Gas Chromatography (GC) is a widely used analytical tool in forensic science because of its high sensitivity, resolution, and ability to separate complex mixtures. Here’s a detailed explanation of how GC is applied in forensic investigations:
1. Analysis of Volatile and Semi-Volatile Compounds
- GC is ideal for volatile substances, which are common in crime-related samples.
- Examples:
- Alcohols in blood (blood alcohol content analysis)
- Narcotics like amphetamines, cocaine, and heroin
- Explosives residues
- Volatile organic compounds from fire debris (arson investigation)
2. Blood Alcohol Determination
- Purpose: To determine the concentration of ethanol in a suspect’s blood.
- How GC helps:
- Blood samples are prepared and injected into the GC.
- Ethanol is separated from other components and quantified using a flame ionization detector (FID).
- Importance: Provides legally admissible evidence in DUI (Driving Under Influence) cases.
3. Drug Identification
- GC can separate and identify illicit drugs in biological fluids (blood, urine) or seized materials.
- Often coupled with mass spectrometry (GC-MS) for definitive identification.
- Example: Differentiating between cocaine and its metabolites or between different amphetamines.
4. Arson and Explosive Investigation
- GC can detect ignitable liquid residues in fire debris: gasoline, kerosene, or accelerants.
- Process:
- Sample (soot, debris) is collected.
- Solvent extraction isolates volatile compounds.
- GC separates components; GC-MS identifies specific compounds.
- Helps prove arson or use of explosives in a crime scene.
5. Toxicology
- GC is used to detect poisons and toxic substances in biological samples.
- Examples: Cyanide, methanol, organophosphates, barbiturates.
- GC provides sensitive, quantitative results, critical in post-mortem investigations.
6. Hair and Body Fluid Analysis
- Drugs or toxins that accumulate in hair, saliva, or sweat can be extracted and analyzed by GC.
- Enables long-term exposure assessment and supports forensic evidence in court.
7. Advantages in Forensic Science
- High sensitivity and specificity for trace amounts of substances.
- Can be combined with mass spectrometry (GC-MS) for structural identification.
- Fast analysis of volatile and semi-volatile compounds.
- Minimal sample requirement—very useful when forensic samples are limited.
In short, GC is essential in forensic labs for toxicology, drug analysis, arson investigation, and blood alcohol testing, making it a key tool for criminal investigations.