Toxicology – Chapter 2: Methods of Toxic Analysis

1. Introduction

Toxicology is the study of poisons, their mechanisms of action, their effects on the body, and their treatment.

Toxic analysis is a crucial part of toxicology, helping to identify the type of poison, its concentration, and the duration of exposure to the poison.

2. The Process of Toxic Analysis

The process of toxic analysis involves the following key steps:

• Sample collection: Collecting samples suitable for the suspected type of poison (e.g., urine, gastric fluid, blood, etc.)
• Sample preparation: Preparing the sample by grinding, homogenization, filtration, centrifugation, etc., to eliminate impurities and preserve the sample.
• Extraction: Extracting the poison from the sample using appropriate methods such as Soxhlet extraction, supercritical fluid extraction, solid phase extraction.
• Separation: Separating the poison from other components in the sample using chromatographic techniques (TLC, column chromatography, gas chromatography, high-performance liquid chromatography, capillary electrophoresis).
• Quantification: Quantifying the poison using spectroscopic methods (UV-VIS, fluorescence, infrared, Raman, flame spectrometry, nuclear magnetic resonance, mass spectrometry).
• Identification: Determining the type of poison using spectroscopic methods (UV-VIS, fluorescence, infrared, Raman, mass spectrometry) or specific chemical reactions.

Note:

• Samples should be collected and stored appropriately to prevent degradation and loss of the poison.
• Choose the appropriate extraction and analysis methods for the suspected type of poison.
• Analysis results should be carefully evaluated, combined with clinical information, to draw accurate conclusions.

3. Methods of Poison Extraction

3.1. Soxhlet Extraction

• Principle: Uses a specific amount of solvent through a reflux system to extract all the necessary substances.
• Advantages:
  • High extraction efficiency.
  • Easy to perform.
• Disadvantages:
  • Solvent-intensive.
  • Long extraction time.
  • Glassware is fragile.
  • The extract may be emulsified.

3.2. Supercritical Fluid Extraction

• Principle: Uses CO2 in its supercritical state to dissolve and extract the poison.
• Advantages:
  • High extraction efficiency.
  • No toxic organic solvents are used.
  • Fast extraction rate.
  • Environmentally friendly.
• Disadvantages:
  • Requires specialized equipment.
  • Not suitable for all types of poisons.

3.3. Solid Phase Extraction

• Principle: Uses an adsorbent material to retain the poison, then washes away impurities and elutes the poison with a suitable solvent.
• Advantages:
  • No toxic organic solvents are used.
  • Fast extraction rate.
  • High extraction efficiency.
  • Easy to perform.
• Disadvantages:
  • Requires specialized equipment.
  • Not suitable for all types of poisons.

Note:

Choose the appropriate extraction method based on the type of poison, the nature of the sample, and the analysis requirements.

4. Chromatographic Techniques for Poison Separation

4.1. Thin-Layer Chromatography (TLC)

• Principle: Uses a thin layer of adsorbent material to separate poisons based on their differences in affinity to the adsorbent and the solvent.
• Advantages:
  • Easy to perform.
  • Solvent-economical.
  • Suitable for qualitative analysis.
• Disadvantages:
  • Low resolution.
  • Difficult to quantify.

4.2. Column Chromatography

• Principle: Uses a column filled with adsorbent material to separate poisons based on their differences in affinity to the adsorbent and the solvent.
• Advantages:
  • Higher resolution than TLC.
  • Suitable for quantitative analysis.
• Disadvantages:
  • Long separation time.
  • Solvent-intensive.

4.3. Gas Chromatography (GLC)

• Principle: Uses a column filled with a non-volatile liquid to separate poisons based on their differences in boiling point and affinity to the liquid.
• Advantages:
  • Very high resolution.
  • Suitable for quantitative analysis.
  • Fast separation rate.
• Disadvantages:
  • Only applicable to volatile poisons.

4.4. High-Performance Liquid Chromatography (HPLC)

• Principle: Uses a column filled with adsorbent material to separate poisons based on their differences in affinity to the adsorbent and the solvent.
• Advantages:
  • Very high resolution.
  • Suitable for quantitative analysis.
  • Applicable to a wide variety of poisons.
• Disadvantages:
  • Requires specialized equipment.
  • Solvent-intensive.

4.5. Capillary Electrophoresis (CE)

• Principle: Uses an electric field to separate poisons based on their differences in charge and size.
• Advantages:
  • High resolution.
  • Fast separation rate.
  • Solvent-economical.
• Disadvantages:
  • Requires specialized equipment.
  • Not suitable for all types of poisons.

Note:

Choose the appropriate chromatographic technique based on the type of poison, the nature of the sample, and the analysis requirements.

5. Spectroscopic Methods for Quantification

5.1. UV-VIS Spectroscopy

• Principle: Based on the ability of the poison to absorb UV-VIS light.
• Advantages:
  • Easy to perform.
  • Low cost.
  • Suitable for quantitative analysis.
• Disadvantages:
  • Low sensitivity.
  • Not suitable for poisons that do not absorb UV-VIS light.

5.2. Fluorescence Spectroscopy

• Principle: Based on the ability of the poison to emit fluorescence when excited by UV light.
• Advantages:
  • Higher sensitivity than UV-VIS.
  • Suitable for quantitative analysis.
• Disadvantages:
  • Not suitable for poisons that do not fluoresce.

