A preconcentration technique, which involves liquid–liquid–liquid microextraction, was developed to determine phenoxy herbicides in bovine milk. A layer of organic phase was impregnated into the pores of a 3.5cm long porous hollow fiber, while the internal volume of the fiber was filled with NaOH solution (the acceptor solution) that was connected directly to the needle of a microsyringe. The fiber was then immersed into 8ml of acidified milk sample. When the sample solution was stirred, acidic analytes were extracted into the organic phase and back extracted simultaneously into the alkaline acceptor medium as the analytes were protonated at low pH and deprotonated at high pH. After extracting for a prescribed time, 5ml acceptor solution was taken back into the syringe and injected directly into a HPLC system for quantification. The analytes were extracted quantitatively from the sample solution into the acceptor solution with a large enrichment factor of 900. Due to its low cost, the hollow-fiber extraction device was disposed of after a single extraction that eliminated the possibility of carry over effects. In addition, because a small volume of organic solvent was required and little waste is generated, the procedure is environmentally friendly, and is compatible with the "green chemistry" concept.

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 The acceptor phase was then withdrawn into a microsyringe and injected into the cLC system directly.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.

The history of polybrominated diphenyl ethers (PBDEs) and the major polybrominated biphenyl congener (BB-153) was studied in dated sediment cores taken from Lakes Michigan and Erie. The surficial concentration of total PBDE (320ng/g dry weight) in Lake Michigan was about 10times higher than that in Lake Erie (40ng/g) and in Lake Superior (12ng/g). The concentrations of total PBDEs in these sediments have increased rapidly, with doubling times of 5-10 years, reflecting the increasing market demand for these flame retardants over the last 30 years. BDE-209 was found to be the predominant congener in both sediment cores, making up 95-99% of the total PBDE load. The inventories of total PBDEs in Lakes Michigan and Erie were 190 and 40ng/cm2, respectively. The total burdens of these compounds in the sediment of Lakes Michigan and Erie were 110 and 10 metric tons, espectively. We estimate that the total burden of these compounds in all of the Great Lakes is on the order of 200 tons. In both lakes, BB-153 was found to increase rapidly during the 1970s and to peak around 1980.

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.

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.