An Optical-Fiber Sensor for Colchicine Using Photo-Polymerized N-Vinylcarbazole

An optical-fiber sensor for colchicine has been fabricated. It is based on the use of the fluorescent dye N-vinylcarbazole, which contains a vinyl unit making it photo-copolymerizable in the presence of a monomer, 1,2-cyclohexanediol diacrylate, on a quartz surface of an optode slide. Prior to the photo-polymerization process the quartz surface was modified with -(methacryloxy)propyl trimethoxysilane to introduce vinyl units. A dye-incorporating optode membrane tightly immobilized on the quartz surface was prepared in this way. The spectral characteristics of the optode for sensing colchicines were evaluated, and the response mechanism was discussed. The optode membrane has a relatively long lifetime and short response and recovering time. The linear range of determining colchicine is from 1.0×10^–6 to 4.0×10^–3molL^–1. The sensor was applied to determine the colchicine content in pharmaceutical tablets the results of which agreed with those obtained by the pharmacopoeia method.Received December 12, 2002; accepted March 25, 2003 Published online July 16, 2003     

Effect of 2-Hydroxypropyl-β-cyclodextrin on Release Rate of Metoprolol from Ternary Metoprolol/2-hydroxypropyl-β-cyclodextrin/Ethylcellulose Tablets

The effect of 2-hydroxypropyl--cyclodextrin (HP--CyD) on the release of a water-soluble ₁-selective adrenoreceptor antagonist, metoprolol (Met), from ternary Met/HP--CyD/ethylcellulose (EC) tablets was investigated. The release rate of Met from the ternary tablets was dependent on amounts of HP--CyD in the tablets, i.e., the rate decreased when small amounts of HP--CyD were added, while large amounts of HP--CyD accelerated the rate. The slowest rate was observed for the tablet consisted of a 30/10/60 weight ratio of Met/HP--CyD/EC. The analyses of the release rates by the Korsmeyer equation and their temperature dependence suggested that Met is released from the EC matrix containing HP--CyD according to the diffusion-controlled mechanism. The water penetration studies and the micro- and macroscopic observations suggested that the retarding effect of HP--CyD is attributable to a viscous gel formation in small pores on the surface of the tablets, where HP--CyD gels may work as a barrier for the water penetration into the tablets and the release of the drug from the tablets. The in-vitro release property of the ternary tablets was reflected in the in-vivo absorption profile in dogs. The results indicated that a combination of HP--CyD and EC is useful for the release control of water-soluble drugs such as Met.     

Determination of pefloxacin in serum and pharmaceutical forms by derivative spectrophotometry

A method for the direct determination of pefloxacin in serum and pharmaceutical forms (tablets and ampoules) has been developed, based on the use of second-order derivative ultraviolet spectra. Spectrophotometric assay of pefloxacin in tablets and ampoules was carried out in 0.1 mol/L NaOH, while in serum it was performed in 0.1 mol/L NaOH with the addition of sodium dodecylsulfate, in 337–347 nm wavelength range. Linear calibration curves were obtained in the concentration ranges 2–30g/mL pefloxacin for tablets and ampoules and 0.12–5 g/ mL for serum samples. Relative error of determination, as criterion for accuracy, was less than 1%, while the precision was better than 4 ng/ml. The minimum detectable concentration of pefloxacin in serum was 15 ng/mL.     

Determination of vitamin A in pharmaceutical preparations by high-performance liquid chromatography with diode-array detection

Summary A very simple high-performance liquid chromatographic method for determination of Vitamin A in pharmaceutical preparations without the need for saponification was developed. A reversed-phase (Nova-Pack C₁₈, 4 m) column was used with a mobile phase of acetonitrile-tetrahydrofuran-water (55378) and a flowrate of 1.5 ml/min. Sample treatment only consisted of the extraction of retinol acetate content from capsules or tablets with methanol. Total extraction was achieved by shaking vigorously with the aid of magnetic stirring for three hours at room temperature. No change of solvent is necessary to introduce the sample in the chromatographic system. This method is suitable for routine quantification of Vitamin A.     

Increasing the solubility characteristics of iomeglamic acid withβ-cyclodextrin

Iomeglamic acid has been successfully applied for radioscopy of the gall-bladder since 1972. This pharmacon has the disadvantageous property that it is practically insoluble in water. Preparations containing the drug in different concentrations were made with-cyclodextrin by different methods, and their dissolution characteristics were determined. In the best situation the solubility increased ten-fold. The tablets were made from the most suitable complex, with-cyclodextrin. The conditions of tableting, the parameters and the dissolution of the tablets were tested.     

