|Author:||Ng, Tsz Tsun|
|Title:||Rapid determination of drugs-of-abuse in urine and oral fluid and rapid authentication of edible oils by mass spectrometry|
|Subject:||Hong Kong Polytechnic University -- Dissertations|
Oils and fats, Edible -- Analysis
|Pages:||xxvii, 244 pages : color illustrations|
|Abstract:||The scope of my study is to develop analytical techniques to facilitate the analysis of two real-life issues, i.e., determination of drugs-of-abuse in urine and oral fluid, and authentication of edible oils. Mass spectrometry (MS), a commonly used analytical tool, has been developed to address these two issues. Drug abuse is a severe problem worldwide. Detection of drugs-of-abuse in the body fluids of drug abusers is the critical step for the law enforcement as well as the treatment and rehabilitation. To handle the huge analytical demand of drug analysis, drug screening using the testing kits is usually employed as the preliminary analysis to screen the submitted samples, and only the positive samples are further subjected to confirmatory analysis using techniques such as gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS). However, such preliminary analysis frequently produces false positive or false negative results, and the confirmatory analysis are usually labour-intensive and time-consuming. Development of new analytical techniques for rapid and reliable drug analysis is thus highly desirable. In this study, wooden-tip electrospray ionization mass spectrometry (WT-ESI-MS), a simple and cost-effective technique recently developed by our group, was attempted for rapid detection and quantitation of six commonly drugs-of-abuse, i.e., ketamine, methamphetamine, cocaine, ecstasy, cannabis and heroin, in urine and oral fluid. The results showed that WT-ESI-MS could be used for detection and quantitation of ketamine, methamphetamine and ecstasy in raw urine and oral fluid, with analysis of one sample within minutes and analytical performances acceptable for analysis of real-life samples. However, the detection and quantitation of cocaine, cannabis and heroin still need to further improve. Rapid extraction and enrichment using solid-phase microextraction (SPME) followed by direct coupling of SPME with electrospray ionization mass spectrometry (SPME-ESI-MS) was then developed for analysis of the six drugs in urine and oral fluid. The results indicated that the limits-of-detection for analysis of the six drugs were much improved with SPME-ESI-MS and could fulfill the requirements of the international standards except for cannabis in oral fluid. Quantitation of all the targeted drugs could be achieved with satisfactory precisions and accuracies by using the SPME-ESI-MS approach.|
Authentication of edible oils is crucial for ensuring the quality and safety of edible oils and becomes more important with the emergence of gutter oils. Conventional gas chromatography-flame ionization detection (GC-FID) method for edible oil analysis requires chemical derivatization and chromatographic separation and is time-consuming. Moreover, there is no universal method for screening of gutter oils yet. In this study, a simplified matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) approach was developed for rapid and high throughput analysis of edible oils. Mass spectra of more than one thousand oil samples were acquired and a spectral database of edible oils was established. The spectra for various edible oils were analyzed and compared, and the characteristic peaks and spectral features of each edible oil were obtained. Edible oils were divided into eight groups based on their characteristic spectral patterns and principal component analysis results. An overall correct rate of 97.2% was obtained for classification of 435 edible oil products using partial least square-discriminant analysis. Differentiation of counterfeit edible oils and gutter oils from normal edible oils could also be achieved based on the MALDI-MS spectra, and analysis of one oil sample could be completed within minutes.
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