bluuebunny/crossref_metadata_2025 huggingface dataset:
Versatile 2,5‐Pyridinedicarboxylate in Linking Transition‐Metal Atoms into 1D and 2D Coordination Polymers and Concomitant Polymorphs
Authors: Chuang Shu‐Ting , Shen Fwu‐Ming , Kuo Ting‐Shen , Shiu Kom‐Bei
Published: May 2015

By employing one bridging ligand, 2,5‐pyridinedicarboxylate (2,5‐pda2−), in the presence or absence of another bridging ligand, 4,4′‐bipyridine (4,4′‐bpy), one one‐dimensional (1D) {[Co2(2,5‐pda)(2,5‐Hpda)2(4,4′‐bpy)(H2O)3]·6H2O}∞ (1) and two two‐dimensional (2D) coordination polymers, {[Cu3(2,5‐pda)3(H2O)3]·6H2O}∞ (2) and {[Co(2,5‐pda)(H2O)]·2H2O}∞ (3) were synthesized. Complexes 2 and 3 are characterized as concomitant polymorphs from a one‐pot reaction at ambient temperature. A comparison of the coordination geometries of all neutral and anionic coordination polymers containing {Mx(2,5‐pda)y(H2O)z}∞ available to date is presented.
Oxidative Desulfurization of Diesel Oil Using Mesoporous Phosphotungstic Acid/SiO2 as Catalyst
Authors: Yan Xue‐Min , Lei Jia‐Heng , Liu Dan , Wu Yang‐Chun , Guo Li‐Ping
Published: May 2015

Ordered mesoporous phosphotungstic acid/SiO2 (HPW/SiO2) with Keggin‐type heteropolyacids (HPAs) encapsulated into a SiO2 framework has been synthesized and used as the catalyst for oxidative desulfurization of diesel fuel. The sulfur compounds in diesel were oxidized and removed at a temperature range of 50–80 °C with H2O2 as the oxidant and acetonitrile as the extraction agent. The sulfur content in diesel was reduced to as low as 48–86 μg/g from the initial level of 438 μg/g. The loss in catalytic activity was negligible even after five cycles of use, and the reduction of the sulfur content was enhanced with increasing the immobilized phosphotungstic acid (HPW) concentration. Oxidation of model compounds showed that in the heterogeneous system both the electron density and the steric hindrance affected the reactivity of these sulfur compounds. The reactivities of these sulfur compounds studied in this work followed the order of dibenzothiophene > 4,6‐dimethydibenzothiophene > benzothiophene.
Kinetic Spectrofluorometric Determination of Thioctic Acid in Bulk and Pharmaceutical Preparations via its Oxidation with Cerium(IV)
Authors: Ibrahim F. A. , Ali F. A. , Ahmed S. M. , Tolba M. M.
Published: May 2015

A highly simple and sensitive kinetic spectrofluorometric method was developed for the determination of thioctic acid. The method is based on the oxidation of the studied drug with cerium(IV) ammonium sulfate in acidic medium. The fluorescence of the produced Ce(III) was measured at 365 nm after excitation at 255 nm. The different experimental parameters affecting the development and stability of the reaction product were carefully studied and optimized. The method is applicable over the concentration range of 0.02 to 0.12 μg/mL with a detection limit of 6.06 × 10−3 μg/mL and a quantification limit of 0.02 μg/mL. The method was successfully applied for the assay of the studied drug in pharmaceutical formulations. The results obtained were in good agreement with those obtained with the reference method.
Potentiometric and Spectrophotometric Studies of Copper(II) Complexes of Some Ligands in Aqueous and Nonaqueous Solution
Authors: Shokrollahi Ardeshir , Ghaedi Mehrorang , Ghaedi Hamed
Published: May 2015

Stoichiometry and equilibrium study of copper‐ligands including mercaptobenzoxazole (MBO), 4‐propyl 2‐thiouracyl (PTU), methyl‐2‐pyridylketone oxime (MPKO), phenyl‐2‐pyridylketone oxime (PPKO), 4,6‐dihydroxy‐2‐mercaptopyrimidine (DHMP), N,N′‐phenylene bis(salicylaldimine) (PBS) and 1,2‐bis(2‐hydroxyphenyl)naphtaldiimine (BHNPDI) were conducted in aqueous and nonaqueous solution by potentiometry and spectrophotometry. Stability constants of the complexes are determined at 25 ± 1 °C and 0.1 or 0.05 M ionic strength in water or acetonitrile solvents. Oximes ligand protonation constants and copper‐ligands complexes' stability and hydrolysis constants were calculated using the BEST program in aqueous solution. The stability constants of copper‐ligands complexes were calculated using the KINFIT program in acetonitrile solution. The results of these two methods are made self‐consistent, then rationalized assuming an equilibrium model including the species, ML, MLH, MLOH and ML2 (where the charges of the species have been ignored for the sake of simplicity) (L = MBO, PTU, MPKO, PPKO, DHMP, BHNPDI and PBS).
Sensitive Determination of Nanogram Levels of Diacerein in a Pharmaceutical Formulation by Flow Injection Chemiluminescence Analysis
Authors: Yao Han‐Chun , Yang Xiao‐Feng , Li Hua
Published: May 2015

A simple, sensitive and inexpensive flow injection chemiluminescence (FI‐CL) method for the determination of diacerein was proposed. It was based on the greatly enhancive effect of diacerein on the CL reaction between luminol and hydrogen peroxide in alkaline medium. The enhanced CL intensity was linear with the concentration of diacerein over the range 1.0–500 ng/mL with a detection limit (3σ) of 0.2 ng/mL. The relative standard deviation was 1.1% (n = 8, 20 ng/mL diacerein) and the sample throughput was about 120 samples h−1. This simple method has been successfully applied for the determination of diacerein in a pharmaceutical formulation without interference from its potential impurities. The degradation of diacerein was also investigated briefly.
N‐Bromosuccinimide (NBS): A Mild and Efficient Catalyst for Tetrahydropyranylation of Alcohols and Phenols under Solvent‐Free Conditions
Authors: Khazaei Ardeshir , Rostami Amin , Raiatzadeh Ayeh
Published: May 2015

Different types of alcohols and phenols are tetrahydropyranylated in the presence of NBS catalyst in good to excellent yields under mild, neutral and solvent‐free conditions.
Synthesis and Reactions of Naphtho[1′,2′:4,5]Furo[3,2‐b]Pyridine and Naphtho[1′,2′:4,5]Furo[3,2‐d]Pyrimidine Derivatives
Authors: Badr M. Z. A. , Kamal El‐Dean A. M. , Moustafa O. S. , Zaki R. M.
Published: May 2015

