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Forensic Chemistry Information

 

Uniform Controlled Dangerous Substances Act

The OSBI Forensic Chemistry Unit identifies and reports out substances controlled under Oklahoma state statute (Title 63).  Oklahoma Statutes, Title 63, Chapter 2, Article 2 (Standards and Schedules) classifies controlled dangerous substances into Schedules I through V based upon the potential for abuse, medical use, and likelihood of abuse leading to physical or psychological dependence.  Schedule I substances have the highest potential of abuse, no accepted medical use in the U.S., and the highest likelihood of abuse leading to physical or psychological dependence.  Schedule V substances have the lowest potential for abuse, current accepted medical use in the U.S., and limited physical or psychological dependence.

Criminalists of the Forensic Chemistry Unit will testify in court on the findings of our analysis upon request.

 

 

 

 

Analytical Methods

Color Tests

Color tests are used presumptively to give an indication of what might be present in the sample.  It also helps to determine which solvents to use in the analysis methods to follow.  The color tests are similar to field test kits used by police officers.  Color tests are screening tools only, therefore, additional analysis is required for identification of a substance.  The OSBI Forensic Chemistry Unit utilizes Marquis and Cobalt Thiocyanate reagents.  Each reagent responds to particular functional groups causing a characteristic color change depending upon the compound and its functional group.

Picture of Color Test Marquis Reagent

 

Analysis by Gas Chromatograph (GC)

Gas chromatography is an instrumental analysis that separates the components of a mixture.  The GC consists of three basic parts: an injection port, a chromatographic column, and a detector.  The sample is diluted into the solvent and placed into a sample vial for analysis.  The sample is then introduced into the GC.  The time from injection of the sample until the detector produces a signal is called the retention time.  The retention time of the unknown sample can be compared to that of a known standard.  The OSBI Forensic Chemistry Unit uses this information as a presumptive indication of what may be present in the sample.

 

Chromatogrm of Various Substances

 

Conclusive Identification by Gas Chromatograph/Mass Spectrometer (GC/MS)

The sample components are separated by the GC portion of the instrument.  Each component is fragmented by an electron beam and then analyzed by the mass spectrometer.  Comparison of the fragment patterns of an unknown substance to that of a known standard allows for a conclusive identification.

 

Mass Spectrum of Cocaine

 

Conclusive Identification by Infrared Detection (IR)

A sample absorbs infrared light based on the chemical structure of its components.  Infrared spectroscopy can be used to identify most organic compounds based on absorption of radiation of the mid-infrared range from 4000 to 400 wave numbers.  Conclusive identification is made by analysis of a sample's spectrum against a known spectrum.  Analysis can be performed on a solid sample using Fourier Transform Infrared (FTIR).

 

IR Spectrum of Methamphetamine

 

 

Identification of Marihuana and Hashish

Samples of a vegetative nature, green leafy substance, green leafy plants, ashes or any other submittal which is suspected to be marihuana or hashish may be examined or analyzed using a series of tests: stereomicroscopic examination, modified Duquenois-Levine examination, and thin layer chromatographic (TLC) examination.  The identification of marihuana requires a positive microscopic examination, modified Duquenois-Levine examination, and TLC examination.  Watch the video below for the analysis and identification of marihuana.

 

Marihuana Analysis Video

Marihuana Analysis Video

Picture of Blind Justice