Relative Error (relative + error)

Distribution by Scientific Domains


Selected Abstracts


Elimination Procedure as a Novel and Promising Mathematical Approach in Voltammetric Methods

ELECTROANALYSIS, Issue 17-18 2010
Nuria Serrano
Abstract In the contribution, it has been demonstrated that Elimination Voltammetry with Linear Scan (EVLS) introduces an enhancement of the linear sweep and/or cyclic voltammetric results, and provides information about the type of the currents involved in the considered process. An extension of EVLS has been developed for any combination of scan rates (integers) for six elimination functions that are capable of conserving or eliminating of some voltammetric current components. Simple procedure to obtain the necessary coefficients from the chosen scan rates has been reported. In addition, the calculation and discussion of the relative error of elimination function (REEF) have been presented. The verification of the presented calculations has been done by studying different ratios of scan rates for reduction and oxidation processes of Cd(II) at a hanging mercury drop electrode (HMDE). [source]


Heavy Metals in Matrices of Food Interest: Sequential Voltammetric Determination at Trace and Ultratrace Level of Copper, Lead, Cadmium, Zinc, Arsenic, Selenium, Manganese and Iron in Meals

ELECTROANALYSIS, Issue 18 2004
Clinio Locatelli
Abstract The voltammetric methods are very suitable and versatile techniques for the simultaneous metal determination in complex matrices. The present work, regarding the sequential determination of Cu(II), Pb(II), Cd(II), Zn(II) by square-wave anodic stripping voltammetry (SWASV), As(III), Se(IV) by square-wave cathodic stripping voltammetry (SWCSV) and Mn(II), Fe(III) by square-wave voltammetry (SWV) in matrices involved in foods and food chain as wholemeal, wheat and maize meal, are an interesting example of the possibility to sequentially determine each single element in real samples. Besides the set up of the analytical method, particular attention is aimed either at the problem of possible signal interference or to show that, using the peak area Ap as instrumental datum, it is possible to achieve lower limits of detection. The analytical procedure was verified by the analysis of the standard reference materials: Wholemeal BCR-CRM 189, Wheat Flour NIST-SRM 1567a and Rice Flour NIST-SRM 1568a. Precision, as repeatability, and accuracy, expressed as relative standard deviation and relative error, respectively, were lower than 6% in all cases. In the presence of reciprocal interference, the standard addition method considerably improved the resolution of the voltammetric technique. Once set up on the standard reference materials, the analytical procedure was transferred and applied to commercial meals sampled on market for sale. A critical comparison with spectroscopic measurements is also discussed. [source]


Surface deformation due to loading of a layered elastic half-space: a rapid numerical kernel based on a circular loading element

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2007
E. Pan
SUMMARY This study is motivated by a desire to develop a fast numerical algorithm for computing the surface deformation field induced by surface pressure loading on a layered, isotropic, elastic half-space. The approach that we pursue here is based on a circular loading element. That is, an arbitrary surface pressure field applied within a finite surface domain will be represented by a large number of circular loading elements, all with the same radius, in which the applied downwards pressure (normal stress) is piecewise uniform: that is, the load within each individual circle is laterally uniform. The key practical requirement associated with this approach is that we need to be able to solve for the displacement field due to a single circular load, at very large numbers of points (or ,stations'), at very low computational cost. This elemental problem is axisymmetric, and so the displacement vector field consists of radial and vertical components both of which are functions only of the radial coordinate r. We achieve high computational speeds using a novel two-stage approach that we call the sparse evaluation and massive interpolation (SEMI) method. First, we use a high accuracy but computationally expensive method to compute the displacement vectors at a limited number of r values (called control points or knots), and then we use a variety of fast interpolation methods to determine the displacements at much larger numbers of intervening points. The accurate solutions achieved at the control points are framed in terms of cylindrical vector functions, Hankel transforms and propagator matrices. Adaptive Gauss quadrature is used to handle the oscillatory nature of the integrands in an optimal manner. To extend these exact solutions via interpolation we divide the r -axis into three zones, and employ a different interpolation algorithm in each zone. The magnitude of the errors associated with the interpolation is controlled by the number, M, of control points. For M= 54, the maximum RMS relative error associated with the SEMI method is less than 0.2 per cent, and it is possible to evaluate the displacement field at 100 000 stations about 1200 times faster than if the direct (exact) solution was evaluated at each station; for M= 99 which corresponds to a maximum RMS relative error less than 0.03 per cent, the SEMI method is about 700 times faster than the direct solution. [source]