2‐Acyl‐3‐aminonaphtho[2,1‐b]furan (1) reacts with activated methylene such as malono nitrile or ethyl cyanoacetate to afford naphtho[1′,2′:4,5]furo[3,2‐b]pyridine 2a,b. Chloroacylation of the amino group in compound (1) gave compound 3 which reacts with different amines to produce compound 4.
5‐(1‐Pyrrolyl)‐2‐Phenylthieno[2,3‐d]Pyrimidine as Building Block in Heterocyclic Synthesis: Novel Synthesis of Some Pyrazoles, Pyrimidines, Imidazo[1,2‐a]Pyrimidines, Pyrazolo[1,5‐a]Pyrimidines, Pyrido‐(Pyrimido)Pyrazolo[1,5‐a]Pyrimidines, 1,2,4‐Triazolo[1,5‐a]Pyrimidine and a 1,2,3,4‐Tetrazolo[1,5‐a]Pyrimidine Derivative
Authors: Ho Yuh‐Wen
Published: May 2015

Treatment of enaminone derivative 6‐(3‐dimethylamino‐acryloyl)‐5‐(1‐pyrrolyl)‐4‐methyl‐2‐phenylthieno[2,3‐d]pyrimidine 1 with appropriate hydrazine compounds 2a,b in refluxing ethanol afforded the corresponding 6‐(1‐substituted‐pyrazol‐5‐yl)‐2‐phenylthieno[2,3‐d]pyrimidines 3a,b. Cyclization of enaminone derivative 1 with appropriate guanidine compounds 13a‐c in the presence of a basic catalyst yields the corresponding 6‐(2‐substituted‐pyrmidin‐6‐yl)‐2‐phenylthieno[2,3‐d]pyrimidines 15a‐c. The compound 15c can be cyclized with appropriate α‐halogenocarbonyl compounds 16a‐d to afford the corresponding 6‐(2‐substituted‐imidazo[1,2‐a]pyrimidin‐7‐yl)‐2‐phenylthieno[2,3‐d]pyrimidines 17a‐d. On the other hand, the pyrazolo[1,5‐a]pyrimidines 20a‐c, pyrido(pyrimido)[2,3:4,3]pyrazolo[1,5‐a]pyrimidines 22a‐c, pyrido[4,5:4,3]pyrazolo[1,5‐a]pyrimidine 24, 1,2,4‐triazolo[1,5‐a]pyrimidine 26a, and 1,2,3,4‐tetrazolo[1,5‐a]pyrimidine derivative 26b were also obtained by the intramolecular cyclization of enaminone derivative 1 with appropriate 5(3)‐amino‐pyrazole derivatives 18a‐c, 21a‐c, 23, 3‐amino‐1,2,4‐triazole 25a and 5‐amino‐1H‐tetrazole 25b under acid conditions, respectively.
Colorimetric Microdetermination of Bromhexine Drug in Aqueous Solution
Authors: Khalil Rabah A. , Saeed Abdussamed M. A.
Published: May 2015

A simple, accurate and sensitive method for determination of bromhexine hydrochloride drug in aqueous solution has been described. The procedure has been based on the reaction of this drug with an excess amount of p‐dimethylaminobenzaldehyde (DAB) in acidic medium (pH =1.6) and the presence of sodium dodecyl sulfate (SDS). The produced yellow color from this reaction has been followed spectrophotometrically at an absorbance maximum of 430 nm. Microgram amounts of bromhexine hydrochloride can be estimated with an accuracy of better than ±1.5% and a relative standard deviation of less than 3.5%. The method has been used for the determination of 0.41–82.5 μg.mL−1 with a molar extinction coefficient of 4699.1–3602.3 L.mol−1.cm−1.

An application of the developed procedure to bulk bromhexine hydrochloride and some of its pharmaceutical preparations has been carried out. The effect of the presence of some other surfactants and common pharmaceutical additives has been investigated. A comparison of the presented method with that in the absence of SDS and the standard method of the British Pharmacopoeia has been explored. The suggestion, according to the results, is to use the developed method as standard in pharmaceutical applications.
Electro‐Oxidation of 3,4‐Dihydroxybenzoic Acid in the Presence of 6‐Methyl‐1,2,4‐Triazine‐3‐Thione‐5‐One: Unique Synthesis of 7H‐Thiazolo[3,2‐b]‐1,2,4‐Triazin‐7‐One Derivative in Aqueous Media
Authors: Fotouhi Lida , Nematollahi Davood , Heravi Majid M.
Published: May 2015

The electrochemical oxidation of 3,4‐dihydroxy benzoic acid (1) has been studied in the presence of 6‐methyl‐1,2,4‐triazine‐3‐thione‐5‐one (2) in aqueous solution. The oxidation mechanism of 1 and its reaction in the presence of 2 was offered. It was confirmed that 1 is converted to 7H‐thiazolo[3,2‐b]‐1,2,4‐triazin‐7‐one derivative 5 through Michael addition reaction of 2 to anodically generated o‐benzoquinone. The results of the research were used for electrochemical synthesis of 5 in an undivided cell in good yield and purity.
The Direct Electron Transfer of Iron‐Containing Superoxide Dismutase (Fe‐SOD) and its Catalysis for the Oxygen Reduction Reaction (ORR) in Room Temperature Ionic Liquids (RTILs) on a Gold Electrode
Authors: Ding Ke‐Qiang
Published: May 2015

In this work, for the first time, the direct electron transfer of iron‐containing superoxide dismutase (Fe‐SOD) was observed by cyclic voltammetry on a gold (Au) electrode in three RTILs, i.e., 1‐ethyl‐3‐methylimidazolium tetrafluoroborate (EMIBF4), 1‐n‐propyl‐3‐methylimidazolium tetrafluoroborate (PMIBF4) and 1‐n‐butyl‐3‐methylimidazolium tetrafluoroborate (BMIBF4). And the results demonstrate that when the scan rate was as low as 1 mV/s, a pair of well‐defined quasi‐reversible peaks of Fe‐SOD was presented, while as the potential scan rate was above 10 mV/s, the reduction peak of Fe‐SOD disappeared though its oxidation peak could be clearly observed even as the potential scan rate was up to 400 mV/s, strongly indicating that these CVs we observed were attributable to Fe‐SOD rather than the impurities in RTILs. Its catalysis for oxygen reduction reaction (ORR) was directly verified by the shifting of formal potential, E0′, of ORR, to the positive direction though the value of standard rate constant, κ0, corresponding to ORR, was not much enhanced. In PMIBF4, for the multi‐walled carbon nanotubes (MWCNTs)‐modified gold electrode, both the reduction peak current and oxidation peak current for oxygen redox reaction were all dramatically enhanced compared to the case of a bare gold electrode, and the value of κ0 was also increased from 3.1 × 10−3 cm s−1 for the bare gold electrode, to 17.5 × 10−3 cm s−1. Hence, in the presence of Fe‐SOD in RTILs, MWCNTs, showing catalysis for the electron transfer process of ORR, coupled with Fe‐SOD, leading to the shifting of formal potential corresponding to ORR to the positive direction, presented us a satisfactory catalysis for ORR in RTILs. Some reasons available for this catalysis behavior stemming from Fe‐SOD, and MWCNTs as well, for ORR are discussed based on the previously developed proposition.
Gold(I) ‐Nickel(II)‐4,4′‐bpy‐Phosphine Complexes: Synthesis and Multinuclear NMR Study
Authors: Byabartta Prithwiraj , Laguna Mariano
Published: May 2015

