Identification and Determination of Nicorandil and its Degradation Products by HPLC and GC/MS

Nicorandil [N-(2-hydroxyethyl)-nicotinamide nitrate NIC] is a novel kind of compound in the treatment of angina pectoris. NIC can be degraded easily in storage. The degradation products include N-(2-hydroxyethy) nicotinamide (HN), nitrate ion (NI), and ni…     

Determination of inorganic nitrate impurity from nicorandil and its tablet dosage form by simple reversed phase liquid chromatographic method

A simple, fast, precise, specific and economical reverse phase liquid chromatographic method was developed for determination of nitrate (NIT) impurity from nicorandil (NIC) and its tablet dosage form. NIT is process impurity as well as a degradation product of NIC. This article is based on application of amino propyl silane (APS) column for determination of NIT in presence of NIC and various excipients using potassium nitrate as a standard. The developed method was validated for its intended use by evaluating various important parameters like linearity, accuracy, recovery and specificity. The developed method was applied to evaluate the compatibility study of NIC with various excipients by monitoring the NIT content.     

Simultaneous analysis of biologically active pyridines in pharmaceutical formulations by capillary zone electrophoresis

A capillary zone electrophoretic method using UV detection is developed for the analysis of four biological active pyridines [i.e., nicotine (NIC), cotinine (COT), nicotinic acid (NA), and nicotinamide (NM)]. The separation of the pyridines is achieved in 25 mM sodium dihydrogen phosphate (pH 2.1) using a fused-silica capillary with an effective length of 56 cm and an inner diameter of 50 μm (extended light path), hydrodynamic injection at 50 mbar for 10 s, a temperature of 25°C, applied voltage of 30 kV, and UV detection at 260 nm. These conditions provide baseline separation of all the analytes [resolution (R(s)) > 3.6] in 9.4 min with good linearity (r(2) > 0.998, in ranges of 50-600 μg/mL for NIC, 8-160 μg/mL for NM, and 10-200 μg/mL for COT and NA), precision (relative standard deviation <2.04%), recovery (96.4-101.6%), limits of detection (<3.0 μg/mL), and quantitation (<10 μg/mL). The method is robust upon the alterations of pH of BGE, separating voltage, and injection time [the RSDs of the relative migration time (migration time of the analyte/migration time of the internal standard) and resolution <3.26%]. The method is efficient, reliable, and simple for the routine analysis of NIC, NA, and NM in various products such as gum and tablets and can be applied to determine COT in thermal degradation of NIC gum.     

Nicotinamide complex of silver(III) with expanded coordination number

Abstract

In strongly alkaline media ([OH^?]?≥?0.12 M), nicotinamide (nica) forms a complex with square-planar Ag(OH)₄^? [nica]?≥?0.05 M. The complex decomposes in seconds to nicotinamide N-oxide. The correlation of maximum absorbance of the complex with concentrations of nicotinamide and hydroxide requires that the complex is either the five-coordinate Ag(OH)₄(H_-1nica)^2? or the six-coordinate Ag(OH)₅(nica)^2?. Comparison with the reactions of Ag(OH)₄^? with nicotinate ion (nic^?) and acetamide under similar conditions indicates that nicotinamide coordinates with Ag(OH)₄^? by the amido group rather than the nitrogen on the pyridine ring or the amido oxygen. Kinetics of the Ag(III)-nica redox reaction are consistent with direct reaction between nicotinamide and uncoordinated Ag(OH₄)^?. Oxidation takes place at the pyridine ring, yielding nicotinamide N-oxide. Silver(III) is reduced to monovalent silver.     

Long-Range Cationic Disordering Induces two Distinct Degradation Pathways in Co-Free Ni-Rich Layered Cathodes

Ni-rich layered oxides are one of the most attractive cathode materials in high-energy-density lithium-ion batteries, their degradation mechanisms are still not completely elucidated. Herein, we report a strong dependence of degradation pathways on the long-range cationic disordering of Co-free Ni-rich Li_1−m(Ni_0.94Al_0.06)_1+mO₂ (NA). Interestingly, a disordered layered phase with lattice mismatch can be easily formed in the near-surface region of NA particles with very low cation disorder (NA-LCD, m≤0.06) over electrochemical cycling, while the layered structure is basically maintained in the core of particles forming a “core–shell” structure. Such surface reconstruction triggers a rapid capacity decay during the first 100 cycles between 2.7 and 4.3 V at 1 C or 3 C. On the contrary, the local lattice distortions are gradually accumulated throughout the whole NA particles with higher degrees of cation disorder (NA-HCD, 0.06≤m≤0.15) that lead to a slow capacity decay upon cycling.     

