8 - The Analysis of Drugs

Question 1

Why would someone be tested for the presence of drugs in their system?

Answer 1

• Medical Reasons – intoxication, over-dose
• Workplace issues – job performance, liability and risk of lawsuit
• Legal system – RTAs, criminal aggravation of another offence
• Drug treatment – therapeutic drug monitoring
• Rehabilitation – abstinence during rehab, methadone compliance

Question 2

Samples which may be analysed for the presence of drugs

Answer 2

Blood
Urine
Saliva
Hair

Question 3

Blood sample

Answer 3

• Invasive – need permission of the person being investigated
• Difficult to add adulterants

Question 4

Urine sample

Answer 4

• Non-invasive – need the co-operation of the person in question
• Adulterants easily added to the sample to invalidate the test e.g. liquid soap, bleach, water from the toilet

Question 5

Saliva sample

Answer 5

• Non-invasive – need the co-operation of the person in question.
• Limited number of analytes accumulate in saliva

Question 6

Hair sample

Answer 6

• Non-invasive – need the co-operation/permission of the person in question.
• Limited number of analytes accumulate in hair

Question 7

Overview of DOA testing

Answer 7

1. Sample taken
2. On-site/Point of Care Screening
3. Confirmatory analysis

Question 8

2. On-site/Point of Care Screening

Answer 8

• Immunoassay based
• Limitations – only gives the class of drug with certainty
• Presence of adulterants

Question 9

Confirmatory analysis

Answer 9

• Chromatography to separate `the compounds

* Spectrometry/Spectroscopy to confirm identity

Question 10

Screening vs Confirmatory testing

Answer 10

On-site or lab-based vs Lab-based testing
Initial test, presumptive vs Definitive
Inexpensive vs Costlier
Quick results vs Delayed results
Sensitive, lacks specificity vs Sensitive and specific
High cut-off limits vs Lower cut-off limits (detect smaller
amounts)
Qualitative, semi-quantitative at best vs Qualitative and Quantitative
Tests for general chemical classes (e.g opiates, benzodiazapines) vs Tests for specific drugs and their metabolites (e.g. oxycodone, oxymorphone, diazepam, oxazepam

Question 11

How do you identify a compound?

Answer 11

There are chemical tests which rely on a reaction with the compound, they can be quick but not always specific.
Identity; Chromatography / Mass Spectrometry / Spectrophotometry infrared
Abundance; Chromatography / Spectrophotometry UV-Vis.

Question 12

Biochip Technology

Answer 12

Randox Biochip Technology
Each Biochip contains arrays of discrete test regions (DTRs) each of which contains a different analyte test.
1 Biochip can produce multiple test results simultaneously.
Up to 49 tests per chip

Question 13

Antibody-based technologies have cross-reactivity issues depending upon the epitope

Answer 13

Antibody-based technologies form the basis of presumptive/screening testing for drugs of abuse.
They are qualitative (semi-quantitative) tests used to detect the possible presence of a drug or drug class

Question 14

Confirmation of compound identity

Answer 14

• In order to get the correct identity of a drug (or metabolite) other analytical methodologies must be used.
• These include:
• Chromatography
• Mass spectrometry
• Infra red spectroscopy
• Hyphenated chromatography e.g GC-MS, HPLC-MS

Question 15

Definition of Chromatography

Answer 15

• Differential distribution of sample components (solute) between 2 phases:
• 1 phase remains fixed (stationary phase)
• 1 phase is moving (mobile phase) – can be liquid, gas or supercritical fluid.
The sample under analysis must be dissolved in this phase
• Separation is based on the differential affinity the solute has for the mobile phase versus the stationary phase

Question 16

Types of Chromatography

Answer 16

• Gas chromatography
• High performance liquid chromatography
• Thin layer/planar chromatography
• Affinity chromatography
• Ion exchange chromatography

Question 17

Thin layer chromatography

Answer 17

• The analytes travel through the stationary-phase with the mobile –phase.
• How far they travel is dependant upon whether they are more attracted to the stationary- or the mobile-phase.

Question 18

TLC of drugs of abuse

Answer 18

The use of different spray reagents give different colours for different analytes.
Detects presence but still need to confirm the identity of the analytes.

Question 19

Gas and High Performance Liquid-Chromatography

Answer 19

provide good resolution.
But, we still cant be certain which peak is which if there is incomplete resolution of analytes !
The answer comes from sending the analyte peaks for mass spectrometry

Question 20

Heroin Metabolism

Answer 20

• Heroin is rapidly metabolised to 6-monoacetylmorphine (6-MAM).
• Heroin enters urine for less than 30 mins as levels in body fall.
• 6-MAM may be found in the urine for up to 24 hours and morphine up to 5 days

Question 21

Similar structures same mass

Answer 21

• Similar structures same mass;
• Naloxone / 6MAM,
• Norcodeine / Morphine,
• Phentermine / Methamphetamine

Question 22

Fragmentation ion signatures

Answer 22

• Similar structures same mass.
• However, they will fragment into parts with different masses.
• The fragmentation profile is distinctive and diagnostic of the parent material.