Simultaneous analysis of first-line anti-tuberculosis drugs in tablets by UV spectrophotometry compared to capillary zone electrophoresis

The development and optimization of a novel UV spectrophotometric methodology was proposed for simultaneous analysis of ethambutol (ETB), isoniazid (ISO), rifampicin (RIF) and pyrazinamide (PYR), using multivariate calibration based on the partial least squares method (PLS). The methodology was successfully applied for analysis of four-drug fixed dose combination (4-FDC) tablets used for tuberculosis treatment. A 3⁴ Box-Behnken design, with triplicate in central point, was used for sample preparation in the calibration step. In the present case, nine latent variables were chosen for the model development that presented the smallest RMSECV and explain 98.76% of data variance in Y block (concentrations of ETB ISO, RIF and PYR) and 99.93% of data variance in X block (spectral data). PLS models for ETB, ISO, RIF and PYR presented RMSEP and R² values of 0.23 mg L^?1 and 0.971; 0.14 mg L^?1 and 0.731; 0.11 mg L^?1 and 0.990 and 0.57 mg L^?1 and 0.972, respectively. A validation step was performed based on the comparison between the UV spectrophotometric proposed methodology and capillary zone electrophoresis (CZE) in 4-FDC real samples and no significant difference was found between two methodologies at 95% of confidence level.      

Determination of lead in solution by solid phase extraction, elution, and spectrophotometric detection using 4-(2-pyridylazo)-resorcinol

Lead (+2) was selectively adsorbed on a solid phase extraction (SPE) gel (molecular recognition technology, MRT), quantitatively extracted, and spectrophotometrically determined as the Pb(II)-PAR (4-(2-pyridylazo)-resorcinol) complex. The linear range was 0.01 to 0.75 mg L^?1 and the detection limit was 6.4 µg L^?1. The MRT-SPE allows selective Pb(II) extraction from complex ion-rich matrices, which is difficult with other techniques. Interference from common matrix ions such as Fe²⁺, Ni²⁺, Cu²⁺ or Co²⁺ is minimized.      

Biodegradation of Benzo[a]Pyrene through the use of algae

In this work for disposal of the biologically hard decomposed pollutant Benzo[a]Pyrene (BaP) photooxidation Chlorella kessleri was used. The simulation model system under the different experimental conditions (varying biomass and light intensity) was evaluated. For quantitative analysis of the decrease in BaP, GC/MS technique was used. The highest degradation efficiency was achieved in the case of biomass from the culture of live algae (29%) and light intensity at level of 13.5 W m^?2. When the dry biomass was used, degradation under the same conditions was lower because of lack of enzymatic activity in the system.      

The use of ultrasonic treatment for improvement of metrological performance of sorption atomic absorption determination of lead(II) and cadmium(II) traces

The optimal parameters for ultrasonic treatment (frequency 200–300 kHz, intensity 2–4 W cm^?2) were obtained to intensify Pb(II) and Cd(II) sorption concentration by carbon sorbent from apricot pit. The combined action of ultrasonic frequency of 18 kHz and 1 MHz on concentrate slurry increases its sedimentation stability from 3 to 180 minutes and decreases S_r value up to 7% at Pb(II), Cd(II) hybrid sorption atomic absorption determination in natural waters, brines, common salt.      

Epoxy resin modified with amine as an effective complexing agent of metal cations

A simple synthesis of a material capable of metal cation removal is proposed. The material was a derivative of epoxy resin containing amine groups. It is insoluble in water and in this study it was characterized by elemental analysis and infrared spectroscopy. The sorbent obtained was tested for its ability to remove coper(II), cadmium(II) and lead(II) from water solutions. The tests were performed for different concentrations of metal ions (10–200 mg L^?1) and at different pH (2.0–9.0). The effects of temperature and stirring time, as well as reusability of the sorbent were also studied in batch experiments. In the optimum conditions, the decrease in the cation concentration in aqueous solutions was observed in the order Cu>Pb>Cd but for each ion the decrease was at least 50% of the initial concentration. The sorbent has demonstrated high effectiveness in cation sorption and after regeneration it can be applied repeatedly in the process described.      