Silver triflate [AgOTf] assisted de‐bromination gives [Ni(dppm/dppe/(PPh3)2) (OTf)2], which on reaction with 4,4′‐bpy and gold(I) phosphines in dichloromethane medium by the self assemble technique leads to [{(L)Ni}{(4,4‐bpy)Au(PPh3)}2](OTf)4, (1,2,3) [{(L)Ni(4,4‐bpy)}4](OTf)8, (4,5,6) [L = dppm/dppe/(PPh3)2 = diphenyl phosphino‐methane, ‐ethane, bis‐triphenylphosphine, OSO2CF3 is the triflate anion]. The maximum molecular peak of the corresponding molecule is observed in the ESI mass spectrum. Ir spectra of the complexes show ‐C=C‐, ‐C=N‐, as well as phosphine stretching. The 1H NMR spectra as well as 31P (1H)NMR suggest solution stereochemistry, proton movement, and phosphorus proton interaction. Considering all the moieties, there are a lot of carbon atoms in the molecule reflected by the 13C NMR spectrum. In the 1H‐1H COSY spectrum of the present complexes and contour peaks in the 1H−13C HMQC spectrum, we assign the solution structure and stereoretentive transformation in each step.
One‐Pot Synthesis of Pyrido[2,3‐d]Pyrimidine‐2‐Thiones and a Study of Their Reactivity Towards Some Reagents
Authors: El‐Gazzar A. B. A. , Hafez H. N. , Yakout E. M. A.
Published: May 2015

A series of pyrido[2,3‐d]pyrimidine‐2‐thione derivatives (5a‐c) were synthesized by the one‐pot reaction of the appropriate aldehyde, malononitrile and 6‐aminothiouracil (1) in dimethyl‐formamide. The same compounds were also synthesized by the reaction of arylidine malononitrile (4) with 6‐aminothiouracil (1). Moreover, the chemical behaviour of the produced pyrimidines towards different reagents was studied.
An Efficient Synthesis of Pyrazolo[3,4‐b]Pyridine Derivatives in Aqueous Media
Authors: Shi Da‐Qing , Shi Jing‐Wen , Yao Hao , Jiang Hong , Wang Xiang‐Shan
Published: May 2015

A series of pyrazolo[3,4‐b]pyridines was synthesized by the reaction of 5‐aminopyrazole with benzylidenemalononitrile in aqueous media. The structures were characterized by IR, 1H NMR, and elemental analysis and were further confirmed by X‐ray diffraction analysis.
The Synthesis of 1,4‐Bis[N‐(4/6‐Substituted Benzothiazole‐2‐yl)‐N′‐Glycosylguanidino]Benzenes
Authors: Tian Tian , Cao Ling‐Hua
Published: May 2015

The starting material O‐protected glycosyl isothiocyanate (1˜3) was refluxed with 1,4‐diaminobenzene in CHCl3 under nitrogen atmosphere to give 1,4‐bis(N‐glycosyl)thioureidobenzene (4˜6). Then 1,4‐bis[N‐(4/6‐substituted benzothiazole‐2‐yl)‐N′‐glycosylguanidino]benzenes (8a˜8e, 9a˜9e, 10a˜10e) were obtained in good yield by reaction of compounds (4˜6) with 2‐amino‐4/6‐benzothizoles (7a˜7e) and HgCl2 in the presence of TEA in DMF. The structures of all 18 new compounds were confirmed by IR, 1H NMR, LC‐MS and elemental analysis. The bioactivity of anti‐HIV‐1 protease (HIV‐1 PR) and against angiotensin converting enzyme (ACE) have been evaluated.
Self‐Assembly, Spectroscopic and Electrochemical Studies of Nickel(II)‐4,8‐Diazaundecanediamide Complex
Authors: Chao Min‐Shiun , Lu Horng‐Hwa , Tsai Ming‐Liao , Ho Mei‐Chan
Published: May 2015

The self‐assembly of NiCl2·6H2O with a diaminodiamide ligand 4,8‐diazaundecanediamide (L‐2,3,2) gave a [Ni(C9H20N4O2)(Cl)(H2O)] Cl·2H2O (1). The structure of 1 was characterized by single‐crystal X‐ray diffraction analysis. Structural data for 1 indicate that the Ni(II) is coordinated to two tertiary N atoms, two O atoms, one water and one chloride in a distorted octahedral geometry. Crystal data for 1: orthorhombic, space group P 21nb, a = 9.5796(3) Å, b = 12.3463(4) Å, c = 14.6305(5) Å, Z = 4. Through NH···Cl–Ni (H···Cl 2.42 Å, N···Cl 3.24 Å, NH···Cl 158°) and OH···Cl–Ni contacts (H···Cl 2.36 Å, O···Cl 3.08 Å, OH···Cl 143°), each cationic moiety [Ni(C9H20N4O2) (Cl)(H2O)]+ in 1 is linked to neighboring ones, producing a charged hydrogen‐bonded 1D chainlike structure. Thermogrametric analysis of compound 1 is consistent with the crystallographic observations. The electronic absorption spectrum of Ni(L‐2,3,2)2+ in aqueous solution shows four absorption bands, which are assigned to the 3A2g → 3T2g, 3T2g → 1Eg, 3T2g → 3T1g, and 3A2g → 3T1g transitions of triplet‐ground state, distorted octahedral nickel(II) complex. The cyclic volammetric measurement shows that Ni2+ is more easily reduced than Ni(L‐2,3,2)2+ in aqueous solution.
Preparation, Characterization and Catalytic Performance of Carbon Nanotubes Promoted Ni‐B Amorphous Alloy
Authors: Hu Chang‐Yuan , Liao Xiao‐Ning , Li Feng‐Yi , Zhang Rong‐Bin , Zhang Rong‐Fa , Liu Ting‐Zhi
Published: May 2015

