2/13 OBJECTIVE: Finish book assignment and copy powerpoint notes. Tape the book assignment into your notebook after you are finished. I will stamp it tomorrow. Go onto my website and copy down the notes on Analytical testing for drugs under the drugs tab.

Screening (Presumptive) test Confirmation test Drug Identification Another difficulty of forensic drug identification comes in selecting analytical procedures that will ensure a specific identification of a drug. Analyzing drugs is done in 2 phases: Screening (Presumptive) test Confirmation test

Presumptive Drug Tests Police officers use rapid presumptive tests to determine whether drugs are present. These are simple color tests adaptable to field use to identify controlled substances. Along with other circumstantial facts, physical appearance, odor, texture, etc., they help the police officer form the probable cause to support their suspicion that the unknown substance is controlled. Presumptive tests may generate false positives. If a presumptive test generates a positive result a more complex confirmatory test is administered.

Preliminary Analysis The unknown substance may be any one of a thousand or more commonly encountered drugs. Screening tests reduce these possibilities to a small and manageable number. A series of color tests that will produce characteristic colors for the more commonly encountered illicit drugs.

Preliminary Analysis Microcrystalline tests: Analyze the size and shape of crystals formed when the drug is mixed with specific reagents. Fig. 3. Microcrystalline response of selected psychoactive stimulants tested with mercury chloride as reagent (a) BZP, (b) caffeine, (c) d-amphetamine, (d) dl-amphetamine, (e) ephedrine hydrochloride, (f) ephedrine sulphate, (g) MDAI freebase, (h) mephedrone, (i) methamphetamine. Note: (a) was taken at 76× magnifications, images (b)–(i) were taken at 19× magnifications.

Confirmational Determination Once this preliminary analysis is completed, a confirmational determination is pursued. Forensic chemists will employ a specific test to identify a drug substance to the exclusion of all other known chemical substances. Typically infrared spectrophotometry or gas chromatography-mass spectrometry is used to specifically identify a drug substance.

Analysis of Controlled Substances For a test method to be considered of value in establishing the forensic identification of a drug, the results shall be considered “positive.” “Negative” test results provide useful information for ruling out the presence of a particular drug or drug class, these results have no value toward establishing the forensic identification of a drug.

Color Tests

Advantages and Disadvantages Scientists are able to use these simple and easy techniques to identify unknown substances. No sophisticated equipment is necessary for color tests. Inexpensive Quick results and analysis Not sensitive for small amounts

Qualitative vs Quantitative Tests Qualitative tests can define what type of drug is present but lacks the ability to determine how much drug is present. Various criminal charges depend on knowing how much of a drug is present. This requires a quantitative test. In a quantitative test, the sample is weighed and then the test is used to estimate what mass of the sample is the drug. The mass of the drug is divided by the total mass to give the percentage of drug in the sample.

Analysis of Controlled Substances The laboratory shall employ quality assurance measures to ensure the results correspond to the exhibit. Example measures are: The use of two separate samplings Sample identification procedures such as bar-coding and witness checks Good laboratory practices (e.g., positive and negative controls, one sample opened at a time, procedural blanks)

Chromatography – separating and Tentatively identifying the components of a mixture.

Gas chromatography (GC)- separates mixtures based on their distribution between a stationary liquid phase and a moving gas phase. Qualitative test Not a definitive test, must be used with other tests.

Thin-Line Chromatography (TLC)- Components of a mixture are separated as they move up a glass plate. Stationary phase is the silica gel or aluminum oxide. The rising liquid is the moving phase. The result is compared to a known sample. Qualitative Test Must be used with another test for an absolute identity

Spectrophotometry: An analytical method for identifying a substance by its selective absorption of different wavelengths of light. Ultraviolet spectrophotometry (UV)- Qualitative test, can also be used as a quantitative test. NOT a confirmation test Infrared Spectrophotometry (IR)- Quantitative and Qualitative test. Used as a definite confirmation test. Produces a “fingerprint” of the drug.

Gas Chromatography/ mass Spectrometry The chromatography sample is funneled into a mass spectrometer to show the mass of the different compounds in a substance. Quantitative test Confirmation Test