Introduction to Analytical Toxicology

Study Notes

Analytical toxicology is the study of poisons.
Toxicology is the branch of science dealing with poisons.
"Toxic" means poison, and "ology" means science.
Toxicology focuses on the origin, physical and chemical properties, physiological action, treatment of effects, and methods of detection of poisons.

A poison is any substance that, when introduced into the body and absorbed by the bloodstream, produces a harmful effect or destroys life.
Any substance can be poisonous at a certain dose and route of administration.

Poisons are classified according to origin, source, or nature; pharmacological action; organs affected; and methods of isolation.

Poisoning is the phenomenon of ingesting or coming into contact with poisonous substances.
Poisoning is categorized based on the medical and legal perspectives.

Full recovery: return to health after treatment, without any sequelae (lasting effects).
Delayed recovery: recovery is delayed without sequelae
Sequelae: persistent disability after recovery
Death: due to respiratory failure, cardiovascular collapse, seizures, hyperthermia, or other organ dysfunction

Poisons can enter the body through the mouth (absorbed after passing through the stomach and intestinal walls), nose (absorbed into the bloodstream from upper respiratory passages or lungs), eyes (transdermal absorption), rectum, vagina, urethra, bladder, and injection (SC, IM, IV).

Diagnosing poisoning is challenging due to the vast number of possible poisons and factors that can modify their effects.
Many symptoms of poisoning are similar to symptoms of other diseases.

The forensic laboratory is responsible for determining the presence or absence of chemical substances in biological or non-biological samples, connected to medico-legal investigations.
It requires analyzing a wide variety of toxic substances.
Analytical chemists must be knowledgeable about the effects of poisons and both older and newer techniques.

Varying content of toxicology screens among laboratories.
Laboratories may adjust procedures to target suspected agents initially.
Knowing suspected dose is vital for employing more sensitive analysis methods for precise therapeutic monitoring.

Knowing both ingestion and sampling time is essential for determining the degree of drug absorption.
Knowledge of the clinical presentation helps the lab select appropriate screening procedures.
Patient's location is also important.

No one specimen type is always the best for identifying toxic agents.
Choosing a specimen type depends on pharmacokinetics of the suspected agent and lab methodology.
Quantitative tests are usually done on either serum or whole blood. Qualitative tests are typically performed on urine or gastric contents.
Heavy metal quantitation typically uses urine, collected in acid-washed, metal-free containers.

Blood: preserved in tubes containing sodium oxalate or anticoagulant, refrigerated with dry ice (good for 72 hours). Avoid alcohol preservation as denaturants may interfere with testing. Formalin is generally not suitable for toxicology examination.
Urine: collected in plastic containers with no preservative.
Gastric contents: collected in plastic containers with no preservative.
Non-biological samples (pills, air samples, clothes): may provide higher concentrations of the substance.

Initial visual examination (naked eye, magnifying glass) is critical for identifying fragments of poisonous plants.
Crystals of inorganic or organic substances provide clues, suggesting further tests.
Carefully noting any odors associated with the substance.
Reaction tests (using indicators like litmus, phenolphthalein, or methyl orange) aid in identifying the class of poison.

Some substances (essential oils, insecticides) require specialised isolation methods.
A sample can be distilled (alone or with steam) to separate volatile poisons.
The Reinsch test can identify common metallic poisons (e.g., arsenic, antimony, bismuth, mercury, silver).
Organic poisons require purification procedures to isolate them from protein in a sample.
Testing pure substances involves colour tests, crystal tests, spectrometric analysis, immunoassays, and chromatographic analysis.