Drug Facilitated Crimes – Analytical Considerations Part 2
Here are some of the techniques that toxicologists and toxicology lawyers use to analyze blood and urine samples for poisonous organic compounds:
Headspace Gas Chromatography: Gas chromatography (GC) is a technique used to detect and identify organic compounds that are volatile and stable up to 350°C. Toxicologists must be careful with the sample preparation. Even being slightly off with the sample’s pH or incubation time can result in a bad sample.
Solid Phase Micro Extraction(SPME): If you do not have the equipment for headspace, this is another good option for forensic analysis. SPME works by using fibers to absorb the drugs within the sample. The sample is then taken off of the fiber inside of an injector.
Non-poisonous organic compounds should be detected using scans to detect the compound, but if you cannot acquire a proper scanner, you could use Mass Spectrometry (HR-MS). This alternative may be used for identifying isotope patterns and the mass to charge ratio of the compound
Gas Chromatography with Flame Ionization: Perfect for finding ethanol in the blood. This method is perfect for identifying if someone has ingested alcohol when it cannot be detected in the blood or urine.
Problems with collection:
Because samples are often collected late, there is often a molecular breakdown of the substance. This breakdown makes identifying the drugs much less likely. This is why forensic toxicologists often use LC-MS-MS or GC-MS-MS. They are more sensitive and more likely to identify the drug.
If performing hair analysis, the sample must be washed to prevent contamination, however, contamination from the environment cannot be eliminated. Hair analysis is useful for differentiating between a single instance of intaking a substance and chronic consumption or addiction.
The following techniques are recommended for hair analysis:
- GC-MS, GC-MS-MS and LC-MS-MS for illicit and prescription drugs.
- LC-MS-MS for hypnotics, benzodiazepines and benzodiazepine-like drugs.
- GC-MS-MS (or LC-MS-MS) for GHB and cannabinoids.
Recommendations for sample preparation:
Sample preparation is an essential step of any analytical procedure, especially when high sensitivity is required. Adequate sample preparation results in an increase in method sensitivity and selectivity and can reduce matrix effects. Even when using sensitive detectors such as MS-MS or HR-MS, samples must be prepared properly to prevent contamination.
Glucuronidation plays an important role in the metabolic fate of many drugs because, even though it is time consuming, hydrolysis may be necessary to detect compounds and provide cleaner samples.
The extraction of analytes from a sample is important and can be done through liquid-liquid extraction (LLE) or solid phase extraction (SPE). LLE has advantages of being fast, inexpensive and efficient, and works especially well with urine. However, LLE may involve high solvent consumption. Also, care must be taken to avoid the formation of emulsions during extraction. For screening, the toxicologist extracting the substance must be sure to use the correct pH value.
Toxicologists may use SPE as an alternative to liquid-liquid extraction. It allows continuous flow of specimens through the SPE cartridges and does not clog. SPE is suitable for both large and small sample volumes and uses less solvent than LLE. It may also be more efficient.
Silylating agents, such as TMCS (trimethylchlorosilane), but also BSTFA or MSTFA, react with hydroxyl carboxyl, and amino-groups to produce volatile products for GC analysis. This makes the process suitable for toxicological analyses (STA) Silylating reagents have an added advantage of not requiring removal of excess reactant prior to GC analysis. However, silylderivatives are very sensitive to moisture so the reaction should occur under dry conditions.
Best practice recommendations for laboratory analysis
Toxicologist should follow procedures according to internationally accepted standards should be available and employed for qualitative and quantitative analysis. When working with a sample. measurement of blood and urine concentrations must be done first Enzymatic hydrolysis rather than acidic hydrolysis should be used for general purpose screening. It also allows lower detection limits in the benzodiazepine assays. Benzodiazepine-like drugs (Z-drugs) in urine are frequently used in cases of sexual assault.
The content of this article is provided by Connectica, LLC and has not been reviewed by a toxicology expert witness.