Previous Analytical Method Research Articles

Development and Performance Evaluation of a New Test Kit for Quantifying the Degree of DNA Fragmentation.

PCR-based genetic testing of agricultural products and foods is widely used for detecting various analytical targets such as genetically modified organisms and food allergens. However, it is difficult to obtain accurate genetic testing results from processed foods because DNA is fragmented by heat and pressure during food processing. Thus, we previously developed an analytical method to quantitatively evaluate the degree of DNA fragmentation for the purpose of QC of genetic testing for processed foods. Our previous analytical method requires four PCR primer sets, resulting in high reagent costs and heavy analytical workloads. Therefore, we attempted to develop an easy-to-use test kit for quantifying the degree of DNA fragmentation and to evaluate its analytical performance. To simplify the analysis procedure, we used only two primer sets. In addition, no-fragmentation control templates were prepared to obtain stable measurement results. The precision of the simplified analysis was evaluated through blind tests between laboratories. It was confirmed that plant species and extracted DNA concentrations had little effect on analysis with the newly developed test kit. In addition, the analytical values indicating the degree of DNA fragmentation exhibited small variability between laboratories. We confirmed the high practicality of the developed test kit. Because DNA fragmentation in cells is a universal phenomenon, we anticipate that the test kit will be used not only for QC of genetic testing but also for food testing, medical diagnostics, and other applications in a range of fields. The newly developed test kit enables quantitative evaluation of the degree of DNA fragmentation in a simple manner.

Accumulation and dietary risks of perfluoroalkyl substances in fish and shellfish: A market-based study in Barcelona

Since the 1940s, per- and polyfluoroalkyl substances (PFAS) have been widely produced and used in various applications due to their unique properties. Consequently, the principal exposure routes of PFAS have been broadly studied, leading to the conclusion that dietary exposure (more specifically, the consumption of fish and seafood) was one of their main contributors. Thus, developing an analytical method that determines the level of PFAS in fish and seafood has become a relevant subject. In this work, a previous analytical method has been optimized to determine 12 PFAS in fish muscle from salmon, tuna, cod, hake, sardine, anchovy, and sole, as well as in seven different seafood species (i.e., cuttlefish, octopus, squid, shrimp, Norway lobster, prawn, and mussel) by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Subsequently, the PFAS profile of the different species was studied to determine if it was consistent with that previously reviewed in the literature and to know the most relevant contribution of PFAS for each species. Finally, human exposure to PFAS through their consumption was estimated by the daily intake for seven different age/gender groups.PFAS were obtained from 0.014 to 0.818 ng g−1 wet weight in fish samples. Sardines, anchovies, and soles presented the highest PFAS levels. However, cod samples also showed some PFAS traces. Regarding seafood, PFAS levels range from 0.03 to 36.7 ng g−1 dry weight for the studied species. A higher concentration of PFAS has been found in the cephalopods' spleens and the crustaceans' heads. PFOS and PFBS were the predominant compounds in each seafood species, respectively. On the other hand, in the case of mussels, which are the less polluted species of the study, contamination by longer-chained PFAS was also observed.Finally, the total intake of PFAS due to fish and shellfish consumption for the Spanish adult population was estimated at 17.82 ng day−1. Nevertheless, none of the analyzed samples exceeded the European Food Safety Authority (EFSA) risk value for the supervised PFAS in any age/gender group reviewed.

Optimized LC-MS/MS quantification of tuberculosis drug candidate macozinone (PBTZ169), its dearomatized Meisenheimer Complex and other metabolites, in human plasma and urine

