Improved accuracy and robustness of electron density profiles from JET's X-mode frequency-modulated continuous-wave reflectometers.

JET's frequency-modulated continuous wave (FMCW) reflectometers have been operating well with the current design since 2005, and density profiles have been automatically calculated intershot since then. However, the calculated profiles had long suffered from several shortcomings: poor agreement with other diagnostics, sometimes inappropriately moving radially by several centimeters, elevated levels of radial jitter, and persistent wriggles (strong unphysical oscillations). In this research, several techniques are applied to the reflectometry data analysis, and the shortcomings are significantly improved. Starting with improving the equilibrium reconstruction that estimates the background magnetic field, adding a ripple correction in the reconstructed magnetic field profile, and adding new inner-wall reflection positions estimated through ray-tracing, these changes not only improve the agreement of reconstructed profiles to other diagnostics but also solve density profile wriggles that were present during band transitions. Other smaller but also persistent wriggles were also suppressed by applying a localized correction to the measured beat frequency where persistent oscillations are present. Finally, the burst analysis method, as introduced by Varela et al. [Nucl. Fusion 46 S693 (2006)], has been implemented to extract the beat frequency from stacked spectrograms. Due to the strong suppression of spurious reflections, the radial jitter that sometimes would span several centimeters has been strongly reduced. The stacking of spectrograms has also been shown to be very useful for stacking recurring events, like small gas puff modulations, and extracting transport coefficients that would otherwise be below the noise level.

Experimental evidence of momentum transport induced by an up-down asymmetric magnetic equilibrium in toroidal plasmas.

The first experimental evidence of parallel momentum transport generated by the up-down asymmetry of a toroidal plasma is reported. The experiments, conducted in the Tokamak à Configuration Variable, were motivated by the recent theoretical discovery of ion-scale turbulent momentum transport induced by an up-down asymmetry in the magnetic equilibrium. The toroidal rotation gradient is observed to depend on the asymmetry in the outer part of the plasma leading to a variation of the central rotation by a factor of 1.5-2. The direction of the effect and its magnitude are in agreement with theoretical predictions for the eight possible combinations of plasma asymmetry, current, and magnetic field.

[Rare complication of duodenal ulcer: intramural hematoma in the gastric antrum]. / A duodenalis ulcus ritka szövdmnye: intramuralis haematoma a gyomorantrumban.

As a rarity in professional literature, the authors raise the case of a 37-year-old female patient who developed gastric antrum intramural haematoma, producing the clinical symptoms of III. grade pyloric stenosis, as a complication of a peptic duodenal ulcer. The authors point out this complication as a rarity.

Planar chromatography: current status and future perspectives in pharmaceutical analysis--I. Applicability, quantitation and validation.

The most important features of capillary action planar chromatographic methods are summarized. Certain properties such as ease in operation, sensitivity to experimental conditions, stationary and mobile phase selection, phase system optimization, separation efficiency and detection possibilities are discussed only briefly. Other aspects such as the applicability of planar chromatographic methods in pharmaceutical analysis, quantitation and validation are considered in more detail. The advantages and limitations of different evaluation techniques (visual comparison, spot elution techniques and in situ densitometry) are also discussed. Validation steps specific to planar chromatographic methods are emphasized.

Planar chromatography: current status and future perspectives in pharmaceutical analysis (short review)--II. Special techniques and future perspectives in planar chromatography.

The state of the art of various special analytical planar chromatographic methods is summarized especially for forced-flow planar chromatography (FFPC), overpressured-layer chromatography (OPLC) and rotation planar chromatography (RPC) as well as for the automated multiple development (AMD) technique. The connection between analytical planar and column liquid chromatographic methods and the identification of separated compounds with chromatographic and spectroscopic data are summarized. Some aspects of future perspectives, such as parallel connected multi-layer FFPC and long distance OPLC (LD-OPLC) are given. A combination of OPLC with the AMD method is predicted as the method of the future. Strategies using FFPC techniques are suggested in the form of a flow chart.

[Analysis of steroids. Part 45: Analytical investigation of pipecuronium bromide (Arduan)]. / Adatok a szteránvázas vegyületek analitikájához 45. Pipecuronium bromid (Arduan) analitikai vizsgálata.

