Tungsten permanent chemical modifier for fast estimation of Se contents in soil by graphite furnace atomic absorption spectrometry

A tungsten carbide coating on the integrated platform of a transversely heated graphite atomizer was used as a modifier for the direct determination of Se in soil extracts by graphite furnace atomic absorption spectrometry. Diethylenetriaminepentaacetic acid (0.0050 mol L(-1)) plus ammonium hydrogencarbonate (1.0 mol L(-1)) extracted predominantly available inorganic selenate from soil. The formation of a large amount of carbonaceous residue inside the atomizer was avoided with a first pyrolysis step at 600 degrees C assisted by air during 30 s. For 20 microL of soil extracts delivered to the atomizer and calibration by matrix matching, an analytical curve (10.0-100 microgram of L(-1)) with good linear correlation (r = 0.999) between integrated absorbance and analyte concentration was established. The characteristic mass was approximately 63 pg of Se, and the lifetime of the tube was approximately 750 firings. The limit of detection was 1.6 microgram L(-1), and the relative standard deviations (n = 12) were typically <4% for a soil extract containing 50 microgram of L(-1). The accuracy of the determination of Se was checked for soil samples by means of addition/recovery tests. Recovery data of Se added to four enriched soil samples varied from 80 to 90% and indicated an accurate method.     

副猪嗜血杆菌感染诊断方法和最新基因分型方法的研究进展

副猪嗜血杆菌可引起猪格拉塞病和其它许多疾病,对与该茵有关的疾病进行诊断通常依赖于临床症状、病理变化和细菌分离,但由于有无毒菌株(nonvirulent strain)的存在及其在健康仔猪上呼吸道上的早期定殖,使得对该菌的诊断变得较为复杂.而且,在同一猪场甚至是同一只猪体内可能存在多种不同的菌株,因此确定可导致临床发病的特定菌株显得尤为重要.最近,科研人员开发了一些针对副猪嗜血杆菌的基因分型方法,目的是确定该茵的基因型与其毒力强度之间的关系.由于缺乏副猪嗜血杆菌完整基因组序列及其致病因子(virulence factor)的知识,因此将副猪嗜血杆菌的基因型与其毒力联系起来极富挑战性.