Chromatography: Concepts and Contrasts / Edition 2

by James M. Miller

Overview

Chromatography has become the most widely used technique for separation and analyses. Because a great deal of information is available on the three main types--gas chromatography (GC), liquid chromatography (LC), and thin layer chromatography (TLC)--they are usually treated separately despite their common theoretical base. This comprehensive work presents a unified study of chromatography which introduces the principles shared by each method while emphasizing the similarities and differences between the three types. The chapters covering these methods build on the introductory coverage of common principles, providing an effective overview of the subject for novices and allowing practitioners to more easily switch from one technique to another. In addition, this approach permits the use of one set of terms and symbols, making learning easier. Includes several practical examples the ways in which GC, LC, and TLC operate, as well as a section on special techniques such as chiral separations and derivatization.

Product Details

ISBN-13:	2900470530251
Publisher:	Wiley
Publication date:	08/17/2009
Edition description:	2nd Revised ed.
Pages:	520
Product dimensions:	6.00(w) x 1.25(h) x 9.00(d)

About the Author

James M. Miller, PhD, is Emeritus Professor in the Department of Chemistry at Drew University in Madison, New Jersey. He is the coauthor of Basic Gas Chromatography with Harold McNair and coeditor of Analytical Chemistry in a GMP Environment with Jonathan Crowther, both published by Wiley. Dr. Miller is a Fellow of the Charles A. Dana Research Institute for Scientists Emeriti (RISE).

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Chromatography

Concepts and Contrasts

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By James M. Miller

John Wiley & Sons

Copyright © 2005 John Wiley & Sons, Inc.
All right reserved.
ISBN: 0-471-47207-7

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Chapter One

IMPACT OF INDUSTRIAL AND GOVERNMENTAL REGULATORY PRACTICES ON ANALYTICAL CHROMATOGRAPHY

Chromatography is a proven method for separating complex samples into their constituent parts, and it is undoubtedly the most important procedure for isolating and purifying chemicals. Using data from the first half of 2003, Ryan estimated that nearly 5% of all chemical research in 2003 would involve chromatography.

In addition, most chromatographic instrumentation is equipped with detectors, making chromatographs true instruments, devices capable of making measurements. Consequently, this monograph will deal not only with the principles of chromatography but also with the practice of quantitative analysis. It is this latter subject that has been greatly influenced by both industry and the federal government because of the need for standards and standardization that go hand-in-hand with governmental regulation. In the modern world, these issues extend to foreign countries as well and have given rise to international organizations and guidances/regulations that need to be recognized by chromatographers worldwide. Since much important information is available on the Internet, all scientists need to be knowledgeableabout its retrieval and its impact on their work. In addition, much effort is being made internationally to provide a cooperative and harmonized approach to analysis and analytical method development. Although this book is written from the perspective of chromatographers in the United States, the principles are applicable internationally, and scientists would be well advised to recognize that fact and become aware of the developments outside their own countries.

Fortunately, the fundamental principles of chromatography and analytical chemistry in general are the same in academia, industry, and government, of course. Their common objective is to perform laboratory tests and procedures that are based on sound scientific principles. However, some industries operate under more stringent controls than others. For example, the pharmaceutical industry in the United States is regulated by the Food and Drug Administration (FDA), which enforces federal regulations known as the Current Good Manufacturing Practices (CGMPs). These regulations were promulgated to ensure the safety and efficacy of drugs by setting forth minimum standards for manufacturing and testing. The GMPs are not prescriptive and, therefore, they have been supplemented by FDA guidance documents that provide more specific details on complying with the regulations. These guidances provide insight for the practice of good chromatography in all venues where analytical chemistry is performed, in the United States and abroad. While it is true that European and Asian counterparts are similarly regulated by their respective agencies, the fundamental analytical principles are the same and are becoming internationally codified.

Because these special regulations and guidances are often omitted from academic courses, this chapter is presented to guide informed readers as they proceed to industrial and governmental employment. It also serves as a general introduction to quantitative analysis practices in chromatography by presenting and summarizing some basics of chromatographic measurement. This chapter examines:

The organization of analytical chemists in a typical industrial corporation

The organization and regulatory agencies of the U.S. government and of nongovernmental agencies

The effect of FDA regulation on the pharmaceutical practices in the laboratory

Some international guidelines for analytical chemistry in general and analytical chromatography in particular.