The following methods are described for the analytical investigation of pipecuronium bromide. 1. HPLC method. Of the several systems tried for the separation and quantification of impurities and degradation products the best results were obtained using silica as the stationary phase and 43:43:14 mixture of methanol, acetonitrile and concentrated aqueous ammonia containing 0.1 mole/l each of ammonium chloride and ammonium carbonate as the eluent. The validation of this method is presented. The above described aggressive eluent can be successfully replaced by an ion-pairing system using silica as the stationary phase and 96:4 mixture of acetonitrile and water containing 0.1 mole/l sodium perchlorate as the eluent. 2. Thin-layer chromatography. TLC systems are described for the separation and densitometric quantification of the impurities and degradation products of pipecuronium bromide. 3. Spectrophotometry. Two methods are described. The ester groups of the molecule can be determined by the iron(III)-hydroxamate method while for the ion-pair extraction of the quaternary ammonium steroid picric acid or bromthymol blue are used as the reagents. 4. Titrimetry. In addition to the titration with acetous perchloric acid for the assay of the bulk material a microtitration method is described for the determination of pipecuronium bromide in individual lyophylized ampoules (potentiometric titration with 0.1 M silver nitrate).

[Some criteria for the planning and evaluation of the ruggedness test of HPLC methods]. / Néhány szempont HPLC "ruggedness"-vizsgálat tervezéséhez és értékeléséhez.

Ruggedness is a measure of the reproducibility of the individual test results when the procedure is used repeatedly to determine the same homogeneous sample in a variety of specified experimental conditions. Ruggedness testing can be divided into two major groups: Type-A, when the influence of the changed environmental conditions (different equipment, analysts, etc.) on the analytical performance parameters and results are tested, and Type-B, when the effect of variation in the experimental conditions are checked. In the latter case, Type-B group can be further classified into two major subgroups: ruggedness testing of sample preparation and chromatographic separation. Checking sample preparation for ruggedness testing includes the investigation of various sample preparation procedures, such as: liquid-liquid extraction, solid phase extraction, direct sample introduction and derivative formation. The investigation of column-to-column variability, changes in the instrumental and experimental conditions belongs to the ruggedness testing of chromatographic separation. In this paper the basic principles of selection for experimental variables for various ruggedness tests are discussed introducing a new possibility to design multivariable-multicriteria system, and the evaluation of a single-variable-single-criterion system, as well. In general, from the work introduced in this paper, it can be concluded that when new analytical methods are developed, it is quite important to be aware the sensitivity of the method to variations in the specified conditions. For adequate performance of ruggedness testing: a) the factors (variables) which have significant influence on the chromatographic results can be firstly selected, b) maximum acceptable deviations from the prespecified experimental conditions can be decided, and c) the acceptable deviations from the values of the prespecified analytical performance parameters can be defined.

Selection of high-performance liquid chromatographic methods in pharmaceutical analysis. III. Method validation.

The most important steps in the validation of high-performance liquid chromatographic (HPLC) methods are discussed. The establishment of system suitability data and the assessment of peak purity are demonstrated on the example of bisquaternary amino steroids. For the recognition of incomplete resolution of adjacent peak pairs, the absorbance-ratio method in which the ratio of absorbances at two preselected wavelengths are plotted as a function of time in combination with the separation of sample components subjected to various chemical and physico-chemical treatments (stress conditions) is applied. The separation power and performance of the HPLC systems are characterized by the system resolution (SR) and system selectivity (SS). The special demands of stability-indicating methods are summarized.

Selection of high-performance liquid chromatographic methods in pharmaceutical analysis. IV. Selection of most applicable separation system.

Different analytical tasks in the pharmaceutical analysis can be classified according to the separation problems into three main groups: trace analysis, assay methods and separation of closely related compounds including isomers. The most important requirements of high-performance liquid chromatographic (HPLC) methods with respect of the separation problems are summarized. Considerations and recommendations for the selection of the most applicable HPLC system to solve particular analytical problems are discussed. HPLC methods can be compared on the basis of the system resolution (SR) and system selectivity (SS). Criteria developed for the characterization of HPLC methods considering the difficulties created by the different analytical problems are established. The principles of the selection of the most applicable separation systems are demonstrated through some practical examples in pharmaceutical analysis.

Selection of high-performance liquid chromatographic methods in pharmaceutical analysis. I. Optimization for selectivity in reversed-phase chromatography.