Polymer conjugates with potential biological activity based on new derivatives of 2-mercaptobenzoxazole-synthesis and characterization

New potentially biologically active compounds derived from 2-mercapto-benzoxazole were synthesized and coupled on polymeric support of poly (maleic anhydride-alt-vinyl acetate) for the preparation of polymer-drug conjugates with controlled drug release. All compounds were characterized by elemental and spectroscopy (FT-IR, ¹H-NMR) analysis. The toxicological tests recommend the products for further laboratory screening.      

Sensitive and fast determination of papaverine by adsorptive stripping voltammetry on renewable mercury film electrode

The renewable mercury film electrode, applied for the determination of papaverine traces using differential pulse adsorptive stripping voltammetry (DP AdSV) is presented. The calibration graph obtained for papaverine is linear from 1.25 nM (0.42 µg L^?1) to 95 nM (32.2 µg L^?1) for a preconcentration time of 60 s, with correlation coefficient of 0.998. For the renewable mercury electrode (Hg(Ag)FE) with a surface area of 9.1 mm² the detection limit for a preconcentration time of 60 s is 0.7 nM (0.24 µg L^?1). The repeatability of the method at a concentration level of the analyte as low as 17 µg L^?1, expressed as RSD is 3.3% (n=5). The proposed method was successfully applied and validated by studying the recovery of papaverine from drugs, urine and synthetic solution.      

A procedure for meaningful unsupervised clustering and its application for solvent classification

Artificial neural networks have proven to be a powerful tool for solving classification problems. Some difficulties still need to be overcome for their successful application to chemical data. The use of supervised neural networks implies the initial distribution of patterns between the pre-determined classes, while attribution of objects to the classes may be uncertain. Unsupervised neural networks are free from this problem, but do not always reveal the real structure of data. Classification algorithms which do not require a priori information about the distribution of patterns between the pre-determined classes and provide meaningful results are of special interest. This paper presents an approach based on the combination of Kohonen and probabilistic networks which enables the determination of the number of classes and the reliable classification of objects. This is illustrated for a set of 76 solvents based on nine characteristics. The resulting classification is chemically interpretable. The approach proved to be also applicable in a different field, namely in examining the solubility of C₆₀ fullerene. The solvents belonging to the same group demonstrate similar abilities to dissolve C₆₀. This makes it possible to estimate the solubility of fullerenes in solvents for which there are no experimental data      

Voltammetric behavior and quantitative determination of ambazone concentrations in urine and in a pharmaceutical formulation

The use of square wave adsorptive stripping voltammetry (SWAdSV) in conjunction with a cyclic renewable silver amalgam film electrode (Hg(Ag)FE) for the analytical determination of ambazone in urine samples and pharmaceutical formulations is described. A single reduction peak in Britton-Robinson buffer at pH 4.0 was detected at about ?1.4 V versus Ag/AgCl. Mechanistic studies have shown that the compound can act as an electrocatalyst. The method was validated. The analytical curve was linear in the concentration range from 1.0×10^?9 to 1.0×10^?7 mol L^?1. The detection and quantification limits were found to be 3.0×10^?10 mol L^?1 and 1.0×10^?9 mol L^?1, respectively. The proposed method was successfully applied to ambazone determination in real samples.      

Investigation of electrical properties of PANI/chalcogenide junctions

Pure Polyaniline (EB) and Polyaniline doped with different protonic acids (ESs) were chemically synthesized using ammonium peroxydisulphate (APS) as an oxidant. Junctions have been prepared by evaporating chalcogenide materials (ZnSe, CdSe) on conducting polyaniline (EB & ESs) pellets using a vacuum evaporation technique. I–V characteristics of junctions have been studied at room temperature using the Keithley electrometer 6517A. I–V measurements show the rectification effect. A junction of ES[PO₄ ^3?] may be preferred over the other junctions due to its low ideality factor and maximum rectification ratio.      

Preparation of selectively protected protoescigenin derivatives for synthesis of escin analogs and neoglycoconjugates

Protoescigenin, the main aglycone of horse chestnut saponin mixture known as escin, was selected as substrate for exploratory chemistry towards selective protection, followed by propargyl ether formation and subsequent condensation with azido-monosaccharides, to obtain novel triazole linked conjugates of the triterpene.      

Supramolecular complexes of podand ligands with xenon

Formation of stable complexes between xenon and podand polyoxyethylene ligands was ascertained. The complexation process was studied by ¹²⁹Xe NMR titration, NMR diffusiometry and heteronuclear NOE measurements. The ligands studied form a 1:1 complexes with Xe(0). Their stability constants depend on the ligand structure, i.e., polyoxyethylene chain length, number of complexating polyether units and the topology of the anchoring centre.      

