Looking Beyond the Column: An Investigation into Method Irreproducibility for an Active Pharmaceutical Ingredient

Irreproducibility during initial development of a high performance liquid chromatography method is seldom investigated in a thorough and careful manner when working in an industrial setting. For a drug project in the early developmental stages, the LC method is often changed, sometimes drastically, if one encounters irreproducibility in the method. Too often a method is deemed irreproducible due to column lot variability, diluent effects, or pH effects with little or no experiments taking place for justification and little thought given to why the irreproducibility may have occurred in the first case. In this paper, a case study is presented in which a systematic approach was carried out in order to determine the exact reason why method irreproducibility was occurring. The findings of the investigation were then drawn onto change a method with poor reproducibility into one that is rugged without the need to start from the beginning and develop a new method.

     

Use of a recyclable poly(<Emphasis Type="Italic">N</Emphasis>-vinyl carbazole) palladium(II) complex catalyst: Heck cross-coupling reaction under phosphine-free and aerobic conditions

A poly(3,6-dibenzaldimino N-vinyl carbazole) Pd(II) complex has been synthesized and characterized by physicochemical and spectroscopic techniques. The complex was found to be highly active toward hydrogenation reactions of various organic substrates under atmospheric pressure at ambient temperature. A tentative reaction mechanism is proposed on the basis of kinetic studies and isolation of reactive intermediates. The catalyst shows good conversion rates, thermal stability and recyclability.     

Nanocrystalline undoped tetragonal and cubic zirconia synthesized using poly-acrylamide as gel and matrix

Nanocrystalline zirconia powders with tetragonal and cubic structure have been prepared from ZrO₂-polyacrylamide gel and precipitated zirconia in polyacrylamide matrix respectively. X-ray diffraction results of the samples annealed at high temperatures show that the tetragonal and cubic form, obtained from the gel, are fairly stable in air up to 1,173 K and partially stable in inert atmosphere, up to 1,273 K. The stability at such high temperatures is due to the presence of oxygen vacancies in zirconia sample, incorporated in the process of decomposition of polymer.     

Synthetic and Thermal Studies of Polymeric Chelates of Some Bis-Biurets with First Transition Series Metals

Some new coordination polymers have been synthesized by combining adipyl bis-biuret and azelyl bis-biuret with metals of first transition series viz Mn(II), Co(II), Ni(II), Cu(II) and Zn(II). They were characterized by elemental analysis, infrared and reflectance spectral and magnetic studies. A detailed thermal study was carried out and thermal stability compared. The results obtained have been discussed.This revised version was published online in November 2005 with corrections to the Cover Date.     

Application of dial-gage and laser speckles for ultra-low thermal-expansion measurements using push-rod dilatometers

Conversion of conventional push-rod dilatometers for ultra-low thermal-expansion measurements is described. The method is based on the determination of the displacement of the probe-rod by ultra-precise dial-gage measurements by means of a laser-speckle technique. The movement of speckles created in space by the laser beam incident on an aluminum foil attached to the needle of the gage is observed for the measurements. It has been found that the sensitivity of the modified dilatometer is orders of magnitude higher than the existing LVDT approach.     

Finslerian Multi-Dimensionality,Associated Gauge Fields,and Stochastic Space-Time

The theory is constructed which elucidates all the gauge fields associated with fibration of the tangent vectors and of the vectors of higher degrees of tangency. The approach synthesizes intrinsically the Einstein equations with the Yang-Mills equations and gives an adequate framework for extending the physical field equations. Then, by considering the statistical behaviour of internal variables, it is possible to get a deeper insight in understanding the origin of quantum laws. Actually, we construct what may be called the general relativity in vector fibrations over space-time manifold.     

Monodromy Deformation Approach to Nonlinear Equations — A Survey

Monodromy deformation approach to nonlinear partial differential equation is discussed in a pedestrian's way. The whole methodology is discussed on the basis of Massive Thirring Model. In the first section of our paper we discuss the basic terminologies amociated with the deformation problem. In the next part the problem is defined on the basis of the Lax pairs for the Thirring model, and it is explicitly demonstrated that how one can determine the asymptotic expansions near a regular and irregular singularity, and hence the Stokes multipliers. Thirdly we show how to determine the “third” equation in according to Its. In the determination of the asymptotic expansion we have discussed the role played by both the WKB approximation and the series solution. In the fourth section we briefly consider the problem when the nonlinear field variables are taken to be fermionic.