已为您找到该学者10条结果 成果回收站
刘维屏, WEIPING LIU AND JAY J. GAN*
J. Agric. Food Chem. 2004, 52, 755-761 ,-0001,():
-1年11月30日
Synthetic pyrethroid (SP) insecticides are of environmental significance because of their high aquatic toxicity. Due to their chirality, SP compounds contain multiple diastereomers and enantiomers. However, due to great structural similarities and lack of isomer standards, gas chromatographic (GC) analysis of SP diastereomers or enantiomers is poorly developed. In this study, we used a HP-5 column to separate the diastereomers and a
Chiral analysis, diastereomer separation, enantiomer separation, synthetic pyrethroids, enantioselectivity
-
117浏览
-
0点赞
-
0收藏
-
0分享
-
2698下载
-
0
-
引用
刘维屏, WEIPING LIU AND JAY J. GAN*
J. Agric. Food Chem. 2004, 52, 736-741,-0001,():
-1年11月30日
Solid phase microextraction (SPME) is an ideal sample preparation technique because of its speed and solvent-free features. Sampling by SPME is selective and only the dissolved concentration is measured, which allows measurement of the bioavailable fraction of a contaminant in aqueous media. One potential application of SPME is for analysis of enantiomers of chiral contaminants in environmental samples. In this study, a method was developed for determining enantiomers of (Z)-cis-bifenthrin and cis-permethrin in water using coupled SPME and enantioselective gas chromatography (GC). Following SPME sampling, enantiomers of (Z)-cis-bifenthrin and cis-permethrin were separated at the baseline on a â-cyclodextrin-based enantioselective column, and analyte enrichment onto the SPME fiber was not enantioselective. The GC response increased as sampling time was increased from 0 to 240 min, and as sampling temperature was increased from 20 to 40℃. Organic solvents such as methanol, acetone, and acetonitrile enhanced, while soil extracts slightly decreased, the GC response. The integrated SPME-enantioselective GC method was used to analyze surface runoff samples. The analysis showed preferential degradation of the 1S-3S enantiomer over the 1R-3R enantiomer for both (Z)-cis-bifenthrin and cis-permethrin. The concentrations detected by SPMEGC were substantially smaller than those determined following solvent extraction, suggesting that SPME-enantioselective GC analysis selectively measured the dissolved fraction.
Solid-phase microextraction, SPME, chiral analysis, enantiomer separation, synthetic pyrethroids, enantioselective analysis
-
97浏览
-
0点赞
-
0收藏
-
0分享
-
353下载
-
0
-
引用
【期刊论文】Influence of Organic Matter and pH on Bentazone Sorption in Soils
刘维屏, KEBIN LI, †, ‡, WEIPING LIU, *, ¶, DONGMEI XU, AND SANGJIN LEE¶
J. Agric. Food Chem. 2003, 51, 5362-5366,-0001,():
-1年11月30日
Bentazone (3-isopropyl-1H-2,1,3-benzonthiadiazain-(4)3H-one 2,2-dioxide) is a postemergence herbicide which is used extensively worldwide, especially in China. The sorption of bentazone in various types of soils and extracted humic acids was investigated using a batch equilibration technique. Significant linearity was observed in sorption isotherms in five different types of soil, with distribution coefficients (Kd) that varied between 0.140 and 0.321mLg-1. The distribution coefficient was determined to be a function of organic matter and pH in the soil. A model based on distribution coefficients was developed to predict bentazone sorption in soils. The organic matter-normalized partition coefficients for the neutral and anionic forms of bentazone were 370.3 and 2.40mLg-1, respectively. Hence, more attention should be given to the potential leaching problem when bentazone is applied in soils containing low organic matter and high pH.
Sorption, bentazone, soil, humic acids, partition coefficients
-
63浏览
-
0点赞
-
0收藏
-
0分享
-
322下载
-
0
-
引用
【期刊论文】PHASE DISTRIBUTION OF SYNTHETIC PYRETHROIDS IN RUNOFF AND STREAM WATER
刘维屏, WEIPING LIU, †, JAY J. GAN, *†, SANGJIN LEE, and JOHN N. KABASHIMA‡
Environmental Toxicology and Chemistry, Vol. 23, No.1, pp. 7-11, 2004,-0001,():
-1年11月30日
Synthetic pyrethroids (SPs) are a group of hydrophobic compounds with significant aquatic toxicity. Their strong affinity to suspended solids and humic materials suggests that SPs in natural surface water are distributed in solid-adsorbed, dissolved organic matter (DOM)-adsorbed, and freely dissolved phases. The freely dissolved phase is of particular importance because of its mobility and bioavailability. In the present study, we used solid-phase microextraction to detect the freely dissolved phase, and we evaluated the phase distribution of bifenthrin and permethrin in stream and runoff waters. In stream water, most SPs were associated with the suspended solids and, to a lesser extent, with DOM. The freely dissolved phase contributed only 0.4% to 1.0%. In runoff effluents, the freely dissolved concentration was 10% to 27% of the overall concentration. The predominant partitioning into the adsorbed phases implies that the toxicity of SPs in surface water is reduced because of decreased bioavailability. This also suggests that monitoring protocols that do not selectively define the freely dissolved phase can lead to significant overestimation of toxicity or water-quality impacts by SPs.
Bioavailability,, Suspended solids,, Bifenthrin,, Permethrin,, Adsorption
-
67浏览
-
0点赞
-
0收藏
-
0分享
-
138下载
-
0
-
引用
刘维屏, WEIPING LIU, *, †, WEI ZHENG, AND JIANYING GAN‡
J. Agric. Food Chem. 2002, 50, 6823-6827,-0001,():
-1年11月30日
Soil organic matter and clay minerals are responsible for the adsorption of many pesticides. Adsorption and competitive sorption of imidacloprid on clay minerals and humic acids (HA) were determined using the batch equilibration method. The sorption coefficient of imidacloprid on humic acids was significantly higher than that on Ca-clay minerals, indicating that soil organic matter content was a more important property in influencing the adsorption of imidacloprid. Competitive sorption was investigated between imidacloprid and its main metabolite imidacloprid-urea on HA and Ca-clay minerals. The results showed that the sorption capacity of imidacloprid on clay minerals and HA was reduced in the presence of the metabolite, implying that imidacloprid-urea could occupy or block adsorption sites of imidacloprid on soil, potentially affecting the fate, transport, and bioavailability of imidacloprid in the environment. The interactions between a Ca-clay or HA-clay mixture and adsorption of imidacloprid and imidacloprid-urea were studied using IR differential spectra on thin films made of the adsorbent. The possible mechanisms were discussed from the shift of characteristic IR absorption bands of imidacloprid and imidacloprid-urea after sorption.
Imidacloprid, imidacloprid-urea, sorption, adsorption, competitive sorption, clay minerals, humic acids
-
67浏览
-
0点赞
-
0收藏
-
0分享
-
211下载
-
0
-
引用