Basic Analytical Toxicology
Preface and acknowledgements
For many years, toxicology, the science of poisons and poisoning, was considered to be no more than a branch of forensic science and criminology. Nowadays, it is clear that the study of applied toxicology in its various forms - clinical, occupational, forensic, nutritional, veterinary, and environmental toxicology, ecotoxicology and related areas - is important, if not vital, to the continued development of life on earth. Yet toxicology is rarely taught as a subject in its own right and then mostly at postgraduate level. In consequence, most toxicologists come to the subject under the auspices of another discipline. Clinical toxicology, dealing with the prevention, diagnosis and management of poisoning, is no exception, being often thought of as a branch of emergency medicine and intensive care on the one hand, and of clinical pharmacology on the other.
The provision of services for the management of poisoned patients varies greatly, from specialized treatment units to, more commonly, general emergency medicine. Analytical toxicology services, which provide support for the diagnosis, prognosis and management of poisoning, are also variable and dependent on local arrangements. In developed countries, they may be provided by a specialized laboratory attached to a clinical toxicology unit, by a hospital biochemistry laboratory, an analytical pharmacy unit, a university department of forensic medicine, or a government forensic science laboratory.
In many developing countries, such services are not available on a regular basis, and where they are available, the physician is generally dependent on a national or regional health laboratory established for other purposes and operating only part of the time. There are, however, many simple analytical techniques that do not need sophisticated equipment or expensive reagents, or even a continuous supply of electricity. Such tests could be carried out in the basic laboratories that are available to most hospitals and health facilities, even in developing countries. With training, hospital laboratory staff could use these techniques to provide an analytical toxicology service to the physicians treating poisoned patients.
This manual, which describes simple analytical techniques of this kind, has been prepared on the recommendation of a group of experts, convened by the International Programme on Chemical Safety (IPCS)a in February 1987.
The draft text was reviewed by a number of experts, as noted under "Acknowledgements", and the procedures described were tested in the laboratory, as far as possible by technicians from developing countries. The work was coordinated for IPCS by Dr J. Haines. The United Kingdom Department of Health, through its financial support to the IPCS, provided the resources for the editorial group to meet and undertake its work.
The aim of this manual is to help hospital laboratories in developing countries to provide a basic analytical toxicology service using a minimum of special apparatus. It is not intended to replace standard texts, but to provide practical information on the analysis of a number of substances frequently involved in acute poisoning incidents. Common pitfalls and problems are emphasized throughout, and basic health and safety precautions for laboratory workers are also discussed.
Problems encountered when using relatively simple methods in analytical toxicology are usually due to interference (false positives) or poor sensitivity (false negatives). Nevertheless, useful information to help the clinician, and thus the patient, can often be obtained if the tests are applied with due caution using an appropriate sample. While every effort has been made to ensure that the tests described are reliable and accurate, no responsibility can be accepted by UNEP, ILO or WHO for the use made of the tests or of the results obtained.
As in all areas of analytical chemistry, problems in interpretation can arise if a result is used for purposes for which it was not intended. This is especially true if the results of emergency toxicological analyses, particularly if poorly defined (for example, "negative drug screen", "opiates positive"), are used as evidence in legal proceedings many months or even years later. In this context,
a.The IPCS is a cooperative programme of the United Nations Environment Programme (UNEP), the International Labour Organisation (ILO) and the World Health Organization (WHO). WHO is the executing agency for the programme, which aims to provide the internationally evaluated scientific data basis for countries to develop their own chemical safety measures and to strengthen national capabilities to prevent and treat harmful effects of chemicals and to manage chemical emergencies.
The importance of consultation between the clinician treating the patient and the analyst in making best use of the analytical facilities available cannot be over-emphasized. To assist this dialogue, some information on clinical interpretation has been included.
IPCS and the editorial group would welcome comments on the content and structure of the manual; such comments should be addressed in the first instance to the Director, International Programme on Chemical Safety, World Health Organization, 1211 Geneva 27, Switzerland. Two areas for further development have already been identified, namely, the requirement for formal training in analytical toxicology, and the need to ensure the supply of essential reference compounds, specialized reagents and laboratory consumables. Comments on either of these problems would also be welcome.
