Einsatz von rechenanlagen in der emissionsspektrochemie für aufstellung,bewertung und linearisierung der analytischen eichgeradenThe use of computers in emission spectrometry for the establishment,evaluation and linearization of analytical calibration curves

(The use of computers in emission spectrometry for the establishment, evaluation and linearization of analytical calibration curves)The problems of establishing optimum linear calibration lines for atomic emission spectrometry are discussed, with emphasis on use of photographic recording techniques. The calculation procedure, which is based on the least-squares method, generates additional statistical values which permit the linearity to be checked. As the desired linearity is not always achieved at the first attempt, the process is repeated after unreliable input data have been removed.     

Determination of trace levels of dinitrophenolic compounds in environmental water samples using hollow fiber supported liquid membrane extraction and high performance liquid chromatography

A hollow fiber supported liquid membrane extraction method for the liquid chromatographic determination of dinitrophenolic compounds at ppt levels has been developed. Different variables affecting the extraction process, such as extraction time, shaking speed, acceptor pH, acceptor buffer concentration, salt content and humic acids have been studied. Enrichment factors up to 7000 times were obtained. Validation of the method included calibration experiments and studies of the linearity of the responses in different matrices. Good linearity was obtained in the environmental matrices evaluated. Detection limits range from 6.0 to 8.0 ng/L, and the relative standard deviations do not exceed 7% in terms of repeatability.     

Chromatographic determination of drotaverine hydrochloride and kinetic modeling of the process of its biodestruction in a R. rhodochrous culture liquid

A method has been developed for the determination of drotaverine hydrochloride in a postfermentation medium of the cultivation of actinobacteria by reversed-phase high-performance liquid chromatography. The specificity, linearity, reproducibility, and accuracy of the method have been evaluated. It has been demonstrated that the process of the biological destruction of drotaverine hydrochloride is adequately represented by a first-order kinetic equation with a variable reaction rate constant. Kinetic modeling has shown the possibility of substantially reducing the size and duration of the experiment, as well as of evaluating the time of completion of the process of drotaverine hydrochloride biodestruction.     

Einsatz von rechenanlagen in der emissions-spektrochemie : II Teil. Aufstellung,Bewertung und Linearisierung der analytischen Eichgeraden

The Use of Computers in Emission Spectroscopy. Part 2. Establishment, Evaluation and Linearization of Analytical Calibration CurvesThe problems of establishing optimum linear calibration plots for atomic emission spectrometry are described, particularly when photographic recording techniques are employed. The calculation procedure, based on the least-squares method, generates additional statistical values which permit linearity to be checked. As the desired linearity is not always achieved at the first attempt, the process is repeated after exclusion of unreliable input data.     

Study of the separation of lactose,lactulose and galactose by liquid chromatography using cationic ion-exchange resin columns

Summary A strong acid cation-exchange resin, Dowex AG50W-X8 in potassium, calcium or sodium form, with water as eluent, has been used to separate three sugars (lactose, lactulose and galactose). The linearity of lactulose equilibrium isotherms was verified. Thermodynamic and kinetic parameters were thus determined by the moment method. Evaluation of the parameters revealed in this work can be considered as the first step in scaling up the process towards industrial use. On the other hand, the equilibrium stage model, which takes mass transfer resistance into account, is shown to provide a fair representation of the system’s behaviour.     

Transfer and Termination Reactions in “Living” Carbocationic Polymerizations

Abstract

The available data concerning the polymerization of three classes of monomers deemed to yield living polymers, vinyl ethers, styrenic monomers and isobutylene, are discussed from the point of view of transfer and termination reaction. In the case of vinylethers, linearity of [Mbar]_n with a yield up to 30,000 has been obtained, but when higher [Mbar]_n are planned, there is evidence for the occurrence of transfer reactions. In the case of isobutylene, indene, and p-Me-styrene, the linearity (up to [Mbar]_n ～ 10⁵) of [Mbar]_n with the amount of monomer polymerized which has been observed (but only at low temperature) is compatible with values of transfer constants to monomer measured in “conventional” systems. In these living systems, irreversible terminations are often not very important but may become significant toward the end of monomer consumption. The main termination process is reversible termination which may lead to narrow molecular weight distributions. The linearity of [Mbar]_n with yield is not conclusive evidence for the absence of transfer and termination and for the presence of particular active centers. The control of the polymerizations achieved up to now can be accounted for by the mechanisms of conventional cationic polymerizations, transfer reactions included.     

