Study On The Novel Method Of Activated Carbon Fiber Solid Phase Microextraction

Solid-phase microextraction (SPME) has been developed rapidly as a new sample pretreatment technique. It is simple, fast, solvent free, highly sensitive and portable. The key to SPME technique lies in the performance of extraction fiber. However, only few coatings are commercially available, which are low thermal and chemical stability and short life time. Therefore, novel activated carbon fiber (ACF) was prepared to suit for SPME. At the same time, some novel method based on ACF-SPME was developed and applied in the determination of persistent organic pollutants in complicated matrices because of the complexity during these samples pretreatment when using traditional methods. The main contents include the following four parts:First, the ACF was prepared by ammonium salt (ammonium dihydrogen phosphate) pretreatment and H2O activation. Compared with commercial fibers, the novel ACF exhibits high adsorption capacity for polychlorinated biphenyls (PCBs), high thermal stability (the maximum operating temperature is 380 oC), high chemical stability, long service life (more than 350 times) and low cost. Those features make ACF well suit for being the fiber of SPME.Second, novel ACF-SPME was used for the determination of PCBs in water and soil samples. When analyzing water samples, the limit of detection of the method is 0.18 ng/L and recovery is 79.20% in spiked lake water; when analyzing the soil samples, under the optimum conditions, the limit of detection of the method is found at 5.20 ng/g of soil and the recovery is 71.50% in spiked soil samples. The methods developed here exhibit higher sensitivity than those reported by other authors. Compared with commercial fibers, ACF has high adsorption capacity for PCBs.Third, the theory of circulating cooling-solid phase microextraction (CC-SPME) was studied. At the same time, some novel methods based on CC-SPME were developed and applied in the determination of persistent organic pollutants in complicated matrices. The main contents include the following three parts: (1) First, the theory of CC-SPME was studied. On the basis of thermodynamics, the conclusion is that the adsorption ability of ACF is increased with the temperature gap between the cold fiber and the hot headspace when using CC-SPME-GC. After that, the novel method was applied to determine organochlorine pesticides (OCPs) residues in soil samples. The experimental conditions, including adsorption time and temperature, desorption temperature and time and the amount of water added were optimized and the novel method was successfully applied to the quantification of OCPs in real agricultural soil. Furthermore, the feasibility of CC-SPME combined with gas chromatography-nitrogen phosphorous detector (GC-NPD) for the determination of five organophosphorous pesticides (OPPs) in tomato samples was evaluated. The experimental conditions, including adsorption time and temperature, ionic strength were optimized. Experimental results show that activated carbon fiber has higher adsorption capacity than those of commercial fibers and CC-SPME method provides higher sensitivity than that of traditional headspace-solid phase microextraction (HS-SPME). (2) A combined analytical method involving ultrasonic extraction- CC-SPME and GC was developed for the determination of polychlorinated biphenyls (PCBs) in marine sediments. The linear ranges are 1.00-80.00 ng/L. The limits of detection obtained using the method range from 0.01 to 0.12 ng/g and recoveries for all the analytes range from 75.04% to 90.35%. Compared with the other method reported, the novel method is simple and high sensitive. (3) A novel analytical method called ultrasonic assisted-circulating cooling-solid phase microextraction-gas chromatography (UA-CC-SPME-GC) was developed for the determination of organochlorine pesticides (OCPs) in marine sediments. Parameters that affect the extraction of OCPs in sediment including adsorption time and temperature, extraction solvent type and volume were investigated and optimized. The novel method exhibits wider linear range (0.50-20.00 ng/g) and lower detection limit (0.01-0.10 ng/g ) than those of HS-SPME. The method can be finished in one step and the sample pretreatment can be simplified substantially.Finally, electrosorption enhanced solid phase microextraction (EE-SPME) using activated carbon fiber was investigated. ACF is conductive and plays double roles as electrode and adsorption material in the proposed adsorption procedure. This technique provides a new perspective in the enhancement of adsorption performance of activated carbon fiber and sensitivity of SPME. Aniline was chosen as the target analyte. Compared with DI-ACF-SPME, the electrosorption enhanced approach was superior due to its wide linear range (0.10 to 100.00μg/L) and low detection limit (0.02μg/L). Due to the electrosorption of ACF, equilibrium time is 10 min and sampling time can be shortened substantially.The main innovation points in this paper are as followings: (1) ACF was prepared by ammonium salt (ammonium dihydrogen phosphate) pretreatment and H2O activation, and the novel ACF-SPME was successfully applied in the determination of PCBs in water and soil samples.(2) The theory of CC-SPME was studied, and CC-SPME was applied in the analysis of organic pollutants in complex matrices in this paper, while the method was only applied in determination of OCPs in water samples in previous study. At the same time, some novel methods based on CC-SPME were developed and applied in the determination of persistent organic pollutants in complicated matrices.(3) Electrosorption was combined with ACF-SPME to enhance the adsorption performance of ACF and to increase the sensitivity of the method. Novel electrosorption enhanced-activated carbon fiber-solid phase microextraction was proposed.