Approximate discharge for constant head test with recharging boundary

GROUND WATER, Issue 3 2005
Philippe Renard
The calculation of the discharge to a constant drawdown well or tunnel in the presence of an infinite linear constant head boundary in an ideal confined aquifer usually relies on the numerical inversion of a Laplace transform solution. Such a solution is used to interpret constant head tests in wells or to roughly estimate ground water inflow into tunnels. In this paper, a simple approximate solution is proposed. Its maximum relative error is on the order of 2% as compared to the exact analytical solution. The approximation is a weighted mean between the early-time and late-time asymptotes. [source]


A new approach using tissue optic theory to research the properties of organisms

HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 5 2008
Yan Zhang
Abstract Based on theories of tissue optics and artificial neural network, the relationship between the optical properties and biological parameters was studied, and a new experimental calculation method was derived. The properties of the organism were obtained indirectly by a black box model derived by self-study of the artificial neural network between optical parameters and thermo-physical parameters. The results calculated from the black box have an average relative error between ,5% and 5% when compared with the actual values, which verifies the neural network method's feasibility for the measurement of parameters in other domains. ©2008 Wiley Periodicals, Inc. Heat Trans Asian Res, 37(5): 283,289, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20207 [source]


Streamflow estimation using optimal regional dependency function

HYDROLOGICAL PROCESSES, Issue 25 2009
Abdüsselam Altunkaynak
Abstract The determination of spatial dependency of regionalized variable (ReV) is important in engineering studies. Regional dependency function that leads to calculation of weighting coefficients is required in order to make regional or point-wise estimations. After obtaining this dependency function, it is possible to complete missing records in the time series and locate new measurement station. Also determination of regional dependency function is also useful to understand the regional variation of ReV. Point Cumulative Semi-Variogram (PCSV) is another methodology to understand the regional dependency of ReV related to the magnitude and the location. However, this methodology is not useful to determine the weighting coefficient, which is required to make regional and point-wise estimations. However, in Point Semi-Variogram (PSV) proposed here, weighting coefficient depends on both magnitude and location. Although the regional dependency function has a fluctuating structure in PSV approach, this function gradually increases with distance in PCSV. The study area is selected in Mississippi river basin with 38 streamflow stations used for PCSV application before. It is aimed to compare two different geostatistical models for the same data set. PSV method has an ability to determine the value of variable along with optimum number of neighbour stations and influence radius. PSV and slope PSV approaches are compared with the PCSV. It was shown that slope slope point semi-variogram (SPSV) approaches had relative error below 5%, and PSV and PCSV methods revealed relative errors below 10%. Copyright © 2009 John Wiley & Sons, Ltd. [source]


A stopping criterion for the conjugate gradient algorithm in the framework of anisotropic adaptive finite elements

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 4 2009
M. Picasso
Abstract We propose a simple stopping criterion for the conjugate gradient (CG) algorithm in the framework of anisotropic, adaptive finite elements for elliptic problems. The goal of the adaptive algorithm is to find a triangulation such that the estimated relative error is close to a given tolerance TOL. We propose to stop the CG algorithm whenever the residual vector has Euclidian norm less than a small fraction of the estimated error. This stopping criterion is based on a posteriori error estimates between the true solution u and the computed solution u (the superscript n stands for the CG iteration number, the subscript h for the typical mesh size) and on heuristics to relate the error between uh and u to the residual vector. Numerical experiments with anisotropic adaptive meshes show that the total number of CG iterations can be divided by 10 without significant discrepancy in the computed results. Copyright © 2008 John Wiley & Sons, Ltd. [source]


Some finite difference methods for a kind of GKdV equations

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 3 2007
X. Lai
Abstract In this paper, some finite difference schemes I, II, III and IV, are investigated and compared in solving a kind of mixed problem of generalized Korteweg-de Vries (GKdV) equations especially the relative errors. Both the numerical dispersion and the numerical dissipation are analysed for the constructed difference scheme I. The stability is also obtained for scheme I and the constructed predictor,corrector scheme IV by using a linearized stability method. Other two schemes, II and III, are also included in the comparison among these four schemes for the numerical analysis of different GKdV equations. The results enable one to consider the relative error when dealing with these kinds of GKdV equations. Copyright © 2006 John Wiley & Sons, Ltd. [source]


Numerical study of the effectivity index for an anisotropic error indicator based on Zienkiewicz,Zhu error estimator

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 1 2003
M. Picasso
Abstract The framework of Formaggia and Perotto (Numerische Mathematik 2001; 89: 641,667) is considered to derive a new anisotropic error indicator for a Laplace problem in the energy norm. The matrix containing the error gradient is approached using a Zienkiewicz,Zhu error estimator. A numerical study of the effectivity index is proposed for anisotropic unstructured meshes, showing that our indicator is sharp. An anisotropic adaptive algorithm is implemented, aiming at controlling the estimated relative error. Copyright © 2003 John Wiley & Sons, Ltd. [source]