Electrochemical Study of the Mixed Ligand Complexes of Co(II) and Ni(II) with Acetylsalicylic Acid and Nicotinamide

The interaction of acetylsalicylic acid (aspirin, aspH) and nicotinamide (NA) with Co(II) and Ni(II) ions was investigated using square-wave and cyclic voltammetry techniques. In the presence of Ni(II)/Co(II),nicotinamide gave new peaks at -0.85V and soh.12 V, corresponding to the reduction of Ni(II)-nicotinamide(log β_1:2 =5.97) and Co(II)-nicotinamide (log β_1:2 =5.19) complexes, respectively. In the presence of Ni(II)/Co(II), acetylsalicylic acid gave new peaks at -0.91V and -1.19 V, respectively, corresponding to the reductionof Ni(II)-salicylate (log β_1:2 =8.48) and Co(II)-salicylate (log β_1:2 =8.14) complexes. In the presence of nicotinamide, Ni(II)-salicylate and Co(II)-salicylate form mixed ligand complexes, reducing at -0.78V (log β_1:2:2 =9.68) and -1.14V (log β_1:2:2 =8.64), respectively.     

New silver(I) pyridinecarboxylate complexes: synthesis,characterization, and antimicrobial therapeutic potential

Silver(I) pyridinecarboxylates (AgPIC (1), AgNIC (2), [Ag(HDIPIC)]·0.75H₂O (3), PIC?=?picolinate, NIC?=?nicotinate, HDIPIC?=?dipicolinate) were prepared by solvothermal syntheses and their characterization were completed by elemental, spectral, and thermal analyses. To assign the pyridinecarboxylate coordination mode in the complexes, detailed mid-infrared spectral data and Δ(ν_as???ν_s) comparisons were accomplished. In addition, silver(I) pyridinecarboxylate antimicrobial activities and stability by ¹H NMR spectra were determined. Moreover, the spectral, thermal, and antimicrobial properties of silver(I) and previously prepared zinc(II) pyridinecarboxylates were compared and discussed.     

Thermal and thermoxidative degradations of starch and thermosensitive starch-g-BAM copolymers

Summary Thermal degradation under N₂atmosphere and thermoxidative degradation under air atmosphere of increasingly grafting efficiency values (i.e. GE%=0.0 to 35.5) for starch and starch grafted with N-tert-butylacrylamide thermosensitive copolymers (starch-g-BAM) by Ozawa and Kissinger methods using thermogravimetric analysis (TG) and differential scanning calorimetry techniques (DSC) at 10, 30 and 50% mass losses respectively have been studied. Influence of physical inter and intra molecular interactions on grafting and consequently on activation energy of degradation (E_a,d) was investigated using Ozawa's method, whereas linear dependence of E_a,don GE% by scaling relations using Kissinger's method was determined. Furthermore, the thermoxidative degradation induces the possibility of molecular rearrangement, cyclization and partial crosslinking that is deduced from the activation energy of degradation (E_a,d) and residual mass of TG profile. Thermal stability of starch does not alter as a result of different grafting efficiency percentages.     

Selective Determination of Nicorandil with a Single Planar Solid-state Potentiometric Ion Selective Electrode

Novel screen-printed electrodes (SPEs) were constructed for the quantitation of nicorandil (NIC) in its pharmaceutical formulations. Different ion-exchangers and plasticizers were investigated, but the optimal potentiometric response was obtained using nicorandil-phosphotungstate (NIC-PTA) ion associate and tricresyl phosphate as a plasticizer. A Nernstian response of 58.80±1 mV/decade was obtained over a concentration range of (1×10⁻⁶–1×10⁻²) M with 1×10⁻⁵ M as a detection limit. Sensor morphology was characterized using scanning electron microscopy (SEM). The method was validated for the assay of NIC with high selectivity, accuracy (average recovery=100.54 %), and precision (%RSD≤2).     

