Techniques and Practice of Chromatography

Raymond P.W. Scott

• Publisher: CRC Press
• Year: 2020
• ISBN:
  9781000723618
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Chemistry
• Index: Chemistry

This work introduces scientists of all disciplines to the chromatographic process and how it functions. The basic principles of chromatographic separation and specific chromatographic procedures, including gas, liquid and thin-layer chromatography, are covered. For each separation method the book details its characteristics, the instrumentation required, the procedures necessary for effective use, areas of application and examples of its use.;This work is intended for analytical chemists, laboratory technicians, and upper-level undergraduate and graduate students in analytical chemistry or separation science courses.

Part 1

The Chromatographic Process

Chapter 1

THE CHROMATOGRAPHIC SEPARATION

Introduction

Chromatography is unique in the history of analytical methodology and is probably the most powerful and versatile technique available to the modern analyst. In a single procedure it can separate a mixture into its individual components and simultaneously determine quantitatively the amount of each component present. The samples may be gaseous, liquid or solid in nature and may range in complexity from a single substance to a multicomponent mixture containing widely differing chemical species. Furthermore, the analysis can be carried out, at one extreme, on a very costly and complex instrument, and at the other, on a simple, inexpensive thin layer plate.

The development of chromatography has been colorful and quite remarkable in many ways. On the one hand the development of liquid chromatography (LC) was painfully slow and arduous, particularly in the early years, whereas, in comparison, the rate of development of gas chromatography (GC) was almost meteoric. In the nine years between its inception in 1951 and 1960, GC evolved from a novel method of separation, used only in a few fortunate laboratories, to a fully fledged analytical technique utilized in all laboratories dealing with volatile compounds. In contrast, in 1960 LC lagged very far behind GC despite the fact that LC had been discovered half a century earlier. Today the performance of the liquid chromatograph is equivalent to that of the gas chromatograph and the technique, perhaps, is even more versatile. To achieve this, however, far more research and development effort was required for LC, which extended over many more years than was necessary for GC. Overlapping the development of GC and LC was the sister technique of LC, thin layer chromatography (TLC). In contrast, TLC progressed steadily and continuously during the development of both GC and LC. It must be said that the performance of TLC relative to LC leaves much to be desired but due to its simplicity and the low cost of the necessary equipment, it is still a very popular technique and is extensively used throughout industry and in many universities.

History of Chromatography

The first scientist to recognize chromatography as an efficient method of separation was the Russian botanist Tswett, who employed a primitive form of liquid solid chromatography to separate and isolate various plant pigments. The colored bands he produced on the adsorbent bed evoked the term chromatography for this type of separation. Although color has little to do with modern chromatography the name has persisted and despite its irrelevance is still used for all separation techniques that employ a mobile and a stationary phase. Chromatography was actually discovered by Tswett in the late 1890s but it was not until 1910 that he published a book (1) describing his chromatographic methods for the separation of chromophylls. Unfortunately, the work of Tswett was not taken up to any significant extent, partly due to the original paper being in Russian and partly due to the condemnation of the method by Willstatter and Stoll (2) in 1913. These scientists repeated Tswett’s experiments without heeding his warning not to use too “aggressive” adsorbents as these would cause the chlorophylls to decompose. The experiments of Willstatter et al. failed and the results and conclusions they published impeded the recognition of chromatography as a useful separation technique for nearly 20 years.

The next significant development was reported by Kuhn et al. (3) in 1931, who used the technique in the manner recommended by Tswett to separate lutein and xanthine. Kuhn and his co-workers also employed the same procedure to separate α-and β-carotene (4,5) and they were the first to demonstrate that LC could be employed for preparative separations (6). Subsequent to 1931 progress in LC was slow and somewhat desultory and this was largely due to a lack of essential instrumentation.

In the late 1930s and early 1940s Martin and Synge introduced liquidliquid chromatography by supporting the stationary phase, in this case water, on silica in a packed bed and used it to separate some acetyl amino acids. They published their work in 1941 (7) and in their paper recommended the replacement of the liquid mobile phase with a suitable gas. They considered the use of a gas to be advantageous as the transfer between the two phases would be faster and thus provide more efficient separations. Thus, the concept of gas chromatography was born but little notice was taken of the suggestion and it was left to Martin himself and A. T. James to bring the concept to practical reality some years later. In the same paper in 1941 Martin and Synge put forward the first general theory of elution chromatography, namely, the Plate Theory. The theory they devised at that time was the exponential form of the plate concept, which had limited use, but nevertheless constituted the first successful attempt to derive an explicit equation for the elution of a solute from a chromatographic column.

Although the renaissance of LC began in 1963 and, in fact, has only recently matured to...

Table of contents

• Cover
• Half Title
• Series Page
• Title Page
• Copyright Page
• Preface
• Table of Contents
• Part 1. The Chromatographic Process
• Part 2. Gas Chromatography
• Part 3. Liquid Chromatography
• Part 4. Thin Layer Chromatography
• Index