Tuberculosis, and especially multidrug-resistant tuberculosis (MDR-TB), is a major global health threat which emphasizes the need to develop new agents to improve and shorten treatment of this difficult-to-manage infectious disease. Among the new agents, macozinone (PBTZ169) is one of the most promising candidates, showing extraordinary potency in vitro and in murine models against drug-susceptible and drug-resistant Mycobacterium tuberculosis. A previous analytical method using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was developed by our group to support phase I clinical trials of PBTZ169. These plasma sample analyses revealed the presence of several additional metabolites among which the most prominent was H2PBTZ, a reduced species obtained by dearomatization of macozinone, one of the first examples of Meisenheimer Complex (MC) metabolites identified in mammals.Identification of these new metabolites required the optimization of our original method for enhancing the selectivity between isobaric metabolites as well as for ensuring optimal stability for H2PBTZ analyses. Sample preparation methods were also developed for plasma and urine, followed by extensive quantitative validation in accordance with international bioanalytical method recommendations, which include selectivity, linearity, qualitative and quantitative matrix effect, trueness, precision and the establishment of accuracy profiles using β-expectation tolerance intervals for known and newer analytes.The newly optimized methods have been applied in a subsequent Phase Ib clinical trial conducted in our University Hospital with healthy subjects. H2PBTZ was found to be the most abundant species circulating in plasma, underscoring the importance of measuring accurately and precisely this unprecedented metabolite. Low concentrations were found in urine for all monitored analytes, suggesting extensive metabolism before renal excretion.

Simplified analytical procedure to calculate the impact behaviour of steel parking-structure columns

The steel supporting frame of automatic mechanical garages is called a parking structure. Presently, for these novel structures, the design codes are without giving detailed guidelines to predict the response of their impacted column. Thus, this paper presents a simplified analytical procedure to calculate the impact behaviour of the column. The proposed method is based on the co-rotational rigid body model and follows the energy-balance principle. Compared with the previous analytical method, it specially targets the parking-structure column and can be used to conveniently and quickly calculate the column transverse displacement with considering the effects of the surrounding structural members and axial loads on the column. The research covers the situation where the column is subjected to the impacts at a low velocity, critical velocity, and overcritical velocity. Primarily, an approach is developed to simplify the overall parking structures. On that basis, the calculation formula for the critical impact velocity, i.e. the velocity that results in the formation of plastic hinges in the column, is derived. To predict the behaviour of the column under the impact beyond the critical impact velocity, the simplified analytical procedure is provided and then its accuracy is examined by validated numerical models. Eventually, according to the procedure, some suggestions are given to improve the design of the column after parametric analyses. It is recommended that control the axial-load levels of the column, particularly the column with a small section area, as well as set stiffeners on the column within the height of 1000 – 1500 mm.

Computational Method for Heat Partition at the Rail-Armature Interface Based on Least Squares Regression

The sliding electrical contact interface will generate a huge total heat source including Joule heat and frictional heat when an armature slides along a pair of rails driven by Lorentz forces. The total heat is partitioned at the contact interface flowing into armature and rail respectively. The heat partition at the rail-armature interface and the resulting temperature rise have important effects on the melt wear characteristics of the contact material. A computational method was proposed for determining heat partition at the rail-armature interface based on least squares regression. Temperatures equations of rail and armature were developed in terms of an unknown heat partition function. Solution equations of heat partition function were derived by matching the average temperature of rail and armature at the contact surfaces. The heat partition function was assumed to be a polynomial form and an estimate for the heat partition function was obtained by minimizing the error term in the least squares sense. Then, effects of polynomial order on the heat partition function are analyzed. Furthermore, the heat partition solution from the least squares regression and previous analytical method are compared. Variation characteristics of heat partition coefficient were also analyzed. In the end, the variation mechanism and influencing factors of heat partition coefficient were discussed.

A refined analytical strain analysis method for offshore pipeline under strike-slip fault movement considering strain hardening effect of steel

ABSTRACTThe rapid development of offshore oil and gas resources in recent years has led to a steadily growing importance of the safety of offshore pipelines. Active faults are some of the main geological hazards to which onshore and offshore pipelines may be subjected. In this study, an improved analytical method for estimating the strains in offshore pipelines subjected to strike-slip fault displacement was proposed. The pipe steel was considered as a linear strain hardening material and the soil constraint on pipe was considered as a series of elastic–plastic nonlinear soil springs. Explicit solutions for pipe elongation under fault displacements were derived and a high efficient iterative algorithm was proposed for accurately estimating the strains in the pipe. Better agreements with finite element results were obtained for the pipe strains derived using the proposed model when compared with the previous analytical method (i.e. Newmark method). This study is therefore considered to be a good reference for the design and safety evaluation of offshore pipelines crossing active faults.