Stability-indicating high performance thin layer chromatographic determination of sulfanilamide in human urine

A simple, sensitive, selective, precise and stability-indicating high-performance thin-layer chromatographic (HPTLC) method was developed and applied to human urine for the densitometric determination of sulfanilamide. A mixture of chloroform-ethyl acetate-xylene (2.5: 4.0: 1.0, v/v/v) was used as a mobile phase. The system was found to give compact spots for sulfanilamide (retardation factor, R _f = 0.21±0.02). The linear regression analysis data for the calibration plots showed good linear relationship with r ² = 0.9970 ± 0.0003 and r ² = 0.9947 ± 0.020 within the concentration range of 50–250 ng per spot and 100–1000 ng per spot with respect to peak area, respectively. The limit of detection (LOD) and quantification (LOQ) were 8 and 25 ng per spot, respectively. Sulfanilamide was subjected to acid and alkali hydrolysis, oxidation, dry heat and wet heat treatment. According to the International Conference on Harmonization (ICH) guidelines the method was validated for precision, recovery and robustness. The ultraviolet (UV) spectra of the degradation products which had different spectra from sulfanilamide were also recorded. The article is published in the original.     

The effect of Cd(II) complexes with nicotinamide (NA) on microalgae growth,production of chlorophylls,oxygen evolution and Cd adsorption

The effects of Cd [Cd(NO₃)₂] and its complexes with nicotinamide (NA) [Cd(ac)₂(NA)₂, Cd(NCS)₂(NA)₂, Cd(NCSe)₂(NA)₂] were examined by using the algae Scenedesmus quadricauda and Chlorella vulgaris as a function of Cd speciation in a well-defined aqueous medium. The parameters observed during the experiments were algal growth inhibition, chlorophyll a and b content, oxygen evolution and Cd adsorption by algal cells. With regard to growth and production of chlorophylls (Chla, Chlb), the most toxic compound was Cd(NO₃)₂. On the basis of EC50 values for these parameters, the following rank order can be arranged for both algae: Cd(NO₃)₂?>?Cd(ac)₂(NA)₂?>?Cd(NCS)₂(NA)₂?>?Cd(NCSe)₂(NA)₂. While Cd(NO₃)₂ in EC50 concentration for algal growth also reduced oxygen evolution nearly by half, all Cd(II) complexes used in EC50 concentrations for the same parameter reduced oxygen evolution less. When a comparison was done for Cd(NO₃)₂, all Cd(II) complexes stimulated oxygen evolution in both algal species. Base on the adsorbed Cd quantity, the tested compounds for both algae could be arranged in the following sequence: Cd(NO₃)₂?>?Cd(ac)₂(NA)₂?>?Cd(NCS)₂(NA)₂?>?Cd(NCSe)₂(NA)₂. The results confirmed that the adsorbed Cd amount markedly exerted its influence on algal growth and intensity of their physiological processes. Higher sensitivity was confirmed for alga S. quadricauda, which adsorbed a higher amount of Cd, and reduction of all observed parameters in this alga was more intensive than in C. vulgaris. As less toxic for both algae was confirmed the complex Cd(NCSe)₂(NA)₂.     

Two multifunctional organic-inorganic hybrid complexes based on polyoxometalates,BiEDTA and sodium linker: crystal structures,photochromic, and catalytic performances

Two 3-D organic–inorganic hybrid supermolecular complexes, Na(BiHEDTA·2H₂O)₃(PW₁₂O₄₀)·2H₃O (BiPW) and Na(BiHEDTA·2H₂O)₃(PMo₁₂O₄₀)·2H₃O·2H₂O (BiPMo) ethylenediamine tetraacetic acid (EDTA) have been synthesized by solution method and characterized by ultraviolet visible (UV–vis) spectroscopy, thermogravimetric-differential thermal analysis, photoluminescence, cyclic voltammetry, and single-crystal X-ray diffraction (XRD). XRD analysis reveals that BiPW and BiPMo are isostructural with 3-D architectures assembled by 2-D layer tetranuclear cation and a Keggin-type polyoxoanion. Although these two hybrids exhibit similar structures, the properties depend on the nature of polyoxoanion [PM₁₂O₄₀]^3? (M = W, Mo). Under UV irradiation, BiPW and BiPMo show fast response of reversible and irreversible photochromism, respectively. BiPW exhibits excellent photocatalytic activity in degradation of methyl orange dyes under irradiation of UV–visible light. It can be reused for at least six cycles without obvious loss of activity in the degradation experiments; BiPMo shows catalytic activity in elimination of methanol. The elimination rate of methanol reaches 56.9% when the concentration of methanol is 2.3 g·m^?3 and the flow velocity is 10 mL·min^?1 at 100 °C.     

