HPLC in the Pharmaceutical Industry

Godwin W. Fong, Godwin W. Fong

• Publisher: CRC Press
• Year: 2022
• ISBN:
  9781000147827
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Chemistry
• Index: Chemistry

A practical guide for chemists in the pharmaceutical industry to making automated analyses of drugs that will meet the standards of regulatory agencies. Reviews the standard techniques of high-performance liquid chromatography, specialized detection methods, automation in pharmaceutical analysis, analyses of pharmaceuticals- helping readers meet rigorous regulatory agency standards for acceptable test results. Written by leading experts in the field, this text describes current liquid chromatographic techniques in pharamaceutical analysis...discusses highly sensitve detailed detection of drugs... considers automatation in pharamaceutical analysis...examines new molecular entities and opitcal isomers... and more.

Part One Contemporary LC Techniques in Pharmaceutical Analysis

1 High Speed HPLC Using Short Columns Packed With 3 μm Particles

Paul Kucera and Nicholas Licato

Lederle Laboratories, A Division of American Cyanamid, Pearl River, New York

DOI: 10.1201/9781003066699-2

HISTORY OF HIGH SPEED CHROMATOGRAPHY

The history of high speed chromatography goes back to 1959, when Purnell and coworkers [1] first attempted to construct high speed gas chromatographic columns. In those days, relatively little was known of the approach to higher analytical speeds. In his article “An Approach to Higher Speeds in Gas-Liquid Chromatography,” Purnell correctly described for the first time the retention time optimization and showed that the speed of the analysis is inherently dependent on the shape of the plate height function, particularly the van Deemter mass transfer coefficients of the solute transfer between the mobile and the stationary phase. Gas chromatography was considered a much faster technique than liquid chromatography, mainly because it was realized that diffusion rates of substances in gas media are four to five orders of magnitude greater than in any liquid systems. Thus any attempts to speed up liquid chromatographic separations were completely neglected.

In 1974, however, when small particles and column packing systems and procedures utilizing high pressure were developed for liquid chromatography, various papers appeared in the literature describing the time optimization [2–10], and since that time public awareness of high speed liquid chromatographic systems has greatly increased. Perhaps the main reason for this new renaissance in liquid chromatography is the fact that the speed of the analysis directly affects the economy and the operating cost of the analysis. It was realized that the optimization of a chromatographic system consists of optimizing the four basic attributes: resolution, speed, load, and scope [11]. The scope of the system was generally considered as the system capacity for separation mixtures of wide polarity range, and it was usually varied by using the technique of gradient elution in liquid chromatography or temperature perature programming in gas chromatography. The load was directly related to column cross-sectional area or column diameter and made all the difference between the preparative systems and analytical separations. For purely analytical chromatography, which will be discussed in this chapter, the load can be replaced with column operating pressure. A typical chromatography tetrahedron with main operating attributes of resolution, speed, scope, and pressure is shown in Figure 1. Attempts to reduce the pressure drop on the column further led to the development of high speed open tubular capillary systems and was allowed to optimize based on the column or particle diameter. It is now well understood that the increase in the resolution of a chromatographic system can be achieved by obtaining high efficiency in terms of plate numbers, long column lengths, and high selectivity, while improvements in speed can be attained by using small particles and short columns operated at high mobile phase velocities. As shown in Figure 2, the chromatographic resolution is of primary importance for any meaningful analytical work, while speed is of secondary importance and tied up to the economy of the operation.

Figure 1 Tetrahedron of basic chromatographic attributes.

Figure 2 Operative considerations of scope, speed, and resolution.

Desty contributed significantly to high speed systems by suggesting the use of theoretical plates or effective theoretical plates per second as a criterion of speed in rapid analyses. Shortly after it was demonstrated that open tubular capillary columns led in speed, Desty showed that 2000 plates/sec can be achieved in gas chromatography using specialized equipment. In 1979, a 25 sec separation of 8 component mixture exhibiting about 600 plates/sec was published by Scott, Kucera, and Monroe [12].

The chromatogram shown in Figure 3 was obtained on a microbore 25 cm × 1.0 mm id column packed with 20 μm silica gel and operated at a 4.5 mL/min flow rate. This chromatogram signaled the advent of a new era in chromatography, because besides the extremely high speed of separation, one never achieved before in liquid chromatography, the economy of analysis was significantly increased by using a microbore column system. As will be seen later, high speed separations theoretically require short columns packed with small particles. Unfortunately, the column pressure drop increases with the reciprocal of the square of the particle diameter, and thus the process of reducing the particle diameter in a column cannot be carried out ad infinitum. From the work of Guiochon [13], it appears that approximately 2 μm is the optimum particle diameter for a packed column. Beyond this limit, any further improvements in the column performance would be impaired by excessively high pressure exerted on the column. It is interesting to note that currently there are not many 3 μm particle columns on the market, and virtually no 2 µm packed columns are available. The majority of commercially available columns are packed with 5–8 μm spherical particles. Perhaps the reasons for the lack of high efficiency columns packed with small particles are the increasing difficulty of p...

Table of contents

• Cover
• Half Title
• Series
• Title
• Copyright
• Preface
• Contents
• Contributors
• Part One Contemporary LC Techniques in Pharmaceutical Analysis
• Part Two Specialized Detection Techniques
• Part Three Automation in Pharmaceutical Analysis
• Part Four HPLC of Peptides, Proteins, and Enantiomeric Drugs
• Index