdem Yesilada
A new validated method for the identification and quantification of the sibutramine was developed by HPTLC-densitometry at 225nm and advantages and disadvantages compared with HPLC-FLD at 225nm emission and 316nm excitation. Both methods were applied to the analysis of three natural slimming products in the market for the quantitative analysis of illegally added sibutramine. HPTLC separations were performed on (20cm×10cm) glass HPTLC plates coated with silica gel 60 F 254 using a mobile phase, n-hexane–acetone–ammonia (10:1:0.1, v/v/v). For HPLC analysis, a phenyl column (5.0μm, 150mm×4.6mm, i.d.) and an isocratic mobile phase of acetonitrile–water–formic acid (pH 3.0; 0.19M) (45:55:0.78, v/v/v) was used. The calibration curve area versus concentration was found to be linear in the range of 250–2000ng/spot⁻¹ and 5–200μg/ml for HPTLC and HPLC, respectively. Both methods were validated for accuracy, precision, linearity, selectivity, recovery and short term stability. As a conclusion, these methods were found to be useful for the routine analysis of illegally added sibutramine in the marketed products.

Risk analysis of analytical validations by probabilistic modification of FMEA

04 April 2012, 10:36:45

Publication year: 2012
Source:Journal of Pharmaceutical and Biomedical Analysis, Volumes 64–65
D.M. Barends, M.T. Oldenhof, M.J. Vredenbregt, M.J. Nauta
Risk analysis is a valuable addition to validation of an analytical chemistry process, enabling not only detecting technical risks, but also risks related to human failures. Failure Mode and Effect Analysis (FMEA) can be applied, using a categorical risk scoring of the occurrence, detection and severity of failure modes, and calculating the Risk Priority Number (RPN) to select failure modes for correction. We propose a probabilistic modification of FMEA, replacing the categorical scoring of occurrence and detection by their estimated relative frequency and maintaining the categorical scoring of severity. In an example, the results of traditional FMEA of a Near Infrared (NIR) analytical procedure used for the screening of suspected counterfeited tablets are re-interpretated by this probabilistic modification of FMEA. Using this probabilistic modification of FMEA, the frequency of occurrence of undetected failure mode(s) can be estimated quantitatively, for each individual failure mode, for a set of failure modes, and the full analytical procedure.

Importance of retention data from affinity and reverse-phase high-performance liquid chromatography on antitumor activity prediction of imidazoacridinones using QSAR strategy

04 April 2012, 10:36:45

Publication year: 2012
Source:Journal of Pharmaceutical and Biomedical Analysis, Volumes 64–65
Marcin Koba, Tomasz Bączek, Michał Piotr Marszałł
Quantitative structure–activity relationships (QSAR) studies for prediction of cytotoxic and antitumor activity of imidazoacridinones (IA) based on experimentally obtained high-performance liquid chromatography (HPLC) retention data and calculated parameters using computational (molecular modeling) medicinal chemistry methods were proposed. The RP-HPLC and affinity-HPLC chromatographic techniques with four diversified HPLC systems applying columns with octadecylsilanes (C18), phosphatidylcholine (IAM), as well as α1-glycoprotein (AGP) and albumin (HSA) were used for the determination of the retention constants log k and log k w which characterize lipophilicity and protein affinity of IA. Moreover, molecular modeling studies were performed using HyperChem and Dragon software's, and structural descriptors were calculated and subsequently used. The QSAR equations using multiple linear regression (MLR) analysis method were derived which indicated that in vivo antileukemia activity of IA depends on cytotoxic activity against leukemia cells, whereas this cytotoxic activity depends on log k and log k w parameters obtained on all HPLC systems. Moreover, the QSRR equations were derived and indicated that log k and log k w parameters depend on calculated non-empirical structural parameters. The predictive power of obtained QSAR and QSRR equations allowed the prediction of cytotoxic and antitumor activity of IA and also their HPLC retention parameters. Finally, the equations can be used for prediction of antileukemia activity of IA without the necessity of carrying out experimental measurements. 