5.3. Infrared (IR) Spectroscopy

• Principle: Based on the ability of the poison to absorb infrared light.
• Advantages:
  • Suitable for qualitative analysis.
  • Provides information about the molecular structure of the poison.
• Disadvantages:
  • Low sensitivity.
  • Difficult to quantify.

5.4. Raman Spectroscopy

• Principle: Based on the scattering of light from the poison when illuminated by a laser beam.
• Advantages:
  • Suitable for qualitative analysis.
  • Provides information about the molecular structure of the poison.
• Disadvantages:
  • Low sensitivity.
  • Difficult to quantify.

5.5. Flame Spectrometry

• Principle: Based on the emission of light from atoms of the poison when introduced into a flame.
• Advantages:
  • Suitable for quantitative analysis of heavy metals.
• Disadvantages:
  • Not suitable for poisons that are not heavy metals.

5.6. Nuclear Magnetic Resonance (NMR) Spectroscopy

• Principle: Based on the absorption of radio waves by atomic nuclei in the poison.
• Advantages:
  • Suitable for qualitative analysis.
  • Provides information about the molecular structure of the poison.
• Disadvantages:
  • Difficult to quantify.

5.7. Mass Spectrometry (MS)

• Principle: Based on the separation of ions of the poison according to their mass-to-charge ratio.
• Advantages:
  • Very high sensitivity.
  • Suitable for both qualitative and quantitative analysis.
  • Provides information about the molecular structure of the poison.
• Disadvantages:
  • Requires specialized equipment.

Note:

Choose the appropriate spectroscopic method based on the type of poison, the analysis goal, and the capabilities of the laboratory.

6. Sample Collection for Toxic Analysis

6.1. Urine

• Advantages:
  • Contains many types of poisons that are excreted via the urine.
  • Easy to collect.
• Disadvantages:
  • Poison concentration in urine varies over time.
  • Not suitable for poisons that are not excreted via the urine.
• Sample collection criteria:
  • Collect 50 ml of urine from adults.
  • Do not add preservatives.
  • Collect the sample as soon as possible, before administering any treatment.

6.2. Gastric Fluid

• Advantages:
  • Contains a large amount of poison that has not been absorbed into the body.
  • Suitable for analyzing poisons that are ingested.
• Disadvantages:
  • Difficult to collect.
  • Poison concentration in gastric fluid varies over time.
• Sample collection criteria:
  • Collect 20 ml of vomit or the initial part of the gastric lavage fluid.
  • Filter or centrifuge before analysis.
  • Do not add preservatives.
  • Collect the sample as soon as possible.

6.3. Blood

• Advantages:
  • Contains many types of poisons that are absorbed into the blood.
  • Suitable for analyzing the concentration of poison in the body.
• Disadvantages:
  • Difficult to collect.
  • Poison concentration in blood varies over time.
• Sample collection criteria:
  • Collect 10 ml of whole blood, plasma, or serum.
  • Store in a tube containing heparin.

Note:

Choose the appropriate sample type based on the suspected type of poison.

Collect and preserve samples appropriately to prevent degradation and loss of the poison.

7. Poison Groups

7.1. Toxic Metals

• Examples: As, Hg, Bi, Cu, Pb, Zn, Mn, Cr, Ni, Co, Ba.
• Separation method: Inorganicization.

7.2. Toxic Acid Radicals

• Examples: Nitrite, oxalate, chlorate, strong acids and alkalis.
• Separation method: Dialysis.

7.3. Organic Poisons

• Examples: Ethanol, cyanide, aldehydes, ketones, chloral hydrate, phenol, hydrocarbons, pesticides, barbiturates, oxalic acid, salicylic acid, glycosides, alkaloids, phenothiazine derivatives, amphetamines, hallucinogens, etc.
• Separation method:
  • Steam distillation.
  • Extraction with organic solvents.
  • Gas chromatographic techniques.

8. Poison Separation Methods

8.1. Inorganicization

• Principle: Burning organic matter to release metals as ions.
• Advantages:
  • Effectively destroys organic matter.
  • Helps determine the concentration of heavy metals.
• Disadvantages:
  • May cause loss of some metals.

8.2. Dialysis

• Principle: Uses a semi-permeable membrane to remove large-sized poisons and retain toxic ions.
• Advantages:
  • Easy to perform.
  • Does not require high temperatures.
• Disadvantages:
  • Not suitable for poisons with small sizes.

8.3. Special Methods

• Steam distillation: Used for volatile poisons.
• Extraction with organic solvents: Used for poisons that are insoluble in water.
• Gas chromatographic techniques: Used for volatile poisons.

Note:

Choose the appropriate separation method based on the type of poison.

9. Qualitative and Quantitative Analysis of Poisons

• Qualitative analysis: Identifies the type of poison.
• Quantitative analysis: Determines the concentration of the poison.

Note:

Analysis results should be carefully evaluated, combined with clinical information, to draw accurate conclusions.

10. Safety in Toxic Analysis

• Always comply with safety regulations in the laboratory.
• Use personal protective equipment (gloves, mask, safety glasses).
• Do not use mouth pipetting.
• Do not eat, drink, or smoke in the laboratory.
• Store chemicals appropriately.

11. Conclusion

Toxic analysis is a complex field that requires understanding of chemistry, biochemistry, toxicology, and analytical techniques.

Applying toxic analysis methods accurately helps to identify the type of poison, its concentration, and the duration of exposure to the poison, thus supporting effective treatment of poisoning.

Note:

• This article provides general information on toxic analysis and does not replace the advice of a healthcare professional.
• If you suspect poisoning, contact your nearest healthcare facility immediately for advice and assistance.