Scattering of flexural–gravity waves by a group of elastic plates floating on a stratified fluid

A hydroelastic problem of flexural–gravity wave scattering by a demarcation between two floating elastic plates is investigated within the frame of linear potential-flow theory, where the method of matched eigenfunction expansions is employed for analysis. The formulations are subsequently generalized to the case of multiple elastic plates on a stratified fluid with multiple layers, which is helpful to the study of the hydrodynamic behaviors of inhomogeneous floating covers as well as the effects of density stratification in seawater. The eigenfunction expansions are numerically calculated by an inner product technique, in which an orthogonal definition involving an explicit differential term exhibits the effectiveness in dealing with the multi-layer matching relations between adjacent regions covered by different elastic plates. By use of Green’s theorem, an energy conversation relation is deduced to assure the convergence of the calculation. The high converging rates are exhibited afterwards. The correctness of numerical results are also verified by comparing with a previous analytical method. The details of the hydrodynamic responses of the generalized extension, especially the impact of the fluid stratification on the inner forces of the elastic plates, are discussed for different situations.

Continued Study on Hohlraum Radiation Source with Approximately Constant Radiation Temperature

An experiment was performed on the Shenguang III prototype laser facility to continue the study on hohlraum radiation source with approximately constant radiation temperature using a continuously shaped laser pulse. A radiation source with a flattop temperature of about 130 eV that lasted about 5 ns was obtained. The previous analytical iteration method based on power balance and self-similar solution of ablation was modified taking into account the plasma movements and it was used to design the laser pulse shape for experiment. A comparison between experimental results and simulation is presented and better agreement was achieved using the modified method. Further improvements are discussed.

Simulation of transport properties in Nb3Sn strand under bending

Superconducting performance of a large-scale Nb3Sn cable-in-conduit conductor (CICC) is degraded by periodic bending of strands subjected to a distributed transverse electromagnetic force during operation. The current transport in a single strand depends mainly on the bending strain and transverse resistivity. In particular, in the case of high-level strain and/or crack occurring among the filaments in the strain-sensitive Nb3Sn strand, these two parameters are required for better understanding of the critical current Ic degradation of a single strand. We use finite element method to simulate transport properties of a single Nb3Sn strand under bending. The simulation allows treating a wider range of transverse resistivity of strand, compared with our previous analytical method (Cryogenic, 58, 2013). Also, the present simulation incorporates the change of the area of strand cross section due to filament fracture into the boundary of the current transport, rather than simply imposes the condition of vanishing current on the filament fracture region as in the previous analytical method. We show the current/field profiles in the strand for various bending loads and transverse resistivities, as well as the Ic degradation of several types of strands under bending.

Monitoring of glutathione concentration during winemaking by a reliable high-performance liquid chromatography analytical method

Background and Aims: Glutathione (GSH) is valued in winemaking as an effective antioxidant in must and white wine if its concentration exceeds a few milligrams per litre. We report the further improvement of a previous analytical method for GSH quantification and its application to the analysis of grapes and wines. Methods and Results: Glutathione was derivatised with p-benzoquinone and detected by HPLC/UV. The analytical method was sensitive (limit of quantification, 0.43 mg/L), linear (R2 > 0.997), accurate (recovery, 101% in grape juice and white wine) and repeatable (relative standard deviation, 3.1). The monitoring of vinifications at commercial wineries showed that Saccharomyces cerevisiae was a main source of GSH in wine, since the GSH of the grape was poorly preserved following juice preparation. Glutathione concentration decreased during wine aging on yeast lees. Conclusion: Glutathione concentration varied considerably during winemaking, and thus monitoring is essential for improving wine flavour and preventing oxidation. This method is suitable for this purpose. Significance of the Study: The analytical method proposed is reliable, fast and easy-to-apply and allows the assessment of the GSH in grape, must and wine. The strong role of the yeast on the GSH concentration in wine is reported.