1.1 LOCUS OF CHROMATOGRAPHY IN CHEMICAL INDUSTRY

Chemical companies and related industries such as pharmaceutical companies and the petroleum industry more than ever need to have laboratories devoted to analysis methods and characterization, including in most cases a section well trained in chromatography. Those that produce and sell chemicals have a laboratory function called quality control QC that monitors the quality of incoming raw materials, evaluates in-process intermediates, and tests the purity of final products. Assurance of the quality of manufactured products, referred to as quality assurance (QA) and carried out in conjunction with manufacturing, is a related function. Both functions may be combined, and the laboratory may be called a QC/QA laboratory. This laboratory usually performs both qualitative identity analyses and quantitative analyses. The latter are often performed by gas chromatography (GC) or liquid chromatography (LC). Usually, these laboratories are situated close to, or within, the manufacturing site. Typical of many companies hiring B.S. chemists, large pharmaceutical firms hire recent bachelors chemists as analytical chemists into their QC laboratories.

Depending on the size of the company, another laboratory may be responsible for developing the methods for the QC laboratories. This function may be in the Research and Development (R&D) Department. The chromatographers in this laboratory are usually responsible for keeping up with the latest developments in chromatography and searching for and evaluating new improved methods of analysis, as well as developing methods for the QC laboratory. Instrument companies manufacturing chromatographs may also have their own instrumental R&D groups that often provide technical support. Generally, R&D groups are staffed by degree chemists at several levels with some Ph.D.s at the highest levels.

Another analytical need is for a group to perform general analytical services to support the chemical activities of the company (synthesis, pilot plant, product support, etc.). These services most often include chromatography, spectroscopy, and microanalytical (elemental) analysis. Often this is a separate group of scientists and engineers and may include a small group of experts that advises and consults with technicians in the other areas who do their own analytical work. Separate groups may exist to support the sales and marketing department or the patent and law department, for analysis of competitors samples or evaluation of patent infringement, for example.

Within a chemical corporation, these various laboratories are responsible for providing accurate and reliable analytical methodology. The interrelated elements required for this process are shown in Figure 1.1. Each part is important, and some of them will be discussed further in this chapter: standards, instrument qualification, and method development and validation.

In general, government laboratories are organized similarly. Some of them are of particular interest to analysts because of the functions they perform, including the regulation of industrial practice.

1.2 GOVERNMENTAL ORGANIZATIONS

Table 1.1 lists some U.S. government laboratories and agencies that are of interest to chromatographers. Those that are part of a governmental department are listed by department in order to show the governmental organization. The ones of greatest interest to chromatographers, and the ones discussed in greatest detail in this chapter, are the National Institute of Standards and Technology (NIST), the Food and Drug Administration (FDA), and the Environmental Protection Agency (EPA) because they are most involved in standards, standardization, method development, and federal regulation. The U.S. government web site (firstgov.gov) can be used to locate additional information on government agencies and federal regulations.

National Institute of Standards and Technology (NIST)

The mission of NIST (formerly the National Bureau of Standards, NBS) is "to develop and promote measurement, standards, and technology to enhance productivity, facilitate trade, and improve quality of life." It was founded in 1901, making it the oldest physical science research laboratory of the federal government. Unlike the FDA and the EPA, it is not a regulatory agency and does not establish or enforce mandatory standards; rather, NIST develops measurement methods, instrumentation, and measurement standards for government and industry.

The main NIST laboratory is outside Washington, D.C., in Gaithersburg, Maryland, and the second one is in Boulder, Colorado. One of the eight laboratory divisions, the Chemical Science and Technology Laboratory (CSTL), includes an Analytical Chemistry section that is divided into five groups. One of them is the Organic Analytical Methods group where separation methods, including most of chromatography, is located. CSTL performs services like those described above for R&D departments; it "conducts research in measurement science and develops the chemical, biochemical, and chemical engineering measurements, data, models, and reference standards" for the United States.

Reference standards are particularly important in analytical chemistry, and a later section of this chapter is devoted to that topic. The Analytical Chemistry section of the CSTL is responsible for 850 of the 1350 NIST standards, called standard reference materials or SRMs. On the occasion of its attaining the age of 100, the NIST published a booklet chronicling the first century of SRMs. Some chromatographic examples of SRMs are:

869a for LC selectivity 870 for LC performance 877 for LC chiral selectivity 1543 for gas chromatography/mass spectrometry (GC/MS) performance.

As an illustration of the nature of SRMs, 869a is a mixture of three polycyclic aromatic hydrocarbons (PAHs) in acetonitrile, useful for characterizing LC column selectivity for the separation of PAHs.

The NIST also provides a wide range of publications and databases. Called the NIST Virtual Library, they can be accessed online at nvl.nist.gov.