Repetitive control of synchronized operations for process applications

INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 4 2007
James D. Ratcliffe
Abstract Repetitive control (RC) algorithms for a plant, which contain pairs of complex conjugate poles at low frequency, resulting in a resonant system, is the subject area of this paper where the experimental results given are for a gantry robot and conveyor system in which the gantry is required to transfer payloads to a constant velocity conveyor by performing a repeating ,pick and place' operation. Initially, the gantry robot is controlled by means of a PID feedback controller in parallel with a proportional (P-type) repetitive feed-forward loop, while the conveyor operates under proportional feedback control. It is found that the RC system is unable to achieve long-term performance. The performance degrades within a relatively small number of repetitions due to the build up of resonant frequencies in the learning loop. To prevent this, a batch aliasing technique, originally developed for iterative learning control, is modified to work in the RC framework, and is implemented in real-time. The superior performance potential of the aliasing system is demonstrated experimentally. In the second part of this paper, multi-machine systems, are considered where the critical new factor is the relative error between the conveyor and the robot. Here a second supervisory learning loop is proposed for use to shift the reference trajectory of one machine so that the relative placement error is also reduced. Again, supporting experimental results are given. Copyright © 2006 John Wiley & Sons, Ltd. [source]


Kinetics and mechanisms of transalkylation and disproportionation of meta -diethylbenzene by triflic acid catalyst

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 11 2003
S. M. Al-Zahrani
The kinetics of transalkylation and isomerization of meta -diethylbenzene in the presence of benzene using triflic acid as a catalyst has been investigated. High catalytic activity of the triflic acid catalyst was observed in homogeneous liquid-phase reactions. On the basis of the product distribution obtained, transalkylation, disproportionation, and isomerization reactions have been considered and the main product of the reaction was ethylbenzene. These reactions are conducted in a closed liquid batch reactor with continuous stirring under dry nitrogen and atmospheric pressure over the temperature range of 288,308 K. The main transalkylation, disproportionation, and isomerization reactions occurred simultaneously and were considered as elementary reactions. The apparent activation energy of the transalkylation reaction was found to be 35.5 kJ/mol, while that of disproportionation reaction was 42.3 kJ/mol. The reproducibility of the experimental product distribution occurred with an average relative error of ±2%. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 555,563, 2003 [source]


Application of different training methodologies for the development of a back propagation artificial neural network retention model in ion chromatography

JOURNAL OF CHEMOMETRICS, Issue 2 2008
Tomislav Bolan
Abstract The reliability of predicted separations in ion chromatography depends mainly on the accuracy of retention predictions. Any model able to improve this accuracy will yield predicted optimal separations closer to the reality. In this work artificial neural networks were used for retention modeling of void peak, fluoride, chlorite, chloride, chlorate, nitrate and sulfate. In order to increase performance characteristics of the developed model, different training methodologies were applied and discussed. Furthermore, the number of neurons in hidden layer, activation function and number of experimental data used for building the model were optimized in terms of decreasing the experimental effort without disruption of performance characteristics. This resulted in the superior predictive ability of developed retention model (average of relative error is 0.4533%). Copyright © 2008 John Wiley & Sons, Ltd. [source]


Modified calculations of hydrocarbon thermodynamic properties

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 5 2006
Min Hsien Liu
Abstract A test set of 65 hydrocarbons was examined to elucidate theoretically their thermodynamic properties by performing the density-functional theory (DFT) and ab initio calculations. All the calculated data were modified using a three-parameter calibration equation and the least-squares approach, to determine accurately enthalpies of formation (,Hf), entropies (S), and heat capacities (Cp). Calculation results demonstrated that the atomization energies of all compounds exhibited an average absolute relative error ranging between 0.11, 0.13%, and an ,Hf of formation with a mean absolute absolute error (M.|A.E.|) ranging from only 5.7,6.8 kJ/mol (1.3,1.6 kcal/mol) (i.e., those results correlated with those of Dr. Herndon's 1.1 kcal/mol). Additionally, the entropy ranged from 3.5,4.2 J/mol K (0.8,1.0 cal/mol K) M.|A.E.|; a heat capacity between 2.3,2.9 J/mol K (0.5,0.7 cal/mol K) M.|A.E.| was obtained as well. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 537,544, 2006 [source]