Dynamic pressure thermal analysis of double-base propellants containing RDX

The thermal decomposition of five double-base propellants modified with RDX was studied by dynamic pressure thermal analysis to determine the effect of RDX content (20–60 wt.%) on performance. All have good stability. Both stability and activation energy increase as RDX increases from 20% to 50% then decrease; 50% RDX performs best. The decomposition mechanism is affected by RDX content and temperature. Increasing temperature induces autocatalysis and accelerates decomposition.      

Reaction of barbituric acid with organic azides and phosphonium ylides

Amination by organic azides has been carried out to provide aminobarbiturates by fusion of a triazole ring to the 5,6-positions of barbituric acid followed by cleavage and thermal elimination of nitrogen, whereas aza-Wittig reaction gave phosphoranylidene barbituric acid salts.      

The first synthesis of 3-deoxyoripavine and its utilization in the preparation of 10-deoxyaporphines and cyprodime

The synthesis of 3-deoxyoripavine (7) was realized as a novel and promising intermediate towards the synthesis of the important class of dopaminergic and/or serotonergic 10-deoxyaporphines and the special pharmacological tool µ opioid antagonist cyprodime. Generally, the preparation of these valuable biologically active compounds was achieved in remarkable yields.      

Determination of some frequently used antibiotics in waste waters using solid phase extraction followed by high performance liquid chromatography with diode array and mass spectrometry detection

This study is focused on the determination of some important antibiotics from different classes in waste water samples using solid phase extraction followed by high performance liquid chromatography with two detectors, diode array and mass spectrometer in positive ionisation mode. The investigated antibiotics include three penicillins (amoxicillin, ampicillin, penicillin G), two cephalosporins (ceftazidime, ceftriaxone), and two tetracyclines (tetracycline, doxycycline). The studied antibiotics were extracted from waste water samples using hydrophilic-lipophilic balanced cartridges. The extraction of antibiotics from water matrices was tested at several pH values. The best recoveries were obtained at pH 3 and 7 respectively. Depending on the nature of antibiotic, the limits of detection and quantification were obtained in the range of 0.07–0.92 µg mL^?1 and 0.21–2.77 µg mL^?1 respectively. Influent and effluent waste water samples were collected from a Waste Water Treatment Plant from Romania in order to detect the studied antibiotics. The antibiotics detected in the influent waste water samples were ceftriaxone (334 µg L^?1), tetracycline (146 µg L^?1) and doxycycline (110 µg L^?1). In effluent waste water samples no target antibiotics were detected.      

Two charge-transfer complex spectrophotometric methods for the determination of sulpiride in pharmaceutical formulations

Two simple, rapid, accurate and sensitive spectrophotometric methods are described for the determination of sulpiride. They are based on charge transfer complexation between the drug as n-electron donor and p-chloranilic acid as π acceptor or iodine as σ-acceptor. These give highly coloured complexes with absorption maxima at 518 and 363, 294 nm, respectively. Beer’s law linear ranges were 13.7–341.4 and 1.7–20.5 µg mL^?1 for the p-chloranilic acid and iodine methods. The methods were successfully applied to the determination of the drug in Dogmatil® Fort tablets and the results compared with the official method. The complex association constants and standard free energy changes were calculated using Benesi-Hildebrand plots.      

Debromination of 2,4,6-tribromophenol coupled with biodegradation

The application effect of aluminium and their alloys and mixtures with nickel was studied for the complete hydrodebromination of 2,4,6-tribromophenol (TBP) to phenol in aqueous NaOH solution at room temperature. It was found that the Raney Al-Ni alloy can rapidly transform TBP to phenol. Removal efficiency of 25 mM TBP solution in aqueous NaOH (15 g L^?1) solution at the end of 1h reaction was 100% using 4 g L^?1 Al-Ni. The hydrodebromination is accompanied by the dissolution of aluminium and formation of soluble Al(OH)₄ ^?1 anions under these reaction conditions. After completion of the hydrodebromination reaction removal of the dissolved metals was achieved by precipitation of appropriate hydroxides by adjustment of the pH value and filtration, the filtrate was treated with Pseudomonas or Rhodococcus bacterial strains to degrade dissolved phenol. The combined application of both (chemical-biological) treatments produced degradations of 100% of aromatic compounds.