Drug analysis (2)

what does the analysis of drugs include?

1. preparation of analytical space
2. physical examination
3. sampling protocol

what are the different analytical techniques?

a.Presumptive testing

b.Thin Layer Chromatography (TLC)

c.High Performance Liquid Chromatography (HPLC) and MS

d.Gas Chromatography (GC) with either FID or MS

e.Fourier Transform Infrared Spectroscopy (FTIR)

f.Ultraviolet – Visible spectroscopy (UV-Vis)

How should your analytical space be prepped?

* benches are washed down with a detergent, dried, and then swabbed with methanol, and the swabs retained for analysis if required
* fresh bench covering each time
* sample packages open individually and bench is cleaned as described between subsequent packages
* frequent changes of gloves, detailed notes

what does the nature of the sample dictate?

the types of analysis which will be undertaken

what do all items need?

full description ( color, smell,logos, marks, packaging)

microscopic examination ( crystals,solids, structure of tablets)

trace samples

1\.Very small sample size, barely visible.

2\.Repetitive analyses will be limited.

3\.Confirmatory testing is required.

bulk samples

1\.Many different sampling protocols (generally developed “in house”).

2\.Sampling by attributes – same morphology.

3\.Never sample from an area that might compromise other evidence (physical fit between resin blocks).

Ensure **homogeneity**

what are the different methods for homogenization?

1. cone and square method
2. shaking in plastic/nylon bag
3. blending

cone and square method

* Sample is ground up & poured onto a flat surface.
* Flattened and divided into quarters at right angles.
* A quarter is chosen and the process is repeated until sample size is sufficient.

shaking in plastic or nylon bag

* Whole sample is placed into a bag and shaken to mix.
* Larger particles may fall to the bottom of the bag.
* Particles can adhere to the sides of the container because of charge differences

Blending

* The sample is placed into blender and mixed mechanically.
* Very effective method.
* Important to ensure the blender is completely clean between samples.

single package material

material should be removed from all packing and weighted to a constant dry weight

more than one package sampling

material in each package should be examined by eye for differences

* statistics : hypergeometric mean
* v

what is the sampling guideline for tablets?

v1-50 doses – sample half (up to 20)

v51-100 doses – sample 20

v101-1000 doses – sample 30

v>1000 doses – sample √N

sampling liquids

* if the liquid is all in one phase, then a sample of the liquid is removed for testing.
* If more than one phase present, then a sample of each phase should be removed for testing.

what is presumptive testing?

make use of a target chemical to establish the possibility that a specific drug is present

establishes:

* the sample is definitely not a certain substance
* the sample probably is the substance

How do you do a presumptive color test?

* Tests are normally carried out on porcelain tiles and include the use of negative and positive control samples.
* Tests indicate the ***drug class*** only and are

  __**not**__ confirmation of identify.

* Results are recorded immediately after

  addition of test solutions, after 5 mins

  and after 10-15 mins.

* Always leave a blank tile between samples and standards.

what are the advantages of presumptive color tests?

1\.Cheap, quick and easy to use.

2\.Portable – various “road side tests” have been designed.

what are the disadvantages of presumptive color tests?

1\.Colors formed are subjective.

2\.May change over time.

3\.\* May be produced by more than one drug compound or non-controlled substances.

4\.Limited sensitivity.

5\.Not suitable for trace samples.

what is high performance liquid chromatography used for ?

mainy for quantification, not much for profiling, some exceptions

what is gas chromatography and gc/ms used for ?

quantification and drug profiling

what is FTIR used for ?

generally identification, for pure compounds

what is ultraviolet-visible spectroscopy used for ?

generally identification, for pure compounds

HPLC analysis : mobile phase

choice of mobile phase depends on the class of drugs

* most acidic or basic so mobile phase which suppresses ions needs to be able to alter pH

why does the mobile phase need to be filtered to less than 2µm?

to prevent particles from blocking the HPLC system or damaging it

which drugs need reverse phase HPLC?

barbiturates

cannabinoids

cocaine

amphetamine

what drugs use normal phase HPLC ?

opiates

advantages of HPLC

1\.It is nondestructive.

2\.The analyte does not need to be volatile.

3\.Generally, does not require pretreatment such as chemical derivatization.

4\.Analysis can be automated.

5\.Quantification can be achieved without and internal standard.

disadvantages of HPLC

1\.Sample needs to possess chromophores for UV or DAD detection.

2\.Sample needs to be soluble in a wide range of solvents.

3\.Quantification can be slow.

4\.Large volume of solvents are used.

what are advantages GC has over HPLC

* GC system has a greater resolving power than HPLC system.
* GC does not have the same problems associated with mobile phase choice.
* GC doesn’t require large volumes of solvents.
* GC does require the compound to be thermally stable, volatile and exhibit good chromatographic qualities.

This often requires **derivatization** of the compounds

what drug compounds do not chromatography well using GC?

barbiturates, benzodiazepines, ecgonine alkaloid ( except cocaine), cannabinoids ( thermally unstable)

what does derivatization do?

modify the chemical structure of the analytes of interest

N,O-bistrimethylsilylicacid (BSA) if a derivatizing agent of what compound?

cannabinoids

opiates

cocaine analogues

N,O-Bistrimethylsilytrifluoroacetamide (BSTFA) is a derivatizing agent of what compound?

LSD and Psilocybin

Trifluroacetic anhydride (TFAA) &

Heptaflurobutyrianhydride (HFBA) are derivatizing agents of what compound?

amphetamines

Gm- MS

* Generally used in drug profiling.
* Minor constituents are linked to major ones in an attempt to link common sources.
* Court requires **two independent** analytical techniques and GC-MS counts as two.
* TLC & presumptive testing do not count.

how are results expressed?

a percentage of analyste salt present in the powder sample

what is the more correct way to expressed results?

percentage of free base in the original powder

what is the other form of Diamorphine, Morphine and Codeine

hydrochloride salts

cocaine can be either free base of hydrochloride salt