Introduction to Analytical Chemistry

Publisher Summary

This chapter focuses on the knowledge and experimental techniques of analytical chemistry that are most often encountered in the field of chemistry, pharmacy, medical technology, medicine, and the biological sciences. There are four major areas of analytical chemistry that are of importance in their application to diverse scientific disciplines. These areas are spectroscopy, acid-base methods, potentiometry, and chromatography. Analytical chemistry deals with the solving of qualitative and quantitative problems. In qualitative analysis, the goal is to determine what the constituents are in the sample. On the other hand, in quantitative analysis, the goal is to determine how much of each constituent is in the sample. An analytical chemist deals with inorganic and organic mixtures composed of metallurgical, biochemical, pharmaceutical, or medicinal compounds. The importance of analytical chemistry in related scientific areas is explained by considering its impact on clinical analysis, in pharmaceutical research and quality control, and in environmental analysis.

TO THE STUDENT

For many of you, this course will be your first experience in analytical chemistry. The authors assume that you are here because you have an interest in chemistry, pharmacy, medical technology, medicine, the biological sciences, or a combination of these fields, and because you want to learn how analytical chemistry will be of use to you. For this reason, the presentation in this book is not designed just for the student majoring in chemistry. Instead, the emphasis is on the knowledge and experimental techniques of analytical chemistry that are most often encountered in the disciplines listed above.

The authors feel that there are four major areas of analytical chemistry that are of importance in their application to diverse scientific disciplines. These areas are spectroscopy, acid–base methods, potentiometry (ion selective electrodes, etc.), and chromatography. Therefore, much of this book is devoted to the background and techniques necessary to understand and carry out these analytical methods.

The goal of the authors in this book is to answer in a concise and logical way the following questions: What is analytical chemistry? What does an analytical chemist do? Where does analytical chemistry fit into the overall scheme of science?

ANALYTICAL CHEMISTRY

Analytical chemistry deals with the solving of qualitative and quantitative problems. In qualitative analysis the goal is to determine what the constituents are in the sample while in quantitative analysis the goal is to determine how much of each constituent is in the sample. Table 1-1 surveys in general terms the types of problems encountered in analytical chemistry.

Table 1-1

A Survey of Analytical Problems

Many paths are available to achieve the information sought, and many individual techniques may be incorporated into the route leading to a completed analysis. An important part of the analytical chemist’s task is choosing the optimum pathway, a choice which is simplified only through the assimilation of knowledge and experience. Thus, in solving analytical problems an analytical chemist is often required to design or repair electronic systems, arrange optical systems, design instruments, interpret spectra and other instrumental data, perform classical analyses with simple chemicals and solutions, develop and evaluate new procedures or modify old ones, separate simple and complex mixtures, purify samples, and write computer programs. It is not likely that any one analytical chemist will be capable in all of these areas.

The nature of the chemical and physical systems which an analytical chemist encounters is a further complication. An analytical chemist must deal with inorganic and organic mixtures composed of metallurgical, biochemical, pharmaceutical, or medicinal compounds. For example, the dissolution and separation of a 12-component, high-temperature alloy, the separation of a mixture of polymeric materials which differ only in molecular weight, or possibly the separation of a mixture of all the amino acids are typical problems. The analytical chemist may be asked to analyze polluted air or the insecticides in fish, birds, plants, or animals; to measure the rate of a reaction; or to determine the number of electrons and intermediates involved in an electrochemical reaction.

ANALYTICAL CHEMISTRY IN ALLIED AREAS

Historically, chemistry could be easily divided into five areas: analytical, biochemical, inorganic, organic, and physical. Today such divisions are very difficult to make because of the contributions of each to one another. Analytical chemistry, like other areas of chemistry and of all sciences, has gone through a period of rapid growth and change. At present, new areas such as chemical physics, biophysics, and molecular biology are rapidly developing. Many advances in these areas were made possible by analytical results.

The importance of analytical chemistry in related scientific areas can be illustrated by considering its impact on clinical analysis, in pharmaceutical research and quality control, and in environmental analysis.

Clinical Analysis

In the past, the medical profession used clinical results qualitatively and many of their diagnoses were based on symptoms and/or X-ray examinations. This was true even though it was known that many physiological diseases were accompanied by chemical changes in the metabolic fluids. Eventually, sensitive chemical and instrumental tests were devised to detect both the abnormal and normal components of body fluids. Furthermore, the tests were improved to the point where it became possible to quantitatively determine these components. As accuracy improved and normal levels were established, it became clear that these results could be used for diagnostic purposes. A patient requesting a general physical examination or the diagnosis of a specific set of symptoms is now often required to have several quantitative tests on their body fluids, and in the future such tests will become more and more numerous. The test results will be available to the doctor at the first meeting with the patient and will play a major role in influencing the diagnosis.

Currently, over one billion laboratory tests are performed in clinical laboratories per year and the number is going to increase. The major portion of these tests deal with blood and urine samples and include the determination of glucose, urea nitrogen, protein nitrogen, sodium, potassium, calcium, HCO3−/H2CO3, uric acid, and pH.

Table 1-2 lists the components of the blood, all of which can be analyzed quantitatively, and gives the range for the amount of each normally present in the blood. Urine contains an even larger number of components, which have much broader normal ranges because of a greater dependency on such factors as diet, liquid intake, and urinary tract conditions.

Table 1-2

Normal Range of Components of Blood and Cerebrospinal Fluid (CSF)a