An HPLC Method for the Separation and Simultaneous Determination of Antihistamines,Sympathomimetic Amines and Dextromethorphan in Bulk Dpug Material and Dosage Forms

Abstract

A high-performance liquid chromatography (HPLC) method for the simultaneous determination of bamipine, phenylephrine or (phenylpropanolamine, ephedrine) and dextromethorphan has been developed. The method proved suitable for the analysis of the compounds in various pharmaceutical formulations. From the sample solutions no interference was observed on the chromatographs. The accuracy of the assay has been assessed. Recovery studies have been also carried out by adding known quantities of the active ingredients to placebo samples (spiking recoveries).     

Use of Temperature- and Humidity-Dataloggers in Food Engineering

The use of dataloggers in food engineering is discussed in two examples. The first example describes the measurement of temperature and humidity in a bulk tank car during transport and unloading. In the case of wheat flour the relative humidity in the air raises from about 80% r.h. to values near 100% r.h. at the air compressors for pneumatical unloading start working. The second example shows the use of the datalogger in education on heat transfer. The device was fixed in an ice cream sample which was placed in a store at –25°C. The measured hardeningtime agrees well to theoretical heat transfer calculation.This revised version was published online in November 2005 with corrections to the Cover Date.     

Macro-Hybrid Variational Formulations of Constrained Boundary Value Problems

In the context of convex analysis, macro-hybrid variational formulations of constrained boundary value problems are presented. Monotone mixed variational inclusions are macro-hybridized on the basis of nonoverlapping domain decompositions, and corresponding three-field versions are derived. Then, for regularization purposes, augmented formulations are established via preconditioned exact penalizations and expressed in terms of proximation operators. Optimization interpretations are given for potential problems, recovering the classic two- and three-field augmented Lagrangian formulations. Furthermore, associated parallel two- and three-field proximal-point algorithms are discussed for numerical resolution of finite element discretizations. Applications to dual mixed variational formulations of problems from mechanics illustrate the theory.     

Self-consistent elastoplastic stress solutions for functionally graded material systems subjected to thermal transients

In this work, a self-consistent constitutive framework is proposed to describe the behaviour of a generic three-layered system containing a functionally graded material (FGM) layer subjected to thermal loading. Analytical and semi-analytical solutions are obtained to describe the thermo-elastic and thermo-elastoplastic behaviour of a three-layered system consisting of a metallic and a ceramic layer joined together by an FGM layer of arbitrary composition profile. Solutions for the stress distributions in a generic FGM system subjected to arbitrary temperature transient conditions are presented. The homogenisation of the local elastoplastic FGM behaviour in terms of the properties of its individual phases is performed using a self-consistent approach. In this work, power-law strain hardening behaviour is assumed for the FGM metallic phase. The stress distributions within the FGM systems are compared with accurate numerical solutions obtained from finite element analyses and good agreement is found throughout. Solutions are also given for the critical temperature transients required for the onset of plastic deformation within the three-layered systems.     

Fracture propagation in brittle materials as a standard dissipative process: General theorems and crack tracking algorithms

The present work frames the problem of three-dimensional quasi-static crack propagation in brittle materials into the theory of standard dissipative processes. Variational formulations are stated. They characterize the three dimensional crack front “quasi-static velocity” as minimizer of constrained quadratic functionals. An implicit in time crack tracking algorithm that computationally handles the constraint via the penalty method algorithm is introduced and proof of concept is provided.     

Mathematical modeling of controlled-release systems of herbicides using lignins as matrices

The herbicides applied in soils can be easily lost, owing to leaching, volatilization, and bio-and photodegradation. Controlled-release systemsusing polymeric matrices claim to solve these problems. The movement of the herbicides in the soilisalso an important phenomenon to be studied in order to evaluate the loss processes. The development of mathematical models is a relevantrequirement for simulation and optimization of such systems. This study reviews mathematical models as an initial step for modeling data obtained for controlled-release systems of herbicides (diuron, 2,4-dichlorophenoxyacetic acid, and ametryn) using sugarcane bagasse lignin as a polymeric matrix. The release kinetic studies were carried out using several acceptorsystems includinga water bath, soil, and soil-packed columns. Generally, these models take into account phenomena such as unsteady-state mass transfer by diffusion (Fick'slaw) and convection, consumption by several processes, and partitioning processes, resulting in partial differential equations with respect to time and space variables.     

Determination of mono and disaccharide content of enteral formulations by gas chromatography

Summary A quantitative GC method has been developed which allows determination of mono and disaccharides in enteral formulations. The method is based on the isolation of the mono and disaccharide fraction on a charcoal-celite column and conversion to trimethylsilylated oximes (TMS-oximes). The repeatability of the complete method and recovery were acceptable. In the five commercial samples assayed, maltose was the main sugar (5.24–8.85 gL⁻¹) followed by glucose (1.06–2.41 gL⁻¹) and lactose (0–1.17 gL⁻¹) Low levels of fructose (0–0.18 gL⁻¹) and sucrose (0–0.07 gL⁻¹) were observed and galactose was detected in two of the samples. The presence of maltulose is reported in enteral formulations for the first time. Maltulose formed from maltose during processing, was present in variable amounts (0.12–1.07 gL⁻¹) and could be a useful indicator for enteral formulation classification.     

A note for tightening 0–1 models

We describe two approaches for 0–1 program model tightening that are based on the coefficient increasing and reduction methods proposed in Dietrich, Escudero and Chance (1993). We present some characterizations for the new formulations to be tighter than the original model. It can be shown that tighter models can be obtained even when applying any of both approaches to a redundant constraint; see Escudero and Muñoz (1998). We also present some situations where these approaches cannot be applied.     

Qualitative and Quantitative Determination of The Polymer Content in Rubber Formulations

The objective of this paper is to show an easy and rapid way to determine qualitatively and quantitatively the type of polymer or polymer blend used in a rubber formulation. The most common polymers used manufacturing rubber products were tested and characterized by both their decomposition temperature and the curve profile. Thermogravimetric analysis, which is considered to be used mainly for quantitative purposes, turned out to be a rather useful analytical tool to obtain qualitative information of such elastomeric mixtures. This revised version was published online in August 2006 with corrections to the Cover Date.