An evaluation of analytical procedures for detection of drug abuse with particular reference to opiates.

The results of a pre-employment drug screening programme for amphetamines, barbiturates, benzodiazepines, cannabinoids, cocaine and opiates involving some 1400 subjects by enzyme immunoassay, carried out by the author, are reported. The corresponding confirmatory tests by GC-MS on samples screening positive by immunoassay are also reported. Deficiencies in the immunoassay screen used resulted in a high proportion of false positive being identified. These are discussed in the text and solutions detailed in the cases of cannabis and amphetamines. For opiate testing, used to detect consumption of heroin, it is established that several generally obtainable and legal opiates are detected by immunoassay and require time consuming and expensive confirmation or elimination by GC-MS techniques. The established techniques of TLC and GC with FID detection were optimised and evaluated in this context. In the case of the opiates it is considered that an intermediate test subsequent to an initial immunoassay screen would be advantageous in the elimination of legal opiates and thus obviate the need for confirmation by GC-MS. These techniques for the set of opiates investigated (morphine, codeine, dihydrocodeine, pholcodine, heroin and 6-monoacetylmorphine) were found to be inadequate in terms of resolution and to have detection limits well above that of immunoassay and above the cut-off specified by the regulatory bodies such as NIDA. Two methods depending on liquid chromatography are developed as potential intermediate tests, each involving solid phase extraction pre-treatment. It is found that complete resolution of all components can be obtained on a reverse phase system incorporating both pairing-ion and organic counter-ions when applied to aqueous standards. It is shown that unremoved endogenous compounds prevent the detection of early eluting components since they merge with the solvent front at the absorbance ranges required. Similar resolution among individual components can be obtained with a normal phase system and in addition all components can be detected and quantified in a urine matrix. Results from experiments to link this normal phase LC method with a mass spectrometer via a particle beam interface are reported and results shown of identification achieved. A method based on free zone capillary electrophoresis and solid phase extraction is developed and reported. This is shown to be capable of resolving all compounds in the set and of quantifying these at levels well below the legal cut-off for opiates of 300ngcm-3. This is shown to be a result of the use of electrokinetic sample injection and comparisons are made of the alternative injection modes with respect to sensitivity and precision. Using urine samples obtained from volunteers following consumption of legal opiates and also samples from the original screening programme, it is shown that both the normal phase LC method and the method based on CE yield drug concentration values consistent with those obtained by the preliminary Emit immunoassay testing in this laboratory, with results from GC-MS measurements and with each other.

Grantor dc:publisher.institution

Robert Gordon University

Year dc:date.issued

1998

Author dc:creator

• Low, Ann Stewart

Advisor dc:contributor.advisor

• R.B. Taylor, R.G. Reid and D.G. Durham

• Pre-employment drug screening
• Immunoassay
• Drug detection
• Analytical sensitivity
• Method optimisation
• Opiates
• Amphetamines
• Cannabinoids
• Barbiturates
• Benzodiazepines
• Cocaine

Language dc:language

en

Identifier

oai:rgu-repository.worktribe.com:2807463
https://doi.org/10.48526/rgu-wt-2807463

OAI identifier oai:identifier

oai:rgu-repository.worktribe.com:2807463