The application of solvent optimization to the development of isocratic reversed-phase liquid chromatography has been reported in several publications. Two different approaches to solvent optimization for controlling band spacing for the maximum resolution of samples are "solvent strength" and "solvent type" optimization. To improve the separation selectivity further the combination of these two approaches was examined, as a (global) optimum mobile phase composition requires the optimization of the solvent strength by varying the percentage of organic component and of the solvent selectivity of methanol, acetonitrile, tetrahydrofuran and water. It was found that the combination of "solvent strength" and "solvent type" optimization provides a markedly better separation than either procedure alone.

Selection of high-performance liquid chromatographic methods in pharmaceutical analysis. II. Optimization for selectivity in normal-phase systems.

Optimization of selectivity in normal-phase chromatography was studied. Using the same optimization criteria (Rs,min, Dmin, Rsb and Rsa) as in Part I the possible combination of "solvent strength" optimization by variation of the percentage of polar modifier in the less polar mobile phase and "solvent type" optimization by measuring the solvent selectivity of chloroform, acetonitrile, tetrahydrofuran and dioxane was examined. From the results it can be concluded that by replacement of medium-polarity solvents (chloroform, acetonitrile, tetrahydrofuran and dioxane) in the mobile phase, the selectivity of the separation can be significantly improved as the elution order is a function of solvent type belonging to Class P. In the separation of a steroid mixture dioxane provides the best properties for improving band spacing.

Enantiomeric separations and their application in pharmaceutical analysis using chiral eluents.

The most important problems of enantiomeric separations using chiral eluents are discussed. The methods have been compared with respect to enantiomeric purity of reagents, reagent selection and separation variables. The most important considerations for methods based on inclusion-complexation with different CDs and on using chiral counter ions are summarised and compared. A new possibility for the separation of enantiomeric compounds with the aid of a combination of ion-pair and inclusion-complex formation has been introduced. As a consequence of this investigation, the selectivity of the separation can be significantly improved; those ionic isomers and enantiomers which cannot be separated or are unsatisfactorily separated by ion-pair chromatography or by inclusion-complex formation, can be separated by the combined technique. Comparison of methods applicable for enantiomeric separations is also given with respect to solving specific analytical tasks in the field of pharmaceutical analysis.

Coordinative interactions in the separation of insulin and its derivatives by high-performance liquid chromatography.

The effects of various inorganic cations and anions on the chromatographic behaviour of insulin and its derivatives have been investigated. It was shown that on an octadecylsilica column at a given eluent composition the retention of insulins depends primarily on the nature of the anions. The cations have a secondary effect, depending on their size and coordination ability. The mechanism of the effect of the ions is complex. It includes the formation of ion pairs, their influence on dissociation processes, a silanophilic effect, coordination processes and changes in the structures of the insulins.

Semi-preparative high-performance reversed-phase displacement chromatography of insulins.

A reversed-phase displacement chromatographic method has been developed for the purification of bovine and porcine insulin samples. Up to 500 mg of raw insulin could be purified on a Nucleosil C8 analytical column using a methanol-containing phosphate buffer carrier and a cetrimide-containing displacer. A proinsulin contamination level as low as 100 ppm in the collected fractions could be achieved.

Quantitative thin-layer chromatography of cobalamin complexes.

Quantitative thin-layer chromatography was used to study the hydroxo-, cyano- and dicyanocobalamin transformation equilibria. A new stereoisomer of cyanocobalamin was shown to be formed from dicyanocobalamin on the chromatographic plate. The formation, stability and UV spectrum of this compound (isocyanocobalamin) was studied.

Determination of ethinylestradiol in tablets by quantitative TLC method.

A new quantitative TLC method was developed for the determination of ethinylestradiol in tablets. The possible adsorption of ethinylestradiol on the starch can be avoided by enzymatic degradation, which enabled the easy extraction of the active ingredients from the tablet powder. The quantitative evaluation of the separated compounds was performed by densitometry at a wavelength of 280 nm. The relative standard deviation of the method was found to be better than +/- 2.6% in every case except Ambosex tablet where this value was +/- 4.7%. On the basis of the results obtained the method can be proposed for the routine analysis of tablets containing small amount of ethinylestradiol.

High-performance liquid chromatography of eburnane alkaloids. I. Separation on reversed phases.

Separation of eburnane alkaloids using reversed-phase high-performance liquid chromatography was investigated on muBondapak C18 in LiChrosorb RP-8 columns with acetonitrile-aqueous 0.01 M ammonium carbonate as eluent. The method can be successfully applied for the group separation of eburnane alkaloids as well as for the separation of stereoisomers and of ester homologues.