Many individuals have contributed to the preparation of this manual by providing support, ideas, details of methods or comments on various drafts. In particular, Professor Bahira Fahim, Cairo, Egypt, Dr I. Sunshine, Palo Alto, CA, USA, and Dr G. Volans, London, England provided initial encouragement. Dr T. J. Meredith, London, England, Dr J. Pronczuk de Garbino, Montevideo, Uruguay, and Professor A. N. P. van Heijst, Utrecht, Netherlands scrutinized the clinical information. Dr A. Akintonwa, Lagos, Nigeria, Dr A. Badawy, Cairo, Egypt, Dr N. Besbelli, Ankara, Turkey, Dr C. Heuck, WHO, Geneva, Switzerland, Professor M. Geldmacher-von Mallinckrodt, Erlangen, Germany, Mr R. Fysh, London, England, Professor R. Merad, Algiers, Algeria, and Mr. J. Ramsey, Mr J. Slaughterr and Dr J. Taylor, London, England kindly commented on various aspects of the final draft. Miss H. Triador, Montevideo, Uruguay, Mrs K. Pumala, Bangkok, Thailand and Mr J. Howard, London, England, undertook the onerous task of critically evaluating many of the tests described. Finally, thanks are due to Dr B. Abernethy and Mr D. Spender, Basingstoke, England for help in preparing the text, and to Mr M. J. Lessiter, Birmingham, England for help with the illustrations of spot tests and thin-layer chromatography plates.
After a brief introduction to the apparatus, reference compounds and reagents needed for an analytical toxicology laboratory (section 1), the manual covers a number of general topics, namely, clinical toxicology (section 2), clinical chemistry and haematology in relation to clinical toxicology (section 3), practical aspects of analytical toxicology (section 4), sample collection and storage, and qualitative poisons screening (section 5). Then, in a series of monographs (section 6), qualitative tests and some quantitative methods are described for 113 specific poisons or groups of poisons. Each monograph also includes some information on clinical interpretation.
The practical sections of the manual have been designed to be followed at the bench so that full experimental details of a test for a particular substance are often given, especially in the monographs (section 6), even though these same details may be repeated elsewhere in another context.
The tests described in sections 5 and 6 have been restricted to those that can be expected to produce reliable results within the limitations described, and that can be performed using relatively simple apparatus. Where appropriate, tests applicable to powders, tablets or other items found with or near the patient (scene residues) and to biological fluids are also included. Additional simple tests for specified pharmaceuticals are given in other World Health Organization publications.a However, these are designed to test the identity and in some cases stability of specific, relatively pure compounds and little consideration is given to, for example, purification procedures, sensitivity and sources of interference.
Primary references to particular methods have not been given, in order to simplify presentation and also because many tests have been modified over the years, so that reference back to the original paper could cause confusion. However, much of the information given in the manual can be found in the references listed in the Bibliography. An attempt has been made to assess the sensitivity (detection limit) of all the qualitative tests given in the monographs (section 6). However, as with description of colour, such assessments are always to some extent subjective. In addition, the sensitivity of some tests, such as those involving solvent extraction, can usually be varied by taking more (or less) sample. These points emphasize the importance of analysing known negative (control) and positive (reference) samples alongside every specimen (see section 4.1.5).
a Basic tests for pharmaceutical substances. Geneva, WHO, 1986; Basic tests for pharmaceutical dosage forms. Geneva, WHO, 1991.
Many of the terms used in this manual are defined in the Glossary and a list of reference compounds and reagents is provided (Annex 1).
Système internationale (International System; SI) mass units (mg/l, µg/l, etc.) have been used throughout to express concentrations of drugs and other poisons. There is a tendency to use SI molar units (mmol/l, µmol/l, etc.) for this purpose, but this can cause unnecessary confusion and has no clear advantage in analytical toxicology, provided that the exact chemical form of a substance is specified. SI mass/molar unit conversion factors for some common poisons are given in Annex 2. In some cases, SI mass units have also been used to express reagent concentrations, but it should be borne in mind that it is often sensible to prepare quantities of reagent smaller than one litre (100 ml, for example), especially for infrequently used tests.
For convenience, trivial or common chemical names have been used throughout the text; where necessary, IUPAC equivalents are given in the index. International nonproprietary names are used in the text for drugs; common synonyms are listed in the index.