Comparison of multivariate calibration techniques applied to experimental NIR data sets

The present study compares the performance of different multivariate calibration techniques applied to four near-infrared data sets when test samples are well within the calibration domain. Three types of problems are discussed: the nonlinear calibration, the calibration using heterogeneous data sets, and the calibration in the presence of irrelevant information in the set of predictors. Recommendations are derived from the comparison, which should help to guide a nonchemometrician through the selection of an appropriate calibration method for a particular type of calibration data. A flexible methodology is proposed to allow selection of an appropriate calibration technique for a given calibration problem.54460862

Evolving neural network optimization of cholesteryl ester separation by reversed-phase HPLC

Cholesteryl esters have antimicrobial activity and likely contribute to the innate immunity system. Improved separation techniques are needed to characterize these compounds. In this study, optimization of the reversed-phase high-performance liquid chromatography separation of six analyte standards (four cholesteryl esters plus cholesterol and tri-palmitin) was accomplished by modeling with an artificial neural network–genetic algorithm (ANN-GA) approach. A fractional factorial design was employed to examine the significance of four experimental factors: organic component in the mobile phase (ethanol and methanol), column temperature, and flow rate. Three separation parameters were then merged into geometric means using Derringer’s desirability function and used as input sources for model training and testing. The use of genetic operators proved valuable for the determination of an effective neural network structure. Implementation of the optimized method resulted in complete separation of all six analytes, including the resolution of two previously co-eluting peaks. Model validation was performed with experimental responses in good agreement with model-predicted responses. Improved separation was also realized in a complex biological fluid, human milk. Thus, the first known use of ANN-GA modeling for improving the chromatographic separation of cholesteryl esters in biological fluids is presented and will likely prove valuable for future investigators involved in studying complex biological samples

A Turke turn'd Quaker: conversion from Islam to radical dissent in early modern England

The study of the relationship between the anglophone and Islamic worlds in the seventeenth century has been the subject of increas- ing interest in recent years, and much attention has been given to the cultural anxiety surrounding “Turning Turke”, conversion from Christianity to Islam, especially by English captives on the Barbary coast. Conversion in the other direction has attracted far less scrutiny, not least because it appears to have been far less com- mon. Conversion from Islam to any form of radical dissent has attracted no scholarship whatsoever, probably because it has been assumed to be non-existent. However, the case of Bartholomew Cole provides evidence that such conversions did take place, and examining the life of this “Turke turn’d Quaker” provides an insight into the dynamics of cross-cultural conversion of an exceptional kind

A comparison of multivariate calibration techniques applied to experimental NIR data sets Part II. Predictive ability under extrapolation conditions

The present study compares the performance of different multivariate calibration techniques when new samples to be predicted can fall outside the calibration domain. Results of the calibration methods are investigated for extrapolation of different types and various levels. The calibration methods are applied to five near-IR data sets including difficulties often met in practical cases (nonlinearity, nonhomogeneity and presence of irrelevant variables in the set of predictors). The comparison leads to general recommendations about what method to use when samples requiring extrapolation can be expected in a calibration application

Comparison of multivariate calibration techniques applied to experimental NIR data sets

The present study compares the performance of different multivariate calibration techniques applied to four near-infrared data sets when test samples are well within the calibration domain. Three types of problems are discussed: the nonlienar calibrtion, the calibration using heterogeneous data sets, and the calibration in the presence of irrelevant information in the set of predictors. Recomandations are derived from the comparison which should help to guide a nonchemometrician through the selection of an appropriate calibration method for a particular type of calibration data

Le dosage par spectroscopie proche infrarouge, Application au test de l'uniformité de teneur des comprimés II

The first part of this article [1] described the methodology to follow to develop a technique for the quantitative analysis of active substance in a solid tablet type formulation using near infrared spectroscopy. It seems appropriate to complete this description by detailing the different steps involved through illustrated examples and by proposing useful guidelines for new users. The quantitative analysis example chosen is that of content uniformity (CU) of tablet type solid forms (cf. Ph. Eur. 2.9.6/2.9.40) [2], a test required in the pharmaceutical industry and for which this alternative quantitative analysis could offer substantial gains. It should be noted that the approach described applies to other types of quantitative analysis (mean assay, water content in raw materials, polymorph assay within a tablet, etc.)

Le dosage par spectroscopie proche infrarouge, Application au test de l'uniformité de teneur des comprimés, I. Méthodologie

This first document describes guidelines to develop a quantification method for active pharmaceutical ingredient content in solid dose formulation, using near-infrared spectroscopy. This new approach offers several advantages over classical techniques, in particular for tablets content uniformity determination. This document is intended to help users addressing the numerous questions pertaining to number and types of samples, usable spectral range for quantification, importance of the reference method, development of a model and potential pitfalls, use of chemometrics tools and method validation. It also offers a statistical support that used as an aid for decision for routine controls, when a sample falls near acceptance limits. The document gathers basic principles and will be complemented by a second article with practical examples to illustrate the methodology

Analyse quantitative par spectroscopie proche infrarouge: Application au test d'unifomité de teneur des comprimés

La spectroscopie Proche infrarouge présente un large potentiel d'applications dans l'industrie pharmaceutique par sa capacité à transmettre des informations reliées à la fois à la structure chimique des échantillons et à leur état physique. Elle peut être mise à profit pour des analyses qualitatives, telles l'identification des matières premières, et également pour des analyses quantitatives telles le dosage d'un principe actif dans un comprimé. Avec pour avantage une rapidité inégalée pour délivrer un résultat comparée aux techniques classiques en vigueur. Attrayante par ses performances, cette spectroscopie nécessite cependant une prise en main qui doit respecter une démarche minutieuse et souvent déroutante par son aspect heuristique (allers-retours) et à la mise en oeuvre d'outils d'analyse statistique multivariée. Si de nombreuses publications témoignent de la puissance de cet outil, il est apparu opportun de rassembler en un même texte la démarche de développement à suivre et les repères à connaître pour permettre son utilisation en analyse quantitative dans un contexte de libération pharmaceutique. Le travail de cette commission a été de rassembler les éléments issus de la pratique industrielle en se concentrant sur l'un des essais les plus intéressants: celui de l'uniformité de teneur des comprimés. Ce test est en effet l'une des applications où la rapidité de mise en oeuvre est le plus appréciable, tout en étant celui qui peut poser le plus de questions quant à la validité des résultats et la prise de décision pharmaceutique