Comparison of headspace and direct single-drop microextraction and headspace solid-phase microextraction for the measurement of volatile sulfur compounds in beer and beverage by gas chromatography with flame photometric detection

Three approaches based on headspace single-drop microextraction (HS-SDME), direct single-drop microextraction (Direct-SDME), and headspace solid-phase microextraction (HS-SPME), have been compared for analyzing volatile sulphur compounds (VSCs) in beer and beverage. Procedures and performance of the three methods have been contrasted through the determination of extraction efficiencies, precision, linearity and limits of detection. The overall process of HS-SDME and HS-SPME was applied to GC-FPD determination of five VSCs in beer and beverage.     

Detection of perfluorocarbons in blood by headspace solid-phase microextraction combined with gas chromatography/mass spectrometry.

A new method of detection of perfluorocarbon molecules (PFCs) in blood sample has been established. After an extraction and pre-concentration step performed by headspace solid-phase microextraction (HS-SPME), the PFCs are detected by gas chromatography-mass spectrometry (GC/MS) with an ion trap mass spectrometer in MS and MS/MS modes. The influence of different parameters on the SPME process is discussed. The limit of detection and the linearity of the procedure have been determined for two PFCs.     

Deviations from linearity in statistical evaluation of linearity in assay validation

Linearity and linear range are the key evaluations of the accuracy in assay validation. The average deviation from linearity (ADL) and the sum of squares of deviations from linearity (SSDL) have been proposed for assessment of the linearity. However, both ADL and SSDL do no consider the variability of the assay for evaluation of linearity. Therefore, we proposed the coefficient of variation of deviations from linearity (CVDL) as an alternative measure for the linearity assessment. For the inference of evaluation of linearity, we proposed testing procedures based on generalized pivotal quantities (GPQ) of ADL and CVDL for evaluation of linearity. The simulation studies were conducted to empirically investigate the size and power between the three methods. The simulation results show that all three methods adequately control size. However, the ADL method is uniformly more powerful than the other two methods. A numeric example illustrates the proposed methods. Copyright © 2009 John Wiley & Sons, Ltd.     

Implementation in MATLAB of the adaptive Monte Carlo method for the evaluation of measurement uncertainties

The ISO 98:1995 Guide to the expression of uncertainty in measurement (GUM) presents important application limitations. For its improvement, different supplements are being developed that will progressively enter into effect. The first of these supplements describes an alternative method for calculating uncertainties, the Monte Carlo method (MCM), which is not restricted to the conditions of the method described in the GUM: the linearity of the model and the application of the central limit theorem. MCM requires computer calculation systems for generating pseudo-random numbers and for evaluating the model a large number of times. There are software applications that have been specifically developed for calculating uncertainties, some of which include MCM; but they do not allow the user to control all factors in the process, particularly the result stabilization criteria. On the contrary, its implementation in a mathematical program for general purposes such as MATLAB, enables total control over the process, is simple and benefits from its calculation speed. This article details programming in MATLAB for the implementation of the adaptive MCM method.     

β-cyclodextrin-bonded silica particles as novel sorbent for stir bar sorptive extraction of phenolic compounds

A stir bar coated with β-cyclodextrin-bonded-silica (CDS) as novel sorbent has been developed and used to analyze seven phenolic compounds in aqueous samples, followed by thermal desorption and gas chromatography-mass spectrometric detection. Significant parameters affecting sorption process such as the time and temperature of sorption and desorption, ionic strength, pH and stirring rate have been optimized and discussed. The coating has a high thermal stability up to 300°C and long application lifetime (80 times). The porous structure of CDS coating provides high surface area and allows high extraction efficiency. Under the selected conditions, linearity range of 0.1-400 μg/L, limit of quantifications of 0.08-3.3 μg/L and method detection limits of 0.02-1.00 μg/L have been obtained. A satisfactory repeatability (RSD ≤ 6.5, n = 7) with good linearity (0.9975 ≤ r(2) ≤ 0.9996) of results illustrated a good performance of the present method. The recovery of different natural water samples was higher than 81.5%.     