Determination of kinetic parameters of the FeCl3/FeCl2 systemvia a novel treatment of chronoamperometric data

Summary Computer based methods for the processing of chronoamperometric datavia convolutions are discussed. On the example of the quasi-reversible Fe³⁺/Fe²⁺ couple, their application for data acquisition and determination of the heterogeneous electrochemical parameters is demonstrated. The plot of Q/i vs. t/i is superior to that employingi/I ₁, being less sensitive to distortions by charging currents once these have died away and by the effects of damping on the initially rapidly varying currents. Cyclic voltammetry is often combined with convolution or deconvolution, and digital simulation studies are also frequently performed to confirm the results.

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Bestimmung kinetischer Parameter des Systems FeCl₃/FeCl₂ mittels einer neuen Verarbeitung chronoamperometrischer Daten

Zusammenfassung Computerunterstützte Verfahren zur Verarbeitung chronoamperometrischer Daten mittels Faltungsintegralen werden diskutiert. Am Beispiel des quasireversiblen Systems Fe³⁺/Fe²⁺ wird die Anwendung der neuen Methoden zur Datenerfassung und zur Bestimmung der heterogenen elektrochemischen Parameter gezeigt. Der Plot von Q/i gegen t/i ist dem voni/I ₁ überlegen, da er durch Ladeströme und Dämpfung der ursprünglich stark variierenden Ströme weniger stark beeinflußt wird. Cyclische Voltammetrie wird häufig im Zusammenhang mit Konvolutions- und Dekonvolutionsmethoden angewandt; digitale Simulation zur Überprüfung der Ergebnisse wird ebenfalls oft eingesetzt.

     

Spectrofluorimetric determination of guanethidine sulphate,guanfacine hydrochloride,guanoclor sulphate and guanoxan sulphate in tablets and biological fluids,using benzoin

A sensitive and rapid Spectrofluorimetric method for the determination of guanethidine sulphate, guanfacine hydrochloride, guanoclor sulphate and guanoxan sulphate in tablets and spiked human serum and urine samples is described. The method is based on the reaction of monosubstituted guanidino compounds in an aqueous potassium hydroxide solution with benzoin, in the presence of -mercaptoethanol and sodium sulphite. Highly fluorescent derivatives were obtained, with excitation and emission maximum wavelengths around 325 and 430 nm, respectively. In optimal reaction conditions, the linearity ranges were 0.04–0.28 g/ml, with relative standard deviations less than 2%. The method has been successfully applied to the determination of these drugs in tablets. The results are highly correlated with the B.P. method. Chloroform (or for guanoxan dichloromethane) was used to extract the drugs from serum and urine at basic pH, followed by the proposed fluorimetric method. The limit of detection is 0.02 g/ml for the selected drugs.     

Determination of iodine anion in dried kelp and iodized throat tablets by reversed-phase ion-pair liquid chromatography with direct UV detection

Summary In this paper, the amount of iodine anion in dried kelp and iodized throat tablets was determined by reversed-phase ion-pair chromatography. A 300×4 mm I.D. columns packed with -Bondapak-C18 (5 m) was used and distilled water containing 10 mmol/l trimethylphenyl ammonium bromide was used as the eluent. UV detection at 231 nm was selected to monitor the iodine anion.     

A Biokinetic Model to Describe Consequences of Inhibition/Stimulation in <Emphasis Type="Italic">DNA</Emphasis>-Proofreading and -Repair,Part 4

