topic 4 and 6 forensic chem analysis

Question 1

what is a drug?

Answer 1

•Adrugisasubstance,wheningested,iscapable
ofinducingaphysiologicalchange.
•Alldrugsaretoxic.
•Itisthedose thatdifferentiatesatherapeuticdrugfrompoison.

Question 2

what is the difference between drug and medicine?

Answer 2

Medicines are combinations of drugs and inert ingredients. drugs do not have combination on inert materials or stabilizers.

Question 3

what are the 3 categories of drugs? what does each do and give some examples

Answer 3

Drugscanbeabused–‘pleasurableeffects’

Categorised into 3 areas according to impact on the central nervous system (CNS) especially the brain :

(a) Stimulant–stimulates brain activities–Amphetamines (ice), Cocaine
(b) Depressants –inhibits brain activity–Alcohol, Barbiturates (sleeping pills), Heroin, Morphine
(c) Hallucinogens–Changes perception and mood (without either stimulating or inhibiting brain activity)-causes hallucinations–Ecstasy, Lysergic acid diethylamide (LSD), Cannabis (mild effect)

Question 4

what are the 4 legal uses of morphine?

Answer 4

• general anesthesia, epidural ansesthesia
• palliative care–alleviate pain without caring
• antitussive for severe cough
• antidiarrheal e.g in aids

Question 5

what is the difference between morphine vs aspirin? why is morphine addictive?

Answer 5

•Aspirinreducespainbyinhibitingthepain inducingevent,
whereasmorphineinterceptsthepainsignalafteritisproduced.
•Aspirinstopsinflammationandpain,butitdoesnotproduceeuphoria.

Question 6

explain the use of Fourier transformInfraredSpectroscopy. what can it be used to identify?

Answer 6

• Analysethestructuresoforganicandinorganiccompounds
• Organicfunctionalgroupswithreferencetocorrelationtable.
• Identify powdereddrugs.

Question 7

explain the use of chromatography? what can it be used to determine?

Answer 7

Drugssubmittedtolaboratoriesareroutinelyexaminedbychromatography todeterminetheirnature andpurity.

Question 8

what is GC used for? what type of samples can be analysed using GC?

Answer 8

separationandanalysisofvolatileorganiccompounds(VOCs).

TypeofsamplesthatcanbeanalysedbyGC: •volatile,lowboilingpoint(lowmolecularweight) •thermallystableunderGCoperatingtemperatures

Question 9

what is HPLC? why does it compliment GC?

Answer 9

HighperformanceLiquidChromatography is a separationtechnique thatusesaliquidmobilephase.

itallowsnon‐volatile,and/or thermallyunstable compoundstobeanalysed.
e.g Highmolecularweightorganiccompounds, Pharmaceuticalcompounds, Hormones

LChaswiderapplicationascomparedtoGCtechnique.

Question 10

what is thin layer chromatography used for ? what surface is the technique carried out on?

Answer 10

initialscreeningtechniquetoscreenmostofthedrugsabuse.

Fast,providesrapididentificationaftertheillicitdrugswasseizedbylaw enforcementagencies.

TLCiscarriedoutonaglassplateorothersupportivebackingcoatedwithasolidphase.

Question 11

what is the retention factor used in TLC? (Rf value)

Answer 11

TheRf valueofacompoundisequaltothedistancetravelledbythecompounddividedbythedistancetraveledbythesolventfront
Rf value: x/y
Xisthedistancefromthespottotheorigin. Yisthedistanceofthesolventfronttravelsfromtheorigin.

Question 12

what can IonSelectiveElectrode(ISE) be used for?

Answer 12

ISEcanbeusedtodeterminetheconcentrations ofthefollowingionsinforensicsamples:
cations:
Ammonium(NH4+),Barium(Ba2+),Calcium(Ca2+),Cadmium(Cd2+),Copper(Cu2+),Lead(Pb2+),Mercury(Hg2+),Potassium(K+),Sodium(Na+),Silver(Ag+),Hydrogen(H+)
Anions:
Bromide(Br‐),Carbonate(CO3‐),Chloride(Cl‐),Cyanide(CN‐),Fluoride(F‐),Iodide(I‐),Nitrate(NO3),Nitrite(NO2‐),Perchlorate(ClO4‐),Sulphide(S‐),Thiocyanate(SCN‐),andCyanide(CN‐)

Question 13

what are the 3 types of active materials used in ISE?

