Transcript Drug Testing - Uplift Grand

DRUG TESTING
17 February 2015
Vocab Review
What is the difference between a presumptive test and a
confirmatory test?
• Presumptive tests have high false positives; they indicate that a
substance may be present.
• Confirmatory tests do not have false positives; a positive result
confirms that a substance really is present.
Why do a presumptive test?
• Presumptive tests are usually quick, inexpensive, and can often be
done on the field. This can help guide police and can let them know
whether a more time consuming and expensive confirmatory test
should be done.
Color Spot Tests
Procedure:
presumptive
or
confirmatory?
• Add a test chemical to an unknown substance. If the drug is
present, the chemical will react and change color.
• Different test chemicals for different drugs
• Investigators can use a well plate quickly and easily check for the
presence of many different types of drugs
Examples:
• Cobalt thiocynate turns
blue when it contacts
cocaine (or benadryl)
• Marquis reagent turns
purple when it contacts
heroin (or medicines with
codeine)
Color Spot Tests
Procedure:
presumptive
or
confirmatory?
• Add a test chemical to an unknown substance. If the drug is
present, the chemical will react and change color.
• Different test chemicals for different drugs
• Investigators can use a well plate quickly and easily check for the
presence of many different types of drugs
Examples:
• Cobalt thiocynate turns
blue when it contacts
cocaine (or benadryl)
• Marquis reagent turns
purple when it contacts
heroin or morphine (or
medicines with codeine)
Color Spot Tests
Procedure:
presumptive
or
confirmatory?
• Add a test chemical to an unknown substance. If the drug is
present, the chemical will react and change color.
• Different test chemicals for different drugs
• Investigators can use a well plate quickly and easily check for the
presence of many different types of drugs
Examples:
• Cobalt thiocynate turns
blue when it contacts
cocaine (or benadryl)
• Marquis reagent turns
purple when it contacts
heroin or morphine (or
medicines with codeine)
IR Spectroscopy
Vibrating molecule
• Spectroscopy involves passing a beam of light through a
substance and recording how much light is transmitted through
the substance.
• Light that is not transmitted must have been absorbed by the
substance.
• Infra-red (IR) light is used to
analyze drugs because IR
light occurs at the right
frequencies to excite the
bonds between molecules.
When the bonds are excited,
the light is absorbed.
• The absorption / transmission patterns are unique to the chemical
since the combination of bonds in a chemical are unique.
Sample IR spectra - cocaine
• X axis are wave numbers (spatial frequency) of light waves
• The overall shape of the spectra and the absorbance peaks
are compared to determine the identity of a chemical
What is the
relationship between
transmittance and
absorbance?
100-TRANS = ABS
What are the major
absorbance peaks for
cocaine?
1282.3, 1713.6, etc.
More IR
Spectra
Why do chemicals
have unique IR
spectra?
Because the
collection of bonds
is unique – though
chemically similar
compounds will
have similar spectra
Is IR-Spectroscopy
a presumptive or
confirmatory test?
confirmatory
GC – Mass Spectrometry
This machine combines two procedures to analyze chemicals:
1) Gas chromatography (GC)
2) Mass spectrometry (MS)
Gas chromatography is used first to
separate a mixture into its
components.
• The mixture is vaporized into
gases
• The gases travel through a long
tube to the MS machine.
• The different components
separate by time according to how
easily each is vaporized and how
quickly each travels.
GC – Mass Spectrometry
The mass spectrometer is then used to produce the mass spectrum of
each component gas.
• Each gas is blasted with electrons
to ionize it – break it into smaller
ions.
• The mass / charge ratio of each
ion is measured (m/z).
• The mass spectra of different
chemicals are nearly unique
(there are a few VERY similar
chemicals that cannot be
differentiated via GC-MS, such as.
stereoisomers)
Watch me!
Presumptive or confirmatory?
Confirmatory – at least for very
closely related compounds
Quick Review
What is actually measured in each of the three tests discussed?
Spot color tests – looking for color change, indicates a chemical
reaction has taken place
IR spectrophotometry – measure absorbance of energy (light) by the
bonds in a molecule
GC-MS – measures the mass and charge of ions produced when a
chemical is first separated then ionized.
Most forensic investigations will utilize two of the three tests. Why use
two tests? Which two would you use?
Use spot color test first because it is quick and cheap. Use EITHER IR
spectrophotometry or GC-MS to confirm.
EXIT TICKET
Closure
• What were our objectives, and what did we learn?
• What was our learner profile trait and how did we demonstrate it?
• How does what we did today tie to our unit question?