SFT Introduces an Improved Supercritical Fluid Extractor

Supercritical Fluid Technologies (SFT) introduces a new bench top supercritical fluid extractor (SFE), the model SFT-110XW. This latest addition to the SFE product line builds upon the strengths of its popular predecessors, the SFT-100 and SFT-100XW. The completely redesigned restrictor valve with integrated micrometer allows for very precise flow control, which is essential for demanding applications. A completely removable oven lid and large side panel allow the user easy access to the high pressure vessel(s). An indicator light on the SFT-10 pump module alerts the user to proper operation of the Peltier pre-cooler, ensuring CO2 is maintained in the liquid state. A robust outlet from the restrictor ensures that users will not accidently damage the outlet tube when inserting it into the collection container.  Extraction vessels up to 500 ml, single or dual configurations, afford maximum versatility. 

Supercritical fluid extraction has become a popular alternative to traditional extraction methods that use organic solvents. Fast, efficient extraction of a variety of materials may be achieved using supercritical carbon dioxide. The SFT-110XW SFE is well suited for both research and process development applications. Precise control of temperature, pressure, and flow rate is essential for successful, reproducible extractions. The use of dual sapphire syringe pump technology, integrated pre-heaters, and precise flow control provides the precision required to achieve these goals. Process parameters developed in the laboratory are the key to the successful scale-up to pilot or production scale equipment.

For more information, please call us at 302-738-3420 or visit us on-line at www.supercriticalfluids.com.

Determination of organic carbon and nitrogen in marine sediment

An optimized technique for direct determination of organic carbon and nitrogen in marine sediment is now available from Exeter Analytical Inc.

The filter based technique, using an Exeter Analytical Model 440 CHN Elemental Analyzer, provides rapid and routine analysis of marine sediment. Results are expressed in micrograms of Carbon and Nitrogen detected simplifying the calculation process. Analytical sensitivity is less than 1 microgram.

As the Model 440 provides complete control over combustion parameters it is able to reproducibly achieve 100% combustion with the widest range of sediment samples. Proprietary Nitrogen analysis software uniquely enables accurate measurement of low Nitrogen levels (in the 0.1-0.2% range) with a high degree of accuracy.

The Model 440 is a static combustion system, with a unique horizontal furnace design, which enables easy removal of filter and sample ash between each sediment analysis.  Consequently one combustion tube will analyze in excess of 1000 sediment samples without the need for removal and cleaning.  In addition the Model 440 provides the capacity to process filters up to 47 mm in diameter in one analytical cycle.  By comparison other elemental analyzers, employing vertical furnace designs, will require cleaning after as little as 20 samples. Further, larger filters have to be sub sampled several times and corrective calculations made to enable analysis.  The gas flow characteristics of the Model 440 analyzer are superior to other elemental analyzers due to the effective elimination of troublesome residue build-up. This thereby provides longer-term calibration stability as well as enhanced accuracy and precision for measured sample data.

For further information please contact Exeter Analytical on +1-978-251-1411 / +44-2476-323223 (in Europe) or email sales@eai1.com.  

Just Published: Journal of Analytical and Applied Pyrolysis

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:

Journal of Analytical and Applied Pyrolysis
http://rss.sciencedirect.com/publication/science/5247

Selected papers from the latest issue:

Mathematical modeling of rubber tire pyrolysis

02 April 2012, 12:04:40

Publication year: 2012
Source:Journal of Analytical and Applied Pyrolysis, Volume 95
Augustine Quek, Rajasekhar Balasubramanian
This article provides a critical review of past efforts over the last three decades at modeling the pyrolysis and gas activation of waste tires. The various forms of the Arrhenius kinetic rate equation as well as other forms of mathematical descriptions related to pyrolysis of waste tires are reviewed. In addition to reaction kinetics, other aspects of the tire pyrolysis such as heat and mass transfer, and reactor-specific models are also reviewed. Both one-step/component and multi-step/component pyrolysis models are discussed in the review. The multi-component models are based on the actual chemical components such as natural rubber and other additives. Kinetic constants reported in the literature are also analyzed.