NEURAL NETWORK MODELING OF END-OVER-END THERMAL PROCESSING OF PARTICULATES IN VISCOUS FLUIDS

JOURNAL OF FOOD PROCESS ENGINEERING, Issue 2010
YANG MENG
ABSTRACT Modeling of the heat transfer process in thermal processing is important for the process design and control. Artificial neural networks (ANNs) have been used in recent years in heat transfer modeling as a potential alternative to conventional dimensionless correlation approach and shown to be even better performers. In this study, ANN models were developed for apparent heat transfer coefficients associated with canned particulates in high viscous Newtonian and non-Newtonian fluids during end-over-end thermal processing in a pilot-scale rotary retort. A portion of experimental data obtained for the associated heat transfer coefficients were used for training while the rest were used for testing. The principal configuration parameters were the combination of learning rules and transfer functions, number of hidden layers, number of neurons in each hidden layer and number of learning runs. For the Newtonian fluids, the optimal conditions were two hidden layers, five neurons in each hidden layer, the delta learning rule, a sine transfer function and 40,000 learning runs, while for the non-Newtonian fluids, the optimal conditions were one hidden layer, six neurons in each hidden layer, the delta learning rule, a hyperbolic tangent transfer function and 50,000 learning runs. The prediction accuracies for the ANN models were much better compared with those from the dimensionless correlations. The trained network was found to predict responses with a mean relative error of 2.9,3.9% for the Newtonian fluids and 4.7,5.9% for the non-Newtonian fluids, which were 27,62% lower than those associated with the dimensionless correlations. Algebraic solutions were included, which could be used to predict the heat transfer coefficients without requiring an ANN. PRACTICAL APPLICATIONS The artificial neural network (ANN) model is a network of computational elements that was originally developed to mimic the function of the human brain. ANN models do not require the prior knowledge of the relationship between the input and output variables because they can discover the relationship through successive training. Moreover, ANN models can predict several output variables at the same time, which is difficult in general regression methods. ANN concepts have been successfully used in food processing for prediction, quality control and pattern recognition. ANN models have been used in recent years for heat transfer modeling as a potential alternative to conventional dimensionless correlation approach and shown to be even better performers. In this study, ANN models were successfully developed for the heat transfer parameters associated with canned particulate high viscous Newtonian and non-Newtonian fluids during an end-over-end rotation thermal processing. Optimized configuration parameters were obtained by choosing appropriate combinations of learning rule, transfer function, learning runs, hidden layers and number of neurons. The trained network was found to predict parameter responses with mean relative errors considerably lower than from dimensionless correlations. [source]


Development and validation of a liquid chromatographic/electrospray ionization mass spectrometric method for the quantitation of prazepam and its main metabolites in human plasma

JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 4 2005
Paraskevi Valavani
Abstract A method was developed and fully validated for the quantitation of prazepam and its major metabolites, oxazepam and nordiazepam, in human plasma. Sample pretreatment was achieved by solid-phase extraction using Oasis HLB cartridges. The extracts were analysed by high-performance liquid chromatography (HPLC) coupled with single-quadrupole mass spectrometry (MS) with an electrospray ionization interface. The MS system was operated in the selected ion monitoring mode. HPLC was performed isocratically on a reversed-phase XTerra MS C18 analytical column (150 × 3.0 mm i.d., particle size 5 µm). Diazepam was used as the internal standard for quantitation. The assay was linear over a concentration range of 5.0,1000 ng ml,1 for all compounds analyzed. The limit of quantitation was 5 ng ml,1 for all compounds. Quality control samples (5, 10, 300 and 1000 ng ml,1) in five replicates from three different runs of analysis demonstrated an intra-assay precision (CV) of ,9.1%, an inter-assay precision of ,6.0% and an overall accuracy (relative error) of <4.6%. The method can be used to quantify prazepam and its metabolites in human plasma covering a variety of pharmacokinetic or bioequivalence studies. Copyright © 2005 John Wiley & Sons, Ltd. [source]


Automated determination of venlafaxine in human plasma by on-line SPE-LC-MS/MS.

