Separation Methods in Drug Synthesis and Purification

Klara Valko

• Publisher: Elsevier Science
• Year: 2020
• Print ISBN: 9780444640703
• eBook ISBN: 9780444640710
• Edition: 2
• Topic: Physical Sciences
• Subtopic: Science Research & Methodology

Separation Methods in Drug Synthesis and Purification, Second Edition, Volume Eight, provides an updated on the analytical techniques used in drug synthesis and purification. Unlike other books on either separation science or drug synthesis, this volume combines the two to explain the basic principles and comparisons of each separation technique. New sections to this volume include enantiomer separation using capillary electrophoresis (CE) and capillary electro- chromatography, the computer simulation of chromatographic separation for accelerating method development, the application of chromatography and capillary electrophoresis used as surrogates for biological processes, and new developments in the established techniques of chromatography and preparative methods.- Features descriptions and applications of all separation methods used in the pharmaceutical industry- Written by the leading scientists in their respective fields, providing solutions for a wide range of industrial separation problems encountered within the pharmaceutical industry- Thoroughly updated with brand new separation science techniques and the latest developments in the established techniques of chromatography

Chapter 1

Comparison of various modes and phase systems for analytical HPLC

Pavel Jandera Department of Analytical Chemistry, University of Pardubice, Pardubice, Czech Republic

Abstract

This chapter addresses principles of the separation modes used in contemporary column liquid chromatography, including reversed-phase organic normal-phase hydrophilic interaction liquid chromatography (aqueous normal-phase chromatography) and ion-exchange separation systems, with respect to the effects of the stationary and mobile phases and the experimental conditions on the separation. This treatment compares the advantages and disadvantages of various types and sizes of column particles, column formats and dimensions on the efficiency of separation, with special attention to the sub-2 μm particles, core-shell and monolithic columns. Theoretical retention models for the individual separation modes deal with the selection of the mobile phase in the isocratic retention models and possible extension to gradient elution separations. Temperature affects the sample diffusivity and hence the separation efficiency on one side, and the thermodynamic contributions of enthalpy and entropy to the energy of retention on the other. Serial, heart-cutting and comprehensive two-dimensional techniques combining independent (orthogonal) separation modes largely increase the peak capacity of liquid chromatography.

Keywords

Core-shell columns; Gradient elution; Hydrophilic interaction liquid chromatography; Liquid chromatography; Mobile phase; Monolithic columns; Multidimensional chromatography; Separation systems; Stationary phase; Ultra-high performance liquid chromatography

1.1. Fundamentals of high-performance liquid chromatography

1.1.1. Characteristics of high-performance liquid chromatography separation

In any chromatographic process, the sample components distribute between two phases, the stationary and the mobile phase. In the ideal chromatographic process, the equilibrium distribution of the sample compounds between the stationary and the mobile phases establishes at any time and in any part of the separation medium (a column or a plane). As the mobile phase flows through the column, the equilibrium distribution between the two phases is continuously disturbed when the fresh mobile phase gets into contact with the stationary phase containing a retained sample compound and a new equilibrium is immediately reestablished. Consequently, the sample compounds move at different velocities along the column, together with – but more slowly than – the mobile phase. This process leads to their eventual separation, either in time (column separation media) or in space (planar chromatography).

Like gas chromatography (GC), liquid chromatography (LC) employs a chromatographic bed for the separation. Unlike GC, the sample components need not be volatile and stable at elevated temperature; they only must be soluble in a suitable solvent. The most important difference in the two techniques is in using different mobile phase states. In a gas carrier in GC, the molecular diffusivity, which controls the chromatographic band broadening, is approximately four orders of magnitude faster than in the liquid mobile phases. Some early workers coming from GC often did not fully realize the practical impacts of these differences on the column dimensions, stationary phase configurations and the mobile phase flow rates needed to accomplish successful separations by the LC techniques, especially in the modern form of LC – the high-performance liquid chromatography (HPLC).

In HPLC, the stationary phase usually is a bed of fine solid particles with narrow size distribution, densely packed in a metal, glass or plastic tube – a chromatographic column. The stationary phase may be either a bulk column packing or only a part of it deposited on or, more frequently, chemically bonded to a more or less inert support material. The mobile phase (eluent) is a liquid, usually a mixture of two or more solvents, often containing suitable additives, forced through the column by applying elevated pressure. HPLC has become one of the most powerful tools in the contemporary organic analysis for the separation and determination of even very complex samples containing nonpolar, moderately or strongly polar and ionic compounds, simple species, high-molecular synthetic polymers or biopolymers. These features of HPLC are especially useful in pharmaceutical, biomedical and clinical analysis.

1.1.2. Elution development and chromatographic peaks

Analytical HPLC usually employs elution devel...

Table of contents

• Cover image
• Title page
• Table of Contents
• Contributors
• Chapter 1. Comparison of various modes and phase systems for analytical HPLC
• Chapter 2. Fast-generic HPLC methods
• Chapter 3. Advances in capillary electrochromatography
• Chapter 4. Coupled chromatography–mass spectrometry techniques for the analysis of combinatorial libraries
• Chapter 5. Experimental design-based optimization strategies for chromatographic and capillary electrophoretic separations
• Chapter 6. Computer-aided HPLC method development for quality control of complex drug mixtures – An application example for DryLab
• Chapter 7. The flexible application of automated preparative purification platforms within drug discovery
• Chapter 8. Strategies for the development of process chromatography as a unit operation for the pharmaceutical industry
• Chapter 9. Recent developments in liquid and supercritical fluid chromatographic enantioseparations
• Chapter 10. Basis and pharmaceutical applications of thin-layer chromatography
• Chapter 11. Recent advances in quantitative structure–retention relationships
• Chapter 12. Capillary electrophoresis for drug analysis and physicochemical characterization
• Chapter 13. Application of HPLC measurements for the determination of physicochemical and biomimetic properties to model in vivo drug distribution in support of early drug discovery
• Index