Ni‐B and Ni‐B/CNTs amorphous alloy catalysts were prepared by chemical reduction and impregnation‐chemical reduction methods, respectively, and characterized by TEM, ICP, XPS, XRD, BET and CO chemisorption techniques. Their catalytic activities were evaluated in acetylene selective hydrogenation reaction. Based on characterizations, the effects of carbon nanotubes on Ni‐B amorphous alloy were attributed to both its structure effect, dispersing Ni‐B particles, leading to bigger surface area of active nickel and enhancing the thermal stability, and the electronic effect, resulting in electron‐rich nickel centers. Therefore, the superior thermal stability and acetylene selective hydrogenation activities of Ni‐B/CNTs to Ni‐B amorphous catalyst were obtained in the present study.
PVC‐Based on Thiopyrilium Derivatives Membrane Electrodes for Determination of Histamine
Authors: Javanbakht Mehran , Mohammadi Ali , Ganjali Mohammad Reza , Norouzi Parviz , Faridbod Farnoush , Pirelahi Hooshang
Published: May 2015

This study describes novel histamine‐selective electrodes, having their basis on thiopyrilium (TP) derivatives as suitable ionophores. The electrodes were prepared by incorporating the TP derivatives into plasticized poly(vinyl chloride) (PVC) membranes. These electrodes demonstrate high selectivity as far as the histamine response is considered, as compared with many common inorganic anions and other kinds of amino acids. The influence of membrane composition, pH and the effect of lipophilic cationic and anionic additives on the response characteristics of the electrode were investigated. The resulting sensor based on 2,6‐bis(4‐dimethyl amino phenyl)‐4‐phenyl thiopyrilium perchlorate (TP4) responds to histamine in a wide concentration range from 5.0 × 10−6 to 1.0 × 10−1 M with a slope of 54.8 ± 0.6 mV decade−1 and detection limit of 3.0 μ mol L−1 (∼0.3 ppm). The electrode illustrates fast response time and good long‐term stability (more than 2 months). The ability to design histamine‐selective electrodes based on new thiopyrilium derivatives and both to alter selectivity and improve the response characteristics through structural changes to the charged ionophore, has been investigated. The prepared electrode was used for the determination of histamine in a synthetic human serum sample. Consequently, satisfactory recovery results were obtained over a wide concentration range of histamine.
Flow‐Injection Chemiluminometric Analysis of Thyroxine Hormone in a KMnO,4‐Na2SO3 System
Authors: Waseem Amir , Yaqoob Mohammad , Nabi Abdul
Published: May 2015

An analytical method consisting of flow injection sampling and chemiluminescence detection for the determination of thyroxine hormone is described. It is based on the weak chemiluminescent reaction of KMnO4 ‐ Na2SO3 in acidic medium, which is enhanced by the addition of thyroxine hormone. The chemiluminescence intensity was correlated linearly with concentration of thyroxine in the range of 1.0 × 10−7 – 2.0 × 10−6 mol L−1 (r2 = 0.9976) with a relative standard deviation (n = 4) in the range of 1.0 – 1.9%. The limit of detection (3σ blank) is 5.0 × 10−9 mol L−1 with a sample throughput of 180 h−1. The method has been applied to the determination of thyroxine in pharmaceutical preparations and the results are in good agreement with the value reported. Metal and non‐metal ions and some organic compounds commonly present in tablets and some amino acids were also studied for thyroxine determination.
Reaction of 1,6‐Dioxo‐2,4‐Diene with Aziridine and Secondary Amine
Authors: Sun Tsung‐Hsien , Ong Chi‐Wi
Published: May 2015

The (2E,4E)‐ and (2E,4Z)‐1‐phenyl‐1,6‐dioxo‐hepta‐2,4‐diene reacts with aziridine to give aziridinecyclopentenol 3. This product arises from an intermolecular Michael addition of a nitrogen lone pair to the less reactive enone, followed by an intramolecular aldol reaction of the enol with ketone. Furthermore, the initially formed enol did not undergo nucleophilic attack onto the aziridine ring to form heterocycles. Interestingly, the reaction with secondary amine did not give the cyclopentenol adduct, and this only leads to the isomerization of (2E,4Z)‐1‐phenyl‐1,6‐dioxo‐hepta‐2,4‐diene to the more stable (2E,4E)‐1‐phenyl‐1,6‐dioxo‐hepta‐2,4‐diene by addition to the more reactive enone.
Activation Mechanisms for Pseudomonas Species Lipase by Cardiovascular Drugs in Vitro
Authors: Lin Ming‐Cheng , Lai Gin‐Win , Lin Chung‐Sheng , Lin Gialih
Published: May 2015

The goal of this work was to determine the reaction mechanism for Pseudomonas species lipase activation by cardiovascular drugs such as lovastatin, simvastatin, amlodipine besylate, nifedipine, and hydralazine hydrochloride based on the results from enzyme kinetics. These drugs are the essential activators of Pseudomonas species lipase in the presence of triton‐X 100 or taurochloate in vitro. Moreover, QSAR studies show that the pKA values are correlated with the molecular weights of these drugs.
Spectrophotometric Studies on Some Arylazo Barbituric Acids and Arylazo Pyrimidine in Organic Solvents and in Buffer Solutions
Authors: Amrallah A. H. , Abdalla N. A. , El‐Haty E. Y.
Published: May 2015

The UV and visible spectra of some arylazo barbituric acids and arylazo pyrimidine in pure and mixed organic solvents of varying polarities have been studied. The different absorption bands displayed in the electronic spectra of these compounds are assigned and the possibility of the existence of these compounds in tautomeric equilibrium as well as in intra‐ and intermolecular H‐bonding were examined. The solute‐solvents molecular complexes liable to exist in polar‐nonpolar mixed solvents are investigated. The structure of the azo compounds were confirmed by 1H NMR and IR spectroscopy. The ionization processes of the compounds were investigated and the possible ionization constants were determined and discussed in terms of molecular structure of the azo compounds.
High Fluorine Content Bis(fluoro‐Ponytailed) Bipyridine Palladium Complexes as Catalyst for Mizoroki‐Heck Reactions under Fluorous Biphasic Catalysis Conditions
Authors: Lu Norman , Chen Shih‐Chieh , Lin Yan‐Chou , Cheng Yao‐Yi , Liu Ling‐Kang
Published: May 2015

