共查询到19条相似文献,搜索用时 843 毫秒
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样品制备简单是扫描电镜的最大特点之一,然而,在多年的实践中,我们感到样品的预处理、样品的上桩粘接技术、非导电样品的镀膜方法和镀膜层厚度的控制都直接影响到样品的分析结果和图象质量。本文主要就显微形貌分析和微区成份定性分析的样品探讨石油地质样品制备技术。 相似文献
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荷电问题常造成扫描电子显微镜(SEM)图像上产生亮度不均、条纹等伪影.提出一种利用导电环氧树脂镶嵌样品以消除SEM图像荷电的方法,并与传统导电胶粘贴制样方法对1 000℃高温混凝土、瓷土与河南双槐树考古土三种样品的适应性进行了对比研究.结果表明,利用铜粉与环氧树脂混合制备导电环氧树脂并将样品镶嵌其中所制备样品的SEM图像基本无荷电问题,而传统导电胶粘贴方法所制备样品的SEM图像存在较严重的荷电问题,通过增加导电层厚度并不能对此进行改善,且易造成微纳结构被掩盖.最后对传统制样方法导致荷电问题的原因与导电环氧树脂对荷电问题的改善原理进行了分析. 相似文献
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王馨楠 《分析测试技术与仪器》2023,(4):400-406
纳米粉末材料是化学化工领域常见的样品,在其扫描电子显微镜表征中,通常会遇到以下几个问题:二次电子产率低,粉末聚集结块从而导致无法观察纳米形貌,以及荷电效应等.以二氧化硅小球粉末、ZSM-5分子筛纳米片以及聚苯乙烯小球粉末为研究对象,在不镀金属膜的前提下,分别采用粉末直接涂抹在导电碳胶或银胶上和溶液分散后滴涂在不同基底上的方法进行样品制备,比较了直接涂抹和分散后滴涂在基底上两种方法对扫描电子显微镜成像的影响.结果表明,样品经过溶液分散能够有效的减小粉末的团聚,其中,滴涂在硅片基底上可以减小荷电效应和背景影响,清晰观察到粉末的纳米级形貌. 相似文献
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原子吸收光谱法测定金银样品前处理的讨论 总被引:9,自引:1,他引:8
讨论了在岩石、矿物及化学探矿样品中金、银的原子吸收光谱分析时,样品前处理应关注的一些问题实践经验表明要注意样品的加工过程和金银的赋存状态,以保证样品有足够的代表性;针对不同矿种类型,选择合适的样品前处理方法,尽量避免样品在处理过程中的挥发损失、包夹、共沉淀吸附等情况的发生;对单矿物金、银的连续测定,建议采用多次湿法酸处理来保证样品的分解,并根据其含量进行必要的分离富集或稀释,以满足测定的要求. 相似文献
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标准样品的均匀性检验及判断 总被引:1,自引:0,他引:1
对标准样品的均匀性检验及判断进行了系统的论述。介绍了标准样品的均匀性检验及判断的各种方法,指出标准样品的均匀性要通过综合评估多方位去判断。 相似文献
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结合样品核磁测试结果,以具体实例的形式,总结了核磁样品分析的基本要求,分析了核磁管和氘代试剂的选择、样品制备及pH值等因素对核磁测试结果的影响,并提出了样品最优测试条件:核磁管管体内外表面要足够光洁均匀,在高温条件下,优先选用升温核磁管.尽量选择小支封装氘代试剂,降低水峰的影响,并且应考虑样品的性质,避免试剂与测试样品发生反应.样品必须与溶剂充分混合均匀,样品量要在溶液粘度与灵敏度之间做好平衡.在分析与氧、氮和硫共价相连的氢原子时,应该选择恰当的pH溶液.以上研究结果可以为其它样品核磁测试提供借鉴指导. 相似文献
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镀膜对FE-SEM纳米尺度形貌观察的影响 总被引:1,自引:0,他引:1
李梅晔 《分析测试技术与仪器》2008,14(2):120-124
通过观察场发射扫描电子显微镜下非导电样品镀膜前后纳米尺度的形貌变化,发现镀膜对样品在几个纳米范围内的形貌有一定的影响和遮盏,分析了使用场发射扫描电镜观察样品高倍数形貌时应注意的问题,并给出了获取真实形貌的方法。 相似文献
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采用液液萃取–气相色谱–质谱法测定水中硝基苯,通过统计全国多家实验室的测定数据,对平行样测定结果相对偏差、空白加标回收率、样品加标回收率、空白加标回收率相对偏差及样品加标回收率相对偏差5个质控指标进行分析,得出质控指标评价标准。在概率P,γ均为0.90时,平行样测定结果允许最大相对偏差应控制在11.0%;当空白加标浓度为0.2~30μg/L时,回收率控制范围为59%~113%;当样品未检出、加标浓度在0.25~50μg/L时,样品加标回收率控制范围为56%~110%;空白加标、样品加标回收率最大相对偏差应分别控制在10.0%和11.1%。在概率P和γ均为0.95时,平行样测定结果允许最大相对偏差应控制在13.5%;当空白加标浓度为0.2~30μg/L时,回收率的控制范围为50%~122%;当样品未检出、加标浓度在0.25~50μg/L时,样品加标回收率控制范围为49%~117%;空白加标、样品加标回收率最大相对偏差应分别控制在12.6%和14.6%。 相似文献
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The concept of sweeping has been used in electrokinetic chromatography to explain the concentrating mechanism in micellar electrokinetic chromatography when the sample matrix is a high resistivity non-micellar aqueous solution. Theoretical and experimental studies were undertaken. It was found that the total focusing effect is brought about by the cumulative effect of sweeping and sample stacking. For better analytical results, compounds showing low to moderate retention factors (k) and compounds showing high values of k must be dissolved in low and high conductivity matrices, respectively. 相似文献
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In this work, a method for direct lead determination in wine, without wet or dry sample attack, by lead hydride generation-atomic absorption spectrometry, is proposed. To do this, ammonium persulphate is employed as the oxidizing agent, and sodium borohydride is used as the reducing agent. The pH value must be 1.0.Lead content in wine is determined by the analyte addition technique, and the result is compared with those obtained by three different methods. 相似文献
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Frank von der Kammer Samuel LegrosThilo Hofmann 《Trends in analytical chemistry : TRAC》2011,30(3):425-436
