Gas chromatographic determination of chlorothalonil and its metabolite 4-hydroxy-2,5,6-trichloroisophtalonitrile (HTI) in water

Summary A gas chromatographic method, with electron capture detection and mass spectrometric confirmation, is described for the determination of chlorothalonil and its metabolite 4-hydroxy-2,5,6-trichloroisophtalonitrile (HTI) in water samples. Water is saturated with sodium chloride and acidified to pH<2 with dilute sulfuric acid. After extraction with dichloromethane, HTI was methylated with diazomethane. The extract obtained was cleaned with basic alumina. Chlorothalonil and the methylated HTI-derivative were determined by gas chromatography with electron capture detection (GC-ECD) and confirmed by gas chromatography-mass spectrometry (GC-MS). The limit of detection, depending on the nature of the water samples is for both compounds between 0.01–0.03 g 1^–1 water. The average recovery in ground water is 87% for chlorothalonil and 82 % for HTI.     

正渗透膜成分与结构分析

用裂解质谱的方法对美国HTI公司三种正渗透膜CTA-ES、CTA-NW和TFC-ES的成分进行了鉴定,并且利用扫描电子显微镜(SEM)对其结构进行了仔细的观察。结果显示,三种膜都是由醋酸纤维素、聚酯、聚砜、聚氨酯等高分子材料组成的层状结构。     

An accurately fast algorithm of calculating reflection/transmission coefficients

For the boundary between transversely isotropic media with a vertical axis of symmetry (VTI media), the interface between a liquid and a VTI medium, and the free-surface of an elastic half-space of a VTI medium, an accurately fast algorithm was presented for calculating reflection/transmission (R/T) coefficients. Specially, the case of post-critical angle incidence was considered. Although we only performed the numerical calculation for the models of the VTI media, the calculated results can be extended to the models of transversely isotropic media with a horizontal axis of rotation symmetry (HTI media). Compared to previous work, this algorithm can be used not only for the calculation of R/T coefficients of the boundary between ellipsoidally anisotropic media, but also for that between generally anisotropic media, and the speed and accuracy of this algorithm are faster and higher. According to the anisotropic parameters of some rocks given by the published literature, we performed the calculation of R/T coefficients by using this algorithm and analyzed the effect of the rock anisotropy on R/T coefficients. We used Snell’s law and the energy balance principle to perform verification for the calculated results. Supported by the Natural Science Foundation of Shaanxi Province, China (Grant No. 2007D15)