Efficient preparation of carbon papers by pyrolysis of iodine-treated Japanese paper

02 April 2012, 12:04:40

Publication year: 2012
Source:Journal of Analytical and Applied Pyrolysis, Volume 95
Mutsumasa Kyotani, Satoshi Matsushita, Shin-ichi Kimura, Kazuo Akagi
A novel carbon paper has been prepared by pyrolysis from traditional Japanese paper called washi in Japan, which is mainly composed of cellulose microfibers. The washi was iodine-treated before pyrolysis. The effect of iodine-treatment on pyrolysis of the washi was investigated using thermogravimetric analysis. The structural and electrical properties of the carbon papers were also investigated using Raman scattering, X-ray diffraction, electron microscopy, and resistivity measurements. The iodine-treatment prevents cellulose from thermally decomposing and is effective in increasing the carbon yield and retaining its fibrillar structure. Porous carbon papers consisting of many micro and nanofibrils were prepared by the pyrolysis of the iodine-treated washi at 800°C. Those prepared at 800°C and then heat-treated at higher temperatures than 1800°C show electrical conductivities of 3Scm⁻¹ and 24–27Scm⁻¹. The degree of crystallinity and the electrical conductivity of the papers are improved by the heat treatment at higher temperatures.

BET, TG–DTG, FT-IR, SEM, iodine number analysis and preparation of activated carbon from acorn shell by chemical activation with ZnCl2

02 April 2012, 12:04:40

Publication year: 2012
Source:Journal of Analytical and Applied Pyrolysis, Volume 95
Cafer Saka
Activated carbons were produced from acorn shell by chemical activation with zinc chloride (ZnCl2) at 600°C in N2 atmosphere and their characteristics were investigated. The effects of activation temperature, duration time, impregnation concentration of agent and impregnation time were examined. Adsorption capacity was demonstrated with BET and iodine number. The obtained activated carbons were characterized by measuring their porosities and pore size distributions. BET surface area of the best produced activated carbon was 1289m²/g. The surface chemical characteristics of activated carbons were determined by FT-IR spectroscopic method. The microstructure of the produced activated carbons was examined by scanning electron microscopy (SEM). Thermal gravimetry (TG) and derivative thermal gravimetry (DTG) analysis of produced activated carbon was carried out.

Synthesis of nanosized rubidium ferrite by thermolysis of ferricarboxylate precursors and combustion method

02 April 2012, 12:04:40

Publication year: 2012
Source:Journal of Analytical and Applied Pyrolysis, Volume 95
Manik Gupta, Balwinder S. Randhawa
Nanosized pure rubidium ferrites have been successfully prepared by thermal decomposition of rubidium hexa(carboxylato)ferrate(III) precursors, Rb3[Fe(L)6]·xH2O (L=formate, acetate, propionate, butyrate), in flowing air atmosphere from ambient temperature to 1000°C. Various physico-chemical techniques i.e. simultaneous TG–DTG–DTA, XRD, Transmission Electron Microscope (TEM), IR and Mössbauer spectroscopy etc. have been employed to characterize the intermediates and end products. After dehydration, the anhydrous precursors undergo exothermic decomposition to yield various intermediates i.e. rubidium carbonate/acetate/propionate/butyrate and α-Fe2O3. A subsequent decomposition of these intermediates, followed by solid state reaction, lead to the formation of nanosized rubidium ferrite (RbFeO2). The same nano-ferrite has also been prepared by the combustion method at a comparatively lower temperature and in less time than that of the conventional ceramic method (>1200°C).

Characterization of the different fractions obtained from the pyrolysis of rope industry waste

02 April 2012, 12:04:40

Publication year: 2012
Source:Journal of Analytical and Applied Pyrolysis, Volume 95
Marta Andrade, José B. Parra, Marta Haro, Ana S. Mestre, Ana P. Carvalho, Conchi O. Ania
A study of the possibilities of pyrolysis for recovering wastes of the rope's industry has been carried out. The pyrolysis of this lignocellulosic residue started at 250°C, with the main region of decomposition occurring at temperatures between 300 and 350°C. As the reaction temperature increased, the yields of pyrolyzed gas and oil increased, yielding 22wt.% of a carbonaceous residue, 50wt.% tars and a gas fraction at 800°C. The chemical composition and textural characterization of the chars obtained at various temperatures confirmed that even if most decomposition occurs at 400°C, there are some pyrolytic reactions still going on above 550°C. The different pyrolysis fractions were analyzed by GC–MS; the produced oil was rich in hydrocarbons and alcohols. On the other hand, the gas fraction is mainly composed of CO2, CO and CH4. Finally, the carbonaceous solid residue (char) displayed porous features, with a more developed porous structure as the pyrolysis temperature increased.