Thermal behavior of some N,N-dimethylbiguanide derivatives displaying antimicrobial activity

N,N-Dimethylbiguanide derivatives (HDMBG)X, where X=CH₃COO (1), Cl (2) and NO₃ (3) respectively, exhibit in vitro antimicrobial activity on representative bacterial and fungal strains. The presence of N,N-dimethylbiguanidium ion for all derivatives was evidenced by IR and ¹H NMR spectra. Thermal analysis gave information on their decomposition steps and also on the accompanying thermodynamic effects. According to TG and DTG curves processes as melting, oxidative degradation as well as oxidative condensation of –C=N– units occur. The different nature of the anions results different melting points. Paracyanide formation at various condensation degrees was observed.     

Synthesis, crystal and molecular structure of tetraaquabis(nicotinamide)cobalt(II) phthalate dihydrate

The coordination compound of cobalt(II) with nicotinamide [CoL₂(H₂O)₄][C₆H₄(COO)₂] · 2H₂O (I) (where L stands for nicotinamide) was synthesized and characterized by IR spectroscopy, conductometry, and thermogravimetry. The X-ray structure of complex I was determined. Crystals are monoclinic: a = 15.630(2) ?, b = 7.550(2) ?, c = 21.035(4) ?, β = 100.90(5)°, V = 2437.4(4) ?³, Z = 4, space group C2/c. The structural units of complex I are centrosymmetrical cations [CoL₂(H₂O)₄]²⁺, anions [C₆H₄(COO)₂]²⁻ (lying on axis 2), and molecules of waster of crystallization. Complex cations are packed into layers are alternate with layers containing anions and free H₂O molecules. This is a classical case of π-π-staking interactions that lead to the formation of supramolecular layered assemblies. Original Russian Text ? A.S. Antsyshkina, G.G. Sadikov, T.V. Koksharova, I.S. Gritsenko, V.S. Sergienko, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 8, pp. 1379–1384.     

Hydrothermal synthesis and structural characterization of a zigzag-chain polymer of {[ p -MeBzlPh3P][ZnCl2(NA)]} n (NA = nicotinic acid)

A metal-organic coordination polymer, { [p-MeBzlPh₃P][ZnCl₂(NA)]} _n (1) (NA?=?nicotinic acid), has been hydrothermally synthesized and characterized by IR, UV-Vis, TG analysis, elemental analysis, fluorescence analysis and single crystal X-ray diffraction. Compound 1 crystallizes in the monoclinic system, space group P2₁/c, a?=?10.1049(3)?Å, b?=?25.3888(6)?Å, c?=?14.7244(3)?Å, β?=?129.2740(10)°, V?=?2924.31(13)?ų, Z?=?4, R ₁?=?0.0639, wR ₂?=?0.1695 and S?=?1.133. The structure of 1 has a one-dimensional structure with [p-MeBzlPh₃P]⁺ counter-cations alternately residing on both sides of the one-dimensional anionic chains of the zigzag-chain polymer. Compound 1 exhibits strong fluorescence in solid state at room temperature.     

Coordination diversity in tin compounds with bis(benzoxazole)phenol as a polydentate ligand: Synthesis and crystal structure studies

Abstract

The reaction of 2,6-bis(benzoxazolyl)-4-tert-butylphenol (HL) with [ⁿBu_xSnCl_4?x] (x?=?0, 1) in 1:1 stoichiometry yielded the tin coordination complexes [(HL)SnⁿBu_xCl_4?x] [x?=?0 (1); x?=?1 (2)]. Deprotonation of HL was performed using reagents having groups with high basicity such as ⁿBuLi or [Sn{N(SiMe₃)₂}₂]. These basic reagents prompted the coordination of the ligand in its anionic form, yielding the complexes [(thf)₂Li(L)SnCl₄] (3) and [(L)Sn{N(SiMe₃)₂}] (4), respectively. The molecular structure of HL displayed an intramolecular hydrogen bond OH—N and a planar arrangement of the bis(benzoxazolyl)phenolic system. In the molecular structures of both complexes containing HL an intramolecular hydrogen bond of NH—O type was also present. The coordination of the ligand in either neutral or anionic form is described by a κO,κN chelate mode toward Sn. All complexes displayed bis(benzoxazolyl)phenolic moieties close to planar; the least planar system was observed in 4 that was also studied by DFT methods.     

