Simultaneous Determination of Pioglitazone and Glimepiride by High-Performance Liquid Chromatography

A rapid and accurate HPLC method has been developed for simultaneous determination of pioglitazone and glimepiride. Chromatographic separation of the two pharmaceuticals was performed on a Cosmosil C₁₈ column (150 mm × 4.6 mm, 5 m) with a 45:35:20 (v/v) mixture of 0.01 m triammonium citrate (pH adjusted to 6.95 with orthophosphoric acid), acetonitrile, and methanol as mobile phase, at a flow rate of 1.0 mL min^–1, and detection at 228 nm. Separation was complete in less than 10 min. The method was validated for linearity, accuracy, precision, limit of quantitation, and robustness [1, 2]. Linearity, accuracy, and precision were found to be acceptable over the ranges 2.50–30.00 g mL^–1 for pioglitazone and 0.10–10.00 g mL^–1 for glimepiride.     

Pyrimidinethiol as a reagent for extraction separation of platinum metals and gold Determination of Pd(II), Os(VIII) and Ru(III)

The solvent extraction separation of Pt(IV), Pd(II), Os(VIII), Ru(III) and Au(III) from one another and also from Rh(III) and Ir(III) with 1-(2'-nitro-4'-tolyl)-4,4,6-trimethyl-(1H, 4H)-2-pyrimidinethiol has been investigated. Photometric procedures have been developed for the determination of Pd(II), Os(VIII) and Ru(III) with the same reagent. The reagent allows the enrichment of Pd(II) and Au(III) at the trace level from a large volume of aqueous medium even in the presence of base metals. The method can be used for the determination of platinum metals and gold in alloys.     

Fluorescence Quenching Studies of the Interaction Between Riboflavin and Norfloxacin and Analytical Application in the Determination of Vitamin B<Subscript>2</Subscript>

The binding of riboflavin (RBF) to norfloxacin (NF) was investigated by spectroscopic techniques. The results revealed that RBF caused the fluorescence quenching of NF by complex formation. The binding parameters and corresponding thermodynamic parameters ΔH, ΔG and ΔS at different temperatures were calculated. The negative enthalpy (ΔH) and positive entropy (ΔS) values indicated that both hydrogen bond and hydrophobic forces played major roles in the binding of RBF to NF. The distance r between donor (NF) and acceptor (RBF) was obtained according to the Forster’s theory of non-radiative energy transfer. The method of quenching was successfully applied for the determination of riboflavin from pharmaceutical samples.     

Interaction of Fluorescein with Felodipine: A Spectrofluorometric and Thermodynamic Study

The interaction between fluorescein and felodipine (FLD) was investigated by the spectrofluorometric method. The fluorescence of FLD was quenched by fluorescein and quenching is in accordance with the Stern-Volmer relation. The binding constants of fluorescein with FLD were obtained at different temperatures. The binding constant and number of binding sites at different temperatures were calculated yielding the corresponding thermodynamic parameters ΔS, ΔH and ΔG. The distance r between the donor (FLD) and acceptor (fluorescein) molecules was obtained according to the fluorescence resonance energy transfer. The optimum conditions for the fluorometric determination of fluorescein were studied and the quenching method was successfully applied to estimate the fluorescein concentration of the pharmaceutical sample directly.     

Optimal design of an uncoupled six degree of freedom dynamometer

A design analysis of a class of six degree of freedom strain-gage dynamometers which are virtually uncoupled in each force and moment component is presented. The method of design is detailed and an optimal design algorithm is implemented. The dynamometer is made of six or more T-sections with thin webs and flanges called shear panel elements (SPE). Complete stress and buckling analyses are carried out for the SPE, and experiments confirm the predictions of the analyses. The optimal design method is illustrated with several case studies. A dynamometer has been built and used in laboratory and field experiments.     

Control of circular-disk stability with membrane stresses

Membrane stresses alter the dynamic behavior and stability of circular-disk elements, such as circular saws and grinding wheels, by shifting the disk's natural frequency spectrum. Such shifts are directly related to variation in the critical rotation speed at which standing-wave-resonance instability occurs. Negative critical-speed variations reduce the disk stability, and positive critical-speed variations increase stability. The present paper theoretically and experimentally investigates the relationship between the state of disk-membrane stress, critical rotation speed, and the frequency spectrum in radially symmetric disk problems. The observed critical-speed variations are theoretically predictable and well understood. The approach of a shifting critical-speed instability can be predicted by monitoring the disk-frequency spectrum.     

Compact and efficient coupler to interface hybrid dielectric-loaded plasmonic waveguide with silicon photonic slab waveguide

A coupler is proposed to interface a hybrid dielectric-loaded plasmonic waveguide (HDLPW) with a silicon photonic slab waveguide. The HDLPW is firstly designed and optimized to attain the best tradeoff between the mode confinement and the propagation distance. The designed coupler is inspired from the taper configuration and numerically modeled through finite-difference time-domain (FDTD) simulation. The results demonstrate that a high confinement and low loss of the energy is achieved from a silicon photonic slab waveguide into the dielectric slot of area 50×200 nm² in the HDLPW. The transmission attained through the coupler with a compact size of 400 nm is found to be as high as 80% (1 dB). Further, the planar nature of taper configuration makes the coupler easy to fabricate using the state-of-the-art CMOS facilities. The proposed coupler is useful in enabling the integration between photonic and hybrid plasmonic waveguides and thus realizing on-chip hybrid integrated circuits.     

Extractive photometric determination of gold(III) with 1-(2',4',6'-trichlorophenyl)-4,4,6-trimethyl-(1H,4H)-2-pyrimidinethiol in presence of tri-iso-octylamine

Tervalent gold was determined spectrophotometrically as its anionic 1:4 gold-thiol complex extracted into chloroform from aqueous acidic medium (1.5M sulphuric acid) in the presence of tri-iso-octylamine. The complex exhibits maximum absorption at 480 nm (molar absorptivity 4.60 x 10(3) l.mole(-1).cm(-1)) and Beer's law is obeyed in the concentration range 5-50 microg of gold(III) per ml. The relative standard deviation and relative error, calculated from ten determinations of solutions containing 15 microg of gold(III) per ml were 1.0% and 0.8%. The method is simple, selective and reproducible. It permits separation of gold(III) from associated elements and its determination in synthetic mixtures.     

ACTION SPECTRUM AND THRESHOLD SENSITIVITY OF ENTRAINMENT OF ORCADIAN RUNNING ACTIVITY IN THE COCKROACH PERIPLANETA AMERICANA

Abstract— The interaction between the compound eye and the circadian timing system for running activity in the cockroach, Periplaneta americana , has been investigated by measuring the action spectrum for entrainment of such behavior by imposed photic stimuli. Test wavelengths were selected which spanned the spectral range of the dichromatic retina of this insect and intensities of such lights for which half of a population of animals failed to be entrained (threshold) were determined. Stimuli were presented either with a 12:12 light–dark regime or for 12h/day on a continuous background of orange light. The latter procedure altered the balance of sensitivity in the two groups of color receptors in the eye. A comparison of the resulting action spectra and the spectral sensitivities of receptors and visual interneurons measured under similar conditions suggest that the entrainment mechanism is dominated by the receptor group most sensitive to long wavelength light. Furthermore, the eye-clock mechanism shows an extraordinarily high sensitivity to such stimuli. We estimate that a mean flux of about 5 photons/eye/s is sufficient to entrain the behavior. The implications of these results are discussed.     

Simultaneous Determination of Pioglitazone and Glimepiride by High-Performance Thin-Layer Chromatography

JPC – Journal of Planar Chromatography – Modern TLC -