4 research outputs found
Enzymatic digestion and selective quantification of underivatised [delta]9-tetrahydrocannabinol and cocaine in human hair using gas chromatography-mass spectrometry.
Gas chromatography-mass spectrometric (GC-MS) methods for drug analysis routinely employ derivatising reagents. The aim of this paper was to develop a method for the analysis of two recreational drugs, delta-9-tetrahydrocannabinol ([delta](9)-THC) and cocaine in hair samples using GC-MS, without prior derivatisation, thus allowing the sample to be reanalysed in its original form. An enzymatic digestion technique was also developed. Ten hair samples, that were known positive for either [delta](9)-THC and/or cocaine, were enzymatically digested, extracted, and then analysed by GC-MS. All samples measured contained [delta](9)-THC and one sample contained cocaine. The limits of detection (LOD) and quantification (LOQ) were 0.02 ng/mg and 0.05 ng/mg, respectively, for cocaine and 0.015 ng/mg and 0.02 ng/mg, respectively, for [delta](9)-THC. The wide detection window, ease of direct analysis by GC-MS, lower detection limits of underivatised samples, and the stability of drugs using this technique may offer an improved method of analysis
Development of methods to determine analytes in a variety of matrices with applications to forensic science
This thesis comprises of studies based on the broad field of forensic analysis and the
development of methods which can be applied to different matrices. The initial
studies focus on the forensic determination of psychoactive drugs in hair matrix
using newly deve1oped gas chromatography-mass spectrometry analytical methods.
The second study focuses on the discrimination and matching of skid marks and
rubber tyre analysis by using novel chemical analysis methods. This thesis reports
the deve1opment and application of a series of innovative analytical methods: gas
chromatography-mass spectrometry, inductively coupled plasma mass spectrometry,
pyrolysis-gas chromatography-mass spectrometry and attenuated total reflection
Fourier transform infrared spectroscopy.
Gas Chromatography-Mass Spectrometric (GC-MS) methods for drug analysis
routinely employ derivatising reagents. The aim of the first study was to develop a
method for the analysis of two recreational drugs, delta-9-tetrahydrocannabinol (delta-9-
THC) and cocaine in hair samples using GC-MS, without prior derivatisation, thus
allowing the sample to be analysed in its original form. Ten hair samples, that were
positive to ELISA analysis for either delta 9-THC and/or cocaine, were enzymatically
digested, extracted and then analysed by gas chromatography-mass spectrometry.
All samples measured contained delta 9-THC and one sample contained cocaine. The
limits of detection (LOD) and quantification (LOQ) were 0.02 ng/mg & 0.05 rig/mg,
respectively for cocaine and 0.015 ng/mg & 0.02 ng/mg, respectively for A9-THC.
The wide detection window, ease of direct analysis by GC-MS, lower detection
limits of un-derivatised samples and the stability of drugs using this technique offers
an improved method of analysis.
This experiment has been designed to develop an immunological screening test
followed by a GC-MS confirmation method for the simultaneous analysis of delta 9-
THC, THC-COOH, , OH-THC, cocaine, Benzoylecgonine (BZ), amphetamine (AP),
methamphetamine (MA), in human hair, thus avoiding the significant factors
responsible for drug degradation by acid and alkali hydrolysis and to obtain optimal
recovery conditions. Enzymatic hair digestion was used to hydrolyse 18 Turkish samples using Proteinase K, Dithiothreitol and Tris HCl buffer. At the beginning, all
18 samples tested screened positive on ELISA, though analysis by GC-MS indicated
that only 2 samples were positive for delta 9-THC and THC-COOH. Cross reaction lead
to false positive results in the pre-screening step as a result of the degradation of the
antibodies in the pre-coated ELISA microplate.
Tyre rubber analysis
Owing to an increase in the number of hit and run accidents, it is quite common for
rubber traces to be left at the crime scene. The Forensic Scientist will have the task
of analysing the tyre striation traces in order to identify the type of tyre involved in
the accident. However, the tyre striations alone do not provide enough detail to show
a high level of discrimination between different tyre manufacturers and individual
models. In this study, Inductively Coupled Plasma Mass Spectrometry (ICP-MS),
Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FI‘IR)
and pyrolysis GC-MS methods were developed to enable greater discrimination
between different tyre rubber samples.
Seventy elements were screened for each sample by ICP-MS in both collision cell
mode and reaction cell mode. ATR-FTIR analysis indicated a low intra-variability
(analysis of similar tyres) which demonstrated high precision of the technique, and
also showed a large inter-variability between different manufacturers and models,
which supports their high potential as indicators to be used for discrimination
between different tyres manufacturers and models. Principal Component Analysis
(PCA) was utilised to distinguish between the different tyres