602 exam 1

accuracy

free of error, measure of the true value

chain of custody

record of possession or control by person(s) of authority

comparison

an examination of two or more items to evaluate similarities or differences

class characteristic

feature of a group or set with common attributes

control

ability to check, test, or verify by experiment

crime scene investigation

inquiry into a place where an illegal act may have occurred

criminalistics

collection and scientific analysis of physical evidence suitable for presentation in criminal cases

expert witness

admitted to the court of law to speak on a subject, test, or result

indicate

points to or suggests

identify

to determine the category or determine the identity

forensic chemistry

scientific analysis of composition, structure, and properties of chemical substances to aid in decision making for a criminal or civil case

forensic science

scientific analysis of physical evidence suitable for presentation in court

precision

level of tolerance in manufacture or measurement

presumptive test

a test for screening or tentative identification of a substance

replicate

a test of one or several samples from the same source using the same technique

quality control

activities designed to ensure reliability and accuracy of a method or test

sample

representative part of a whole

standard

criteria established by an authority as a model; meeting a set value, quantity, quality, weight or composition; the level of quality that is acceptable

chromophore

a molecule that absorbs light at a specific frequency that results in a color in the visible region

color test

a combination of reagents that reacts with a substance to yield a visible response upon absorbance of light

decision tree

a written conclusion based on sequential testing or information collection

microcrystalline test

a crystal resulting from a reaction with a metal salt solution visible only under a microscope

presumptive

believed to be true or likely based on available results though not yet proven

tentative

not fully determined or elucidated

Marquis test analytes + colors

morphine (purple), heroin (purple), codeine (purple), amphetamines (orange)

Nitric acid test analytes + colors

morphine (blood red), heroin (pale yellow), codeine (light green-yellow)

Duquenois-Levine test analytes + colors

THC/marijuana (purple in organic layer)

Scott test analytes + colors

cocaine (blue)

Dille-Koppanyi test analytes + colors

barbiturates (light purple)

Phosphate test analytes + colors

psilocybin (yellow precipitate)

Ferric chloride test analytes + colors

salicylates (purple)

Ehrlich/DMAB/van Urk test analytes + colors

psilocin and psilocybin (purple)

T/F: false positives are a drawback of color tests

true

purpose of wet chemical tests

determine the chemical identity of a compound or functional group. screening illicit drugs, explosive residues, toxicological evidence

difference between color tests and microcrystalline tests

color tests color produced upon reagent addition. microcrystalline tests formation of microscopic crystals of a characteristic form and habit

advantages of color tests

low cost, easy to use, rapid results, portable, can be used for elimination purposes and to obtain a warrant for further search

disadvantages of color tests

generally cannot be used in court, do not definitively identify a drug, do not quantify amount

subset of colorimetric tests for drugs

Marquis, Duquenois-Levine, Nitric acid, Mayer’s, Scott, Cobalt thiocyanate, Mecke

how do chemical color tests generally work?

use reagents that produce specific colors when reacting with certain classes of compounds. target the functional groups (phenols, aromatic rings, alcohols, carboxylic acids, amines). chemically adding an auxochrome to drug molecule that shifts the optical absorption into the visible

chemical color tests detection limits

1 to 50 ug

T/F: chemical color tests can be used as developers for thin layer chromatography (TLC) plates

true

how are color tests performed?

obtain ceramic spot plates or disposable, single use plastic spot plates. add small amount of suspected drug. add drop(s) of reagent(s). record color. alternatively, use commercial tests in sealed pouches

color tests results will be affected by:

concentration of the sample, concentration of the reagent, adulterants and diluents, age of the reagent, recipe used to prepare the reagent, temperature of reaction, length of time the reaction is observed

how are results of color tests reported?

report color, method used to prepare reagents and date prepared, quantity of drug tested, which sample or standard tested, time elapsed since test started. lot numbers

the _______ test is often the first screening test; the results are used to determine the pathway for further testing