Two highly fluorinated bipyridine derivatives, (4,4′‐bis(RfCH2OCH2)‐2,2′‐bpy) {Rf = n‐C10F21 (1a), n‐C10F23 (1b)}, have been synthesized starting from 4,4′‐bis(BrCH2)‐2,2′‐bpy and the corresponding fluorinated alkoxides. The fluorine contents of ligands 1a‐b are 62.3% and 63.3%, respectively, both being white solids, virtually insoluble in CH2Cl2 or DMF and highly fluorophilic with a partition ratio between DMF and n‐C8F18 less than 1:1000. The reaction of ligands 1a‐b with [Pd(CH3CN)2Cl2] results in novel Pd complexes [PdCl2(4,4′‐bis‐(RfCH2OCH2)‐2,2′‐bpy)] where Rf = n‐C10F21 (2a), n‐C10F23 (2b), respectively. The Pd complexes 2a‐b are pale yellow solids, soluble only in fluorinated solvents. The Pd complexes 2a‐b have been satisfactorily tested for Mizoroki‐Heck arylation under fluorous biphasic catalysis conditions in that the Pd complexes 2a‐b are easily recovered and maintain good catalytic activity after 8 consecutive cycles (> 90% yield). The TGA studies indicate that the Pd complexes 2a‐b are thermally stable up to 300 °C.
Atomic Simulations of Aurivillius Oxides: Bi3TiNbO9, Bi4Ti3O12, BaBi4Ti4O15 and Ba2Bi4Ti5O18 Doped with Pb, Al, Ga, In, Ta
Authors: Rosyidah Afifah , Onggo Djulia , Khairurrijal  , Ismunandar
Published: May 2015

The Aurivillius oxides were originally of interest for their ferroelectric properties and have recently been explored in the field of oxide ion conductivity. Atomistic simulation methods have been carried out for Bi3TiNbO9, Bi4Ti3O12, BaBi4Ti4O15 and Ba2Bi4Ti5O18 doped with Pb, Al, Ga, In, Ta to determine defect energy in the materials by employing efficient energy minimization procedures. The calculations rest upon the specification of an interatomic potential model, which expresses the total energy of the system as a function of the nuclear coordinates. The Born model framework, which partitions the total energy into long‐range Coulombic interactions and a short‐range term to model the repulsions and van der Waals forces between electron charge clouds, is employed. This is embodied in the GULP simulation code. Dopant solution energy versus ion size trends are found for both isovalent and aliovalent dopant incorporation at Bi and Ta sites. Trivalent dopants (Al, Ga, In) and Pb are more favorable on the Bi site, whereas Ta dopants preferentially occupy the Ti site.
Kinetic Spectrophotometric Determination of Ascorbic Acid in Pharmaceutical Samples by Oxidation of Ponceau 4R by Hydrogen Peroxide
Authors: Grahovac Zora M. , Mitić Snežana S. , Pecev Todor G. , Pecev Emilija T. , Pavlović Aleksandra N.
Published: May 2015

A new sensitive and simple kinetic method is developed for determination of traces of ascorbic acid based on its activated effect on oxidation of trisodium‐2‐hydroxy‐1‐(4‐sulphonato‐1‐naphthylazo)naphthalene‐6,8‐disulphonato (red artificial color Ponceau 4R) by hydrogen peroxide, in the presence of Cu(II) as catalyst, in borate buffer. The reaction is followed spectrophotometrically by tracing the oxidation product at 478.4 nm within 1 min after addition of H2O2. The optimum reaction conditions are: borate buffer (pH = 11.00), Ponceau 4R (9.6·10−6 mol/L), H2O2 (2·10−2 mol/L), Cu(II) (8·10−7 mol/L) at 22 °C. Following this procedure, ascorbic acid can be determined with a linear calibration graph up to 1.76 ng/mL and a detection limit of 0.28, based on 3S criterion. The relative error ranges between 6.77‐1.66% for the concentration interval of ascorbic acid 1.76‐17.61 ng/mL. The effects of certain foreign ions upon the reaction rate were determined for an assessment of the selectivity of the method. The method was applied for determination of ascorbic acid in pharmaceutical samples, and spectrophotometric method was used like an comparative method.
Polarographic (DCP & DPP) Determination of Ellagic Acid in Strawberries & Pharmaceutical Formulations
Authors: Thakur Kirti , Pitre K.S.
Published: May 2015

Direct Current (DC) and Differential Pulse (DP) Polarographic methods have been developed for the qualitative as well as quantitative analysis of ellagic acid in plant products (i.e. strawberries) and pharmaceutical formulations (Ellagic insurance formula). Ellagic acid produces a well‐defined polarographic wave/peak in pyridine hydrochloride at pH 6.8 ± 0.1 with E1/2 /Ep = −1.298 V vs. SCE.

The wave/peak height is found to be proportional to the concentration of ellagic acid. The developed procedure was used for the analysis of ellagic acid in an extract of strawberries (Fragaria × ananassa) and pharmaceutical formulations. Statistical treatment of the observed polarographic data revealed high accuracy and good precision of determination.

The work has been supplemented by FTIR screening of the sample. The percentage of ellagic acid in pharmaceutical formulations was determined by the developed method, which is in close agreement with the labeled amount.
Genetic‐Algorithm‐Based Wavelength Selection in Multicomponent Spectrophotometric Determination by PLS: Application on Ascorbic Acid and Uric Acid Mixture
Authors: Khajehsharifi Habibllah , Pourbasheer Eslam
Published: May 2015

Genetic algorithm (GA) is a suitable method for selecting wavelengths for partial least squares (PLS) calibration of mixtures with almost identical spectra without loss of prediction capacity using the spectrophotometric method. In this study, the concentration model is based on absorption spectra in the range of 200‐320 nm for 25 different mixtures of ascorbic acid (AA) and uric acid (UA). The calibration curve was linear over the concentration range of 1‐15 and 2‐16 μg mL−1 for ascorbic acid and uric acid, respectively. The root mean square deviation (RMSD) for ascorbic acid and uric acid with GA and without GA were 0.3071 and 0.3006, 0.3971 and 0.7063, respectively. The proposed method was successfully applied to the simultaneous determination of both analytes in human serum and urine samples.
Synthesis and Reactions of Some Novel Triazolo‐, Azolo‐, Tetrazolo‐Pyridopyrimidine and Their Nucleoside Derivatives
Authors: Abu‐Zied Kh. M. , El‐Gazzar A. B. A. , Hassan N. A.
Published: May 2015

