What is a color test in forensics?
Color testing is a presumptive identification technique indicating the presence or absence of a particular drug class using rapid and uncomplicated chemical methods.
Why are color tests used?
Color tests are a key tool for the rapid and simple identification of seized illicit drugs. This chapter outlines a series of color tests that can be used for the preliminary identification of new psychoactive substances such as cathinones, piperazines, tryptamines, and amphetamine-type stimulants.
What is a color test in toxicology?
One of the oldest analytical procedures used by forensic chemists or forensic toxicologists is broadly classified as ‘color tests’. Color tests or spot tests are chemical tests which involve the reaction of a sample with a reagent or a series of reagents to produce a color or change in color.
What does the Duquenois-Levine test for?
Abstract. The Duquenois-Levine test for tetrahydrocannabinol (THC) has been used in the forensic science community for over 80 years. This three-part color test is one of many tests used to confirm the presence of THC.
Is the positive results of color test are conclusive evidence why?
A positive result from a presumptive test for blood indicates the possibility that blood is present. A positive result from a confirmatory test allows one to conclude that blood is present.
What are the different color tests for drugs?
Indicators and Presumptive Color Tests
| Test | Reagents | Color Change |
|---|---|---|
| Nitric acid | Concentrated HNO3 | Strong brown Dark orange yellow Brilliant yellow |
| p-DMAB | Para-dimethylamino-benzaldehyde in ethanol, HCl | Deep purple |
| Ferric Chloride | Ferric chloride solution | Dark green |
| Froehde | Molybdic acid in sulfuric acid | Greenish black Strong yellow |
What is the importance of color test in chemistry?
It follows that colour tests are only an indication of the presence of a compound or class of compounds and that all tests must be confirmed by more specific methods. This is especially important in forensic cases!
What is Fast Blue B test forensics?
The principal screening test used by the Brazilian Forensic Police is a colorimetric test called Fast Blue B or BB salt, in which the development of a reddish color in a basic medium indicates the presence of cannabinoids such as Δ9-THC, cannabinol (CBN) and/or cannabidiol (CBD).
What test may be used to determine whether a stain is blood?
Phenolphthalein tests are typically conducted on suspected bloodstains prior to collection. While a positive phenolphthalein reaction is indicative of blood, it is only a presumptive test and false positives are possible.
What is the preliminary blood color test?
Abstract. Luminol, leuchomalachite green, phenolphthalein, Hemastix, Hemident, and Bluestar are all used as presumptive tests for blood.
How does the Takayama test work?
How it works: Through the application of a specific solution developed by Takayama, hemochromogen crystals form by treating a small amount of blood or a stain fragment. The crystals are observable under a microscope and look like salmon-pink rhomboid crystals.
What determines the color of a material?
The ‘colour’ of an object is the wavelengths of light that it reflects. This is determined by the arrangement of electrons in the atoms of that substance that will absorb and re-emit photons of particular energies according to complicated quantum laws.
What is colorimetric test for trace evidence?
Colorimetric Test for Trace Evidence. This simple, two-part presumptive test will help you quickly determine whether or not a surface has recently been exposed to a discharged firearm. Simply wipe down the surface in question, add the chemical reagents, and observe the results.
Why is white the best color to examine soil evidence?
This research was the first time image processing software was used to examine trace soil evidence on clothing fabric. To make this task easier, white fabric was chosen to provide a visual contrast to the color of all soils tested and thereby make it easier to identify microscope traces of soil particles transferred to clothing fabric.
How do you test for presumptive color?
Presumptive Color Tests. Use reagents that produce specific colors when reacting with certain classes of compounds. Target the functional groups. Phenols. Aromatic rings.
What is the current approach to analyzing forensic soil evidence?
The current approach to analyzing forensic soil evidence is to focus on profiling the chemistry of the soil to indicate a possible origin. Because of this focus, police photographs are not generally taken of soil mark/pattern evidence on suspects/victim’s clothing at the crime scene; before the body is moved or clothing removed.