Study on the operational safety of high-speed trains exposed to stochastic winds

The characteristic wind curve (CWC) was commonly used in the previous work to evaluate the operational safety of the high-speed trains exposed to crosswinds. However, the CWC only provide the dividing line between safety state and failure state of high-speed trains, which can not evaluate the risk of derailment of high-speed trains when exposed to natural winds. In the present paper, a more realistic approach taking into account the stochastic characteristics of natural winds is proposed, which can give a reasonable and effective assessment of the operational safety of high-speed trains under stochastic winds. In this approach, the longitudinal and lateral components of stochastic winds are simulated based on the Cooper theory and harmonic superposition. An algorithm is set up for calculating the unsteady aerodynamic forces (moments) of the high-speed trains exposed to stochastic winds. A multi-body dynamic model of the rail vehicle is established to compute the vehicle system dynamic response subjected to the unsteady aerodynamic forces (moments) input. Then the statistical method is used to get the mean characteristic wind curve (MCWC) and spread range of the high-speed trains exposed to stochastic winds. It is found that the CWC provided by the previous analytical method produces over-conservative limits. The methodology proposed in the present paper can provide more significant reference for the safety operation of high-speed trains exposed to stochastic winds.

Constructal optimization of a disc-shaped body with cooling channels for specified power pumping

The thermal performance of a disc-shaped heat generation body with cooling channels is investigated by using constructal theory based on previous model of heat convection on a disc and previous analytical method of heat conduction on a disc. By taking minimum dimensionless maximum thermal resistance as optimization objective, the optimal aspect ratio of the elemental sector in the radial-pattern disc is obtained for the specified power pumping of the elemental sector; the optimal width ratio of the first- order and elemental cooling channels and the optimal dimensionless radius of the elemental sector are obtained for the specified power pumping of the disc. There exists a critical radius of the disc to determine whether the radial-pattern design and branched-pattern design should be adopted. These conclusions are different from those obtained by Wechsatol et al.'s model, and the essential reason for these differences is that the power pumping is specified in this article, but not the specified flow rate number in Wechsatol et al.'s model. Finally, the assumption about the heat capacity of the coolant and the thermal conductivity of the disc is validated. An analytical method is introduced in this article, which can provide another thought for the constructal optimization of disc with heat convection. The optimal constructs of the discs are obtained for the specified power pumping, which provides some different guidelines for the design of disc with heat convection.

A New Chaos Analysis Method: Exclusion Analysis Method and its Application: Simulation and Comparison

In this paper, a new analytical analysis method for chaos: exclusion method is used to analyze ferro-resonance in power system. Its basic idea is that for any systems, there are only four different solution types, that is, constant solutions (equilibrium solutions), periodic solutions, almost periodic solutions and chaotic solutions. If the parameter spaces corresponding to the solutions except chaotic solutions are excluded, the remaining parameter spaces are only the scopes corresponding to chaotic solutions, and then the analytical conditions for the chaotic solutions are obtained. This new method has been applied to the chaos analysis of vibrations equation and electronic circuit successfully. The analytical conditions for chaotic ferro-resonance solutions are obtained for the first time in a recently published paper and the conclusions are proved correct theoretically. In this paper, the resulted conditions are simulated numerically and compared with the Melnikov method to identify the efficiency of the exclusion analysis method. Compared with classical Melnikov method, the conclusion of this article shows that the new method is much more accurate than previous analytical method and is suitable for the system with any degree, especially for high dimensions system.

Concurrent profiling of indole-3-acetic acid, abscisic acid, and cytokinins and structurally related purines by high-performance-liquid-chromatography tandem electrospray mass spectrometry.

