Colorimetric determination of isoniazid and its pharmaceutical formulations

Two colorimetric methods for the estimation of isoniazid are developed. The first method depends on coupling of isoniazid with diazotized 1-amino anthraquinone zinc chloride salt (fast red AL salt) to form a red colour (lambda(max) 510 nm). The second one is based on the formation of a green complex (lambda(max) 655 nm) between the acid hydrazide and 2,6-dimethoxy-1,4-benzoquinone (DMBQ). All measurements of the two procedures were carried out in the presence of sodium hydroxide at room temperature (20 +/- 3 degrees C). The two methods are applied for the determination of isoniazid in presence of congenial drugs, vitamins and additives normally encountered with it in pharmaceutical dosage forms. The reliability of these methods was established by parallel determination with the reported and official methods.     

Utility of copper(II) oxide as a packed reactor in flow injection assembly for rapid analysis of some angiotensin converting enzyme inhibitors

A new simple, sensitive, rapid and precise flow injection (FI) procedure based on the formation of copper complexes with some angiotensin converting enzyme (ACE) inhibitors has been developed and evaluated for the analysis of lisinopril (LN), enalapril maleate (EP), ramipril (RP) and perindopril tert-butylamine (PD). In this method, samples were injected into a flowing stream of distilled-deionized water, carried through the packed reactor of CuO for derivatization followed by ultraviolet (UV) detection. The flow rate was 1.5 ml min⁻¹ and column temperature was ambient (25 °C). Lisinopril was injected directly into the flowing stream and the detector response was measured at 262 nm. The hydrolysis products of enalapril maleate, ramipril and perindopril tert-butylamine in 0.2N NaOH were injected after neutralization with 1N HCl and the detector response was measured at 272, 265 and 252 nm, respectively. The developed method was successfully applied to the determination of tested drugs in pharmaceutical preparations at a sampling rate of 60 samples h⁻¹ and a recovery near 100% for all compounds.     

Thermodynamics of Ion-Association of NaClO4 in Aqueous-Methanol and Aqueous-Glycerol Using Conductance Measurements

The conductance of NaClO₄ at (25–45)°C in methanol-H₂O, and glycerol-H₂O mixtures in a concentration range up to 10^?2 M has been measured. The association constant, K_A, values have been determined, where the conductometric data were analysed by a M S X computer using the Fuoss-Aprano method. The K_A values for NaClO₄ in methanol-H₂O are higher than in glycerel-H₂O mixtures, Also K_A values increase as the proportional of methanol or glycerol increases in mixture. The thermodynamic parameters ΔH°, ΔG°, and ΔS° were also calculated. It is obvious that the entire process of the ionic association in those systems are endothermic ones. The Walden products, Λ_oη were calculated for all systems investigated.     

Development and validation of a stability-indicating RP-HPLC method for the determination of paracetamol with dantrolene or/and cetirizine and pseudoephedrine in two pharmaceutical dosage forms

A stability-indicating reversed-phase high-performance liquid chromatography (RP-HPLC) method has been developed which can separate and accurately quantitate paracetamol, dantrolene, cetirizine and pseudoephedrine. The method was successfully validated for the purpose of conducting stability studies of the four analytes in quality control (QC) laboratories. The stability-indicating capability of the method was demonstrated by adequate separation of these four analytes from all the degradant peaks. A gradient mobile phase system consisting of (A) 50 mmol L⁻¹ sodium dihydrogen phosphate, 5 mmol L⁻¹ heptane sulfonic acid sodium salt, pH 4.2 and (B) acetonitrile was used with Discovery reversed-phase HS C₁₈ analytical column (250 mm × 4.6 mm i.d., 5 μm particle size). Quantitation was achieved with UV detection at 214 nm, based on peak area.The proposed method was validated and successfully applied for the analysis of pharmaceutical formulations and laboratory-prepared mixtures containing the two multicomponent combinations.     

Action of Hydrazines on 2‐(2‐Oxindolin‐3‐ylidene)malononitrile, (E,Z)‐Ethyl 2‐cyano‐2‐(2‐oxindolin‐3‐ylidene)acetate and Isatin‐β‐thiosemicarbazone as a Source of Spiro Indoline‐pyrazole Systems

2‐(2‐Oxindolin‐3‐ylidene)malononitrile ( 1a ) or (E,Z)‐ethyl 2‐cyano‐2‐(2‐oxindolin‐3‐ylidene)acetate ( 1b ) or isatin‐β‐thiosemicarbazone ( 1c ) undergoes reactions with prototype hydrazine hydrate itself and some of its simple congeners to give hydrazone derivatives bearing indoline‐2‐one moiety ( 2 ). The hydrazone derivatives ( 2 ) when heated with acetyl acetone or ethyl acetoacetate in dry pyridine afforded the spiro indoline derivatives ( 3a , 3b ). Also, cinnoline derivative ( 9 ) is obtained by action of hydrazine hydrate on the N‐acetyl derivative of ( 6a ). The structures of the newly synthesized compounds were evaluated by IR, ¹H‐NMR spectroscopy, mass spectra and elemental analyses.     

