电热板加热消解-氢化物原子荧光法测定鱼虾中的总砷

本文采用加入硝酸-硫酸-高氯酸的电热板加热消解方法处理样品,以氢化物原子荧光法测定鱼虾中的总砷,试验了不同酸介质和还原剂用量对测定总砷的影响,选择了仪器最佳工作条件及氢化物发生条件。通过试验,用该法测定了标准物质对虾(GBW08572)中的砷,其结果与推荐值吻合。     

L-半胱氨酸预还原氢化物-原子荧光法测定氧化铜中砷

研究了氢化物发生-原子荧光光谱法测定高含量氧化铜中痕量砷的适宜条件,试验了不同酸介质和还原剂对测定砷的影响。在最佳条件下,砷的线性范围为0.1～40μg/L,检出限为0.075μg/L。样品分析结果的相对标准偏差为2.28%(n=11),加标平均回收率为96.4%。     

应用AFS—930型双道原子荧光光度计联合测定水中的砷和硒

本文采用原子荧光光谱法,研究了联合测定水样中砷和硒的技术。用10%盐酸和1%硫脲-1%抗坏血酸混合试剂处理样品,并以2.0%硼氢化钾和0.5%氢氧化钠为还原剂,在5%的盐酸介质测定砷和硒。砷和硒的检出限分别为:0.20μg/L和0.13μg/L,本方法具有操作简便、快速、基体干扰少、灵敏度高等优点,可用于水样中砷和硒的联合测定。     

氢化物—原子荧光法测定饮用水中砷的方法研究与改进

应用氢化物—原子荧光法测定生活饮用水中的砷含量,实验过程中发现绘制的标准曲线和已知浓度水样的测定结果均存在较大误差,通过分析确定起还原剂和掩蔽作用的抗坏血酸在测定过程中存在干扰。在改进方法后,只用硫脲作为还原剂和稳定剂而不加抗坏血酸后测定的标准曲线的线性相关系数为0.9997、检出限为0.035μg/mL,用砷标准溶液6.00μg/L的浓度测得相对标准偏差RSD=2.67%,加标回收率为96.5%-102.5%。实际水样的测定结果也符合国家标准。证明该改进方法对于测定低含量砷且杂质离子未达到影响结果测定浓度时的水样具有过程简单、可靠性强的优点。     

氢化物发生——原子荧光法测定土壤中砷的方法研究

建立氢化物发生--原子荧光法测定土壤中砷的方法,研究反应酸度、还原剂浓度、仪器条件等因素对测定的影响。在最佳条件下,测定土壤中砷的含量,该法操作简便、快速、准确、重复性好、灵敏度高。     

氢化物发生原子荧光法测中毒检材中砷

本文研究了用氢化物发生原子荧光法测中毒检材中砷含量。本方法是将中毒检材进行有机质的破坏,使检材中砷全部还原为三价砷,在盐酸介质中,以硼氢化钾作还原剂,将三价砷转化为砷化氢。以高纯氩气作为载气将砷化氢从母液中分离,并导入石英炉原子化器中原子化。以砷特种空心阴极灯作激发光源,激发砷原子发出荧光,荧光强度值在一定范围内与砷的含量成正比。本方法灵敏度高,精密度好,检出限为0.0550μg/L。     

氢化物发生-电加热原子吸收光谱法测定铁精矿中砷

本文研究了采用过氧化钠溶解铁精矿,经水浸取,硫酸酸化后用氢化物技术将痕量的砷从铁精矿中分离、富集,用碘化钾、抗坏血酸和酒石酸作还原剂和掩蔽剂测定铁精矿中的砷。用标准加入电加热原子吸收光谱法消除基体效应,该方法具有灵敏度高,干扰少、快速、准确度高等优点。     

原子荧光光谱法测定首饰金中砷含量的不确定度评定

本文对根据GB/T 11066.9-2009《金化学分析方法砷和锡量的测定氢化物发生-原子荧光光谱法》,检测首饰金中砷的测量不确定度进行评定,分析了方法中不确定度的来源,得出影响砷测定结果的主要影响因素。     

氢化物发生-原子荧光光谱法测定炉渣中微量砷

研究了氢化物发生-原子荧光光谱法对微量砷的测定,方法灵敏度高,准确度好。在最佳条件下,荧光强度与砷浓度4×10-4～0.20μg·ml-1范围内呈线性关系,检出限达1×10-4μg·ml-1。用此法测定了炉渣中微量砷,结果满意。     

含砷废渣水泥固化/稳定化技术研究进展

含砷废渣作为一种持久性污染物被广泛关注,固化/稳定化技术是治理含砷废渣的一种行之有效的途径。对硅酸盐水泥基胶凝材料固砷效果以及其固化机理等方面的研究进行了综述,水泥水化过程中产生的大量Ca(OH)_2与可溶性砷酸盐反应生成较为稳定的砷酸钙盐,降低砷的浸出浓度,从而实现砷的有效固化,但其存在污染物包容量小、耐久性差等缺点。本课题组提出了利用地聚物水泥(地聚物材料)固化含砷废渣,通过在地聚物材料水化聚合过程中,以同晶取代的方式实现AsO43-与SiO_4~(4-)、AlO_4~(5-)之间的化学键合,并辅以地聚物材料的高强、耐久性好的优良特性,利用地聚物材料固化含砷废渣实现砷的大容量、持久性地安全稳定固封。     