Worldwide coordination and cooperation between the individual standardization agencies is also a task of NIST. Globally recognized measurements and standards are being developed through the efforts of many national metrological institutes worldwide, through the signing of a Mutual Recognition Arrangement (MRA) whereby 50 national standards laboratories have agreed to participate in formal interlaboratory comparisons. The responsibility for this effort in the United States is carried mainly by the Analytical Chemistry section of the NIST.

Food and Drug Administration (FDA)

The FDA is a regulatory agency formed as a result of the government's Food, Drug and Cosmetic Act (FD&C act) in 1938. Simply stated, its mission is "to promote and protect the public health by helping safe and effective products reach the market in a timely way, and monitoring products for continued safety after they are in use." In addition to food and drugs, the FDA regulates cosmetics, medical devices (such as pacemakers), biologics (such as vaccines), animal feed and drugs, and radiation-emitting products such as cell phones). Its web site contains a wealth of information, some of which is indicated in the flowchart in Figure 1.2. The focus in this chapter will be on drugs.

There are about 10,300 FDA-approved drugs in the United States today, and the division of the FDA responsible for most of them is the Center for Drug Evaluation and Research (CDER). The Center for Biologics Evaluation and Research (CBER) is responsible for biologicals, and the Center for Veterinary Medicine (CVM) regulates veterinary drug products. The CDER reviews applications for new drugs (NDAs) and generic products (ANDAs) and oversees the quality and manufacturing of drugs by participating in on-site inspections with the office of regulatory affairs (ORA). The regulations it enforces are federal laws called Good Laboratory Practice (GLP) and Good Manufacturing Practice (GMP), or alternatively, Current Good Manufacturing Practice (CGMP) as noted earlier. One might think that chromatographers would be most concerned with GLPs, but that is not the case. It is primarily the GMPs that provide the regulations applied by laboratories to give assurance that the manufactured products meet specifications. GLPs mostly concern the conduct of nonclinical laboratory (toxicology) studies, while GCPs address Good Clinical Practices. All of these regulations are sometimes lumped together and referred to as GXPs when not referring to a specific regulation.

The necessity to conform to the applicable GXPs has had major effects on the operation of analytical laboratories in the pharmaceutical industry; many of these basic business principles outlined in the GMPs have been adopted by others in the wider analytical community. A major requirement regarding analytical methods is that they must be validated. Method validation is the process of acquiring data and documentation to prove that a specific method will produce reliable data with a high degree of assurance and is therefore acceptable for its intended purpose. The measures for evaluating a quantitative method, such as a high-pressure liquid chromatographic (HPLC) analysis, include accuracy, precision, specificity, linearity, range, limit of detection (LOD), limit of quantitation (LOQ), robustness, and sensitivity [added later by an International Conference on Harmonisation (ICH) guideline]. An equally important requirement is that instrumentation used in the testing method and during validation activities must also meet stringent controls referred to as instrument qualifications. As a matter of clarification, in general, instruments are qualified and processes (methods) are validated. Further details on these subjects are deferred until later in this chapter.

There are other key compliance issues in addition to method validation and instrument qualification including:

Management systems

Operating procedures

Personnel training

Data accountability

Facility adequacy and compliance

Certification documentation

Surely this list represents requirements that one would expect to address when attempting to improve one's laboratory practices. Although detailed discussion of all of these topics is beyond the scope of this monograph, some of the most important issues are addressed; additional information can be found in the published literature.

The GMPs are published by the National Archives and Records Administration and the Government Printing Office (GPO) in the Code of Federal Regulations (CFR), which is a codification of the general and permanent rules published by the executive departments and agencies of the federal government. It can be accessed online from the FDA web site or directly at gpoaccess.go(r)rcfrrindex.html.

Continues...

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Table of Contents

Introduction to Chromatography.
Kinetic Processes in Chromatography.
Physical Forces and Molecular Interactions.
Optimization and the Achievement of Separation.
Comparisons between Chromatographic Modes.
Qualitative Analysis.
Quantitative Analysis.
Gas Chromatography.
Liquid Chromatography in Columns.
Liquid Chromatography on Plane Surfaces.
Other Topics.
Selection of a Method.
Appendixes.
Index.

Editorial Reviews

"…a practical, hands-on approach…" (CHOICE, July 2005)

"…an excellent introduction to all the chromatographic techniques for both the industrial practitioner and the…student because of its unified treatment, its modern approach, and up-to-date references." (Journal of the American Chemical Society, June 29, 2005)

"Professor Miller should be congratulated for the book...should be on the shelf of every practicing chromatographer...students taking separations science courses could also use it as their standard textbook." (Chromatographia, February 2005)

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