Summary. In previous papers a strongly simplified physical-mathematical (biokinetic) model has been presented, which dealt with the factors influencing the timely development of DNA mismatches dependent cells (malignant cells) in their kinetic competition to the development of normal somatic cells (i.e. cells with correct genetic information). The kinetic results have been studied by comparing them with experimental results reported in the literature upon inhibiting the organisms own enzymatic DNA-proofreading and repair machinery. In spite of the fact that the model uses fully the chances of kinetics, which allows to describe even rather complicated systems with many regulation circuits and feed back loops in a rather simple, summarizing way, it has been demonstrated that the model does not only well describe the experimentally found significant increases of mutants in cases when the DNA repair system has been inhibited, but it can also reflect cancer-development and the efficacy of classical cancer therapies like surgery or chemotherapy as well.In applying the predictions of the model as to the opposite of an inhibition of the DNA repair system, i.e., in testing the results, if the organisms own repair systems were stimulated, the model shows that there could be a chance for a new, adjuvant cancer-therapy if this concept was combined with biochemical facts and clinical findings which are reported in the literature.In continuation of this concept, the predictions of the model have been compared with findings upon cancer-therapies by apoptosis-triggerers like tamoxifen. Further, according to the fact that there exists literature by which it is demonstrated by clinical facts that it is not necessary to use living cells (e.g. from umbilical cords blood or bone-marrow) to achieve surprising therapeutic successes in cancer therapy, but also cell-free human-placenta-extracts (HPEs) can be similarily effective, it has been tried in a first preliminary analytical effort to characterize effector-substances contained therein.Received January 27, 2003; accepted (revised) March 25, 2003 Published online August 18, 2003     

Synthesis of Side Chain Substituted 3-Butylisocoumarins and Absolute Configurations of Natural Isocoumarins from <Emphasis Type="Italic">Artemisia dracunculus</Emphasis>

Summary. A series of 3-hydroxy- and 3-bromobutyl-substituted isocoumarins was synthesized. The absolute configurations of three isocoumarin derivatives from Artemisia dracunculus, namely (–)-epoxyartemidin, (–)-2-methoxydihydroartemidin, and (+)-3-hydroxyartemidin were determined by chemical means via derivatization, kinetic racemate resolution (Horeau method), and comparison of the circular dichroism (CD) spectra.DeceasedReceived March 17, 2003; accepted March 19, 2003 Published online August 18, 2003     

Education by Teaching Analytical Chemistry in Romania

A review is given on the history of the development of analytical chemistry in Romania, its present role in University teaching, and on measures that are planned in order to improve teaching and education.Received January 12, 2003; accepted March 7, 2003 Published online July 16, 2003     

Synthesis of Spiro and Fused Five Membered <Emphasis Type="Italic">N</Emphasis>-Heterocycles from Alkylidenephosphoranes

Summary. Triketoindan-2-oxime reacted readily with ethoxycarbonylmethylene triphenylphosphorane to give mainly the corresponding spiro-pyrrole (38%) along with the fused 1-hydroxydihydropyrrole (14%), whereas the spiro-dimer (29%) was obtained from the reaction of the oxime with methoxycarbonylmethylenetriphenyl phosphorane in addition to the corresponding 1-hydroxydihydropyrrole (31%). Conversely, Wittig products, mono-olefin (52%) and diolefin (<7%) along with the reduced substrate (10%), were observed when the oxime was treated with a cyano ylide. The reactions of the oxime with allyl- and vinyl phosphonium salts proceeded under phase-transfer catalysis to afford fused oxazole (46%) and spiro[2]oxazole (17%), while with the latter the fused 1-hydroxypyrrole (55%) was produced.Received February 26, 2003; accepted (revised) March 19, 2003 Published online August 28, 2003     

Serum Chloride Optical Sensors Based on Dynamic Quenching of the Fluorescence of Photo-Immobilized Lucigenin

This article describes the preparation and performance of an optical sensor for continuous measurement of chloride at extracellular (serum) levels (20–200mM). The sensor is based on dynamic quenching of the fluorescence of lucigenin which was photo-immobilized on a hydrogel. Quenching occurs via a collisional mechanism, and the decrease in fluorescence intensity on exposure to 100mM chloride typically is –60%. It allows the determination of chloride in the 1 to 200mM concentration range, with a precision of ±3mM at 120mM. Bromide, iodide and salicylate act as interferents, while the effect of pH and oxygen is negligibly small. The sensor displays strong fluorescence intensity, excellent reproducibility, long-term stability, response times in the order of 2–5min, and is used in a commercial serum and blood chloride analyzer.Received January 21, 2003; accepted April 6, 2003 Published online July 28, 2003     

Study of the Microtexture of Recrystallized Aluminium

The nucleation of recrystallized grains in deformed, high-purity aluminium were examined in relation to the microstructural heterogeneities in the form of shear bands (SBs) and transition bands (TBs). The experiments were carried out on single crystals deformed in channel-die compression at 77 K to true strains within the range of 1–1.5. The substructures were identified by means of a combination of transmission (TEM) and scanning (SEM) electron microscopes. Local texture measurements in particular places of samples were mostly investigated by means of TEM and convergent beam electron diffraction (CBED), with on-line diffraction pattern analysis. The coarser analyses were performed by SEM and electron back scattered diffraction (EBSD). The and the oriented single crystals are stable in the global sense and form clearly defined SBs. The , and the shear orientations are very unstable and tend to form TBs. The nuclei of new grains formed along the band are misoriented by ( ) with respect to the orientations identified within the neighbouring banded material. The author attempts to explain, from the crystallographic point of view, the processes operating within high stacking fault energy metals at the very early stages of recrystallization.     

