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Questions and Answers
Gas chromatography generally uses a liquid mobile phase.
Gas chromatography generally uses a liquid mobile phase.
False
High Performance Liquid Chromatography is suitable for heat-labile substances.
High Performance Liquid Chromatography is suitable for heat-labile substances.
True
Gas chromatography destroys the chemical in its detector.
Gas chromatography destroys the chemical in its detector.
True
Gas chromatography is slower than High Performance Liquid Chromatography.
Gas chromatography is slower than High Performance Liquid Chromatography.
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HPLC is the method of choice for substances that are easy to volatilize.
HPLC is the method of choice for substances that are easy to volatilize.
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Mass spectrometry sorts ions based on their mass-to-charge ratio.
Mass spectrometry sorts ions based on their mass-to-charge ratio.
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False positives occur when a drug is present but not detected.
False positives occur when a drug is present but not detected.
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The use of HPLC/MS is considered the 'gold standard' for drug detection.
The use of HPLC/MS is considered the 'gold standard' for drug detection.
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Cross-reactivity can lead to false positives in drug testing.
Cross-reactivity can lead to false positives in drug testing.
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The mission related to poisoning does not include conducting research.
The mission related to poisoning does not include conducting research.
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Immunoassay is not useful for preliminary screening of drugs.
Immunoassay is not useful for preliminary screening of drugs.
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Gas chromatography combined with mass spectrometry is considered a gold standard in toxicology.
Gas chromatography combined with mass spectrometry is considered a gold standard in toxicology.
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In forensic toxicology, the identity of the specimen must be proved.
In forensic toxicology, the identity of the specimen must be proved.
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Patients do not need to consent to be tested in clinical toxicology.
Patients do not need to consent to be tested in clinical toxicology.
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NSIAD drugs like ibuprofen and naproxyn can cause a false positive reaction in immunoassays.
NSIAD drugs like ibuprofen and naproxyn can cause a false positive reaction in immunoassays.
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The screening results in clinical toxicology are sufficient for legal actions.
The screening results in clinical toxicology are sufficient for legal actions.
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True positive results in forensic toxicology do not require confirmation.
True positive results in forensic toxicology do not require confirmation.
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Anti-histamines can give a positive reaction for morphine.
Anti-histamines can give a positive reaction for morphine.
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The principles behind immunoassays include antibody-antigen reactions.
The principles behind immunoassays include antibody-antigen reactions.
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Immunoassays are considered sufficient for final confirmation in toxicology tests.
Immunoassays are considered sufficient for final confirmation in toxicology tests.
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Study Notes
Toxicological Aspects of Substance Abuse
- Toxicology is the study of the harmful effects of toxins.
- It has both clinical and forensic applications.
Clinical vs. Forensic Toxicology
- Clinical toxicology focuses on emergency screening (e.g., overdose), toxic exposure, and therapeutic drug monitoring (TDM).
- Forensic toxicology focuses on postmortem examinations, criminal investigations, workplace drug testing, and sports doping.
Clinical Toxicology
- Requires no patient consent.
- Specimen identity is presumed.
- Screening results are sufficient for medical decisions.
- Results are used for medical evaluations.
Forensic Toxicology
- Subject consent is required.
- Specimen identity must be proven.
- Only confirmed positive results are considered valid.
- Results are used for legal action.
Analytical Problems in Toxicology
- Endogenous substances (e.g., cholesterol, fats, proteins), putrefactive amines are present in samples, making analysis complex
- Drug concentrations vary greatly, spanning over 100,000-fold.
- Some drugs cannot be easily detected.
- Analytical conditions may not be appropriate for all samples, some drug/poisons are unknown or very unusual.
Analytical Basis of Toxicology
- Immunoassay
- Chromatography (TLC, GC, HPLC)
- Mass spectrometry
Immunoassay
- Used for preliminary screening.
- An antibody-antigen reaction detects even small amounts of drugs/metabolites.
- Its specificity can be compromised by cross-reactivity.
- Examples include ELISA and RIA.
Immunoassay Disadvantages
- Specificity issues may result in false positives.
- Some drugs (e.g., NSAIDs) may produce false positive results when using cannabinoid detection methods.
- Some antihistamines may produce false positive reactions for amphetamines.
- Immunoassays are good screening tests, but not sufficient for confirmation.
Chromatography
- Separates mixtures based on the affinity between mobile and stationary phases.
- Commonly used with mass spectrometry for confirmation (e.g., GC/MS).
- GC/MS methods are considered gold standard for drug identification, often combined with immunoassays for reduced false negative results.
HPLC and Other Chromatography
- HPLC is primarily used for drugs difficult to vaporize or heat labile compounds.
GC (Gas Chromatography) vs. HPLC (High-Performance Liquid Chromatography)
| Feature | GC | HPLC |
|---|---|---|
| Destruction of Sample | Destroys the sample. | Does not destroy the sample (less destructive). |
| Mobile Phase | Gas | Liquid |
| Sampling | Large | Low |
| Specificity | High | High |
| Speed | Faster | Slower |
GC/MS (Gas Chromatography/Mass Spectrometry)
- GC physically separates (purifies), and MS fingerprinting (identifies) the drug/chemical.
- The combination of GC and MS is a gold standard for accurate identification.
- These methods are chosen for substances difficult to volatilize.
- Results from a combination of assays are more reliable.
Mass Spectrometry
- Ionizes chemical samples and sorts ions based on mass-to-charge ratio.
Cocaine and Amphetamine
- Compounds are complex and their structural properties affect analysis.
- Characteristic fragments for definitive identification are needed.
- Presented in molecular structure and fragmentation for determination by mass/spectroscopy.
- Fragmentation patterns are characteristic of the drug, and used in mass spectrometry to accurately determine drug type.
Interpreting Test Results
- False Negatives: Drug is present but not detected e.g. due to a very low concentration or threshold is too high.
- False Positives: Drug is detected, but isn't present. This can happen due to interfering substances (like OTC meds or poppy seeds), cross reactions with reagents, or intentional sabotage.
National Poison Centre Mission
- Reduce poisoning mortality and morbidity by providing excellence, compassion, and innovation.
- Poisoning risk and occurrence reduction is aided by;
- optimizing poison treatment via information management.
- poison awareness and prevention via education.
- analyzing and interpreting lab results (for determination).
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Description
Test your knowledge on the toxicological aspects of substance abuse, focusing on clinical and forensic toxicology. Understand the differences between their applications and the challenges faced in analytical procedures. This quiz covers critical concepts that are essential for both medical and legal professionals.