Pyridopyrimidine reacted with aromatic aldehydes afforded the arylhydrazone 2a,b which could be cyclized into the pyrido[2,3‐d][1,2,4]triazolo[4,3‐a]pyrimidine 3a,b, with formic acid, and carbon disulphide to give pyrido[2,3‐d][1,2,4]traizolo[4,3‐a]pyrimidine 4, 5. Reaction of 1 with nitrous acid afforded tetrazolo[1,5‐a]pyrido[2,3‐d]pyrimidine 6, which was reduced by zinc dust to give 2‐amino‐pyrido‐[2,3‐d]pyrimidine 7. Finally the reaction of 2‐hydrazino 1 with D‐xylose or D‐glucose afforded the acyclic N‐nucleoside 8, 11 which were converted into tetra/penta O‐acetate acyclic C‐nucleoside 9, 12 in acetic anhydride/pyridine. De‐acetylation of compounds 9, 12 afforded C‐nucleosides 10, 13.
Oxidation of Organic Substrates Using Two Triethylammonium Halochromates(VI), (C2H5)3NH[CrO3X], (X=F, Cl) Supported on Silica Gel
Authors: Ghammamy Shahriare , Dastpeyman Samaneh
Published: May 2015

Triethylammonium fluorochromate(VI), (C2H5)3NHCrO3F, TriEAFC and triethylammonium chlorochromate(VI), (C2H5)3NHCrO3Cl, TriEACC were prepared, supported on silica gel and used to quantitatively oxidize a number of organic substrates. These supported triethylammonium halochromates are versatile reagents ensuring effective oxidation of organic compounds, in particular of alcohols, under mild conditions. The durability, ease of work up and efficiency of TriEAFC and TriEACC are considerably increased upon their absorption on silica gel.
Adsorptive Voltammetric Behaviors of Resveratrol at Graphite Electrode and its Determination in Tablet Dosage Form
Authors: Liu Jin‐Xia , Wu Yan‐Ju , Wang Fei , Gao Lin , Ye Bao‐Xian
Published: May 2015

The adsorptive voltammetric behavior of resveratrol was studied at a graphite electrode in B‐R buffer (pH = 6.0) solution using adsorptive cyclic voltammetric technique. The oxidation of resveratrol is an irreversible adsorption controlled process. The oxidation mechanism was proposed and discussed in this work. The dependence of the current on pH and the concentration and nature of buffer were investigated to optimize the experimental conditions for the determination of resveratrol. It was found that in the range of 8.0 × 10−9 ∼ 2.0 × 10−6 mol/L, the currents measured by differential pulse voltammetries presented a good linear property as a function of the concentrations of resveratrol. In addition, validation parameters, such as reproducibility, sensitivity and recovery were evaluated as well. The proposed method was also successfully applied for the determination of resveratrol in Chinese patent medicine with good results.
Study of Complex Formation between 5,7‐Diiodo‐8‐hydroxyquinoline and Zn2+, Cd2+, Pb2+ and Tl+ Cations in Binary Non‐Aqueous Solvents Using Square Wave Polarography Technique (SWP)
Authors: Nezhadali Azizollah , Langara Padideh , Hosseini Hassan Ali
Published: May 2015

The complexation reaction between Zn2+, Pb2+, Cd2+ and Tl+ cations by 5,7‐diiodo‐8‐hydroxyquinoline (IQN) was studied in the Dimethylformamide /Acetonitril (DMF‐AN) binary system using square wave polarography technique. The stoichiometry and stability of the complexes were determined by monitoring the shifts in half‐wave or peak potential of the polarographic waves of metal ions against the ligand concentration. The stoichiometry of the complexes was found to be 1:1. The results obtained show that there is an inverse relationship between the formation constant of the complexes and the donor number of solvent base on the Guttmann donocity scale. In all cases the formation constants increased with increasing amounts of AN in these binary systems. The selectivity order for IQN complexes with the cations is Zn2+ > Pb2+ > Cd2+ > Tl+.
Extraction and Spectrophotometric Determination of Diclofenac in Pharmaceuticals
Authors: Kormosh Zh. O. , Hunka I. P. , Bazel Ya. R.
Published: May 2015

A new simple, rapid and sensitive spectrophotometric method has been developed for the determination of diclofenac sodium (Dicl) in pharmaceutical preparations. This method is based on the reaction of diclofenac sodium with an analytical reagent 1,3,3‐trimethyl‐5‐thiocyanato‐2‐[3‐(1′,3′,3′‐trimethyl‐3′‐H‐indol‐2′‐ylidene)‐propenyl]‐indolium cloride (TIC) at pH 8.0‐11.0 and the extraction of ion associate colored complex. Optimal conditions for the complex formation between Dicl and TIC were studied. This ion associate complex (1:1) was detected and extracted with toluene and an absorption maximum at 566.2 nm against a blank reagent. The calibration graph was linear from 0.9‐11.0 μg/mL of diclofenac and the detection limit was 0.86 μg/mL.
Synthesis of N‐Tosylhomosphinganine and N‐Tosylsedridine
Authors: Chang Meng‐Yang , Lin Chun‐Yu , Wu Tsun‐Cheng , Sun Pei‐Pei
Published: May 2015

A straightforward synthesis of N‐tosylhomosphinganine and N‐tosylsedridine has been achieved from trans‐4‐hydroxyproline by Grignard addition, regioselective Baeyer‐Villiger reaction, cross or ring‐closing metathesis and hydrogenation as the key steps.
Practical Preparation of 2‐Halomethyl‐Allyl Carboxylates
Authors: Sun Chong‐Si , Cheng Hsiu‐Yi , Lin Yu‐Shiang , Hou Duen‐Ren
Published: May 2015

An improved, efficient preparation of 2‐(halomethyl)allyl carboxylates starting from diethyl bis(hydroxymethyl)malonate and hydrobromic acid is reported. The allylic halogen of 2‐(chloromethyl)acrylate and 2‐(bromomethyl)acrylate are readily exchanged during esterification.
An Expedient Synthesis of Novel N,N′‐Diglycosylguanidine Derivatives in the Presence of Hg(II)
Authors: Chen Hong‐Mei , Li Gen , Cao Ling‐Hua
Published: May 2015

The reactions of N,N′‐diglycosythiourea with 2‐amino‐benzothiazoles in the presence of Hg(II) (HgCl2 or HgO) for the synthesis of N‐(4/6‐substituted‐benzothiazol‐2‐yl)‐N′,N″‐diglycosylguanidines have been reported.
Deprotection of Oximes, Phenylhydrazones, Semicarbazones and Thiosemicarbazones to the Corresponding Carbonyl Compounds Using Cetyltrimethylammonium Peroxodisulfate as a New and Selective Oxidizing Agent
Authors: Norouzi Mohammad , Tajbakhsh Mahmood , Alinezhad Heshmatollah , Urimi Azade Geran
Published: May 2015