BackgroundCytokinins (CKs) are a group of plant growth regulators that are involved in several plant developmental processes. Despite the breadth of knowledge surrounding CKs and their diverse functions, much remains to be discovered about the full potential of CKs, including their relationship with the purine salvage pathway, and other phytohormones. The most widely used approach to query unknown facets of CK biology utilized functional genomics coupled with CK metabolite assays and screening of CK associated phenotypes. There are numerous different types of assays for determining CK quantity, however, none of these methods screen for the compendium of metabolites that are necessary for elucidating all roles, including purine salvage pathway enzymes in CK metabolism, and CK cross-talk with other phytohormones. Furthermore, all published analytical methods have drawbacks ranging from the required use of radiolabelled compounds, or hazardous derivatization reagents, poor sensitivity, lack of resolution between CK isomers and lengthy run times.ResultsIn this paper, a method is described for the concurrent extraction, purification and analysis of several CKs (freebases, ribosides, glucosides, nucleotides), purines (adenosine monophosphate, inosine, adenosine, and adenine), indole-3-acetic acid, and abscisic acid from hundred-milligram (mg) quantities of Arabidopsis thaliana leaf tissue. This method utilizes conventional Bieleski solvents extraction, solid phase purification, and is unique because of its diverse range of detectable analytes, and implementation of a conventional HPLC system with a fused core column that enables good sensitivity without the requirement of a UHPLC system. Using this method we were able to resolve CKs about twice as fast as our previous method. Similarly, analysis of adenosine, indole-3-acetic acid, and abscisic acid, was comparatively rapid. A further enhancement of the method was the utilization of a QTRAP 5500 mass analyzer, which improved upon several aspects of our previous analytical method carried out on a Quattro mass analyzer. Notable improvements included much superior sensitivity, and number of analytes detectable within a single run. Limits of detection ranged from 2 pM for (9G)Z to almost 750 pM for indole-3-acetic acid.ConclusionsThis method is well suited for functional genomics platforms tailored to understanding CK metabolism, CK interrelationships with purine recycling and associated hormonal cross-talk.

Trajectory generation for road vehicle obstacle avoidance using convex optimization

This paper presents a method for trajectory generation using convex optimization to find a feasible, obstacle-free path for a road vehicle. Consideration of vehicle rotation is shown to be necessary if the trajectory is to avoid obstacles specified in a fixed Earth axis system. The paper establishes that, despite the presence of significant non-linearities, it is possible to articulate the obstacle avoidance problem in a tractable convex form using multiple optimization passes. Finally, it is shown by simulation that an optimal trajectory that accounts for the vehicle's changing velocity throughout the manoeuvre is superior to a previous analytical method that assumes constant speed.

π-Mode Stopband Characteristics Caused by Asymmetries of Support Rod and Loaded Metal in Helix Structures

A fully three-dimensional (3-D) helix traveling-wave tube (TWT) simulation model has been developed using a commercial electromagnetic (EM) finite-element-method (FEM) code. The model is used to simulate the π-mode stopband characteristics caused by asymmetries of support rods and metal loading in helix TWTs. Compared with the previous analytical method, the present simulation method can calculate the natural stopband of the π-mode, the absolute π-mode frequency, and the asymmetric effect of metal loading.

Method Validation for HPLC Assay of 7-Chloro-1-cyclopropyl-fluoro-1,4-dihydro-4-oxo-1,8-naphthylidine-3-carboxylic acid

Gemifloxacin (Factive, LB20304a), a new chemical entity developed by LG Life Science Ltd. and approved by FDA on April 2003, is broad-spectrum fluoroquinolone antibiotic used to treat respiratory infections. It was synthesized by the coupling reaction of the two key intermediates, 7-chloro1-cyclopropyl-fluoro-1,4-dihydro-4-oxo-1,8-naphthylidine3-carboxylic acid (QN09) and 3-aminomethyl-4-hydroxypyrrolidine (AM19), as shown in Figure 1. Recently, we have developed a new QN09 synthetic process that is more cost-effective, operationally simpler than the previous one. The QN09 has two impurities and three intermediates that were not found in QN09 synthesized by the previous process. The impurities and intermediates were not separated completely from QN09 by using high performance liquid chromatographic (HPLC) separation conditions that was applied to analysis of QN09 produced by the previous synthetic process. The report on the previous analytical method and its validation is registered on the LG Life Science’s Drug Master File of Gemifloxacin. The objective of this study is to develop and validate the analytical method by which QN09 is separated and determined from the impurities and intermediates produced by the new synthetic process. The new analytical method for the assay of QN09 has baseline separation with its degradation products, the new impurities and the intermediates with the resolution of 8 and the number of theoretical plates of > 20000. The method validation was done by evaluating specificity, linearity, accuracy, precision (i.e., repeatability and intermediate precision), robustness and solution stability complying with the International Conference on Harmonization (ICH) guideline Q2(R1). The new assay of QN09 was applied for the production of FACTIVE. The validation result will be reported to FDA. Experimental