Marquis (NIK A)

the Marquis test is a test for _________

alkaloids

analyzer

polarizing filter placed in the path between the sample and the eyepiece lens

anisotropic

different value measurement when measured from a different angle due to their crystal lattice and arrangement of atoms and ions

aperture diaphragm

the optical limit (center aperture) when thin overlapping blades or leaves that increases or reduces the amount of light that can reach the sample

arm

structural spine of a microscope

birefringence

the refraction of light by an anisotropic material in two slightly different directions

base

support for attaching illuminator and other optical components

becke line

optical halo of light that appears on the edges of the sample when viewed under a microscope in a liquid with a different refraction index

brightfield illumination

a standard optical microscopy technique in which a sample is illuminated with white light from the illuminator below the stage, producing a darker outlined specimen against a bright background

body tube

connects the eyepieces to objective lenses and aligns the light path and interaction with the lenses

chromatic

relating to color, color fringing is caused at the edges of lenses where they fail to focus (the wavy interference seen at edges of slide)

coarse adjustment

moves the stage up or down by a visible amount

comparison microscopy

two optical microscopes are connected by a bridge so a user can view two samples side by side in the field of view

compensator (wedge)

an optical accessory used in a polarizing light microscope to introduce a fixed, known or variable phase shift or retardation of orthogonal (perpendicular) light waves

compound light microscope (CLM)

a high magnification light microscope that uses visible light and a system of two or more lenses to magnify small and thin-sectioned samples

condenser

a lens system below the stage that gathers light from the illuminator and focuses it into onto the sample

dichroism

an optical property of a material or crystal in which it absorbs or transmits ight differently depending on the direction of the polarized light or the angle from which it is viewed often making the material appear to be of two different colors

extinction

complete or partial dimming of the light reaching a mineral or crystal making it appear dark or black when viewed using crossed polarizers

fine adjustment

moves the stage up or down by a small or precise amount

fluorescence

a light technique in which a sample is exposed to different wavelengths of light to see which ones it is excited with causing it to emit light of a specific wavelength that can be captured or detected

illuminator

a built-in light source such as a halogen bulb or LED used to view a sample

isotropic

a material that has identical properties when interacting with light waves from all directions

iris diaphragm

the thin overlapping blades or petals that increase or reduce the amount of light that can reach the sample

koehler illumination

a technique used in microscopy to provide uniform and bright lighting on a sample by adjusting the field diaphragm (controls the illuminated surface area) and the aperture diaphragm (light angle) to improve contrast and glare

macroscopic examination

visual examination, may involve low magnification stereoscope magnification

microspectrophotometer

an instrument that combines a light microscope and a spectrophotometer to measure the spectra of small samples or areas in samples

michel-levy chart

a tool used to compare the highest-order interference colors displayed by the sample whose thickness is known to those contained on the chart to determine birefringence

nosepiece/turret

the rotating circular component on which objective lenses are affixed that can be rotated to switch lenses

numerical aperture

a unitless value used to describe a microscope’s ability to gather light and resolve fine details in a sample (NA=n(sin(O)))

parfocal

a microscope that stays generally in focus when an objective lens is switched out needing little adjustment

phase contrast

an imaging technique in which converts invisible phase shifts of light as it passes through a sample to visible changes in image brightness

pleochroism

a material exhibits three different colors when interacting with plane polarized light

polarized

restricting light of only one phase or direction to pass

polarized filter

restricts which planes of light come through

reflection

change in direction of light when they encounter material or a sample causing it to bounce back

refraction

bending of light waves as they pass from one substance to another due to a change in speed

resolution

the ability to see two items as separate

retardation

slowing down or phase shift of light waves as they pass through a birefringent material

scanning electron microscopy

a tool that uses a focused beam of electrons instead of light to create highly very high magnification three-dimensional image of the surface of a sample (use if want to see beyond 1000x magnification)

stage

a flat platform that holds the sample for investigation

stereomicroscope

a tool that uses two separate light paths and binocular lenses to magnify samples and reveal detail with depth and in three dimensions at low magnification

transmission electron microscopy

a tool that uses a focused beam of electrons instead of light to create highly very high magnification used to view internal structures of a sample

SWGDRUG category A analytical techniques

infrared spectroscopy, mass spectrometry, nuclear magnetic resonance spectroscopy, raman spectroscopy, x-ray diffractometry

SWGDRUG category B analytical techniques

capillary electrophoresis, gas chromatography, ion mobility spectrometry, liquid chromatography, macroscopic examination (cannabis only), microcrystalline tests, microscopic examination (cannabis only), pharmaceutical identifiers, thin layer chromatography

SWGDRUG category C analytical techniques

color tests, fluorescence spectroscopy, immunoassay, melting point, UV spectroscopy

two ; A

at least ___ validated techniques must be used if a category _ method is used

three ; two ; B

if no category A method is used, at least _____ different validated techniques must be employed including at least ___ uncorrelated category _ methods

marijuana ; duquenois-levine

in the case of _________, category B macroscopic and microscopic investigation techniques may be used if the submitted evidence has sufficient observable detail; the additional technique is frequently the ________________ color test