|dc.description.abstract||The general developed microextraction methods were time-consuming, higher cost, eco-unfriendly, and carryover problems. A dispersive micro solid-phase extraction (DmSPE) coupled solvent/thermal desorption techinque was able to improve these disadvantages, and the parameters were optimized by experimental design, which was proposed by this thesis.
This thesis was divided into three parts: the first part developed and validated an optimized method for the determination of seven synthetic target musks in water samples. The method involves a DmSPE plus ultrasound-assisted solvent desorption (UASD) prior to their determination by gas chromatography-mass spectrometry (GC-MS). Factors affecting the extraction efficiency of the target analytes from water samples and UASD were optimized by a Box-Behnken design (BBD) method. The optimal extraction conditions involved immersing 10.1 mg of a octadecyl (C18) bonded silica adsorbent in a 50 mL water sample. After 10.4 min of extraction by vigorously shaking, the adsorbent was collected and dried on a filter, and the target musks were desorbed by ultrasound for 38 sec with n-hexane (200 μL) as the desorption solvent. A preliminary analysis of the effluents from municipal wastewater treatment plants (MWTP) and river water samples revealed that galaxolide (HHCB) and tonalide (AHTN) were the two most commonly detected synthetic musks; their concentration were determined to range from 88 to 690 ng/L for effluent samples, and 5 to 320 ng/L for river water samples.
In the second part, a simple, rapid, and solvent-free method involves the use of DmSPE coupled with direct thermal desorption (TD) -GC-MS for the analysis of ﬁve target musks in water samples. The parameters affecting the extraction efﬁciency of the target analytes from water sample and the thermal desorption conditions in the GC injection-port were optimized using a central composite design (CCD) method. The optimal extraction conditions involved immersing 3.2 mg of a C18 adsorbent in a 10 mL water sample. After extraction by vigorously shaking for 1.0 min, the adsorbents were collected and dried on a ﬁlter. The adsorbents were transferred to a micro-vial, which was directly inserted into GC temperature programmed injector, and the extracted target analytes were then thermally desorbed in the GC injection port at 337 °C for 3.8 min. Using a standard addition method, a preliminary analysis of the river water samples revealed that the concentrations of HHCB and AHTN were determined to in the range from 11 to 140 ng/L.
Finally, a solvent-free method involves the use of DmSPE followed by the simultaneous silylation and thermal desorption (SSTD) -GC-MS for the rapid analysis of six benzophenone-type UV absorbers in water samples. A Plackett-Burman design was used for screening and a CCD for optimizing the major factors was applied. The optimal experimental conditions involved immersing 1.5 mg of the Oasis HLB adsorbent in a 10 mL portion of water sample. After vigorous shaking for 1 min, the adsorbents were transferred to a micro-vial, and were dried at 122 °C for 3.5 min, after cooling, 2 μL of the BSTFA silylating reagent was added. For SSTD, the injection-port temperature was held at 70 °C for 2.5 min for derivatization, and the temperature was then rapidly increased to 340 °C to allow the thermal desorption of the TMS-derivatives into the GC for 5.7 min. Using a standard addition method, a preliminary analysis of the MWTP efﬂuent and river water samples revealed that 2-hydroxy-4-methoxybenzophenone (BP-3) was the most common benzophenone-type UV absorber present. The concentrations of BP-3 ranged from 5.1 to 39.7 ng/L.
The preliminary results of this dissertation reveals that these methods can satisfy analytical validation criteria, allow precise measurement of the trace levels of emerging contaminants in aqueous samples, and they are simple, low cost, effective, and eco-friendly method. In the future, these methods also can be further studied to apply in other fields, e.g., food, beverage, pharmaceutical, cosmetic, etc.||en_US|