Separation and identification of different therapeutic pharmaceutical drugs on humic acid-based HPLC column: Method optimization using central composite design

Multimode chromatographic separations are highly desirable in pharmaceutical and environmental sciences. Current study deals with the application of newly developed mixed-mode end capped-immobilized humic acid onto an aminopropyl silica based chromatographic column for separation and identification of six drugs belonging to different therapeutic groups for its applicability in pharmaceutical industries. For this, central composite design was used to evaluate the separation and resolution by optimization of three most effective parameters (acetonitrile%, flow rate, and pH of mobile phase). Second-order quadratic model was used to evaluate their effect on resolution of peaks; the probability value (<0.05) obtained from analysis of variance suggested the best applicability of the model. Desirability function was applied to calculate optimum conditions (44.8% acetonitrile, 1.75 mL/min of flow rate, and 7.5 pH) required to achieve maximum separation with good resolution within 11 min. The method was validated for linearity, precision accuracy, selectivity, and sensitivity. The results revealed a highly precise (coefficient of variance > 1%), linear (R² = 0.99), and highly selective method. Moreover, the limit of detection/quantification values revealed acceptable sensitivity of the method. The developed column was compared for its efficiency with a commercially available column and found to be highly applicable for industrial applications.     

Carbon nanotube-chitosan modified disposable pencil graphite electrode for vitamin B12 analysis

A single walled carbon nanotube-chitosan (SWCNT-chitosan) modified disposable pencil graphite electrode (PGE) was used in this study for the electrochemical detection of Vitamin B(12). Electrochemical behaviors of SWCNT-chitosan PGE and chitosan modified PGE were compared by using cyclic voltammetry (CV), square-wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS) techniques. SWCNT-chitosan modified electrode was also used for the quantification of Vitamin B(12) in pharmaceutical products. The results show that this electrode system is suitable for sensitive Vitamin B(12) analysis giving good recovery results. The surface morphologies of the SWCNT-chitosan PGE, chitosan modified PGE and unmodified PGE were characterized by using scanning electron microscopy (SEM).     

Optical properties of metamaterial-based devices modulated by a liquid crystal

Due to the fact that it is possible to manipulate light with photonic crystals (PCs), PCs hold a great potential for designing new optical devices. There has been an increase in research on tuning the optical properties of PCs to design devices. We presented a numerical study of optical properties of metamaterial-based devices by liquid crystal infiltration. The plane wave expansion method and finite-difference time-domain method for both TE and TM modes revealed optical properties in photonic crystal structures in an air background for a square lattice. E7 type has been used as a nematic liquid crystal and SrTiO₃ as a ferroelectric material. We showed the possibility of the metamaterials for a two-dimensional photonic crystal cavity on a ferroelectric base infiltrated with a nematic liquid crystal.     

Photoprocesses of molecules with 2-nitrobenzyl protecting groups and caged organic acids

The 308 nm photoinduced formation of the nitroso product and the intermediacy of the aci-nitro form(s) were studied for a series of 2-nitrobenzyl alkyl and aryl esters (1a-4e) and bis-(nitrophenyl)methyl acetates (5a-6b) by time-resolved UV-vis spectroscopy. A triplet state appears as major transient, when 2-nitrobenzyl derivatives 1 are substituted by 4,5-dimethoxy (2) and 4,5-methylenedioxy (3/4) groups. This triplet of charge transfer character is, however, not part of the route via the aci-nitro into the 2-nitroso form. The activation energy and preexponential factor of the longest lifetime component (tau(aci)), i.e. the major part of the aci-nitro decay, were determined. The carboxylic acids as leaving groups have rather small effects on tau(aci). An additional nitrated phenyl ring in alpha-position (5) leads generally to shorter tau(aci) value. Otherwise, the photogeneration of nitroso products is similar. The quantum yield (Phi(d)) varies only moderately with structure, the yield of the aci-nitro form and Phi(d) are correlated and little affected by solvent properties.     

Electrical conductivity,photoconductivity, and optical properties of poly(1,4‐diaminoanthraquinone) organic semiconductor for optoelectronic applications

The electrical conductivity and optical properties of the poly(1,4‐diaminoanthraquinone) [poly(1,4‐DAAQ)] have been investigated. The electrical conductivity of the polymer increases with temperature and room temperature conductivity was found to be 2.68 10^?5 S cm^?1. The optical band gap of the polymer is 1.87 eV due to the direct optical transitions. The photoconductivity of the polymer is higher than that of dark conductivity. When the light is switched on, the resistance decreases abruptly and when it is switched off, the resistance increases. This confirms that the polymer is a photoconductive material. The obtained results indicate that the poly(1,4‐DAAQ) is a photoconducting organic semiconductor with photovoltaic and dark current properties. Copyright © 2008 John Wiley & Sons, Ltd.     

A self-powered "sense-act-treat" system that is based on a biofuel cell and controlled by boolean logic

Bio-logic-al: an autonomous, integrated "sense-act-treat" system that is based on an enzymatic biofuel cell has been developed. The system couples a biocomputing logic-detection method with a drug-release system to provide a logic-activated therapeutic intervention in response to a simulated abnormal physiological state, without the need for an external power source, control electronics, or microelectromechanical actuators.     

Sensitive sepiolite-carbon nanotubes based disposable electrodes for direct detection of DNA and anticancer drug-DNA interactions

A new surface based on the natural clay mineral sepiolite and a single-walled carbon nanotubes-modified graphite electrode was developed for the electrochemical detection of DNA, and also for anticancer drug-DNA interactions.     

Synthesis,structure, and solvent-extraction properties of tridentate oxime ligands and their cobalt(II), nickel(II), copper(II), zinc(II) complexes

Synthesis of four different types of ligands Ar[COC(NOH)R] _n (Ar = biphenyl, n = 1, HL¹; Ar = biphenyl, n = 2, H₂L²; Ar = diphenylmethane, n = 1, HL³; Ar = diphenylmethane, n = 2, H₂L⁴; R = furfurylamine in all ligands) and their dinuclear Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ complexes is reported herein. These compounds were characterized by elemental analysis, ICP-OES, FT-IR spectra, and magnetic susceptibility measurements. The ligands were further characterized by ¹H NMR. The results suggest that dinuclear complexes of HL¹ and HL³ have a metal to ligand mole ratio of 2: 2 and dinuclear complexes H₂L² and H₂L⁴ have a metal to ligand mole ratio of 2: 1. Square pyramidal or octahedral structures are proposed for complexes of oxime ligands. Furthermore, extraction abilities of the four ligands were also evaluated in chloroform using selected transition metal picrates such as Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Pb²⁺. The ligands show strong binding ability towards Hg²⁺ and Cu²⁺ ions.