Evaluation technique of kinetic parameters for irreversible charge transfer reactions from steady-state voltammograms at microdisk electrodes

An explicit approximate expression for half-wave potentials of irreversible steady-state current-voltage curves at a microdisk electrode was derived from the diffusion equation and the Butler–Volmer equation on the basis of the previous analytical method [K. Aoki, K. Tokuda, H. Matsuda, J. Electroanal. Chem. 235 (1987) 87]. The plot of the half-wave potential, E 1/2 against ln(1− exp(−( E 1/2− E 0)) F/RT) showed a linear relation with the slope of RT/ αF, irrespective of the values of the kinetic parameters, where a is the radius of the electrode and α is the transfer coefficient. Values on the both axis in this plot are readily accessible from the voltammograms. The intercept gave the rate constant. Values of kinetic parameters obtained from the disk model were very close to those from the hemisphere model although there is big difference in current distribution on the two model electrodes.

Determination of Benzo[a]pyrene, Benz[a]anthracene and Dibenz[a,h]anthracene in Creosotes and Creosote-Treated Woods

The amount of benzo[a]pyrene (BaP), benz[a]anthracene (BaA), and dibenz[a,h]anthracene (DBA) has been restricted to a concentration of 10 μg/g each in creosotes, and 3 μg/g each in creosote-treated woods, respectively, because of the possibility of the risk of skin cancer in consumers, and creosotes can otherwise contain high concentrations of each chemical. We already reported the content of 16 polycyclic aromatic hydrocarbons (PAHs) and phenols in creosotes and creosote-treated wood as determined by gas chromatography-mass spectrometry (GC-MS) and absorptiometry [Chemosphere, 60, 1279-1287 (2005)]. However, the limit of determination of each PAH per sample was > 40 μg/g according to that method, the sensitivity of which was insufficient for determining the allowable levels of these 3 compounds. Moreover, a substantial amount of time was needed for GC-MS analysis. In the present study, we improved upon our previous analytical method in order to increase the sensitivity of the test and to reduce the duration of GC-MS analysis. Creosote was extracted from treated wood samples by dichloromethane-soak incubation, and was placed on a Sep-Pak silica cartridge and eluted with dichloromethane. The eluates were evaporated and dissolved in dichloromethane. The sample solution spiked with the internal standard solution was injected into the GC-MS system. The limit of determination of each chemical in the test solution was approximately 0.2 μg/ml, which corresponded to 1-2 μg/g in each sample. The duration of GC-MS analysis was approximately 17 min. A collaborative study was also carried out in order to evaluate the reproducibility of the method for determining low levels of BaP and related compounds in creosotes. The present method was applied for the analysis of certain commercially available creosotes and creosote-treated wood samples in Japan. It was confirmed that some creosotes and railway sleepers contained these compounds in high concentrations, thus exceeding the allowed control value.

Analysis of human urine for fifteen phthalate metabolites using automated solid-phase extraction

We improved our previous analytical method to measure phthalate metabolites in urine as biomarkers for phthalate exposure by automating the solid-phase extraction (SPE) procedure and expanding the analytical capability to quantify four additional metabolites: phthalic acid, mono-3-carboxypropyl phthalate, mono-isobutyl phthalate (miBP), and monomethyl isophthalate. The method, which involves automated SPE followed by isotope dilution-high performance liquid chromatography (HPLC)-electrospray ionization (ESI)-tandem mass spectrometry (MS), allows for the quantitative measurement of 15 phthalate metabolites in urine with detection limits in the low ng/ml range. SPE automation allowed for the unattended sequential extraction of up to 100 samples at a time, and resulted in an increased sample throughput, lower solvent use, and better reproducibility than the manual SPE. Furthermore, the modified method permitted for the first time, the separation and quantification of mono- n-butyl phthalate (mBP) and its structural isomer miBP. The method was validated on spiked pooled urine samples and on pooled urine samples from persons with no known exposure to phthalates.