Rilievo di sostanze esogene o xenobiotiche in matrici biologiche alternative quali peli e capelli
Tesi di Dottorato
Data di Pubblicazione:
2007
Citazione:
Rilievo di sostanze esogene o xenobiotiche in matrici biologiche alternative quali peli e capelli / C. Pecoraro ; Tutor: Veniero Gambaro ; Coordinatore: Marina Carini. DIPARTIMENTO DI SCIENZE FARMACEUTICHE "PIETRO PRATESI", 2007. 20. ciclo, Anno Accademico 2004/2005.
Abstract:
Hair is considered an alternative specimen for the identification of drugs. It is routinely used as a tool for the detection of xenobiotics (drugs of abuse, pharmaceuticals, environmental contaminants, doping agents, etc.) in forensic science, traffic medicine, occupational medicine and clinical toxicology. Analysis of drugs and their metabolites which are incorporated in the hair shaft, can provide information about the quantity and historical pattern of individual drug use. This type of information is not available from any other specimens.
The Toxicological Chemistry Analysis laboratory co-ordinated by Prof. Veniero Gambaro, where this research doctorate was carried out, analyses hair in cases of poisoning or investigation of dependency on substances of abuse. As a result, participation in an external quality control project on the search for substances of abuse in hair was decided for improving the identification of critical passages in the context of this matrix. This project, known as HAIRVEQ, is promoted by the Senior Health Institute.
Some reported research describing various operational procedures for the search for substances of abuse in hair was taken into consideration, the critical points analysed further and new hypotheses of work to improve or innovate the control procedures were assessed. The traditional procedure consists of several steps:
• sampling: hair is best collected from the area at the back of the head;
• washing: this is required to rule out surface contamination;
• hydrolysis: this is required to enhance drug solubility;
• extraction: liquid-liquid or SPE extraction were applied for drug purification;
• derivatization;
• analysis by GC/MS.
Initially, this procedure was applied on drug-free control hair spiked with a standard solution of cocaine, opiates and cannabinoids. Then the method developed was used to analyse hair samples, including pubic hair, collected from drug abusers.
The washing stage is particularly important to avoid any external contamination. It is an operation which could already lead to a preliminary, unwanted extraction of analyte from the biological sample. The next, equally important, step is the amount of material to subject to analysis. This choice has a considerable effect of the final result expressed, in this field of application, as nanograms of analyte over milligrams of hair weighed. As a result, the sensitivity of the method can be augmented by increasing the amount of material to examine. This is possible because the hair matrix does not contain high amounts of interfering endogen substances and a correct assessment of samples with concentrations near to the cut-off level can be made.
The cut-off levels are concentration values below which a sample is considered negative. This parameter is used in diagnostic comparison in Forensic Medicine or checks carried out for suitability to drive motor vehicles. Hydrolysis of the keratin matrix was carried out chemically, both in basic or acid conditions depending on the substance to be looked for. Enzymatic-type hydrolysis is also being experimented for use in the preparation of the sample for the application of immune-enzymatic tests. This technique is faster as it does not require ‘overnight’ incubation of the sample and is, therefore, more suitable for routine analyses.
Today, chromatographic procedures, especially those coupled with mass spectrometry, are the gold standard for the identification and quantification of drugs in hair owing to their separation ability and sensitivity of detection. In this work, procedures for the detection of opiates, cocaine and its metabolite benzoylecgonine, amphetamines and cannabinoids were carried out. GC/MS in the electron impact mode (EI) and chemical ionization
Tipologia IRIS:
13 - Tesi di dottorato discussa entro ottobre 2010
Elenco autori:
C. Pecoraro
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