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|Title: ||The development of surfactant-medicated analytical methods for the determination of cyanobacterial toxins in natural waters|
|Other Titles: ||Biao mian huo xing jie zhi fen xi fa jian ce zi ran shui ti zhong de zao du su de fang fa jian li|
|Authors: ||Man, Kwok Wai (文國威)|
|Department: ||Dept. of Biology and Chemistry|
|Degree: ||Doctor of Philosophy|
|Issue Date: ||2005|
|Publisher: ||City University of Hong Kong|
|Subjects: ||Cyanobacterial toxins|
Water -- Microbiology
|Notes: ||CityU Call Number: QP632.C87 M36 2005|
Includes bibliographical references.
Thesis (Ph.D.)--City University of Hong Kong, 2005
xviii, 198 leaves : ill. ; 30 cm.
|Abstract: ||Eutrophication of waters due to natural or anthropogenical processes induces algal blooms. The presence of toxin-producing algal species in freshwaters and coastal environments threatens our daily lives as drinking water and seafood may be contaminated by bio-toxins. Numerous intoxication events have been reported in the literature. Therefore, fast and sensitivity analytical methods for the determination of algal toxins are required to safeguard public health. Due to the polar nature of many of these algal toxins, conventional trace organic analytical techniques may not be applicable or their determination. In this study, a series of ionic surfactant enhanced analytical techniques were developed for the purpose of quantification of various algal toxins in natural waters. Solid phase microextraction (SPME) was developed by Prof. J. Pawliszyn in 1988. Since then, it has been widely applied to determine various kinds of environmental pollutants. However, most of the commercial available fiber coatings can only extract non-polar to medium polar substances. In order to facilitate the determination of the highly polar algal toxins by SPME, a special surfactantenhanced SPME technique making use of an ionic surfactant, Aliquat-336 (tricaprylylmethylammonium chloride), was developed. Analytical ability of such a SPME technique was demonstrated by the successful extraction and preconcentration of cyanobacterial toxins, microcystins, in water samples. At pH 6 – 7, the surfactant-enhanced SPME process showed an outstanding selectivity in the preconcentration of anionic analytes. Only MC-LR and MC-YR, which are known to be predominately anionic, were extracted. MC-RR, which is likely to be amphoteric at the above pH range, was not detectable. Besides surfactant-enhanced SPME, a novel ionic surfactant cloud-point extraction (CPE) and pre-concentration method has been developed for the determination of microcystins in natural waters. Sodium sulfate was used to induce phase separation at 25 °C. The phase behavior of Aliquat-336 with respect to concentration of Na2SO4 was studied. The cloud-point system revealed very high phase volume ratio compared to other established systems of non-ionic, anionic and cationic surfactants. Coupled to HPLC/UV separation and detection, the cloud-point extraction method (with 2.5 mM Aliquat-336 and 75 mM Na2SO4 at 25 °C) offered detection limits of 150 pg/ml and 470 pg/ml (n = 7, p > 0.05) for MC-LR and MC-YR, respectively, in 25 ml of deionized water. Repeatability of the method was 7.6% for MC-LR and 7.3% for MC-YR (n = 6, p > 0.05). The cloud-point extraction process can be completed within 10 – 15 min with no cleanup steps required. Applicability of the new method to the determination of microcystins in real samples was demonstrated using natural surface waters collected from a local river and a local duck pond spiked with realistic concentrations of microcystins. Effects of salinity and organic matters (TOC) content in the water sample on the extraction efficiency were also studied. This novel cloud point extraction method was further applied to the extraction and preconcentration of another cyanobacterial hepatotoxin, nodularin-R, from natural waters. Cloud point phase separation of Aliquat-336 at ambient temperature was again induced by the addition of sodium sulfate. The Aliquat-336 / Na2SO4 CPE|
|Online Catalog Link: ||http://lib.cityu.edu.hk/record=b1988787|
|Appears in Collections:||BCH - Doctor of Philosophy |
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