Search results
Results from the WOW.Com Content Network
Most people who take a drug test take a presumptive test, cheaper and faster than other methods of testing. However, it is less accurate and can render false results. The FDA recommends for confirmatory testing to be conducted and the placing of a warning label on the presumptive drug test: "This assay provides only a preliminary result.
As with all presumptive tests, this technique can produce false positive results due to metals and strong chemicals, such as bleach, that will also react. Another common presumptive test is the Kastle-Meyer or Phenolphthalein test. This is a catalytic test that detects the heme group in blood that transports oxygen and carbon dioxide. [5]
The Kastle–Meyer test is a presumptive blood test, first described in 1903, in which the chemical indicator phenolphthalein is used to detect the possible presence of hemoglobin. It relies on the peroxidase -like activity of hemoglobin in blood to catalyze the oxidation of phenolphthalin (the colorless reduced form of phenolphthalein) into ...
Despite the well-known problems with the kits, they're used in half of the roughly 1.5 million drug arrests in this country every year.
The above photo shows the positive results of the number 2 Marquis reagent presumptive drug test when used with a sample of opium. It is the primary presumptive test used in Ecstasy reagent testing kits. It can also be used to test for such substances as opiates (e.g. codeine, heroin), and phenethylamines (e.g. 2C-B, mescaline).
Crime scenes are normally carefully searched for blood residue. Flashlights held at an angle to the surfaces under examination assist in this, [1] as do luminol sprays which can detect even trace amounts of blood. Presumptive tests exist with which blood can be distinguished from other reddish stains, such as of ketchup or rust, found at the ...
The test is performed by placing paper bound with the Phadebas substrate to a sample, and applying pressure. [5] It is a more sensitive and selective method to identify saliva stains than alternate light sources as these stains do not strongly fluoresce and may be confused with other biological fluids such as semen. [ 6 ]
although the test is presumptive, large areas of suspected material can be examined rapidly; dried and decomposed blood gave a stronger and more lasting reaction than fresh blood; and if the luminescence disappears, it may be reproduced by the application of a fresh luminol–hydrogen-peroxide solution; dried bloodstains may thus be made ...