Reaction of Metal Alkoxides with Lysine: Substitution of Alkoxide Ligands vs. Lactam Formation

Summary. Reaction of Ti(OEt)₄ with lysine results in the formation of Ti(OEt)₃(lysinate), as previously reported. Contrary to that, Al(O^sBu)₃ only catalyzes the formation of 3-aminocaprolactam, and no substitution product was observed. The reaction of Zr(OBu)₄ with lysine at room temperature produced both 3-aminocaprolactam and Zr(OBu)₃(lysinate); the lysinate complex was not observed when the reaction was performed at elevated temperatures.Received February 17, 2003; accepted February 21, 2003 Published online June 12, 2003     

Validation of the RP–HPLC method for analysis of hydrochlorothiazide and captopril in tablets

A rapid and sensitive reverse-phase high performance liquid chromatography (RP–HPLC) method with ultra-violet (UV) detection for a routine control of hydrochlorothiazide and captopril in tablets was developed. The chromatographic system Hewlet Packard 1100 consisted of a HP 1100 pump, HP 1100 UV–VIS detector and HP ChemStation integrator. The samples were introduced through a Rheodyne injector valve with a 20-L sample loop. The isocratic system consisted of a Beckman Ultrasphere ODS 4.6 mm x 15 cm, 5-m-particle column and a mobile phase containing methanol/water (45:55 v/v). The pH of the mobile phase was adjusted to 3.8 with 85% ortophosphoric acid. Quantitation was accomplished using the internal standard method. At the selected conditions, the other excipients of the tablets did not interfere in the assay of active substances. The developed RP–HPLC method was validated, so linearity, precision, accuracy, robustness, limit of quantitation and limit of detection were investigated. For the robustness test, three factors were considered: the composition of the mobile phase , the pH of the mobile phase, and temperature. With the aid of response surface metodology (RSM), it was possible to precisely define the robustness of the method.     

Screening and Identification of the Metabolites of Water Extracts of Raw and Honey-Processed <Emphasis Type="Italic">Astragalus</Emphasis> in Rat Urine Based on UHPLC/ESI-Q-TOF-MS and Multivariate Statistical Analysis

Radix Astragali is a famous traditional Chinese medicine and honey-processed Astragalus is a product of Radix Astragali acquired by honey-processing. These two products are widely utilized to treat various diseases. In this study, we screened bioactive components and metabolites of raw and honey-processed Astragalus in rat urine by ultra-performance liquid chromatography equipped with electrospray ionization/quadrupole time-of-flight mass spectrometry (UHPLC/ESI-Q-TOF-MS) combined with multivariate statistical analysis. In total, 62 compounds, including 7 parent compounds and 55 metabolites, were detected and 11 metabolites were characterized for the first time. The identified metabolites indicated that the metabolic reactions of Astragalus in rats included hydroxylation, glucuronidation, deglucosidation, monomethylation, demethylation, sulfation, hydrogenation, and dehydroxylation. The metabolic pathways of raw and honey-processed Astragalus in rat urine also were clarified. Through multivariate statistical analysis of the data of the raw and honey-processed Astragalus groups, we found that 20 compounds were differential components and that 1 metabolite only existed in the honey-processed Astragalus group. The differences in these ingredients between these two groups might provide the basis for interpreting the biologic activity differences in traditional Chinese medicine treatments.

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Graphical Abstract

     

Azoles 48 [1]: Synthesis of Some 4-Amino-2-methyl-5-nitro-1-phenacylimidazoles

Summary. Reactions of 1-phenacyl derivatives of 2-methyl-4,5-dinitroimidazole with primary or secondary amines (aniline, morpholine, piperidine, pyrrolidine) yielded the 4-amino-5-nitroimidazole derivatives only.Received January 23, 2003; accepted (revised) February 5, 2003 Published online June 2, 2003