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 4 2009
Application to a bioequivalence study
Abstract A new automated SPE-LC-ESI-MS/MS method was developed and validated to quantify venlafaxine in human plasma using fluoxetine as an internal standard. The analytes were automatically extracted from plasma by C18 SPE cartridges, separated on a C8 RP column and analyzed by MS in the multiple reaction-monitoring (MRM) mode. The method has a chromatographic run time of 4.0 min and a linear calibration curve over the range of 0.25,200 ng/mL (r >0.997). The between-run precisions, based on the percent RSD for replicate quality controls (0.75; 80, and 200 ng/mL), were < 8.5% for all concentrations. The between-run accuracies, based on the percent relative error, were < 4.0%. This method was successfully employed in a bioequivalence study of two venlafaxine capsule formulations (test formulation from Eurofarma (Brazil) and Efexor XR, reference formulation, from Wyeth-Whitehall, Brazil) in 48 healthy volunteers of both sexes who received a single 150 mg dose of each formulation. More than 3000 samples were analyzed eliminating the analyst's exposure to hazardous organic solvents normally employed in off-line liquid,liquid extractions. The 90% confidence interval (CI) of the individual ratio geometric mean for Test/Reference was 91.6,103.4% for AUC0,48 h and 102.2,112.6% for Cmax. Since both 90% CI for AUC0,48 h and Cmax were included in the 80,125% interval proposed by the US Food and Drug Administration (FDA) and the Brazilian National Health Surveillance Agency (ANVISA), the test formulation was considered bioequivalent to Efexor XR according to both the rate and extent of absorption. [source]


Precision in differential field-flow fractionation: A chemometric study

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 16 2007
Letizia Bregola
Abstract In the present paper, the capabilities of differential field-flow fractionation, i. e., the determination of an incremental quantity of a colloidal species, e. g., an uptake adsorbed mass, determined by the joint use of two independent FFF measurements, over a species and the same modified species respectively, are considered. The different error types, those related to the retention time determinations and those coming from the operating parameter fluctuations were considered. The different components were computed with reference to SdFFF determinations of bare polystyrene (PS) submicronic particles and the same PS particles covered by IgG. Comparison was made between theoretically computed precision and experiments. The error coming from the experimental measurement of retention times was identified to be the main source of errors. Accordingly, it was possible to make explicit the detection limits and the confidence intervals of the adsorbed mass uptake, as a function of experimental quantities such as the retention ratio, the detector calibration ratio, the injected quantity, the baseline noise, and the void time relative error. An experimentally determined and theoretically foreseen dependence of both the experimental detection and confidence limits (, ± 10,17 g) on the square root of the injected concentration, for constant injected volume, was found. [source]


Accurate Prediction of , (Lower Critical Solution Temperature) in Polymer Solutions Based on 3D Descriptors and Artificial Neural Networks

MACROMOLECULAR THEORY AND SIMULATIONS, Issue 2-3 2008
Jie Xu
Abstract Quantitative structure-property relationships were studied between descriptors representing the three-dimensional structures of molecules and , (LCST, lower critical solution temperature) in polymer solutions with a database of 169 data containing 12 polymers and 67 solvents. Feed-forward artificial neural networks (ANNs) combined with stepwise multilinear regression analysis (MLRA) were used to develop the models. With ANNs, the squared correlation coefficient (R2) for , (LCST) of the training set of 112 systems is 0.9625, the standard error of estimation (SEE) is 13.43 K, and the mean relative error (MRE) is 1.99%; in prediction of , (LCST) using the test set of 57 systems, the MRE is 2.26%. With MLRA, the MREs for the training and test sets are 4.02% (R2,=,0.8739, SEE,=,25.88 K) and 5.05%, respectively. [source]


Particle Size of Pneumatically Conveyed Powders Measured Using Impact Duration

PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 6 2007
Peter J. Coghill
Abstract CSIRO Minerals has developed a technique for measuring particle size in pneumatically conveyed powders [1] by measurement of the acoustic waves produced by particle impacts upon a specially designed transducer. Previous work has focused on using the peak acoustic wave amplitude to determine particle size. This produces a spectrum that is hard to determine the particle size from, as the peak amplitude is a non-linear function of particle diameter, and is strongly affected by angle of incidence and velocity of the impacting particle. In this paper impact duration measurements are used to overcome these difficulties while retaining the advantages of being able to measure in high solids loadings of up to at least 0.5,kg/m3 of powder. In laboratory tests the impact size monitor's (ISM) results have been correlated with optical diffraction measurements of the mean (by number) powder size with a correlation coefficient of 0.985 and a relative error of 5.5,%. The ISM operated successfully in the laboratory at a loading of 0.5,kg/m3 of powder and measured particles down to 50,microns in size. [source]


Characterisation and cleaning of oxide support materials for cavity ring-down spectroscopy

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2010
Aras Kartouzian
Abstract Cavity ring-down spectroscopy (CRDS) has been applied to characterise different oxide materials (amorphous silica, borosilicate and yttria stabilised zirconia YSZ) which are suitable to be used as support material for size-selected metal clusters. The sensitivity of the spectroscopic method was improved by means of transversal mode matching and spatial filtering of the laser beam profile, reducing the relative error by 50%. The high sensitivity of CRDS allows the detection of trace amounts of impurities and defect sites in the samples, based on their absorption properties. In YSZ, traces of Nd have been detected. The optical quality of the substrates was determined qualitatively according to the measured optical losses. CRDS surface maps have been used to monitor the homogeneity of the support materials, and the influence of ion bombardment on the surface has been studied. It is shown that in the case of BK7® substrates, sputtering with low energy Ar+ ions could remove deposited gold clusters almost completely causing very low damage to the surface. These results were confirmed analytically. [source]