Chemical composition of bio-oil produced by co-pyrolysis of biopolymer/polypropylene mixtures with K2CO3 and ZnCl2 addition

02 April 2012, 12:04:40

Publication year: 2012
Source:Journal of Analytical and Applied Pyrolysis, Volume 95
Piotr Rutkowski
The chemical composition of liquid products of cellulose and lignin co-pyrolysis with polypropylene at 450°C with and without the potassium carbonate or zinc chloride as an catalyst was investigated. The yield of liquid products of pyrolysis was in the range of 26–45wt% and their form was liquid or semi-solid highly depending on the composition of sample and pyrolysis conditions. The potassium carbonate and zinc chloride addition to blends has also influenced the range of samples decomposition as well as the chemical composition of resulted bio-oils. All bio-oils from biopolymer and polypropylene mixtures were three-phase (water, oil and solid). While zinc chloride acted as catalyst, all bio-oils obtained from biopolymer and polypropylene mixtures were yellow liquids with well-separated water and oil phases. All analyses proved that the structure and quality of bio-oil strongly depends on both the composition of the blend and the presence of the additive. The FT-IR and GC–MS analyses of oils showed that oxygen functionalities and hydrocarbons contents highly depend on the composition of biomass/polypropylene mixture. Results confirmed the significant removal and/or transformation of oxygen containing organic compounds, i.e. levoglucosan, 1,6-anhydro-β-d-glucofuranose and phenol derivatives due to the zinc chloride presence during pyrolysis process. All analyses showed that zinc chloride as catalyst was generally much more effective for removal of hydroxyl and methoxy groups than was potassium carbonate. It was demonstrated in this study that catalysts used in present work lead to the increased char yield and improved the fuel quality of bio-oil.

High-pressure pyrolysis of n-heptane: Effect of initiators

02 April 2012, 12:04:40

Publication year: 2012
Source:Journal of Analytical and Applied Pyrolysis, Volume 95
Jyoti Prasad Chakraborty, Deepak Kunzru
Pyrolysis of n-heptane was carried out in a tubular reactor, in presence of three initiators viz., di-tert-butyl peroxide (DTBP), diisopropylamine (DIPA) and triethylamine (TEA), in the temperature range of 773–953K, pressure range of 0.1–2.93MPa and mole ratio of 0.005–0.03mole initiator per mole of n-heptane. Influence of temperature, pressure and space time on the conversion and product distribution was studied. All the initiators increased the conversion. This was primarily due to the initiative release of organic radicals after breaking of the weak CN or OO bonds. The product distribution was marginally affected, especially at low conversions. TEA was found out to be the best initiator and the kinetic parameters for n-heptane pyrolysis in the presence of TEA (mole ratio 0.03) were determined at 2.93MPa and 773–813K. The activation energy and pre-exponential factors, determined using a non-linear optimization technique, were 156.8kJmol⁻¹ and 1.01×10⁹ s⁻¹, respectively.

Effects of heat treatment on physicochemical properties of cerium based nickel system

02 April 2012, 12:04:40

Publication year: 2012
Source:Journal of Analytical and Applied Pyrolysis, Volume 95
N.M. Deraz
Cerium based nickel catalysts synthesized by impregnation method have been characterized by XRD and TEM techniques. These catalysts can be described as a mixture of nickel oxide and ceria modified by the insertion of a part of nickel in the ceria lattice. The surface and catalytic properties of Ni/Ce mixed oxide solids were determined by nitrogen adsorption at 77K and catalytic conversion of isopropanol at different temperatures. The results revealed that the heat treatment brought about different modifications in the structural, morphological, surface and catalytic properties of the as synthesized catalysts. From the characterization of the as prepared catalysts, it was concluded that the as prepared catalysts contain highly dispersed NiO, well crystalline NiO and CeO2 and also Ni–Ce–O solid solution. This treatment led to a slightly increase in the crystallite size of ceria particles. On the other hand, the increase in the heat treatment resulted in an increase in the crystallite size, lattice constant and unit cell volume of nickel oxide. The formation of Ni–Ce–O solid solution with subsequent creation of oxygen vacancies increase as the heat treatment increases. However, the specific surface area, total pore volume and catalytic activity of the investigated system decrease as the preparation temperature increases from 500 to 700°C. The sintering activation energy of NiO and ceria were found to be 2.8 and 12.7kJ/mol, respectively.

