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drugs of abuse > presumptive tests > Flashcards

presumptive tests Flashcards

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
Q

mixing and sampling

A

Opposite quarters are combined to give half the sample, and the process is repeated until a suitable sample size is obtained.

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26
Q

distribution heterogeneity

A

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.

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27
Q

constitution heterogeneity

A

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

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28
Q

how do sampling errors occur

A

• Arise from differences in composition of particles of the material and from the segregation of different particles

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29
Q

homogenisation of the whole material reduces the sampling error

A

Normally by mortars and pestles

Very impractical for larger seizures

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30
Q

why do labs take a portion from the bulk material as primary sample?

A

Taking only one portion (increment) from one place of the bulk material can generate error

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31
Q

taking several increments from different spatial positions can reduce error

A

The smaller the size of the increments the greater the error arising from particulate structure and ‘microscopic’ heterogeneity of the material

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32
Q

name 4 hallucinogens

A

LSD
Ectasy
magic mushrooms
cannabis

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33
Q

physical examination LSD

A

LSD is commonly applied to a substrate

Paper dosage units – blotting paper

Small tablets

Microdots

Gelatin forms

Normal dosage: 30-100 mg of LSD

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34
Q

sampling -LSD

A

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

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35
Q

what is a presumptive test for LSD

A

ehrlich reagent

36
Q

ehrlich reagent

A

1g p-dimethylaminobenzaldehyde in 50 mL ethanol and 50mL concentrated hydrochloric acid

37
Q

what colour shows a positive of LSD with ehrlich reagent

A

grey/violet

38
Q

problem with ehrlich reagent - LSD

A

difficult to conduct in field due to small quantities of drug normally present

39
Q

TLC analysis LSD

A

Using chloroform and methanol mixtures as solvent (mobile phase)

Spray with Ehrlich reagent when finished

40
Q

TLC visualisation LSD

A

Visualise TLC plate under UV light

  • 254nm: dark spots on fluorescent background
  • 365nm: fluorescent spots and black background
41
Q

what is a preemptive test for opiates

A

marquis test

42
Q

marquis reagent

A

5 mL 40% formaldehyde in 100 mL conc. sulphuric acid

43
Q

what colour occurs when morphine or diamorphine is present in marquis reagent

A

red/purple

44
Q

what colour occurs when codeine is present in marquis reagent

A

blue/purple

45
Q

what colour occurs with fentanyl is present in marquis reagent

A

yellow-orange

46
Q

what happens when heroin is present in marquis reagent

A

Crystal formations in sodium acetate compared with heroin crystals in mercuric iodide

47
Q

melting point of morphine

A

254-256 degrees

48
Q

melting point of codeine hydrochloride

A

280 degrees

49
Q

melting point of heroin

A

173 degrees

50
Q

magic mushrooms

A

Blue Bruising (feature of psilocybin-containing mushrooms)

Microscopy

Scanning electron microscopy

  • Marquis reagent
  • Ehrlich reagent

Thin Layer Chromatography

DNA

51
Q

name 5 sedatives

A 
cannabis
barbiturates
alcohol
solvents
tranquillisers
52
Q

physical examination - cannabis

A

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
Q

what is a presumptive test for cannabis

A

duquenois - levine test

54
Q

what are the 3 solvents in duquenois - levine test - cannabis

A

Solvent A – 2g vanillin, 2.5mL acetaldehyde in 100mL ethanol

Solvent B – conc HCl

Solvent C – Chloroform

55
Q

what colour does cannabis go in the duquenois -levine test

A

purple

56
Q

TLC - cannabis

A

cannabinoids are extracted from plant material or resin

Plate of silica gel eluted with toluene or xylene:hexane: dimethaylamine (25:10:1)

57
Q

cannabinol - TLC

A

orange colour when treated with Fast Blue (fluorescent dye)

58
Q

cannabinol - TLC

A

violet colour when treated with Fast Blue

59
Q

Δ9-THC - TLC

A

red colour when treated with Fast Blue

60
Q

how are barbiturates normally found

A

normally pills

free acid or salt

61
Q

physical examination fo alcohol

A

smell

62
Q

physical examination of tranquillisers

A

manufacturers marking

63
Q

how are barbiturates tested

A

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
Q

what is the presumptive test for barbiturates

A

dille-koppanyi test

65
Q

dille-koppanyi test - barbiturates

A

1% cobalt acetate in methanol (added to the suspected material)

5% isopropylamine in methanol

66
Q

what colour do barbiturates go in the dille-koppanyi test

A

blue

67
Q

barbiturates - TLC

A

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
Q

tranquillisers - TLC

A

silica gel plate eluted with range of different solvent systems

E.g. chloroform:methanol (90:10)

69
Q

give 4 examples of stimulants

A

Amphetamine

Cocaine

Caffeine

Tobacco (nicotine)

70
Q

physical examination - amphetamine

A

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
Q

what are the 4 presumptive tests for amphetamines

A

marquis test

ninhydrin reagent

simons reagent

microcrystalline test to differentiate between optical isomers

72
Q

marquis test - amphetamine colour

A

positive immediate orange but turning brown

73
Q

ninhydrin reagent - amphetamine

A

used to detect primary and secondary amines

amphetamine is a primary amine

74
Q

ninhydrin reagent - amphetamine colour

A

pinkish orange with heating

75
Q

what does simons reagent react with

A

amines

76
Q

what two solutions are involved in simons reagent

A

Solution A: 1g nitroprusside in 50mL distilled water and 2ml acetaldehyde

Solution B: 2% sodium carbonate in distilled water

77
Q

simons reagent - amphetamine colour

A

blue colour for secondary amines

78
Q

what can give false positives in simons reagent for amphetamines

A

cutting agents

79
Q

microcrystalline test to differentiate between optical isomers (enantiomers)

A

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
Q

what is a presumptive test for cocaine

A

scott test

81
Q

3 solutions of scott test

A
  • 2% cobalt tiocyanate in 1:1 water:glycerine (Solution A)
  • Conc HCl (Solution B)
  • Chloroform (Solution C)
82
Q

scott test -cocaine colour

A

blue

Blue when adding A, pink when adding B and then blue again when add C.

83
Q

melting point of cocaine

A

96-98 degrees

84
Q

melting point of amphetamine phosphate

A

150 degrees

85
Q

melting point for amphetamine sulphate

A

300 degrees

drugs of abuse (11 decks)

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