Chun-Gang Yuan

Determination of estrogens in water by HPLC-UV using cloud point extraction

A method based on cloud point extraction was developed to determine four kinds of estrogens: estriol (E3), estradiol (E2), estrone (E1), and progesterone (P) in water by high performance liquid chromatography separation and ultraviolet detection (HPLC-UV). The non-ionic surfactant Triton X-114 was chosen as extractant solvent. The parameters affecting extraction efficiency, such as concentrations of Triton X-114 and Na(2)SO(4), equilibration temperature, equilibration time and centrifugation time were evaluated and optimized. Under the optimum conditions, preconcentration factors of 99 for E3, 73 for E2, 152 for E1 and 86 for P were obtained for 10mL water sample. The detection of limitation was 0.23ngmL(-1) for E3, 0.32ngmL(-1) for E2, 0.25ngmL(-1) for E1 and 5.0ngmL(-1) for P. The proposed method was successfully applied to the determination of trace amount of estrogens in wastewater treatment plant (WWTP) effluent water and exposure water with 10ngmL(-1) E2 for toxicological study in our lab. For the case of WWTP effluent water samples, no estrogen was found. The accuracy of the proposed method was tested by recovery measurements of spiked samples and good recoveries of 81.2-99.5% were obtained.

Evaluation of the extraction methods for arsenic speciation in rice straw, Oryza sativa L., and analysis by HPLC-HG-AFS

The most important and difficult step during arsenic speciation analysis is to extract the various arsenic species in the original forms from the samples. In this work, a study has been carried out to compare the different extraction methods by using different extraction solvents including water, methanol, water–methanol, water–ethanol and water–acetonitrile. Different techniques (shaking, ultrasonic, Soxhlet and microwave-assisted extraction) were applied during the procedure. A new, nontoxic and effective extraction method for arsenic speciation in the terrestrial plant material, rice straw, with water–ethanol mixture as extraction solvent using microwave-assisted extraction was found to provide good extraction efficiency without internal species conversion. The extraction of arsenic from the rice straw and subsequent determination of individual arsenic species by high performance liquid chromatography-hydride generation-atomic fluorescence spectrometry (HPLC-HG-AFS) is described. By using the proposed extraction method, the total arsenic extraction efficiency was 90.3%. The arsenic species in rice straw were analyzed and four normal chemical forms, AsIII, AsV, MMAV and DMAV, in straw shoots were found, but no MMAV was found in the straw roots.