Synergistic effects on co-pyrolysis of lignite and high-sulfur swelling coal

02 April 2012, 12:04:40

Publication year: 2012
Source:Journal of Analytical and Applied Pyrolysis, Volume 95
Jinxia Fei, Jie Zhang, Fuchen Wang, Jie Wang
Co-pyrolysis of a lignite coal and a bituminous coal was carried out on a fixed-bed reactor. The lignite was enriched with calcium, and the bituminous coal featured in high sulfur and strong swelling. Experiments were also conducted for the blends using the acid-washed lignite and/or the acid washed bituminous coal to address the influences of calcium in the lignite on the synergistic behaviors. Calcium in the lignite exhibited some aspects of synergy including the catalytic cracking reactions of tar, the retention of sulfur in the char, and the catalyzed polyaromatization and gasification of char. These synergies impacted the differences in the product distribution and gas composition between the co-pyrolytic results and the additive ones. Moreover, there appeared to be a synergistic effect on the cross-linking reaction of volatile matter, resulting in an increase in the char yield irrespective of coal demineralization. The co-pyrolysis was also observed to destroy the swelling of coal. This synergistically increased the tar yield due to less resistant escaping of tar from the intra-particles of coal.

Effects of phosphoric acid as additive in the preparation of activated carbon fibers from poly(p-phenylene benzobisoxazole) by carbon dioxide activation

02 April 2012, 12:04:40

Publication year: 2012
Source:Journal of Analytical and Applied Pyrolysis, Volume 95
M. Beatriz Vázquez-Santos, Amelia Martínez-Alonso, Juan M.D. Tascón
Poly(p-phenylene benzobisoxazole) (PBO) was impregnated with small amounts of H3PO4, and the effects of this additive on the porosity and other characteristics of chars and activated carbon fibers (ACFs) derived from this polymer were investigated. To this end, PBO-AS impregnated with 5, 10 or 15wt.% H3PO4 was pyrolyzed at 850°C, and the resulting chars were physically activated with carbon dioxide at 800°C to different burn-off (BO) degrees. Thermal analysis techniques only detected minor effects of H3PO4 on PBO pyrolysis. The char yield and char reactivity towards CO2 increased following PBO-AS impregnation with H3PO4. Structural (X-ray diffraction), porous textural (CO2 adsorption) and surface chemical (temperature-programmed desorption, X-ray photoelectron spectroscopy) characterizations of the pyrolysis chars indicated that the increase in char reactivity is probably associated with a higher content of oxygenated functionalities. Following CO2 activation, the surface area and pore volume of the obtained ACFs chiefly depended on the BO degree, but impregnation with H3PO4 restricted the pore size to the micropore and narrow mesopore range, thus producing adsorbents with a slightly narrower pore size distribution than in the absence of H3PO4. The results are compared with those previously obtained under equivalent conditions with other high-crystallinity polymers as precursors for ACFs. 

Training Courses in Laboratory Freeze Drying

SP Scientific has announced new Summer and Fall 2012 dates for its popular hands-on laboratory training courses in freeze drying and cycle optimization techniques.

The training courses, due to take place in June and October 2012, will focus upon the freeze drying process from formulation and thermal analysis to cycle development and optimization, packaging and troubleshooting.

The course director is Dr. Jeff Schwegman and equipment demonstration and use is provided by industry experts  including TA Instruments, McCrone Microscopes and Metrohm. The new extended 4-day training courses have been designed to enable people involved with lyophilisation, at all levels of experience, to gain considerable benefit and to reinforce their classroom training with extensive laboratory work.

The training will be held in the newly designed Warminster, PA laboratory on June 5-8th and October 23rd-26th. In order to provide the best possible learning experience, the course is limited to approximately 16 attendees. For further information or to reserve a place, please visit www.spscientific.com/LabTraining or contact SP Scientific on +1-845-255-5000 x2445 / cindy.reiter@spscientific.com.