Influence of transition metals on the surface acidic properties of titania prepared by sol-gel route

A series of titania catalysts containing chromium, molybdenum as well as tungsten has been prepared by colloidal sol-gel route using metatitanic acid as the precursor. Structural characterization of the prepared catalysts was done with Energy dispersive X-ray analysis, X-ray diffraction, BET surface area and pore volume measurements. The influence of different transition metals like chromium, molybdenum and tungsten on the surface acidic properties of titania is investigated in detail. Two independent methods have been used to study the surface acidity of these catalyst systems: temperature programmed desorption of ammonia which is a measure of total acidity and thermodesorption studies using 2,6-dimethyl pyridine which is a measure of Bronsted acidity. Cumene cracking reaction is carried out over the prepared systems for further characterizing the acidity of the prepared catalysts. Remarkable enhancement in the surface acidity is observed after transition metal incorporation. The catalytic activity of the prepared catalysts was tested towards the dehydrogenation of cyclohexane.     

Elucidation of interactive effects of synthesis conditions on the characteristics of mesoporous silicas templated using polyoxide surfactant

A series of mesoporous silicas (MS-1–MS-9) were synthesized at different gel compositions using a triblock copolymer (TCP), poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide), as the surfactant. The interactive effects of acidity, the contents of tetraethyl orthosilicate (TEOS) and the surfactant, and the gelling temperature on the characteristics of the final material were simultaneously characterized. Increasing acidity favored mesopore formation. A material with a surface area of 760 m²/g, mostly in the mesoporous range, was obtained at 1.0(TEOS):0.017(TCP):7.3HCl:115.7H₂O. Mesopore formation was predominantly determined by the TEOS:TCP ratio and was promoted with its increase from 1.56:1 to 2.09:1. A further increase to 2.61:1 was detrimental. Whereas increasing the TCP content to 3.5% w/w improved micellization, a further increase to 4.6% should be avoided. Mesoporous silicas showed low crystallinity but a high degree of hexagonal mesoscopic organization. The weak surface acidity was attributed to surface silanols, the number of which was proportional to mesoporosity.     

植酸自组装单分子膜对白铜B30缓蚀作用的研究

用一种环境友好型金属处理剂植酸在白铜B30表面制备了自组装单分子膜(SAMs),研究了该膜在3%NaCl中对白铜B30的缓蚀作用.通过交流阻抗法和极化曲线法的研究表明,在酸性和碱性环境中,植酸SAMs对白铜B30均有良好的缓蚀效果,其对白铜B30的缓蚀效果在酸性环境中要优于碱性环境;且组装时间6h效果最好,缓蚀率为84.87%,同时分析表明其缓蚀机理为化学吸附过程.     

Influence of Solid-State Acidity on the Decomposition of Sucrose in Amorphous Systems II (Effect of Buffer)

It was of interest to investigate the solid-state acidity using indicator probe molecules and sucrose degradation. Amorphous samples containing lactose, sucrose, buffers (citrate, malate, tartarate, or phosphate) with different pH values, and sodium chloride (to adjust the ionic strength) were prepared by freeze-drying. The lyophiles were characterized using powder X-ray diffraction, differential scanning calorimetry, and Karl Fischer titrimetry. The solid-state acidity of all lyophiles was measured using diffuse reflectance spectroscopy and suitable indicators (thymol blue or bromophenol blue). Selected lyophiles were subjected to a temperature of 60°C and were analyzed for sucrose degradation using the Trinder kit. The results obtained from this study have shown that good correlation can be obtained between the solid-state acidity and the molar ratio of the salt and the acid in solution. The degradation of sucrose in the lyophiles is extremely sensitive to the solid-state acidity and might be able to provide a better estimate for the acidity than the indicator probe molecules. The Hammett acidity-rate profile for sucrose degradation in the lyophiles (using four different buffers) was also obtained. The profile showed similarity to the pH-rate profile in solution, and no buffer catalysis for sucrose degradation was detected in this study.     

Studies on the dehydration of glycerol over niobium catalysts

The dehydration of glycerol over nanosize niobium catalysts was conducted in a stainless steel autoclave reactor. The catalysts were prepared by the calcination of niobium oxalate between 200 and 700 degrees C. Catalysts were characterized by N2 Physisorption, XRD and TPD of ammonia to investigate the effect of the calcination temperature and water on catalytic performance, catalysts' structures and acidity. Acrolein was mainly produced about 51-71% with useful by-products such as acetaldehyde and methanol. Amorphous Nb2O5 catalysts calcined at 200-400 degrees C significantly showed higher conversion of glycerol than the crystallized Nb2O5 catalyst calcined at 500-700 degrees C. Also the conversion of glycerol and selectivity of acrolein was increased with increasing the acidity of catalyst, which can be controlled by calcination temperature.     

