Kevin D. Altria. Analysis of Pharmaceuticals by Capillary Electrophoresis

Transcription

1 Kevin D. Altria Analysis of Pharmaceuticals by Capillary Electrophoresis

2 CH ROMAIOGRAPH IA Edited by Kevin D. Altria, Glaxo Wellcome R&D, UK CE Series There are currently a number of general textbooks covering Capillary Electrophoresis where information on a range of applications and techniques can be found. Readers who are interested in a specific area of CE struggle to find truly comprehensive treatments of their areas of interest. The CHROMATOGRAPHIA CE series has been established to allow comprehensive books to be produced covering individual topics. The books are written by well known authors in their specialist application areas and cover CE topics such as DNA analysis, analysis of pharmaceuticals, chiral separations, MECC, carbohydrate analysis, biomedical applications and troubleshooting ince. Volume 1: C. Heller (Ed.), Analysis of Nucleic Acids by Capillary Electrophoresis Volume 2: K. D. Altria, Analysis of Pharmaceuticals by Capillary Electrophoresis

3 Kevin D. Altria Analysis of Pharmaceuticals by Capillary Electrophoresis II vleweg

4 All rights reserved Friedr. Vieweg & Sohn Vedagsgesellschaft mbh, BraunschweiglWiesbaden, 1998 Softcover reprint of the hardcover 1st edition 1998 Vieweg is a subsidiary company of Bertelsmann Professional Information. No part of this publication may be produced, stored in a retrieval system or transmitted, mechanical, photocopying or otherwise, without prior permission of the copyright holder. Produced by Lengericher Handelsdruckerei, Lengerich ISBN-13: DOl: / e-isbn-13:

5 v Preface During the 1980's the analysis of pharmaceuticals was dominated by the use of High Performance Liquid Chromatography (HPLC). Other separative techniques such as Gas Chromatography and Thin Layer Chromatography offered alternatives but their quantitative capabilities and/or solute range could not approach that of HPLC. The majority of pharmaceuticals are ionic and it would be reasonable to assume that electrophoresis may be useful in the analysis of pharmaceuticals. However, the electrophoretic instruments available in the 1980's were labour intensive and employed post-separation detection procedures. During the late 1980's and early 1990's extensive research was conducted into the possibilities of conducting electrophoretic separations in capillaries. This approach allowed on-line detection and could be performed on fully automated equipment. This research led to the advent of modern day capillary electrophoresis (CE) instruments which offer similar performance and automation levels to that of HPLC. Research was also focused on developing applications for CE and particular attention was paid to applications within the pharmaceutical analysis area. These applications proved that CE could be applied to a wide range of drug types including water insoluble and neutral compounds. The ability to achieve efficient chiral separations of drugs also increased the popularity of the technique. CE with indirect UV detection has become established as a simple and effective alternative to ion-exchange chromatography for the determination of small inorganic or organic ions. Routine CE methods are now used in many industrial pharmaceutical companies and applications include determination of related impurities, main component assay, chiral separations and drug residue determinations. Research into CE continues to broaden the application range in drug analysis. In particular current research is focused in the area of nonaqueous solvent systems and the developing technique of capillary electrochromatography (CEC). In CEC the capillaries used in CE are packed with HPLC stationary phase material and a high voltage is used to achieve separations by combining electrokinetic and chromatographic processes. All of these application and development areas are covered in individual chapters within this book. CE is still a rapidly developing technique and new applications and developments appear on a weekly basis. This book broadly reflects the current state of the art for CE analysis of pharmaceuticals and contains several hundred references to specific applications and methods. The main purpose of the book is to present the application possibilities of CE but I hope the extensive use of tabulated application data should also make the book useful as a reference point for specific applications. London 1998 Kevin D Altria

6 VI Preface Acknowledgement I would like to extend my appreciation to Dr. Angelika Schulz from Vieweg Publishing who has kindly supported the creation of the Chromatographia CE Series throughout its continued development. My thanks are also extended once again to my family and friends who have helped me to retain? a little sanity during the preparation of this volume. In particular my gratitude is extended to my wife Fatima and my colleagues Dave Rudd and Simon Bryant. Contact details Adress: Phone: Fax: Website: Kevin D Altria, Pharmaceutical Development, GlaxoWellcome R&D, Park Road, Ware, Herts. SGl2 ODP, UK KDA8029@ggr.co.uk

7 VII Contents Preface... V Contents... VII 1 Introduction to CE and the Use of CE in Pharmaceutical Analysis Capillary Electrophoresis (CE) Theory and Background CE Instrumentation Capillaries Temperature control Sampl~ introduction Detectors Band Broadening Effects in CE Heat dissipation Electroendosmotic flow On-capillary detection Molecular diffusion Injection related broadening Separation Modes Available Free Solution Capillary Electrophoresis (FSCE) Micellar electrokinetic capillary chromatography (MECC) Capillary Gel Electrophoresis (CGE) Capillary Isoelectric Focusing (ClEF) Capillary electrochromatography (CEC) Application of CE to Specific Drug Classes The Role of CE in Pharmaceutical Analysis References Main Component Assay by CE Introduction Reported Applications Low ph High ph MECC Identity Confirmation Testing General Considerations in Quantitative Analysis Precision Accuracy Linearity Comparison of CE and HPLC for Drug Assay References Determination of Drug Related Impurities Introduction Separations Using Low ph Electrolytes High ph... 52

