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presumptive tests Flashcards

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1
Q

brief

A

a chemical solution that reacts with a specific chemical or functional group

Reaction results in a visual colour change

If reaction positive, then follow up is required

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2
Q

drugs

A

Usually colorimetric

If drug present, a colour is observed; if not present another colour is observed

Indicative and only qualitative

Followed by confirmatory analysis in lab – quantitative results

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3
Q

what colour is a positive of amphetamine in the marquis test?

A

orange - brown

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4
Q

what colour is a positive of aspirin in the marquis test?

A

pink

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5
Q

what colour is a positive of codeine in the marquis test?

A

purple

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6
Q

what colour is a positive of diphenhydramine in the marquis test?

A

yellow

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7
Q

what colour is a positive of fentanyl in the marquis test?

A

orange

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8
Q

what colour is a positive of heroin in the marquis test?

A

purple

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9
Q

what colour is a positive of meperidine in the marquis test?

A

orange

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10
Q

what colour is a positive of methamphetamine in the marquis test?

A

orange - brown

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11
Q

what colour is a positive of morphine in the marquis test?

A

purple

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12
Q

what colour is a positive of opium in the marquis test?

A

purple

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13
Q

what colour is a positive of propoxyphene in the marquis test?

A

black

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14
Q

what colour is a positive of psilocybin in the marquis test?

A

yellow

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15
Q

3 advantages of presumptive tests

A

simple
cheap
sensitive

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16
Q

3 disadvantages of presumptive tests

A

not specific
false positives
false negatives

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17
Q

2 advantages of confirmatory tests

A

definite answer

specific

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18
Q

3 disadvantages of confirmatory tests

A

less sensitive
costly
errors can still occur

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19
Q

give 3 areas in forensic science where presumptive and confirmatory tests are employed?

A

Body fluids
Drugs of abuse
Explosives

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20
Q

microcrystalline tests - analysis of drugs

A

Used to identify specific drug substances by studying the size and shape of crystals formed when the drug is mixed with specific reagents

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21
Q

thin layer chromatography - analysis of drugs

A

Separation technique that uses the solubility and physical properties of the controlled substance to separate compounds

Multiple samples and standards can be spotted on the same TLC plate and the results of the separation compared

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22
Q

how do you work out the Rf value in TLC

A

distance from origin to centre of spot / distance from origin to solvent front

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23
Q

what are the 5 steps of analysis of drugs scheme

A 
Physical examination
Sampling and extraction
Presumptive tests
Preparation of evidence for analysis
Bench and instrumental analysis
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24
Q

what are the two types of material heterogeneities which will influence the sampling of illicit drugs