Development and validation of a liquid chromatographic/tandem mass spectrometric method for the determination of sertraline in human plasma

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 16 2006
Xiaoyan Chen
A sensitive and rapid liquid chromatographic/tandem mass spectrometric method was developed and validated for the determination of sertraline in human plasma. The analyte and internal standard (IS, diphenhydramine) were extracted with 3,mL of diethyl ether/dichloromethane (2:1, v/v) from 0.25,mL plasma, then separated on a Zorbax Eclipse XDB C18 column using methanol/water/formic acid (75:25:0.1, v/v/v) as the mobile phase. The triple quadrupole mass spectrometry was applied via an atmospheric pressure chemical ionization (APCI) source for detection. The fragmentation pattern of the protonated sertraline was elucidated with the aid of product mass spectra of isotopologous peaks. Quantification was performed using selected reaction monitoring of the transitions of m/z 306,,,159 for sertraline and m/z 256,,,167 for the IS. The method was linear over the concentration range of 0.10,100,ng/mL. The intra-day and inter-day precisions, expressed by relative standard deviation, were both less than 6.7%. Assay accuracies were within ±6.9% as terms of relative error. The lower limit of quantification (LLOQ) was identifiable and reproducible at 0.10,ng/mL with a precision of 8.3% and an accuracy of 9.6%. The validated method has been successfully applied for the pharmacokinetic study and bioequivalence evaluation of sertraline in 18 healthy volunteers after a single oral administration of 50,mg sertraline hydrochloride tablets. Copyright © 2006 John Wiley & Sons, Ltd. [source]


The accuracy and efficiency of alternative option pricing approaches relative to a log-transformed trinomial model

THE JOURNAL OF FUTURES MARKETS, Issue 6 2002
Hsuan-Chi Chen
This article presents a log-transformed trinomial approach to option pricing and finds that various numerical procedures in the option pricing literature are embedded in this approach with choices of different parameters. The unified view also facilitates comparisons of computational efficiency among numerous lattice approaches and explicit finite difference methods. We use the root-mean-squared relative error and the minimum convergence step to evaluate the accuracy and efficiency for alternative option pricing approaches. The numerical results show that the equal-probability trinomial specification of He (12) and Tian (25) and the sharpened trinomial specification of Omberg (21) outperform other lattice approaches and explicit finite difference methods. © 2002 Wiley Periodicals, Inc. Jrl Fut Mark 22:557,577, 2002 [source]


Viscosity models for New Zealand black liquor at low solids concentrations

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2010
S.B. Alabi
Abstract Availability of accurate models for prediction of the viscosity of black liquor (BL) from the chemical pulping of pine will facilitate its online monitoring and control and subsequently the optimisation of combustion in a recovery boiler. New Zealand (NZ) BL viscosity data are limited, and no predictive model is available. The viscosities of the NZ BL samples at solids concentrations (SCs) < 50% were obtained at temperature of 25,85 °C and shear rate up to ,2000 s,1. The samples showed Newtonian behaviour. Existing models from the literature and a binomial model developed in this work were used to fit the viscosity data as a function of SC and temperature. Accuracies of these models were examined for both the log-transformed and the untransformed viscosity data using coefficient of correlation (R) and maximum absolute relative error (MARE) (between the actual and predicted viscosities), respectively, as indices. Although the existing models fit NZ BL viscosity data well when they were log-transformed, they performed poorly when not transformed. Conversely, the new binomial model gave accurate predictions with both the log-transformed and untransformed viscosity data (R = 0.9997; MARE = 5.7%). It is concluded that at low SCs, the viscosity of Newtonian BL can be accurately predicted using the new binomial model. Copyright © 2010 Curtin University of Technology and John Wiley & Sons, Ltd. [source]


Equilibrium and heat of adsorption of phosphine on CaCl2 -modified molecular sieve

