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Questions and Answers
Toxicology is defined as the study of harmful effects caused by toxins.
Toxicology is defined as the study of harmful effects caused by toxins.
True
Clinical toxicology does not require patient consent for testing.
Clinical toxicology does not require patient consent for testing.
True
Forensic toxicology requires the identity of the specimen to be presumed.
Forensic toxicology requires the identity of the specimen to be presumed.
False
Immunoassays are used for preliminary screening due to their ability to detect small amounts of drugs and metabolites.
Immunoassays are used for preliminary screening due to their ability to detect small amounts of drugs and metabolites.
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Mass spectrometry is not considered a part of chromatographic techniques.
Mass spectrometry is not considered a part of chromatographic techniques.
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NSAID drugs, such as ibuprofen, can yield false positive results in drug screenings.
NSAID drugs, such as ibuprofen, can yield false positive results in drug screenings.
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Gas chromatography combined with mass spectrometry is regarded as a gold standard in toxicology.
Gas chromatography combined with mass spectrometry is regarded as a gold standard in toxicology.
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Immunoassays can be used for confirmation of positive drug testing results.
Immunoassays can be used for confirmation of positive drug testing results.
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Gas Chromatography does not change the chromatographic characteristics of substances.
Gas Chromatography does not change the chromatographic characteristics of substances.
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High Performance Liquid Chromatography is suitable for heat-labile substances.
High Performance Liquid Chromatography is suitable for heat-labile substances.
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GC/MS is considered the gold standard for drug detection.
GC/MS is considered the gold standard for drug detection.
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The mobile phase in High Performance Liquid Chromatography is a gas.
The mobile phase in High Performance Liquid Chromatography is a gas.
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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 negatives occur when a drug is detected but not present.
False negatives occur when a drug is detected but not present.
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High Performance Liquid Chromatography is generally faster than Gas Chromatography.
High Performance Liquid Chromatography is generally faster than Gas Chromatography.
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Interfering substances can cause false positives in drug testing.
Interfering substances can cause false positives in drug testing.
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Study Notes
Toxicology
- Defined as the study of the harmful effects of toxins
- Distinction between Clinical and Forensic toxicology
Clinical vs. Forensic Toxicology
| Feature | Clinical | Forensic |
|---|---|---|
| Specimen consent | Not required | Required |
| Specimen identity | Presumed | Must be proven |
| Screening results | Sufficient for medical decisions | Only confirmed positive results are admissible |
| Purpose | Medical evaluation | Legal action |
| Examples | Emergency screening (overdose), therapeutic drug monitoring (TDM), toxic exposure | Postmortem, criminal cases, workplace drug testing, sports cases |
Analytical Challenges
- Endogenous substances such as cholesterol, fats, proteins, and putrefactive amines can pose challenges in forensic toxicology
- Wide range of drug concentrations exist, varying from therapeutic concentrations (potentially over 100,000-fold) down to very low levels potentially present in samples.
- Some drugs and metabolites are extremely challenging to detect due to their low concentrations in samples, as well as inherent difficulties in accurately measuring them.
Analytical Basis of Toxicology
-
Immunoassay
- Used for preliminary screening
- Based on antibody-antigen reaction; small amounts of drugs or metabolites can be detected.
- Various types (e.g., ELISA, RIA)
- Could have certain disadvantages such as false positives; cross-reactivity (i.e. detecting substance A when substance B was actually present)
-
Chromatography (TLC, GC, HPLC)
- Separates components of a mixture based on their affinity for the mobile and stationary phases
- Followed by Mass Spectrometry for confirmation
- GC-MS is a common gold-standard method, often preceded by immunoassay
-
Mass Spectrometry
- Ionizes samples, sorts the ions according to their mass-to-charge ratio
- Used to identify and quantify substances after separation
- Useful for identifying metabolites and confirms results obtained from other methods
Disadvantages of Immunoassay
- Specificities can cross-react producing false positives
- Cannabinoids use carboxylic acid metabolite detection
- NSAID and other drugs like ibuprofen and naproxen can yield false positive results for other substances
- Codeine can create a positive reaction for morphine
- Antihistamines can yield false positive results with amphetamines
Interpretation of Test Results
- False Negatives: Drug present but not detected (threshold too high, quantity too low, dilution).
- False Positives: Drug detected when it's not present (interfering substances, cross-reactivity with reagents (e.g., OTC meds, herbal teas, poppy seeds), or intentional sabotage).
Additional Details
-
Cocaine
- Chemical structure
- Fragmentation (EI)
- Mass spectrum
-
Amphetamine
- Fragmentation
- Mass spectrum
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Description
Explore the key differences between clinical and forensic toxicology in this quiz. Understand the roles and requirements of each field, from specimen consent to the purpose of testing. Perfect for students and professionals interested in the science of toxins and their impact.
