不同条件对硫酸钙结晶影响的实验研究

近年来由于微波化学的快速发展使人们认识到微波作为一种手段对化学反应的过程有着深刻的影响,在材料领域更是得到了日益广泛的应用,因此把微波应用于结晶过程也成为人们关注的热点。早在1966年磁场就被应用于晶体的生长。近年来,已有很多文献报道电场、磁场对晶体生长的影响。     

半导体氧化物光催化裂解水制氢

本文综述了半导体氧化物光催化裂解水制氢的反应机理,以及近年来半导体光催化裂解水制氢的研究进展。讨论了各种因素对材料光催化性能的影响以及改性方法,并对今后的研究方向提出了一些建议。     

浊点萃取光度法测定水样中亚硝酸根

A new method for the determination of trace nitrite by spectrophotometric after cloud point extraction was proposed.The effects of experimental conditions such as acidity,concentration of chromogenic reagent and surfactant,equilibration temperature and time on cloud point extraction were discussed.Under the optimum conditions,a good linear relationship was obtained in the range of 4.0～200 μg/L of the nitrite(r=0.9998),the detection limits of 0.43 μg/L.The recoveries fell in the range from 97.7% to 102.4% an...     

环境水样中百菌清残留的单滴微萃取-反相液相色谱测定

应用单滴微萃取(SDME)-反相液相色谱(RPLC)检测了环境水样中的百菌清残留.优化了单滴微萃取条件:环己烷萃取剂6 μL、单滴体积2 μL、搅拌速率350 r/min、萃取时间40 min、水溶液温度35 ℃、无盐度.水样经单滴微萃取后,使用Hypersil C18柱反相液相色谱分离测定百菌清.反相液相色谱条件:100%甲醇流动相、流速1.0 mL/min、柱温25 ℃、224 nm检测.方法的线性范围、检出限、相对标准偏差和富集倍数分别为1.0 ～50 μg/L、0.02 μg/L、6.1%和427倍.采用该法对环境水样中的百菌清残留进行了测定,环境水样的加标回收率为98% ～106%.     

离子液体-水体系中二苯甲酮的合成

二苯甲酮是一种重要的精细化工中间体和添加剂[1,2],主要应用于光敏剂、化学合成药物、香料香精、涂料、日用化工及电子化学品等领域。目前,二苯甲酮在工业上有多种合成工艺路线[3-6],其中包括光气法、苯甲酰氯法、三氯甲苯法、苯甲酸法、格式试剂法等。然而这些方法在不同程度     

北五味子的液相色谱指纹图谱的建立

利用反相高效液相色谱法建立中药材北五味子的指纹图谱,为科学评价及有效控制北五味子质量提供了新方法。实验分析了10个不同产地的北五味子样品,采用国家食品药品监督管理局推荐的“中药色谱指纹图谱相似度评价系统(2004 A版)”计算处理,建立了由26个指纹峰和19个共有峰组成的北五味子指纹图谱,确定了5个主要的指纹峰。通过夹角余弦法和相关系数法计算了北五味子10个样本与指纹图谱间的相似度,得到了满意的结果。所建立的指纹图谱可以用来区别不同产地北五味子药材的优劣,为进一步控制北五味子的质量提供依据。     

基于定量指纹图谱技术的中药质量控制

定量指纹图谱技术是中药指纹图谱技术与多指标成分定量分析相结合的中药质量控制模式。定量指纹图谱技术的发展包括定量组分的制备、过程控制的指纹图谱技术和产品含量测定3个主要部分。本文以丹参为例,通过水提、醇沉、过膜、大孔树脂分离和工业色谱分离5个工艺流程制备了丹参定量组分,对各个工艺步骤以指纹图谱技术考察其稳定性和重复性。对丹参定量组分中的原儿茶醛、迷迭香酸、丹酚酸B 3个成分进行含量测定。3个成分的含量总和大于50%。定量组分的制备以现有的活性成分为目标,经过去粗存精的工艺过程,其质量标准得到了有效的提高。     