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009
Qiongfen Yu
Abstract Adsorption characteristics of the virgin and CaCl2 -immersed molecular sieves at 298 K were investigated to select the adsorbent with high adsorption capacity to phosphine. Adsorption isobars and adsorption isotherms over the phosphine partial pressure and temperature ranged 0 , 1000 Pa and 298 , 343 K were measured. The adsorption equilibrium data for phosphine at various temperatures were fitted to Langmuir and Freundlich isotherm models and their isosteric heats of adsorption were determined by the Clausius-Clapeyron equation. It was found the Freundlich was more suitable for description of phosphine adsorption process through calculating average absolute relative error, and the fitted result about Langmuir model showed the heterogeneous characteristics of modified adsorbent. The isosteric heat of adsorption was about 15 kJ/mol, which indicated adsorptive phosphine removal performance may be a dominant of physical adsorption being easy for desorption. The isosteric heat of adsorption decreased with an increase of the surface loading on CaCl2/5A, which means that CaCl2/5A molecular sieve had an energetically heterogeneous surface. The present study confirmed that the CaCl2/5A molecular sieves would be one of the candidates for separation and recycle of phosphine. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]


Determination of a hydrophilic paclitaxel derivative, 7-xylosyl-10-deacetylpaclitaxel in rat plasma by LC,MS/MS

BIOMEDICAL CHROMATOGRAPHY, Issue 5 2009
Shou Gang Jiang
Abstract A LC-MS/MS method for the determination of a hydrophilic paclitaxel derivative 7-xylosyl-10-deacetylpaclitaxel in rat plasma was developed to evaluate the pharmacokinetics of 7-xylosyl-10-deacetylpaclitaxel in the rats. 7-Xylosyl-10-deacetylpaclitaxel and docetaxel (IS for 7-xylosyl-10-deacetylpaclitaxel) were extracted from rat plasma with acetic ether and analyzed on a Hypersil C18 column (4.6 × 150 mm i.d., particle size 5 µm) with the mobile phase of ACN/0.05% formic acid (50:50, v/v). The analytes were detected using an ESI MS/MS in the multiple reaction monitoring mode. The standard curves for 7-xylosyl-10-deacetylpaclitaxel in plasma were linear (r >0.999) over the concentration range of 2.0,1000 ng/mL with a weighting of 1/concentration2. The method showed a satisfactory sensitivity (2.0 ng/mL using 50 µL plasma), precision (CV , 10.1%), accuracy (relative error ,12.4 to 12.0%), and selectivity. This method was successfully applied to the pharmacokinetic study of 7-xylosyl-10-deacetylpaclitaxel in rat plasma after intravenous administration of 7-xylosyl-10-deacetylpaclitaxel to female Wistar rats. Copyright © 2008 John Wiley & Sons, Ltd. [source]


Simultaneous clinical monitoring of lactic acid, pyruvic acid and ketone bodies in plasma as methoxime/tert-butyldimethylsilyl derivatives by gas chromatography,mass spectrometry in selected ion monitoring mode

BIOMEDICAL CHROMATOGRAPHY, Issue 5 2008
Man-Jeong Paik
Abstract Simultaneous determination of lactic acid, pyruvic acid, 3-hydroxybutyric acid and acetoacetic acid for clinical monitoring of lactic acidosis and ketone body formation in human plasma (20 µL) was performed by gas chromatography,mass spectrometry in selected ion monitoring (SIM) mode after generating methoxime/tert-butyldimethylsilyl derivatives. All of the targeted carboxylic acids were detected by characteristic fragment ions, which permitted sensitive and selective identification in the presence of co-extracted free fatty acids and other acidic metabolites at much higher levels. The method was linear (r , 0.9991), reproducible (% relative standard deviation = 1.2,5.8), and accurate (% relative error = ,7.2,7.6), with detection limits of 0.05,1.7 ng/mL. This rapid, accurate and selective method using minimal plasma samples (20 µL) is useful in the clinical monitoring of lactic acidosis and ketone body formation in plasma. Copyright © 2008 John Wiley & Sons, Ltd. [source]


Simple determination of pirfenidone in rat plasma via high-performance liquid chromatography

BIOMEDICAL CHROMATOGRAPHY, Issue 12 2006
Yongsheng Wang
Abstract A simple, rapid and reliable high-performance liquid chromatographic method was developed and validated for the determination of pirfenidone and its major metabolites in rat plasma. Plasma proteins were precipitated with perchloric acid (10%, v/v) and the supernatant after centrifugation was determined using high-performance liquid chromatography. The analysis was carried out on a Lichrospher C18 column (250 × 4.6 mm i.d., 5 µm). The mobile phase consisted of acetonitrile,water containing 0.2% acetic acid (23:77, v/v) at a flow-rate of 1 mL/min. The eluant was detected at 310 nm. The calibration curves were linear over a concentration range from 0.15 to 76.67 µg/mL. The accuracy (relative error) of the assay ranged from -2.6 to 7.9% and the precision (coefficient of variation) was less than 4.5%. The established method has been successfully applied to a pharmacokinetic study of pirfenidone following a single oral dose to rats. Copyright © 2006 John Wiley & Sons, Ltd. [source]


