Application of molecularly imprinted solid phase extraction, enzyme-linked immunosorbent assay and liquid chromatography tandem mass spectrometry to forensic toxicology

Harun, Norlida (2010) Application of molecularly imprinted solid phase extraction, enzyme-linked immunosorbent assay and liquid chromatography tandem mass spectrometry to forensic toxicology. PhD thesis, University of Glasgow.

Abstract

The rapid growth of ketamine and amphetamine misuse worldwide has led to the development of methods for the detection and analysis of ketamine and amphetamines in biological specimens. Most methods previously developed in forensic toxicology for the detection of ketamine and amphetamines used GC-MS. The present work developed alternative methods based on LC-MS/MS. Ketamine was chosen as the drug of interest because there are no data currently available on the extent of ketamine abuse in Malaysia even though a large amount of ketamine has been seized by the Malaysian Royal Police, while amphetamines are the most widely abused synthetic drugs in South East Asia including Malaysia.

The study addressed some of the challenges facing the forensic toxicologist, such as the need to use new technology (LC-MS/MS) and improve sensitivity and selectivity in forensic toxicology analysis through efficient sample preparation techniques. The general requirements of method validation, including as the parameters linearity, limit of detection (LOD) and Lower Limit of Quantification (LLOQ), recovery, precision and matrix effects were observed. Three main techniques were used in the study: enzyme-linked immunosorbent assay (ELISA), liquid chromatography tandem mass spectrometry (LC-MS/MS) and molecularly imprinted polymer solid phase extraction (MISPE). MISPE is a new extraction technique in forensic toxicology applied to biological samples.

Initially work was carried out on the optimization, development and validation of the Neogen® ELISA for screening ketamine and norketamine in urine. The Neogen® ketamine ELISA kit was found to be adequately sensitive and precise for ketamine screening at a cut-off concentration of 25 ng/mL. The ELISA test was shown to be highly specific to ketamine and demonstrated minimal (2.1%) cross-reactivity to its main metabolite norketamine compared to ketamine.

Subsequently, an LC–MS/MS confirmation method for ketamine and norketamine in urine samples was developed and validated with application of the method to urine samples from chronic ketamine users in Malaysia. The method demonstrated good linearity, LOD, LOQ, accuracy and precision and had acceptable matrix effects.
The efficiency of ELISA as a screening method at cut-off of 25 ng/ml and LC-MS/MS as a confirmation method at 2 ng/ml was evaluated. These methods complemented each other and both ELISA and LC-MS methods were 100% sensitive and specific with no false positive results for ketamine and norketamine in urine samples. The results demonstrated that a combination of these two methods can be reliably used for routine screening and confirmation of ketamine and norketamine in urine specimens. Preliminary data from this study provided information on the concentrations of ketamine and norketamine typically found in urine samples collected from individuals frequenting pubs in Malaysia.

The main work in this thesis involved molecularly imprinted polymer materials which were used as sorbents in solid phase extraction (MISPE). Ketamine was used as a model substance for novel in-house synthesised MIPs as no anti-ketamine MIP have previously been reported and because the ketamine structure is suitable for the synthesis of molecularly imprinted polymers. The study was intended to improve the selectivity and sensitivity of the extraction method (MISPE) prior to LC-MS/MS analysis. Evaluation of polymer imprinting was carried out using HPLC-UV.

MIP extraction and LC-MS/MS analysis were applied to the determination of ketamine and norketamine in hair samples and compared with a conventional SPE-based method. MISPE extraction was selective and sensitive with fewer matrix effects than the conventional SPE method and could also be applied to norketamine, the principal metabolite of ketamine, due to the group-selective binding nature of the MIP, but not to structurally dissimilar analytes such as PCP and tiletamine. MISPE was superior to conventional SPE for trace detection of ketamine and norketamine in hair, in terms of improved sensitivity, lower limits of detection and reduced matrix effects.

In addition, the commercial product Amphetamine SupelMIPTM was evaluated for identification of amphetamines in post mortem blood coupled with LC-MS/MS analysis. This work assessed whether the MIP, sold by the manufacturer for the extraction of amphetamines in urine, could also be used for whole blood. The results demonstrated that the MIP can be used successfully for the determination of amphetamines in post mortem blood. The recoveries of five amphetamines were lower than with a comparable GC-MS method but the LODs and LLOQs of the LC-MS/MS method were better and suitable for detection of low levels amphetamines in post mortem blood. Further optimisation is needed to develop an improved protein precipitation method prior to MISPE.

Liquid Chromatography Electro-Spray Ionization Mass Spectrometry (LC–ESI-MS) was used with the MISPE and SPE methods for detection and quantification of ketamine, norketamine and amphetamines in urine, whole blood and hair samples. LC-ESI-MS was found to be easy to use and could detect lower concentrations of drugs and gave reproducible results for all the methods developed in this thesis.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: The author's postgraduate study was sponsored by Ministry of Health, Malaysia.
• Keywords: Ketamine, amphetamines, molecularly imprinting, ELISA, LC-MS/MS, forensic toxicology, hair, whole blood, urine
• Subjects: Q Science > QD Chemistry; R Medicine > RM Therapeutics. Pharmacology
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Cancer Sciences
• Supervisor's Name: Anderson, Dr. Robert A.
• Date of Award: 2010
• Depositing User: Dr Norlida Harun
• Unique ID: glathesis:2010-1992
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 17 Aug 2010
• Last Modified: 10 Dec 2012 13:49
• URI: https://theses.gla.ac.uk/id/eprint/1992