Cetyltrimethylammonium peroxodisulfate (CTA)2S2O8 was quantitatively prepared and used for the deprotection of oximes, phenylhydrazones, semicarbazones and thiosemicarbazones to the corresponding carbonyl compounds in acetonitrile. Its agent is more efficient and has advantages over similar reagents in terms of the amount of oxidant, short reaction time, simple work up, and high yield.
Sol‐Gel‐Derived Biosensor Based on Plant Tissue: The Inhibitory Effect of Atrazine on Polyphenol Oxidase Activity for Determination of Atrazine
Authors: Majidi Mir Reza , Asadpour‐Zeynali Karim , Gholizadeh Sima
Published: May 2015

This work presents a sol‐gel based biosensor for atrazine determination which has been obtained by introducing the enzyme polyphenol oxidase from apple tissue in a sol‐gel matrix. Apple tissue acts as a molecular recognition element. Atrazine is an inactive compound electrochemically; redox coupling of dopamine was used for studying atrazine behavior. Atrazine was determined by monitoring the inhibition power of polyphenol oxidase activity. The measurements were performed in 0.1 M KH2PO4‐NaOH buffer (pH 7.5). The effect of various experimental parameters such as pH, concentration of buffer, concentration of dopamine, incubation time and matrix composition has been investigated for optimum analytical performance. The biosensor consisted of 10.3% (w/w) of apple tissue. The bioelectrode exhibits a linear response for dopamine and atrazine concentrations in the range of 5.66 × 10−6−2.27 × 10−3M and 1 × 10−5 −1 × 10−4 M with a detection limit of 4.2 × 10−6 and 5.5 × 10−6 M, respectively. A correlation coefficient of 0.9945 and a relative standard deviation (R.S.D.) of 3.29% for dopamine, 0.9944 and 3.69% for a trazine were achieved.
Theoretical Description of the Geometry, Electronic Structure and Reactivity Analysis for a Set of Tris‐Chelates with Application in Organic Light Emitting Diodes
Authors: Vivas‐Reyes Ricardo , Núñez‐Zarur Francisco , Padilla Angélica
Published: May 2015

We have computed and compared the geometries, the electronic properties and reactivity sites of a set of Alq3‐derivatives (5AP‐Mq3, M=Al, Ga, In) with potential use in organic light emitting diodes (OLED), using electronic and chemical reactivity descriptors. All the geometries were optimized with the ab initio Hartree‐Fock (HF) method and the 3‐21G basis set and the different descriptors were calculated at a B3LYP/3‐21G level of theory. The results show that the geometric structures were all distorted octahedral, where the geometrical parameters increase in the order 5AP‐Alq3 < 5AP‐Gaq3 < 5AP‐Inq3. The frontier molecular orbitals HOMO and LUMO are split in energy and strongly localized in a specific region of the ligands. The reactivity analysis shows that the atoms that receive electrons are those associated with the lowest unoccupied molecular orbital, LUMO.
The Transition State of Free Radical SH2′ Reaction of Allyl Chloride with Organomercurial Study by Inverse Secondary α‐Deuterium Kinetic Isotope Effect
Authors: Wu Yuh‐Wern , Chen Ming‐Dar , Yang Jyh‐Ferng
Published: May 2015

The concerted mechanism of free radical SH2′ reaction of 2‐substituted allyl chloride was suggested again by inverse secondary α‐deuterium isotope effect. The transition state of free radical SH2′ reaction of allyl chlorides seems to be symmetrical and is not as early as that of a free radical addition reaction.
N,N,N′,N′‐Tetrabromobenzene‐1,3‐Disulfonamide and Poly(N‐Bromo‐N‐Ethyl‐Benzene‐1,3‐Disulfonamide) as Efficient Catalysts for the Methoxymethylation of Alcohols under Solvent‐Free Conditions
Authors: Ghorbani‐Vaghei Ramin , Zolfigol Mohammad Ali , Amiri Mostafa , Veisi Hojat
Published: May 2015

Methoxymethylation of a variety of alcohols was performed using formaldehyde dimethyl acetal in the presence of N,N,N′,N′‐tetrabromobenzene‐1,3‐disulfonamide [TBBDA] and poly(N‐bromo‐N‐ethylbenzene‐1,3‐disulfonamide) [PBBS] as catalysts at room temperature and solvent‐free conditions. The methoxymethyl ethers (MOM‐ethers) were obtained with good to excellent yields.
Selective and Convenient Protection of Aldehydes as Azines under Solvent‐Free Conditions
Authors: Eshghi Hossein , Hosseini Mosayyeb
Published: May 2015

Aldehydes can be easily protected as azines in the presence of hydrazine monohydrochloride and ferric chloride under solvent‐free conditions. The major advantages of this method are: operational simplicity, ready availability, selectivity, general applicability, mild reaction conditions with low cost of the reactants, short reaction times and excellent yields.
A Novel and Efficient Catalyst to One‐Pot Synthesis of 2‐Amino‐4H‐Chromenes by Methanesulfonic Acid
Authors: Heravi Majid M. , Baghernejad Bita , Oskooie Hossein A.
Published: May 2015

Methanesulfonic acid efficiently catalyzes the one‐pot, three component reaction of an aromatic aldehyde, malonitrile and α or β‐naphthol to yield 2‐amino‐4H‐chromenes in very good yields.
Synthesis of Deuterium Labeled Standards of 1‐Benzylpiperazine, Fenetylline, Nicocodeine and Nicomorphine
Authors: You Zong‐Yi , Chen Yi‐Jing , Wang Yu‐Yun , Chen Chinpiao
Published: May 2015

Increasingly abused, 1‐benzylpiperazine (BZP), fenetylline, nicocodeine and nicomorphine are central nervous system stimulants with neurotoxic properties. In recent years, many controlled substance analogs (designer drugs) with a large variety of structures have reached illegal markets, making their identification difficult. This work studies the synthesis of BZP‐d7, fenetylline‐d4, nicocodeine‐d4 and nicomorphine‐d8, as internal standards for use in gas chromatography‐mass spectrometry (GC‐MS) analysis for identification of these controlled substances.
Microwave Absorption and Infrared Stealth Characteristics of Bamboo Charcoal/Silver Composites Prepared by Chemical Reduction Method
Authors: Ting Tzu‐Hao , Wu Kuo‐Hui , Hsu Jen‐Sung , Chuang Ming‐Ho , Yang Cheng‐Chien
Published: May 2015