8 VIII Contents 3.4 MECC Comparison with HPLC Sensitivity Peak: identity confirmation Applications Chemical purity testing of drug substance Chemical purity testing of formulated product Stability testing Impurity profiling References Separation and Quantitation of Enantiomers Introduction Cyclodextrins Low ph electrolytes containing cyclodextrins Cyclodextrins at high ph Cyclodextrins in Non-aqueous CE Crown ethers Crown ethers in Non-aqueous CE SDS-CD MECC Carbohydrates Proteins Bile salt MECC Antibiotics Synthetic surfactants Method development Selector type Temperature Electrolyte selection MECC electrolyte optimisation Quantitative Applications Enantiomeric purity testing Reaction rate monitoring Formulation stability testing Clinical applications Method Validation Detection limits Precision Linearity Recovery Cross-validation Freedom from interference Selectivity Robustness evaluation Method transfer Conclusions Stop press update References... 94

9 IX 5 Determinations of Drug Counter-Ions and Ionic Impurities by CE I0l 5.1 Introduction Separation of inorganic anions Indirect detection of anions Direct detection of anions Metal Ion Determinations Determination of metal ion content by indirect UV detection Direct UV detection of metal ion complexes Quantitative Procedures Determination ofinorganic Anion Counter-Ion Levels in Basic Drugs Determination of Organic Acid Anion Counter-Ion Levels in Basic Drugs Quantitation of Metal Counter-Ion Levels in Acidic Drugs Determination of Ionic Contaminants in Drug Substance Benefits and Disadvantages of CE Methods in Stoichiometric Analysis Disadvantages Advantages References Trace Analysis and Residues Determination Introduction Drug Residue Analysis Basic drugs residues Acidic drug residues Detergent Solution Residue Analysis Surfactant residues Metal ion residues from detergent solutions EDTA residues Drug Doping Levels Environmental Analysis Advantages and Disadvantages of the Use of CE in Residues Analysis Disadvantages Advantages References Pharmaceutical Raw Materials and Excipients Analysis Introduction Alcohols Carbohydrates Cyc10dextrins Dyes Fatty Acids Flavouring Agents Inorganic Anions Lecithins Metal Ions Organic Acids Polycarboxylic Acids Preservatives

10 x Contents 7.14 Starting Materials Surfactants Water Purity References Analysis of dissolution test sample solutions Introduction Total Drug Content Release Testing Dissolution Profile Monitoring Monitoring of the Dissolution of Chiral Drugs Multi-Component Analysis Benefits and Disadvantages of Adopting CE for Dissolution Analysis References Determination of Vitamins by Capillary Electrophoresis Introduction Assay Related Impurities Determinations Clinical Determinations Identity Confirmation Microemulsion Electrokinetic Capillary Chromatography (MEEKC) Conclusions References Overview of Application of CE to determine drugs in biofluids Introduction Sample Pretreatment Procedures Direct Sample Injection Sample Matrix Effects Sensitivity Enhancement Quantitative Precision Applications Chiral Clinical Applications Non-Aqueous CE and CEC Clinical Applications References Method Validation Introduction Specific method validation aspects Specificity (selectivity) Linearity Sensitivity Accuracy/recovery Injection Repeatability Method Repeatability Method Robustness Cross-Validation Solution Stability Response factors Peak Homogeneity

11 XI 11.5 Method Transfer System Suitability Conclusions References Capillary Electrochromatography Introduction CEC Instrumentation CEC Operation Detection Options in CEC Analytical Performance of CEC Applications Pharmaceutical applications Chiral CEC Benefits and Disadvantages of CEC Compared to CE and HPLC Advantages ofcec Current disadvantages of CEC Conclusions Stop press update References Use of non-aqueous electrolytes in pharmaceutical analysis Introduction Basic Drugs Acidic Drugs ImpuritylMetabolites Determinations Chiral Separations Excipients and Raw Materials Main Component Assay Inorganic Ions and Small Organic Ions Practicalities of Routine NACE Operation Comparison of the Advantages ofnace and Aqueous CE References The Use of Chemometrics and Experimental Designs in CE Method Development and Robustness Testing Introduction Full and Fractional Factorial designs Central Composite and Overlapping Resolution Mapping Designs Simplex optimisation MECC Method Development FSCE Method Development Chiral CE Method Development CEC Method Development Robustness Testing Peak Identification Selection of Experimental Design References

12 XII Contents 15 Forensic Applications of CE Introduction Identity Confirmation Assay Clinical Applications Purity Determination Inorganic Ions Non-Aqueous CE Chiral References Determination of Radioactive Compounds by CE Introduction Radioactivity Detectors Radiopharmaceutical Purity and Assay Determinations References Miscellaneous Pharmaceutical Analysis Related Areas of CE Drug Diet Determinations Regulatory Aspects Biopharmaceuticals Proteins Peptides Oligonucleotides Combinatorial Libraries Physicochemical Property Determinations Using CE Binding constants Dissociation constants Partition coefficients Isoelectric point determinations References Subject Index