Presumptive tests cocaine

In terms of gross morphology, characteristically, coca leaf has two lines which run parallel to the mid-rib on the underside of the leaf. Taxonomically, however, it is difficult to identify leaf and plant material to species on the basis of morphology (leaf and fiower structure) alone and indeed hybridization between species is common [5]. In order to establish that the material comes from the genus Erythroxylon and contains controlled substances, it is therefore necessary to demonstrate the presence of cocaine. In bulk (those which can be seen by the naked eye) samples, this is achieved through a good physical description of the materials and packaging, followed by a combination of presumptive tests, TLC and a tandem technique, usually GC-MS. 

There are a number of presumptive tests for cocaine available from the literature. These are described below. 

Although there are several presumptive tests available for cocaine and related compounds, none alone is specific to cocaine itself. A very simple test for cocaine... 

If positive tests are obtained in the presumptive tests, the next stage in the analysis is to undertake TLC or to proceed directly to a spectroscopic evaluation. The use of TLC will allow a rapid, inexpensive means of discriminating samples containing cocaine from the false positives and a determination of what should be used in the standard mixtures for GC-MS analyses. 

Liebermann test A presumptive test sometimes used for cocaine and morphine. 

Mayer s test A general presumptive test for cocaine, morphine, heroin, and other alkaloids. Mayer s reagent is a solution of potassium mercury iodide in water. A positive result is indicated by a cream precipitate. 

Scott s test (cobalt thiocyanate test Ruybal test) A presumptive test for cocaine. Scott s reagent has an initial solution of 2% cobalt thiocyanate (Co(SCN)2) in glycerine and water. This is followed by concentrated hydrochloric acid, and then chloroform. A positive test is indicated by a blue colour in the chloroform layer. 

Suppose a forensic chemist designs a sampling plan for the 100-baggie seizure that calls for presumptive testing of all 100 exhibits. All of the tests indicate cocaine, and a subset of 25 is selected for complete characterization. AH 25 are confirmed to be cocaine. The analyst is then asked to determine the purity of the seizure. Once again, options abound Should aU 100 be quantitated Each of the 25 A composite of the 100 A composite of 25 The answer will depend on the analytical results in hand. Once again, there is no single correct protocol. 

Cocaine drug testing kits either manufactured for law enforcement purposes or produced by the underground. These testing kits are simply presumptive color tests. The basic color test used for cocaine is cobalt thiocyanate. The cocaine or any of the other substances from the caine family will form a brilliant blue flaky precipitate in the cobalt thiocyanate. This is an indication that the product is cocaine, procaine, tetracaine, etc. In order to determine whether there is actually any cocaine and not all procaine, stannous chloride is added to the precipitate causing all of the caines except cocaine to dissolve. 

The initial screening test for cocaine (benzoylecgonine) is typically immunoassay. For confirmation of a presumptive... 

Workplace drug testing typically involves the analysis of urine samples from job applicants and/or employees to determine whether they have recently used drugs of abuse such as heroin, marijuana, amphetamines or cocaine. Test samples are normally screened by a relatively inexpensive immunoassay, and all presumptively positive samples are submitted for mass spectral analysis to confirm the presence of the drug or drugs. Similarly, for determination of... 

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