Bamboo charcoal coated with silver (BC/Ag) was prepared by activation and chemical reduction processes at different AgNO3 contents (10‐30 wt.%). The spectroscopic characterizations of the formation processes of BC/Ag composites were studied using X‐ray diffraction, scanning electron microscopy and transmission electron microscopy. These composites were introduced in epoxy resin to be a microwave absorber and mixed polyethylene to be an infrared stealth plate. Microwave absorbing properties were investigated by measuring complex permittivity, complex permeability and reflection loss in the 2‐18 and 18‐40 GHz microwave frequency range using the free space method. The thermal extinction measurements in the 3‐5 and 8‐12 μm were done to evaluate the shielding affectivity of infrared. The results showed that a significant thermal extinction and a wider absorption frequency range could be obtained by adding silver to bamboo charcoal.
Determination of Nitrophenols in Water Using Dynamic Liquid‐Liquid‐Liquid Microextraction under Non‐Equilibrium Consideration
Authors: Lin Che‐Yi , Huang Shang‐Da
Published: May 2015

To pursue optimum condition in liquid‐liquid‐liquid microextraction (LLLME), extraction parameters dominating extraction efficiency were investigated by theoretical considerations. The theoretical considerations discussed equilibrium model for equilibrium LLLME and non‐equilibrium model for dynamic LLLME. A method described here is a dynamic LLLME technique combined with high‐performance liquid‐chromatography ultraviolet absorbance detection (HPLC/UV) to determine traces of nitrophenols in water. Analytical parameters such as organic phase, acceptor phase volume, sample agitation, extraction time, acceptor phase NaOH concentration, donor phase HCl concentration, salt addition, and absorption wavelength were identified as variable settings. Relative standard deviation (RSD, 1.8‐4.4%), coefficient of estimation (R2, 0.9994‐0.9999), and detection limit (0.032‐0.065 ng mL−1) were achieved under the variable settings. The proposed method was successfully applied to the analysis of a lake water sample, and the relative recoveries of nitrophenols from spiked water sample were up to 92.5%. The variable settings of LLLME close to optimization was responsible for an acceptable extraction efficiency.
Ionic Liquid as an Efficient Promoting Medium for Synthesis of Bis‐Pyrazolo[3,4‐b:4′,3′‐e]Pyridines
Authors: Shi Da‐Qing , Yang Fang
Published: May 2015

The preparation of a series of bis‐pyrazolo[3,4‐b:4′,3′‐e]pyridines by the reaction of 5‐aminopyrazole with aldehydes in ionic liquid [bmim]Br is described. This new method has the advantages of easier work‐up, milder reaction conditions, high yields and environmental friendliness compared with other methods.
Amberlyst‐15‐Catalyzed Novel Synthesis of Quinoline Derivatives in Ionic Liquid
Authors: Hou Rei‐Sheu , Wu Jian‐Long , Cheng Hui‐Ting , Xie You‐Teng , Chen Ling‐Ching
Published: May 2015

In recent years, ionic liquids have attracted much attention as useful synthetic solvents. Compared with classical molecular solvents, the ionic liquids are environmentally benign reaction media. A variety of quinoline derivatives have been synthesized under ionic liquid conditions using Amberlyst‐15 as catalyst.
Synthesis and Evaluation of the Cytotoxicities of Neoflavenes
Authors: Li Sie‐Rong , Chen Hsing‐Ming , Chen Po‐Yuan , Tsai Jui‐Chi , Chen Liang‐Yeu , Wang Eng‐Chi , Huang Yi‐Ting , Wei Yun‐Chen , Lu Pei‐Jung
Published: May 2015

The synthesis of neoflavene and neoflavenes with methoxy substituents at different positions are described. As starting materials, various salicylaldehydes were run through sequential reactions such as O‐allylation, Grignard reaction, oxidation, Wittig reaction, and ring‐closing metathesis to yield the target neoflavenes in good yield. Among the prepared neoflavenes, 7‐methoxy‐4′‐methoxyneoflavene (6e) and 8‐methoxy‐4′‐methoxyneoflavene (6f) exhibiting potential cell toxicities against various cells were disclosed. In particular, 6f which exhibited an IC50 value of 6.5 ± 2.0 and 5.1 ± 1.1 μM against gastric carcinoma and lung carcinoma cells in vitro was found, respectively. Meanwhile, the structure and activity relationship of our synthesized neoflavenes is further discussed briefly.
Vanadium Hydrogen Sulfate (I): Chemoselective Trimethylsilylation of Alcohols and Deprotection of Trimethylsilyl Ethers
Authors: Shirini Farhad , Zolfigol Mohammad Ali , Abedini Masoumeh , Sakhaei Ali Reza
Published: May 2015

Trimethylsilylation of alcohols with hexamethyldisilazane (HMDS) catalyzed by V(HSO4)3 under mild and completely heterogeneous reaction condition is reported. The method is highly chemoselective for the protection of alcohols in the presence of phenols, amines and thiols. Also, the deprotection of trimethylsilyl ethers is performed in the presence of V(HSO4)3 at room temperature in good to high yields.
Derivative and Derivative Ratio Spectrophotometric Analysis of Antihypertensive Ternary Mixture of Amiloride Hydrochloride, Hydrochlorothiazide and Timolol Maleate
Authors: Abdel‐Hay Mohamed H. , Gazy Azza A. , Hassan Ekram M. , Belal Tarek S.
Published: May 2015

Two simple, rapid and reliable spectrophotometric methods are described for the resolution of the three‐component mixture of amiloride hydrochloride (AMD), hydrochlorothiazide (HCT) and timolol maleate (TIM). The first method involves the use of derivative spectrophotometry with the zero‐crossing technique where AMD was easily determined using its 0D and 1D(Δλ = 6) amplitudes at 365 and 385 nm, respectively, while HCT and TIM were determined by measuring the 3D(Δλ = 6) amplitude at 265 nm and the 1D(Δλ = 8) amplitude at 315.4 nm, respectively. The second method involves the application of the ratio‐spectra zero‐crossing first and second derivative spectrophotometry where two points have been used for the quantification of each compound. For the determination of AMD, HCT was used as divisor and the 1DD (Δλ = 4) and 2DD (Δλ = 6) values at 299.4 and 311 nm, respectively, were plotted against AMD concentration; while — by using TIM as divisor — the 2DD (Δλ = 6) amplitudes at 264.2 and 290 nm were found to be proportional to HCT concentration. TIM was assayed in the mixture using its 1DD (Δλ = 6) amplitudes at 289.8 nm (Divisor was AMD) and 314.8 nm (Divisor was HCT). Synthetic mixtures of different proportions and laboratory‐made tablets were assayed by the proposed methods and the results revealed good accuracy and repeatability of the developed methods.