Answer 13

1. Glass–pHmeasurement
2. Insolubleinorganicsalts
3. Long‐chainion‐exchangematerials

Question 14

how does gas sensors operate? what does it do?

Answer 14

•Incorporateaconventionalion‐selectiveelectrode
•Real‐timemonitoringofgases–e.g.CO2,O2andNH3
greatimportanceinmanypracticalenvironmental,clinicalandindustrialsituations

Question 15

what are the advantages and disadvantages of gas sensors?

Answer 15

Advantages:
•Non‐destructive
•Fast
•real‐timemonitoring
•Suitableforsingleelemental/gasanalysis
•Cheapercomparedtospectroscopyinstruments.

Disadvantages:
•Lesssensitive
•Interferenceduetopresentofothersionsinsamples.

Question 16

what is spectroscopy? what kind of process is it?

Answer 16

• interactionbetweenelectromagneticradiationandmatter.

* Excitation oremission process.

Question 17

what are the advantages and disadvantages of atomic absorption spectrometer (AAS)

Answer 17

advantages:
•Fast(singeelement)
•Sensitive(ppm–ppb) 
•Smallsamplesize 
•Qualitative&Quantitative analysis

disadvantages:
•Destructive
•Lowersamplethroughput compared to AESi.e.multiple elementsanalysis

Question 18

what are the advantages and disadvantages of atomic emission spectrometer (AES)

Answer 18

advantages:
•Fast(multipleelements)
•Sensitive(ppm–ppb) 
•Smallsamplesize 
•Highersamplethroughputi.e. multiple elementsanalysis 
•Qualitative&Quantitative analysis

disadvantage:
•Destructive
•Spectralinterference.

Question 19

what is ScanningElectronMicroscope(SEM)? what is its operating principal?

Answer 19

•Non‐destructive,qualitativeanalysis.
•Imagesthesamplesurfacebyscanningitwithahigh energybeamofelectronsinarasterscanpattern •Electronsinteractwiththeatomsthatmakeupthesampleproducing
signalsthatcontaininformationaboutthesample’ssurface
topography,composition etc.

Question 20

what is SEM‐EnergydispersiveX‐RaySpectroscopy(SEM‐EDX) ?

Answer 20

SEM can coupled with EnergydispersiveX‐RaySpectroscopy(EDX)
toprovidebothsurfacetopographyinformation(elementalidentification,qualitative)
andquantitativecompositionalinformation. •Non‐destructivetechnique.

Question 21

what is NeutronActivationAnalysis(NAA)? what is its advantage?

Answer 21

Thismethodrequiresirradiationofthesamplewithneutronsthat
transformtheelementsintoradioactiveisotopes.
•Non‐destructive
•Qualitative&quantitative
•Multi‐elementanalysissimultaneously
•Superioraccuracyandsensitivity

Question 22

what are the disadvantages of NAA?

Answer 22

• Slow
• Expensive
• Requiresanuclearreactor
• Radioactivewastedisposalsystem

Question 23

what are the two categories of NAA?

Answer 23

Inprinciple,therefore,withrespecttothetimeofmeasurement,NAAfallsintotwocategories:

PGNAA(Promptgamma‐rayneutronactivationanalysis)
–Measurementstakeplaceduringirradiation
‘de‐excite’intoamorestableconfigurationthroughtheemissionofcharacteristicgammaray.

•DGNAA(Delayedgamma‐rayneutronactivationanalysis)
Radioactivenucleus‘de‐excites’byemittingacharacteristicdelayedgammaray(ataslowerrateaccordingtotheuniquehalf‐lifeoftheradioactivenucleus.)
Measurementsfollowradioactivedecay(slowerrate)
Morecommonmode;thus,whenonementionsNAAitisgenerallyassumedthatmeasurementofthedelayedgammaraysisintended.
–About70%oftheelementshavepropertiessuitableformeasurementbyNAA.
•non-destructive
•slow
•requires a nuclear reactor
•bulk analysis