核磁共振法定量测定替米考星含量

用核磁共振(^1H NMR)法测定了药品替米考星(tilmicosin)的含量，给出了完整的实验条件和注意事项，线性实验测得线性回归系数为0.9985，重复性实验测得RSD为0．327％。表明此方法做为一种药物的定量方法具有简单易行、结果准确的优点，可用做某些没有对照品的药物定量方法的补充。     

Development and validation of a reversed-phase HPLC method for quantitative determination of ginsenosides Rb1, Rd, F2, and compound K during the process of biotransformation of ginsenoside Rb1

A simple and rapid gradient RP-HPLC method for simultaneous separation and determination of related ginsenosides during the process of biotransformation of ginsenoside Rb1 has been developed. As many as four process ginsenosides have been separated and identified on an Eclipse XDB C(18) column (4.6 mm x 150 mm, 5 mum) with gradient elution using water and ACN as a mobile phase. The column was maintained at 30 degrees C and the eluents were monitored with diode array detection at 203 nm. The method was validated in terms of linearity, sensitivity, precision, and accuracy. The correlation coefficients (r) for calibration curves of ginsenosides were in the range of 0.9996-1.0000. The proposed RP-HPLC method was successfully applied to the analysis of fermentation broth and the recoveries of ginsenosides were in the range of 94.4-103.1% with RSD <2.87%. The method could be of use for rapid and routine evaluation of the quantity of ginsenosides during the biotransformation process of ginsenoside Rb1.     

Measurement of Total and Unbound Mycophenolic Acid and Its Glucuronide by LC Coupled with MS. Application to a Pharmacokinetic Study of Mycophenolate Mofetil in Patients with Autoimmune Diseases

Liquid chromatography coupled with mass spectrometry for the determination of total and unbound mycophenolic acid and its major metabolite in human plasma has been developed. Sample preparations were based on a fully automated solid-phase extraction process and ultrafiltration. Mass spectrometric data were acquired in a single-ion monitoring method. The analytes and nevirapine (internal standard) were well separated in an isocratic mode over 8 min. Validation study exhibited excellent linearity, with intra- and inter-day precision and accuracy of less than 12%. The assay was successfully applied to the pharmacokinetic study of mycophenolic acid in patients with autoimmune diseases.     

Dynamic range and response speed of heat-flux differential calorimeters

A technique for the linearization of calorimeter cell (CC) thermal feedback in differential calorimeters was investigated. The technique was shown to ensure the linearity of the tract of rapid compensation measurements of thermokinetics (W _in(t)) in a dynamic range of heat-fluxes limited in principle only by the linearity of the CCs themselves, while their original identity is not required. The technique was employed in prototype models of updated DAK calorimeters, in which W _in(t)_max reached 0.5 W while the duration of the transition process associated with the insertion of the test specimen was reduced by a factor of 2.3. This was shown to reduce calorimeter inertia, extend the possibilities of thermokinetic measurements, and record earlier stages of the initial thermokinetics.     

Non-linear dielectric spectroscopy: antifouling and stabilisation of electrodes by a polymer coating

Non-linear dielectric spectroscopy (NLDS) has previously been shown to produce quantitative information that is indicative of the metabolic state of various organisms, by modeling the non-linear effects of their membranous enzymes on an applied oscillating electromagnetic field using supervised multivariate analysis methods. However, the instability of the characteristics of the measuring apparatus rendered the process temperamental at best in the laboratory and impractical for field use. The main practical problem, of the non-stationarity of the electrode-solution interface and the ease with which the electrode surfaces are subject to protein fouling. It is addressed by applying a thin, electrically transparent antifouling coat to the electrodes. This reduces the interminable cleaning procedures previously required to prepare the electrodes for use, increases their usable lifetime before recleaning, and also improves the precision and linearity of multivariate models on NLDS data.     