Analysis of cocaine and its principal metabolites in waste and surface water using solid-phase extraction and liquid chromatography–ion trap tandem mass spectrometry

A validated method based on solid-phase extraction (SPE) and liquid chromatography-ion trap tandem mass spectrometry (LC-MS/MS) is described for the determination of cocaine (COC) and its principal metabolites, benzoylecgonine (BE) and ecgonine methyl ester (EME), in waste and surface water. Several SPE adsorbents were investigated and the highest recoveries (95.7 +/- 5.5, 91.8 +/- 2.2 and 72.5 +/- 5.3% for COC, BE and EME, respectively) were obtained for OASIS HLB(R) cartridges (6 mL/500 mg) using 100 mL of waste water or 500 mL of surface water. Extracts were analysed by reversed-phase (RP) or hydrophilic interaction (HILIC) LC-MS/MS in positive ion mode with multiple reactions monitoring (MRM); the latter is the first reported application of the HILIC technique for drugs of abuse in water samples. Corresponding deuterated internal standards were used for quantification. The method limits of quantification (LOQs) for COC and BE were 4 and 2 ng L(-1), respectively, when RPLC was used and 1, 0.5 and 20 ng L(-1) for COC, BE and EME, respectively, with the HILIC setup. For COC and BE, the LOQs were below the concentrations measured in real water samples. Stability tests were conducted to establish the optimal conditions for sample storage (pH, temperature and time). The degradation of COC was minimal at -20 degrees C and pH = 2, but it was substantial at +20 degrees C and pH = 6. The validated method was applied to a set of waste and surface water samples collected in Belgium.     

气相色谱-质谱法检测饮用水新生含氮消毒副产物氯代乙酰胺

建立了气相色谱-质谱(GC-MS)法检测饮用水中新生致突变含氮消毒副产物(N-DBPs)二乙酰胺(DCAcAm)和三乙酰胺(TCAcAm)的分析方法.考察了GC/MS和GC/ECD两种检测仪器及不同样品前处理技术对氯代乙酰胺(CAcAms)的检测效果.对比发现,酸催化水解+GC/ECD的分析方法容易受其它消毒副产物(DBPs)的影响,直接液液萃取(LLE)+GC/MS更适合CAcAms的分析;乙酸乙酯(ETAC)的萃取效果优于DBPs分析常用萃取剂甲基叔丁基醚(MTBE).在选定条件下,DAcAm和TAcAm在10～1000 μg/L的范围内线性关系良好,r＞0.9995; 方法回收率在82.0%～111.9%之间;RSD小于10%;检出限(MDL)和测定限(RQL)均低于1 μg/L.     

Effect of water on the performance of Pd-ZSM-5 catalysts for the combustion of methane

Palladium-based catalysts were prepared using impregnation （I） and ion-exchange method （E） with ZSM-5 as support. Pd-ZSM-5（I） and Pd-ZSM-5（E） catalysts presented the high activity for the combustion of methane. The order of activity was consistent with Brcnsted acidity of the catalysts： Pd-ZSM-5（I）〉Pd-ZSM-5（E）. It was shown by FT-IR that methane was adsorbed on the acidic bridging hydroxyl groups of ZSM-5-supported Pd catalysts. The effect of water on the activity of Pd-ZSM-5 was investigated. The inhibition effect of water on the conversion of methane was observed. However, water promoted the stability of Pd-ZSM-5 obviously during extended time periods. XPS measurement showed that Pd/Si ratio near the surface of Pd-ZSM-5（E） decreased more pronouncedly with time in dry stream than that of Pd-ZSM-5（I）, this is attributed to the dispersion of Pd into the micropores. The addition of water, however, retarded Pd dispersion. And high partial pressure of methane reduced this effect of water vapor. The decrease in activity during the stability test can be explained on the basis of the reduction of Pd/Si ratio.