Determination and pharmacokinetic study of bergenin in rat plasma by RP-HPLC method

BIOMEDICAL CHROMATOGRAPHY, Issue 10 2006
Yan-Bin Shi
Abstract A validated reversed-phase high-performance liquid chromatographic (RP-HPLC) method was developed for the determination of bergenin in rat plasma. Bergenin in rat plasma was extracted with methanol, which also acted as a deproteinization agent. Chromatographic separation of bergenin was performed on a C18 column, with a mobile phase of methanol,water (22:78, v/v) at a flow-rate of 0.8 mL/min and an operating temperature of 40°C, and UV detection was set at 220 nm. The calibration curve was linear over the range 0.25,50 µg/mL (r = 0.9990) in rat plasma. The limit of quantification was 0.25 µg/mL using a plasma sample of 100 µL. The extraction recoveries were 83.40 ± 6.02, 81.49 ± 2.40 and 72.51 ± 2.64% at concentrations of 0.5, 5 and 50 µg/mL, respectively. The intra-day and inter-day precision and accuracy were validated by relative standard deviation (RSD%) and relative error (RE%), which were in the ranges 3.74,9.91 and ,1.6,8.0%. After intravenous administration to rats at the dose of 11.25 mg/kg, the plasma concentration,time curve of bergenin was best conformed to a two-compartment open model. The main pharmacokinetic parameters indicated that bergenin exhibited a wide distribution and moderate elimination velocity in rat. Copyright © 2006 John Wiley & Sons, Ltd. [source]


Determination of S -phenylmercapturic acid in human urine using an automated sample extraction and fast liquid chromatography-tandem mass spectrometric method

BIOMEDICAL CHROMATOGRAPHY, Issue 6-7 2006
Yinghe Li
Abstract S -phenylmercapturic acid is widely accepted as a specific biomarker for the evaluation of benzene exposure. Here, we describe a fast, specific and sensitive high-performance liquid achromatography coupled with tandem mass spectrometry (LC-MS/MS) method that has been developed and validated for the determination of S- phenylmercapturic acid in human urine. Isotope-labeled S- phenylmercapturic acid- d5 was used as internal standard to improve the method ruggedness. The fully automated solid-phase extraction method on a 96-well Oasis MAX (mix-mode anion exchange) plate was employed to clean up the urine samples before analysis. The rapid LC-MS/MS analysis of extracted samples was achieved on a Genesis C18 column with a run time of only 3 min. Negative electrospray ionization with multiple reaction monitoring (ESI-MRM) mode was used to detect S- phenylmercapturic acid (m/z 238 , 109) and S- phenylmercapturic acid - d5 (m/z 243 , 114). The method fulfils all the standard requirements of method validation. The calibration curve was linear within the concentration range 0.400,200 ng/mL. The method performed accurately and precisely in validation with <7.5% relative error and <6.5% relative standard deviation of quality control samples. The method efficacy was also verified by the analysis of urine samples from 12 smokers and 12 non-smokers. With the fully automated sample cleanup procedure and the fast LC-MS/MS analysis, a sample analysis throughput of 384 samples per day could be achieved. Copyright © 2006 John Wiley & Sons, Ltd. [source]


Determination of trimebutine maleate in rat plasma and tissues by using capillary zone electrophoresis

BIOMEDICAL CHROMATOGRAPHY, Issue 4 2001
Famei Li
A simple and rapid capillary zone electrophoresis method was developed for the determination of trimebutine maleate in rat plasma and tissues. Rat plasma and tissue homogenates were mixed with acetonitrile containing internal standard, ephedrine hydrochloride, and then centrifuged. The supernatant was dried under a stream of nitrogen, and the residue was reconstituted in methanol,water (1:1). The electrophoresis was performed in uncoated capillary with 30,mmol/L phosphate buffer of pH 6.0 as the separation electrolyte. The applied voltage was 10,kV and the UV detection was set at 214,nm. The peak height ratio vs concentration in plasma or homogenates was linear over the range of 5,500,ng/mL and the limit of quantitation was 5,ng/mL. The intra- and inter-day precision was RSD,<,14% and <15%. The accuracy was relative error (RE) within,±,14%. This method was applied to studying the pharmacokinetics and tissue distribution after a single dose of trimebutine maleate was administrated to the rats. The Tmax, AUC, Cmax and t1/2 were 30,min, 7.8,×,102 (ng/mL),min, 39,ng/mL and 1.7,×,102,min. The drug distribution was found in a decreasing order of liver, kidney, spleen, lung and heart. Copyright © 2001 John Wiley & Sons, Ltd. [source]