The release of fluoride is an impodant factor in evaluating a composite restorative material due to its anticariogenic effect, Field amplified stacking injection in capillary electrophoresis was studied to determine the concentration of fluoride released from dental restorative materials, A detection limit of 20ng/mL was obtained with good reproducibility (relative standard deviation <4%), The method was applied to the ana-lysis of fluoride released from four different types of commercially available dental composites ever 28 days. Resutis showed that fiald-amplified stacking injection-capil-lary electrophoresis was effective in monitoring the fluonde release process and pro- duct quality of different kinds of restorative materials,

A simple liquid-liquid-liquid microextraction device utilizing a 2cm 30.6mm I.D. hollow fiber membrane was used to preconcentrate nitrophenols from water sample prior to capillary liquid chromatography (cLC) analysis. The extraction procedure was induced by the pH difference inside and outside the hollow fiber. The donor phase outside the hollow fiber was adjusted to pH～1 with HCl; the acceptor phase was NaOH solution used at various concentrations. Organic solvent was immobilized into the pores of the hollow fiber. With stirring, the neutral nitrophenols outside the fiber were extracted into the organic solvent, then back extracted into 2ml of basic acceptor solution inside the fiber. The acceptor phase was then withdrawn into a microsyringe and injected into the cLC system directly. This technique used a low-cost disposable extraction "device" and is very convenient to operate. Up to 380-fold enrichment of analytes could be achieved. This procedure could also serve as a sample clean-up step because large molecules and basic compounds were not extracted into the acceptor phase. The RSD (n56) was less than 6.2%, while the linear calibration range was from 1 to 200 mg/ml with r.0.998. The procedure was applied to the analysis of seawater.

A procedure that combines two common stacking techniques, field-amplified sample injection and water removal, with an electroosmotic flow pump, is used to separate phenoxy acid herbicides by capillary zone electrophoresis. Before sample loading, a long plug of water was hydrodynamically injected into the capillary both to serve as the medium to permit a high electric field strength and to contain sample anions. Because of this long length of water, the number of ions injected into the capillary was greatly increased. Electrokinetic injection at reversed voltage was then used for introducing negatively charged ions from the diluted sample into the column. The water was removed from the capillary using the electroosmotic flow (EOF) pump when the EOF of the background electrolyte was suppressed. This method afforded a sensitivity enhancement of greater than 3000 times. Combined with solid-phase extraction, detection limits for the phenoxy acid herbicides as low as 0.01ng/mL could be achieved.

A highly chlorinated flame retardant, Dechlorane Plus (DP), was detected and identified in ambient air, fish, and sediment samples from the Great Lakes region. The identity of this compound was confirmed by comparing its gas chromatographic retention times and mass spectra with those of authentic material. This compound exists as two gas chromatographically separable stereoisomers (syn and anti), the structures of which were characterized by one-and two-dimensional proton nuclear magnetic resonance. DP was detected in most air samples, even at remote sites. The atmospheric DP concentrations were higher at the eastern Great Lakes sites (Sturgeon Point, NY, and Cleveland, OH) than those at the western Great Lakes sites (Eagle Harbor, MI, Chicago, IL, and Sleeping Bear Dunes, MI). At the Sturgeon Point site, DP concentrations once reached 490 pg/m3. DP atmospheric Concentrations were comparable to those of BDE-209 at the eastern Great Lakes sites. DP was also found in sediment cores from Lakes Michigan and Erie. The peak DP concentrations were comparable to BDE-209 concentrations in the sediment core from Lake Erie but were about 30 times lower than BDE- 209 concentrations in the core from Lake Michigan. In the sediment cores, the DP concentrations peaked around 1975-1980, and the surficial concentrations were 10-80% of peak concentrations. Higher DP concentrations in air samples from Sturgeon Point, NY, and in the sediment core from Lake Erie suggest that DP's manufacturing facility in Niagara Falls, NY, may be a source. DP was also detected in archived fish (walleye) from Lake Erie, suggesting that this compound is, at least partially, bioavailable.

During the analysis of brominated flame retardants in sediment cores taken from Lake Michigan, a group of unknown brominated compounds were observed. To identify their chemical structures, a variety of gas chromatographic mass spectrometric techniques were used. With the help of high-resolution and positive chemical ionization mass spectrometry, the molecular formula of the most abundant congener was established to be C12H5Br4N. On the basis of the electron impact and electron capture negative ionization mass spectra, this chemical was suspected of being a tetrabromocarbazole. The structure was confirmed by comparing the mass spectra and gas chromatographic retention times of an authentic standard of 1,3,6,8-tetrabromocarbazole with those of the most abundant unknown. The other unknown compounds may be other bromocarbazole congeners. The time trend determined by measuring these compounds as a function of depth in the Lake Michigan sediment cores indicated that the concentration of 1,3,6,8-tetrabromocarbazole peaked around 1920-1935. This is the first time that bromocarbazoles have been found in the environment.