The thorough analysis of natural nanoparticles (NPs) and engineered NPs involves the sequence of detection, identification, quantification and, if possible, detailed characterization. In a complex or heterogeneous sample, each step of this sequence is an individual challenge, and, given suitable sample preparation, field-flow fractionation (FFF) is one of the most promising techniques to achieve relevant characterization.The objective of this review is to present the current status of FFF as an analytical separation technique for the study of NPs in complex food and environmental samples. FFF has been applied for separation of various types of NP (e.g., organic macromolecules, and carbonaceous or inorganic NPs) in different types of media (e.g., natural waters, soil extracts or food samples).FFF can be coupled to different types of detectors that offer additional information and specificity, and the determination of size-dependent properties typically inaccessible to other techniques. The separation conditions need to be carefully adapted to account for specific particle properties, so quantitative analysis of heterogeneous or complex samples is difficult as soon as matrix constituents in the samples require contradictory separation conditions. The potential of FFF analysis should always be evaluated bearing in mind the impact of the necessary sample preparation, the information that can be retrieved from the chosen detection systems and the influence of the chosen separation conditions on all types of NP in the sample. A holistic methodological approach is preferable to a technique-focused one. 相似文献
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PTV splitless injection cannot compete with on-column injection as far as simplicity, reliability, and accuracy of quantitative analysis is concerned. However, PTV splitless injection is attractive for trace analysis of samples containing high concentrations of involatile sample by-products. Maximum injection volumes are limited by the amount of liquid that can be retained within the PTV injector chamber and are around 20–30 μl injected at once. Solvent evaporation must be carried out in such a way that injector overflow is avoided. 相似文献
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Uncertainty calculations in the certification of reference materials. 2. Homogeneity study 总被引:4,自引:0,他引:4
Many reference materials undergo a batch certification, which implies that a small number of samples is taken from a batch,
characterised, and these results are then assumed to be representative of all remaining samples. An important aspect in this
design is the translation of the characterisation data to a single sample, as usually the laboratory will be using only one
sample of the batch. This form of homogeneity is very important and can be influenced to a certain extent by well-designed
sample preparation procedures. Another subsampling problem associated with many reference materials is that only a small test
portion is drawn from the sample to carry out the measurement. Obviously, this test portion must be representative of the
sample, otherwise the certified value is still not applicable. Both kinds of homogeneity tests are examined in the paper and
evaluated using practical examples.
Received: 31 May 2000 · Accepted: 29 July 2000 相似文献
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María Dolores Luque de Castro 《Journal of separation science》2022,45(1):166-171
A wide number of analytical terms have been applied erroneously for many years by analytical chemists, and they apply at present yet, by considering the time makes their use correct. The question is, may precedents validate the present use of incorrect scientific terms? Misused terms are found along the analytical process, starting with giving the name of the sample to the exiguous fraction of the original sample that reaches the detector or the high-resolution equipment after sample pretreatment and sample preparation. All the steps of the analytical process are considered in this article, with special emphasis on sample preparation and, within this, on the use of ultrasound, mainly for assisting extraction more unequivocally named as leaching or lixiviation. A call of attention in this respect is considered by the author to be of help to the analytical community. 相似文献