LMI based design of constrained fuzzy predictive control

Predictive control of nonlinear systems subject to output and input constraints is considered. A fuzzy model is used to predict the future behavior. Two new ideas are proposed here. First, an added constraint on the applied control action is used to ensure the decrease of a quadratic Lyapunov function, and so guarantee Lyapunov exponential stability of the closed-loop system. Second, the feasibility of the finite-horizon optimization problem with the added constraints is ensured based on an off-line solution of a set of LMIs. The novel stability method is compared to the existing methods, such as the techniques based on the end-point constraints (terminal constraint set), and the robust stability techniques based on the small gain theory. The proposed method ensures Lyapunov exponential stability, does not need an auxiliary controller and can be used with any feasible controller parameters. Illustrative examples including the predictive control of a highly nonlinear chemical reactor (CSTR) are discussed.     

Syntheses, spectroscopic characterization and thermal behavior on novel binuclear transition metal complexes of hydrazones derived from 4,6-diacetylresorcinol and oxalyldihydrazine

4,6-Diacetylresorcinol (DAR) serves as precursor for the formation of different hydrazone ligands, which are di-, tetra- or hexa-basic with two symmetrical sets of O(2)N tridentate, O(2)N(2) tetradentate or O(4)N(2) hexadentate chelating sites. The condensation of 4,6-diacetylresorcinol (DAR) with oxalyldihydrazine (ODH), in the molar ratio 1:1 and 1:2, yields the corresponding hydrazone, H(6)L(a) and H(4)L(b), ligands, respectively. The structures of these ligands were elucidated by elemental analyses and IR, mass, (1)H NMR and UV-vis spectra. Reactions of the hydrazone ligands with cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), iron(III) and chromium(III) ions in 1:2 molar ratio afforded the corresponding transition metal complexes. A variety of binuclear transition metal complexes were obtained in its di-, tetra- or hexa-deprotonated forms. The structures of the newly prepared complexes were identified by elemental analyses and IR, UV-vis, mass, (1)H NMR and ESR spectra, as well as, magnetic susceptibility measurements and thermal gravimetric analysis (TGA). The bonding sites are the azomethine and CO oxygen atoms in either keto or enol forms and amino nitrogen atoms, and phenolic oxygen atoms. The metal complexes exhibit different geometrical structures such as tetrahedral and octahedral arrangements.     

New HPLC method to detect individual opioids (heroin and tramadol) and their metabolites in the blood of rats on combination treatment

Drug abuse is both an age-old and a constantly evolving problem in society. Trends in illicit drug use are highly fluid, with new formulations increasing in popularity. For this reason, methods for illicit drug detection and analysis need to be continually updated so they remain useful and relevant. A recent trend in street heroin production has seen it diluted with large amounts of tramadol in addition to the classical diluents such as acetaminophen and caffeine. This study describes a sensitive, simple and accurate high-performance liquid chromatographic method with ultraviolet detection for the simultaneous detection of heroin, 6-acetylmorphine, morphine, tramadol and O-desmethyltramadol in the blood of rats using a liquid-liquid back-extraction method. The separation was performed on LichroCART RP-18e with particle size of 5 μm (250 × 4.6 mm) with mobile phase acetonitrile-50 mM KH(2)PO(4) buffer, pH 7.1, using a gradient mode with a 1.0 mL/min flow rate. The calibration curves were linear in the concentration ranges 0.25-100 and 0.1-100 μg/mL for morphine and other analytes, respectively. Recovery values for the substances ranged between 59 and 83%. This technique was successfully used in pharmacokinetic studies measuring 6-acetylmorphine, morphine, tramadol and O-desmethyltramadol in the blood of rats intraperitoneally treated with a blend of 10 mg/kg heroin and 70 mg/kg tramadol. This technique shows promise for analysis of confiscated street heroin.     

Tetraammine(selenito‐O,O′)cobaltate(III) nitrate monohydrate

The title compound crystallizes as the mono­hydrate, [Co(SeO₃)(NH₃)₄]NO₃·H₂O. The crystallographic mirror symmetry coincides with the molecular symmetry; the mirror plane passes through the cation, anion and water mol­ecule. The CoN₄O₂ octahedron is distorted, with the selenito group acting as a bidentate ligand through two bridging O atoms to the cobalt. The coordinated Se—O distance is 1.742 (2) Å, whereas the uncoordinated Se—O distance is 1.646 (3) Å. A three‐dimensional hydrogen‐bonded network exists between [Co(SeO₃)(NH₃)₄]NO₃ and the water mol­ecule. The nitrate anion and water mol­ecule form open pores in the structure when hydrogen bonded to two neighboring [Co(SeO₃)(NH₃)₄]⁺ cations. Selenium participates in two types of relatively close intermolecular interactions with neighboring charged species (Se?N1 and Se?O3), but does not participate in an interaction with a neighboring O2 atom, the nearest contact distance being 4.638 (3) Å.     

Simulation of transient flow in pipelines for computer‐based operations monitoring

Computer models can provide the basis for real‐time monitoring and control of fluid flow in pipelines. Problems of fluid flow in pipelines are mathematically represented by a non‐linear system of coupled partial differential equations. In this paper, several numerical techniques are evaluated with respect to their suitability for the purpose of real‐time monitoring of fluid flow in pipelines. The proposed techniques are evaluated in terms of the L₁, the L₂, and the L_∞ error norms. Moreover, the developed simulators will be compared in terms of their speed of response and settling time which are essential factors for an effective real‐time monitoring scheme. Finally, the selected simulation scheme is further tested under assumed pipeline leak conditions. Copyright © 2004 John Wiley & Sons, Ltd.