ISOLATION AND IDENTIFICATION OF POISONS Flashcards
heating a sample to convert the substance into vapor, cooled and condensed back into a liquid state
distillation
separation of a crystalloid from a colloid by filtration through a semi-permeable membrane
only applicable if we are trying to separate a crystalloid from a colloid
dialysis
based on the miscibility/solubility of the substance in solvents
the substance you are trying to extract has to be miscible or soluble in your solvent for the extraction to occur
miscible: when two liquids with similar polarity are combined and the liquids mix
solvent extraction
potent agents present only in very low concentrations
poisons
if not properly administered, poisons will not be detected
sample preparations
extraction
first step in sample preparations
in order to separate target substances from possible interferences which may also be present in the sample
purposes of extracting poisons from drugs or specimen
to increase the concentration of the substance comparative to the coextracted matrix (sample or specimen) compounds
purposes of extracting poisons from drugs or specimen
if carried out effectively, extraction will increase the chance of an effective analysis.
purposes of extracting poisons from drugs or specimen
carried out in cases of poisoning involving heavy metals
precipitating agent, sedimentating agent: milk, raw egg, etc
precipitation and sedimentation
usually applied in qualitative detections of drugs of abuse and toxins
chromatography
the presence or absence of drugs of abuse and toxins
qualitative detection
definite concentration/value of drugs of substance
better than qualitative
quantitative detection
part of screening of drugs of abuse/ illicit drugs
central to identifying drugs of abuse
thin-layer chromatography
based on relative affinities of substances for polar solid stationary phase and a nonpolar mobile liquid phase
principle of thin-layer chromatography
equivalent to the distance travelled by the substance you are trying to separate/ distance travelled by the sol
rf = retention factor
best sample for tlc
you can collect a lot of sample in a non-invasive manner
urine
usually collected from patients when the mode of introduction of poison is via ingestion
gastric contents
samples that are not collected from an individual
non-biological samples
sample –> concentration to increase possibility of extracting more –> extraction (basis is whether the substance is acidic (strip1) or basic (strip2) –> separation –> identification
steps in processing sample for tlc
mobile liquid phase = solvent = non polar
solid stationary phase = silica gel strip = polar
point a and b = strip1 and strip2
from point a and b, solvent will migrate towards the end portion of silica gel strip
sample A travelled shorter distance = more polar = affinity is in the polar component = more attracted to solid
sample B travelled farther distance = more nonpolar = affinity is in the nonpolar component = more attracted to mobile liquid phase = has more RF
process in thin-layer chromatography
the gel strips for the separation are dipped into reagents
there will be unique color reaction
characteristic color reaction and RF = basis for identification
in identification during tlc
0.14 rf value
has dark red, purple color reaction
a nonfluorescent substance
morphine
required level for detection in tlc
concentration of toxin/poison that should on the strip
1 ug/mL
inefficient extraction = insufficient concentration of analyte = negative results
major problem
allows quantitative detection of drugs
better than tlc
used for the analysis of tricyclic antidepressants and their metabolites
*absorbance in directly proportional to the concentration of the substance
high-performance liquid chromatography
amitriptyline, imipramine, nortriptyline, desipramine, protriptyline
they are the most commonly prescribed drugs and they are also used in excess as a drug of abuse in cases of suicide attempts
tricyclic antidepressants
gold-standard for the detection and quantitation of volatile drugs and poisons due to high sensitivity and high specificity
*ultimate reference method and confirmatory procedure
gas chromatography - mass spectroscopy
the method is capable of detecting the substance that is supposed to detect
ability to focus on the substance it is supposed to measure
can avoid false positives or false negatives
high specificity
the method can detect at even low concentrations
high sensitivity
the compound/substance are directly heated into gas phase via gas chromatography
then, the metabolites will be measured/quantitated via mass spectroscopy
principle of gas chromatography - mass spectroscopy
volatilized compound is moved by a gas source into column rings which are encased in an oven.
inside the column rings, substances can be separated.
once bombarded with electrons, it will be ionized thus carrying a charge.
the ionized molecule will be passed on to electric quadrupole field.
the quadrupole field serves a a filter. only ions that have narrow range than mass to charge ratios can only pass through
then, the data will now be stored in data acquisition computer
fragmentogram = results shown in the computer , unique for every substance analyzed in the laboratory, fingerprint pattern
principle of gas chromatography - mass spectroscopy
based on the migration of charged solutes or particles in an electrical field
utilized for the detection of illicit drugs/highly addictive/illegal substances
electrophoresis
charged particles migrates toward the opposite charged electrode
- cations = positively charged, attracted to negatively charged or cathode
- anions = negatively charged, attracted to positively charged electrode or anode
migration pattern/rule
net charge
size of particle
shape of particle
characteristic that affect the migration of substances
driving force = electrical power applied on electrophoresis setup
support medium = gel: agarose gel, polyacrylamide gel, starch gel
buffer = to maintain the ionized state of particles
sample
detecting system
5 components of electrophoresis
allows the separation and quantification of chemical substance in a wide variety of complex matrices
capillary electrophoresis
exceptional separating power
rapid analysis
high mass sensitivity
more economical in terms of reagents required, and only requires minimal sample
advantages of capillary electrophoresis
detect gamma-hydroxybutyric acid (GHB): recreational drug known for euphoric effects, rape facilitation drug due to its capacity to reduce inhibitions, doping agent for muscle growth enhancement
3,4-methylenedioxymethampethamine (ECSTASY): recreational drug/club drug
toxins and venoms: they are polypeptide complexes, thus cannot be assayed using GC-MS
ink analysis: in cases of fraud, estafa, tax evasion
gun shot resides and explosives
application of capillary electrophoresis
detect the presence of a drug or several drugs of abuse
*immunoassays/immunochemical methods, TLC
screening test
identify the drug and its concentration
*HPLC, GC-MS
confirmatory test
process that provides documentation of proper sample identification from the time of collection to the receipt of laboratory results
*donor, subject
chain of custody
