Solid Phase Extraction Techniques for the Analysis of Pesticides and Drugs in Biological Specimens

Asri, Kamarruddin (2001) Solid Phase Extraction Techniques for the Analysis of Pesticides and Drugs in Biological Specimens. PhD thesis, University of Glasgow.

Abstract

The aims of the project were to investigate the potential of solid phase extraction techniques for the detection and quantification of organophosphate pesticides in human biological specimens. Achievement criteria which were applied were that analytical methods should be sufficiently sensitive, specific, robust and cost effective for use in routine forensic toxicology, and, if possible, were inexpensive and within the economic and technical means of laboratories in developing countries. The procedures developed were based on established chromatographic and spectrometric techniques, drawing on analytical methods for environmental samples such as foodstuffs (which resemble target matrices such as autopsy blood and tissue) but also incorporated the more recently available technique of solid phase micro extraction (SPME). The project evaluated the application of these methods to real specimens from forensic cases, which occurred in Malaysia and elsewhere during the course of the study, as the incidence of pesticide poisoning cases in the United Kingdom is very low. The SPME technique was also evaluated for analysis of benzodiazepines in urine. An overview is given of pesticides and organophosphates in particular, with respect to their chemistry, usage, metabolism and biological effects. Problems encountered in sample pretreatment and preparation for analysis are reviewed, with emphasis on techniques, which aim to reduce or avoid the use of environmentally damaging solvents. This review also focuses on the history and theory of SPME. The SPME process has two steps, equilibrium partitioning of analytes between the SPME fibre coating and sample matrix and then transfer of absorbed analytes to the analytical instrument. In step 1, the extraction is considered to be complete after equilibrium is reached, i.e. the stage at which absorption is constant within the limits of experimental error and independent of further increase in extraction time. However, SPME is an equilibrium, but not an exhaustive, extraction. Parameters that contribute to extraction efficiency include sampling time, temperature, pH and ionic strength. Application of SPME under non-equilibrium conditions requires adequate control of these parameters. In the initial method development study, SPME in combination with capillary column gas chromatography and nitrogen-phosphorus detection were evaluated as a method sequence for the analysis of organophosphate pesticides in whole blood and urine. Eleven pesticides were used initially in the study as model compounds representing the range of commonly-used substances and also representing different functional groups found in these phosphates. Two types of fiber were evaluated, with coatings of polydimethylsiloxane (PDMS) or polyacrylate (PA). Parameters affecting the adsorption of analytes on the SPME fibre were examined, including fiber pretreatment, sampling time, temperature, the use of sample agitation, and modification of the ionic strength and pH of the samples. The best conditions for extraction involved a PDMS fiber along with a sample temperature of 90

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Adviser: R A Anderson
• Keywords: Analytical chemistry, Forensic anthropology, Toxicology
• Date of Award: 2001
• Depositing User: Enlighten Team
• Unique ID: glathesis:2001-76096
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 19 Nov 2019 16:40
• Last Modified: 19 Nov 2019 16:40
• URI: https://theses.gla.ac.uk/id/eprint/76096