Phase transformation in a nanostructured M300 maraging steel obtained by SPS of mechanically alloyed powders

New complexes of type [Cu(HTBG)₂]Cl₂ (1), [Cu(TBG)₂]·3H₂O (2) and [CuL]·nH₂O (3) L:L¹, n = 2 and (4) L:L², n = 1 (HTBG: 2-tolylbiguanide, L¹ and L²: ligands resulted from 2-tolylbiguanide, ammonia/hydrazine and formaldehyde one pot condensation) were synthesised and characterised. The features of complexes have been assigned from microanalytical, IR and UV–Vis data. Redox behaviour was established by cyclic voltammetry. The in vitro qualitative and quantitative antimicrobial activity assays showed that the complexes exhibited variable antimicrobial activity against Gram-negative and Gram-positive strains isolated from the hospital environment. The thermal analyses have evidenced the thermal intervals of stability and also the thermodynamic effects that accompany them. After water elimination, complexes have a similar thermal behaviour. Processes as water elimination, melting, chloride anion removal as well as oxidative degradation of the organic ligands were observed. The final product of decomposition was copper (II) oxide.     

Synthesis and crystal structure of a rhenium(V) complex containing a tridentate imido-coordinated Schiff base

The complex salt trans-[Re(mps)Cl(PPh₃)₂](ReO₄) (1) (H₃mps?=?N-(2-amino-3-methylphenyl)salicylideneimine) was prepared by reaction of trans-[ReOCl₃(PPh₃)₂] with a twofold molar excess of H₃mps. The compound was characterized by spectroscopy and X-ray crystallography. The results show that the trianionic ligand mps acts as a tridentate chelate via the doubly deprotonated amino nitrogen (which is present in 1 as an imide), the neutral imino nitrogen and the deprotonated phenolic oxygen atoms. The imido nitrogen and phenolate oxygen atoms coordinate trans to each other in a distorted octahedral geometry around the rhenium(V) centre.     

Simultaneous determination of levofloxacin hemihydrate and ambroxol hydrochloride in tablets by thin-layer chromatography combined with densitometry

This paper describes the application of thin-layer chromatography (TLC) combined with densitometry to simultaneous determination of levofloxacin hemihydrate (LEV) and ambroxol hydrochloride (AMB) in bulk and tablets. The separation was achieved on aluminum sheet of silica gel 60 F ₂₅₄ using chloroform: methanol: toluene: ammonia (10: 6: 3: 0.8 v/v/v/v) as mobile phase. Quantification was carried out densitometrically at 245 nm. This system was found to give compact spots for LEV (R _f value of 0.4) and AMB (R _f value of 0.7). The calibration curves for LEV and AMB was found to be linear between 9960–16600 ng/spot (r ² = 0.999) and 600–1000 ng/spot (r ² = 0.999), respectively. The mean percentage recoveries from tablets for LEV and AMB were 99.45% and 99.58%, respectively. The TLC-densitometry method has many advantages, such as simplicity, reasonable sensitivity, rapidity, and low cost, and it can be successfully used in routine analysis of both these drugs in tablet formulations.     

Two diverse temperature-directed cobalt-based coordination polymers: environmentally friendly photocatalysts for degradation of organic dyes

Two new cobalt-based coordination polymers (CPs) based on a semirigid naphthalene-bridged bis-pyridyl-bis-amide ligand, namely [Co(4-bmnpd)(5-HNIP)₂(H₂O)₂] (1) and [Co₄(4-bmnpd)₄(5-NIP)₄]·2H₂O (2) (4-bmnpd?=?N,N′-bis(4-methylenepyridin-4-yl)-2,6-naphthalenedicarboxamide, 5-H₂NIP?=?5-nitroisophthalic acid), have been prepared under hydrothermal conditions and structurally characterized by single-crystal X-ray diffraction analyses, infrared (IR) spectroscopy, and powder X-ray diffraction (PXRD). The structural analyses show that 1 has a one-dimensional (1D) chain structure while 2 exhibits a two-dimensional (2D) network. The effect of temperature on the structures of the CPs is discussed. The solid-state fluorescent properties of 1 and 2 were determined at room temperature. Furthermore, their photocatalytic degradation properties were also studied. Photocatalysts 1 and 2 are environmentally friendly and can effectively degrade organic dye Congo Red (CR) under ultraviolet (UV) light. In addition, the possible degradation mechanism was also investigated.