The influence of chemistry on the adhesion at the interface of carbon/epoxy composites

A method of determining surface acidity has been developed by using adsorption isotherms to interpret the uptake of labelling ions from solution. X-Ray photoelectron spectroscopy (XPS) can be used to measure the concentration of ions taken up directly so that gas adsorption isotherms can be applied and a monolayer coverage calculated. Concentration of acidity can be calculated if the number of ions per acid group is known. For the particular fibre tested the surface acidity correlated well with interfacial adhesion and increased with surface treatment up to the optimum adhesion level determined by single-fibre fragmentation and pull-out tests.     

壳聚糖-植酸复合涂膜对黄岩蜜橘保鲜效果的影响

目的探究壳聚糖和植酸涂膜对黄岩蜜橘保鲜效果的影响。方法采用壳聚糖(质量分数为1%)、植酸(质量分数为1%)和壳聚糖植酸(质量分数为1%)复合涂膜处理黄岩蜜橘,研究其贮藏期腐烂率、质量损失率、可溶性固形物含量、可滴定酸含量、过氧化物酶POD活性、多酚氧化酶PPO活性、MDA含量、呼吸强度、霉菌、酵母的变化情况。结果在贮藏期间,壳聚糖-植酸复合涂膜表现出较好的保鲜效果,在贮藏30 d时复合涂膜的腐烂率为5.7%,仅是对照组的30.0%;质量损失率为3.3%,是对照组的38.0%。复合涂膜相较于单一涂膜更好地延缓了贮藏期间黄岩蜜桔可溶性固形物含量和可滴定酸含量的变化速率,使黄岩蜜桔维持了较好的POD和PPO活性,减缓了霉菌、酵母等微生物的侵染进程,减少了果实中MDA的积累。结论壳聚糖-植酸复合涂膜在黄岩蜜橘表面形成了一层保护膜,较好地维持了其贮藏期的品质,延缓了其衰老进程,效果优于壳聚糖或植酸单一涂膜处理。     

Elucidation of interactive effects of synthesis conditions on the characteristics of mesoporous silicas templated using polyoxide surfactant

A series of mesoporous silicas (MS-1-MS-9) were synthesized at different gel compositions using a triblock copolymer (TCP), poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide), as the surfactant. The interactive effects of acidity, the contents of tetraethyl orthosilicate (TEOS) and the surfactant, and the gelling temperature on the characteristics of the final material were simultaneously characterized. Increasing acidity favored mesopore formation. A material with a surface area of 760 m²/g, mostly in the mesoporous range, was obtained at 1.0(TEOS):0.017(TCP):7.3HCl:115.7H₂O. Mesopore formation was predominantly determined by the TEOS:TCP ratio and was promoted with its increase from 1.56:1 to 2.09:1. A further increase to 2.61:1 was detrimental. Whereas increasing the TCP content to 3.5% w/w improved micellization, a further increase to 4.6% should be avoided. Mesoporous silicas showed low crystallinity but a high degree of hexagonal mesoscopic organization. The weak surface acidity was attributed to surface silanols, the number of which was proportional to mesoporosity.     

基于因子-聚类分析的水蜜桃分级方法研究

目的为了研究水蜜桃大小与内在品质的相关性,探索合理的分级方法,为优质水蜜桃的分级、贮运生产提供理论依据。方法以"玉露"水蜜桃为实验材料,测定单果质量、纵径、横径、可溶固形物含量、可滴定酸含量、固酸比等指标,并对各指标进行因子-聚类分析。结果水蜜桃大小指标(单果质量、纵径、横径)与品质指标(可溶固形物含量、可滴定酸含量、固酸比)相关性不显著;通过因子分析提取了2个因子成分,其累计方差贡献率为78.401%,较好地代替原有指标来综合评价水蜜桃的品质,再通过聚类分析将桃分成4个等级,各等级桃果的品质指标均呈现梯度变化。结论基于因子-聚类分析的水蜜桃方法能按照桃果的综合品质进行分级,符合生产实际和消费需求。     

30CrNi3A合金钢高温锰系磷化工艺研究

部分高合金钢磷化效果不佳,甚至难以磷化.通过正交试验,对30CNi3A合金钢黑色锰系磷化工艺进行了优化研究,分析了磷化过程中总酸、酸比、Fe2+浓度、表调时间、磷化时间等因素对磷化膜耐腐蚀性能和膜重的影响.结果表明,适当的总酸、酸比、磷化时间以及降低Fe2+浓度有利于提高磷化膜的耐腐蚀性能.为提高磷化膜的耐腐蚀性能,应尽量使磷化膜晶粒细小均匀,增加膜重,提高磷化膜中锰的含量,降低磷化膜中铁的含量.