Optimization of a derivatization-solid-phase microextraction method for the analysis of thirty phenolic pollutants in water samples

Solid-phase microextraction (SPME) coupled to gas chromatography-mass spectrometry has been applied to the extraction of 30 phenol derivatives from water samples. Analytes were in situ acetylated and headspace solid-phase microextraction was performed. Different parameters affecting extraction efficiency were studied. Optimization of temperature, type of microextraction fiber and volume of sample has been done by means of a mixed-level categorical experimental design, which allows to study main effects and second order interactions. Five different fiber coatings were employed in this study; also, extraction temperature was studied at three levels. Both factors, fiber coating and extraction temperature, were important to achieve high sensitivity. Moreover, these parameters showed a significant interaction, which indicates the different kinetic behavior of the SPME process when different coatings are used. It was found that 75 microm carboxen-polydimethylsiloxane and 100 microm polydimethylsiloxane, yield the highest responses. The first one is specially appropriated for phenol, methylphenols and low chlorinated chlorophenols and the second one for highly chlorinated phenols. The two methods proposed in this study shown good linearity and precision. Practical applicability was demonstrated through the analysis of a real sewage water sample, contaminated with phenols.     

A dynamic study on nonlinear viscoelastic behavior of isotactic polypropylene/carbon black composite melts

The influence of the filler loading and the kinetic aggregation process on the nonlinear viscoelastic behavior of the isotactic polypropylene/carbon black composite melts is studied. The limit of linearity decreases with increasing filler loading. The composite melt with a percolating rheological network has an additional strain-softening process at the low strains which is attributed to the breakdown of the filler network. The simultaneous measurement of the conductivity during the strain sweep demonstrates that the rheological network is more easy to be broken than the conductive network, and that some of the aggregated structures formed during melt annealing can be retained even after experiencing high strains.     

Comparative dimerization of 1-butene with a variety of metal catalysts, and the investigation of a new catalyst for C=H bond activation

Catalytic dimerization of 1-butene by a variety of catalysts is carried out, and the products are analyzed by gas chromatography and mass spectrometry. Catalysts based on cobalt and iron can produce highly linear dimers, with the cobalt-based dimers exceeding 97 % linearity. Catalysts based on vanadium and aluminum prefer to make branched dimers, which are most often methyl-heptenes in the case of vanadium and almost exclusively 2-ethyl-1-butene in the case of aluminum. The vanadium catalyst also produces substantial amounts of dienes and alkanes, suggesting a competing hydrogenation/dehydrogenation pathway that appears to involve vinyl Cbond;H bond activation. Nickel catalysts are generally less selective than those based on iron or cobalt for making linear dimers, but they can make dimers with 60 % linearity. The major by-products for the nickel systems are trisubstituted internal olefins. An important side reaction that must be considered for dimerization reactions is 1-butene isomerization to 2-butene, which makes recycling the butene difficult for a linear dimerization process. Aluminum, iron, and vanadium systems promote very little isomerization, but nickel and cobalt systems tend to isomerize the undimerized substrate heavily.     

Structural and fluorescence quenching characterization of hematite nanoparticles

Nanoparticles of the dominant hematite form (α-Fe(2)O(3)) of iron oxide have been prepared by a simple route of dropping FeCl(3) solution into boiling water. The nanoparticles have been characterized by transmission electron microscopy (TEM), UV-visible electronic absorption spectroscopy, chemical stoichiometry, thermal analysis methods (TGA, DSC and DTA), XRD, FTIR and magnetic susceptibility measurements. Kinetic analysis of the DSC calorigram of thermal dehydration of the nanoparticles reveals one stage of the dehydration process of energy of activation of 29.0 kJ mol(-1). The role of iron oxide nanoparticles in fluorescence quenching of coumarin thiourea derivatives (I-IV) was investigated at room temperature (296 K) by means of steady-state fluorescence spectroscopy. The quenching process was characterized by Stern-Volmer (S-V) plots which display a positive deviation from linearity. This could be explained by static and dynamic quenching models. The positive deviation in the S-V plot is interpreted in terms of ground-state complex formation model and sphere of action static quenching model. Various rate parameters for the ?uorescence quenching process were determined by using the modi?ed Stern-Volmer equation. The sphere of action static quenching model agrees very well with experimental results. Quenching constants for iron oxide nanoparticles are about four orders of magnitudes higher than quenching by Fe(3+) ions.