A

distribution heterogeneity

constitution heterogeneity

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25
mixing and sampling
Opposite quarters are combined to give half the sample, and the process is repeated until a suitable sample size is obtained.
26
distribution heterogeneity
Differences in how the pieces (fragments, particles or molecules) are distributed spatially - How well mixed or segregated the material is due to density, particle size and other factors Different pieces of material make different contributions to the average concentration - E.g. THC concentration in cannabis plants will differ between bud, leaves, stalk etc.
27
constitution heterogeneity
Differences in the constitution of the material - How alike or different the individual particles or molecules are For solids – variation between individual fragments or particles For liquids and gases – individual molecules
28
how do sampling errors occur
• Arise from differences in composition of particles of the material and from the segregation of different particles
29
homogenisation of the whole material reduces the sampling error
Normally by mortars and pestles Very impractical for larger seizures
30
why do labs take a portion from the bulk material as primary sample?
Taking only one portion (increment) from one place of the bulk material can generate error
31
taking several increments from different spatial positions can reduce error
The smaller the size of the increments the greater the error arising from particulate structure and ‘microscopic’ heterogeneity of the material
32
name 4 hallucinogens
LSD Ectasy magic mushrooms cannabis
33
physical examination LSD
LSD is commonly applied to a substrate Paper dosage units – blotting paper Small tablets Microdots Gelatin forms Normal dosage: 30-100 mg of LSD
34
sampling -LSD
Samples must represent the bulk of the material - Statistical or non-statistical May be necessary to perform assays on two separate samples - Instead of combining and pooling If prepared separately, wide variations in dosage often occurs
35
what is a presumptive test for LSD
ehrlich reagent
36
ehrlich reagent
1g p-dimethylaminobenzaldehyde in 50 mL ethanol and 50mL concentrated hydrochloric acid
37
what colour shows a positive of LSD with ehrlich reagent
grey/violet
38
problem with ehrlich reagent - LSD
difficult to conduct in field due to small quantities of drug normally present
39
TLC analysis LSD
Using chloroform and methanol mixtures as solvent (mobile phase) Spray with Ehrlich reagent when finished
40
TLC visualisation LSD
Visualise TLC plate under UV light - 254nm: dark spots on fluorescent background - 365nm: fluorescent spots and black background
41
what is a preemptive test for opiates
marquis test
42
marquis reagent
5 mL 40% formaldehyde in 100 mL conc. sulphuric acid
43
what colour occurs when morphine or diamorphine is present in marquis reagent
red/purple
44
what colour occurs when codeine is present in marquis reagent
blue/purple
45
what colour occurs with fentanyl is present in marquis reagent
yellow-orange
46
what happens when heroin is present in marquis reagent
Crystal formations in sodium acetate compared with heroin crystals in mercuric iodide
47
melting point of morphine
254-256 degrees
48
melting point of codeine hydrochloride
280 degrees
49
melting point of heroin
173 degrees
50
magic mushrooms
Blue Bruising (feature of psilocybin-containing mushrooms) Microscopy Scanning electron microscopy - Marquis reagent - Ehrlich reagent Thin Layer Chromatography DNA
51
name 5 sedatives
``` cannabis barbiturates alcohol solvents tranquillisers ```
52
physical examination - cannabis
Microscopic analysis to look at characteristic Short hairs (cystolythic) – upper side of leaf Trichomes – non-glandular hairs on the underside of the leaves Other features relate to male and female parts of the plant and flowers
53
what is a presumptive test for cannabis
duquenois - levine test
54
what are the 3 solvents in duquenois - levine test - cannabis
Solvent A – 2g vanillin, 2.5mL acetaldehyde in 100mL ethanol Solvent B – conc HCl Solvent C – Chloroform
55
what colour does cannabis go in the duquenois -levine test
purple
56
TLC - cannabis
cannabinoids are extracted from plant material or resin Plate of silica gel eluted with toluene or xylene:hexane: dimethaylamine (25:10:1)
57
cannabinol - TLC
orange colour when treated with Fast Blue (fluorescent dye)
58
cannabinol - TLC
violet colour when treated with Fast Blue
59
Δ9-THC - TLC
red colour when treated with Fast Blue
60
how are barbiturates normally found
normally pills free acid or salt
61
physical examination fo alcohol
smell
62
physical examination of tranquillisers
manufacturers marking
63
how are barbiturates tested
Test bulk powder (crushed pills) by examining solubility in water and ethyl acetate Free acids are soluble in organic solvent (ethyl acetate) but not in water Determine pH in water when pill is dissolved pH 8 or more indicates that barbiturates are present as sodium or calcium salt
64
what is the presumptive test for barbiturates
dille-koppanyi test
65
dille-koppanyi test - barbiturates
1% cobalt acetate in methanol (added to the suspected material) 5% isopropylamine in methanol
66
what colour do barbiturates go in the dille-koppanyi test
blue
67
barbiturates - TLC
silica gel plate eluted with isopropyl alcohol and chloroform:acetone mix (4:1) TLC plate developed using a range of reagents to identify individual components 10% NaOH solution sprayed on plate and heated to 1000C for 5 minutes When fluorescein is sprayed on – pink spots for bromobarbiturates
68
tranquillisers - TLC
silica gel plate eluted with range of different solvent systems E.g. chloroform:methanol (90:10)
69
give 4 examples of stimulants
Amphetamine Cocaine Caffeine Tobacco (nicotine)
70
physical examination - amphetamine
Amphetamine is normally found as powders Salts are usually amphetamine sulphates, phosphate or methamphetamine hydrochloride These can be identified from their crystal size and colour - Range from white to dark brown/red
71
what are the 4 presumptive tests for amphetamines
marquis test ninhydrin reagent simons reagent microcrystalline test to differentiate between optical isomers
72
marquis test - amphetamine colour
positive immediate orange but turning brown
73
ninhydrin reagent - amphetamine
used to detect primary and secondary amines amphetamine is a primary amine
74
ninhydrin reagent - amphetamine colour
pinkish orange with heating
75
what does simons reagent react with
amines
76
what two solutions are involved in simons reagent
Solution A: 1g nitroprusside in 50mL distilled water and 2ml acetaldehyde Solution B: 2% sodium carbonate in distilled water
77
simons reagent - amphetamine colour
blue colour for secondary amines
78
what can give false positives in simons reagent for amphetamines
cutting agents
79
microcrystalline test to differentiate between optical isomers (enantiomers)
5% HAuCl4 in H3PO4 with 5% NaOH Use the ‘hanging drop’ technique Reagent crystals with amine vapour to form yellow rod-like crystals for d- and l- forms Forms oily drops and plate crystals for d-amphetamine
80
what is a presumptive test for cocaine
scott test
81
3 solutions of scott test
- 2% cobalt tiocyanate in 1:1 water:glycerine (Solution A) - Conc HCl (Solution B) - Chloroform (Solution C)
82
scott test -cocaine colour
blue Blue when adding A, pink when adding B and then blue again when add C.
83
melting point of cocaine
96-98 degrees
84
melting point of amphetamine phosphate
150 degrees
85
melting point for amphetamine sulphate
300 degrees

drugs of abuse (11 decks)

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