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111.
采用微波消解土壤并结合螯合树脂类SPE预处理柱去除消解液中重金属,原子荧光光谱法测定土壤中的汞。本方法前处理操作过程简单,用酸量少,避免了测定元素的挥发损失,汞加标回收率为92．8％-104．5％,方法准确度与精密度均令人满意。  相似文献   
112.
    
Dielectric barrier discharges （DBD） have been used in the degradation of dioxins due to the large number of excimers and free radicals produced in discharge process. In this article, the density functional theory （DFT） is used to study the degradation mechanism of octachlorinated dibenzo-p-dioxin （OCDD） with the atomic oxygen O（3P） in DBD reactor. The reactants, intermediates, transition states and products are optimized at the MPWB1K/6- 31 ＋ G（d,p） level. The vibrational frequencies have been calculated at the same level. The reaction pathways and mechanisms are analyzed in detail. The effect of removing the chlorine atom on environment also has been discussed.  相似文献   
113.
利用原子吸收法固体进样装置测定土壤中镉的含量,并对其测量过程进行了不确定度评定,从而明确了测定时的主要不确定度来源是曲线拟合过程,在测定过程中需进一步改进。  相似文献   
114.
目前水质分析部门对测定水中铅一般采用双硫腙比色法和原子吸收光谱法这两种方法,但都需要萃取、分离富集等繁琐的操作手段,分析时间长,用样品量大,有机溶剂污染环境等弊端。本文采用流动注射、氢化物原子吸收测定铅,它具有分析速度快、灵敏度等优点,回收率在95%-102%。  相似文献   
115.
    
PVDF blended different graft ratio of PVDF-g-PEGMA were systematically studied. Tuning the amphiphilic copolymer synthesis time to control membrane performance. The PVDF membrane with PVDF-g-PEGMA at 19 h possesses most surface oxygen content. The synthesis time of PVDF-g-PEGMA at 9 h is good for high flux UF membrane. Polyvinylidene fluoride grafted with poly(ethylene glycol) methyl ether methacrylate (PVDF-g-PEGMA) was synthesized using atomic transfer radical polymerization (ATRP) at different reaction times (9 h, 19 h, and 29 h). The corresponding conversion rates were 10%, 20% and 30%, respectively. PVDF was blended with the copolymer mixture containing PVDF-g-PEGMA, solvent and residual PEGMA under different reaction times. In this study, we explored the effect of the copolymer mixture additives with different synthesis times on cast membrane performance. Increasing the reaction time of PVDF-g-PEGMA causes more PVDF-g-PEGMA and less residual PEGMA to be found in the casting solution. Incremental PVDF-g-PEGMA can dramatically increase the viscosity of the casting solution. An overly high viscosity led to a delayed phase inversion, thus hindering PEGMA segments in PVDF-g-PEGMA from migrating to the membrane surface. However, more residual PEGMA contributed to helping more PEGMA segments migrate to the membrane surface. The pure water fluxes of the blended membrane with reaction times of 9 h, 19 h, and 29 h are 5445 L·m−2·h−1, 1068 L·m−2·h−1and 1179 L·m−2·h−1, respectively, at 0.07 MPa. Delayed phase inversion can form smaller surface pore size distributions, thus decreasing the water flux for the membranes with PVDF-g-PEGMA at 19 h and 29 h. Therefore, we can control the membrane pore size distribution by decreasing the reaction time of PVDF-g-PEGMA to obtain a better flux performance. The membrane with PVDF-g-PEGMA at 19 h exhibits the best foulant rejection and cleaning recovery due to its narrow pore size distribution and high surface oxygen content.  相似文献   
116.
    
The DCA (Drug Control Authority), Ministry of Health, Malaysia implemented the phase three registration of traditional medicines on January 1st, 1992. As such, a total of 100 products in various pharmaceutical dosage forms of a herbal preparation obtained in Malaysia, containing tongkat Ali hitam, either single or combined preparations, were analyzed for the contamination of a heavy toxic metal, lead, using atomic absorption spectrophotometer, after performing a simple random sampling to enable each sample an equal chance of being selected in an unbiased manner. Results showed that 17% of these products contained 10.3–20.3?ppm of lead, and therefore, do not comply with the quality requirement for traditional medicines in Malaysia. The quality requirement for traditional medicines in Malaysia is not exceeding 10?ppm for lead. Out of these 17 products, 7 products have been registered with the DCA, Malaysia whilst the rest, however, have not registered with the DCA, Malaysia. Although this study showed that 83% of the products complied with the quality requirement for traditional medicines in Malaysia pertaining to lead, however, they cannot be assumed safe from lead contamination because of the risk of batch-to-batch variability.  相似文献   
117.
气相色谱与原子吸收联用的几种连接方法的比较及其评价   总被引：1，自引：0，他引：1  
对气相色谱与原子吸收联用的几种连接方法进行了比较,对几种连接方法的性能做了评价,并就操作条件选择、影响分离和测定的一些因素等进行了讨论。  相似文献   
118.
纳米TiO_2固相萃取原子吸收光谱法测定工业废水中铅与镉   总被引：2，自引：0，他引：2  
主要研究了纳米TiO2固相萃取与原子吸收光谱法测定工业废水中铅与镉的方法。合成了3种不同粒径的纳米TiO2,探讨了粒径对铅与镉离子分离富集效率的影响,发现其萃取效率随着粒径的增大而降低。在原子吸收光谱仪最佳操作条件下,工业废水样品中镉与铅的检出限分别为0.010和0.046μg/L。工业废水中铅与镉的分析结果表明,该方法具有灵敏度高、简便快速、相对误差较小等特点。  相似文献   
119.
我们通过对YYG-2型冷原子测汞仪荧光室和相应气路系统的改进,克服了原仪器在操作过程中汞蒸汽直接排于工作台面的现象,提高了仪器的稳定性能和灵敏度,减少了操作步骤和节省了载气,在不同程度上还减化了原仪器结构。通过实践证明改进后的仪器基本上满足了环境监测或其它测试分析的要求。  相似文献   
120.
本文分析了国产火焰型原子吸收分光光度计的结构原理和特点,指出他们的优势和缺陷;根据实践经验,总结了仪器的调试,使用和维护的方法和程序;同时分析一些仪器故障的产生原因及排除方法。对保障仪器的准确高效运转有一定的参考价值  相似文献   
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